Return-Path: X-Processed-By: Virex 7 on prxy.net X-Real-To: stagecraftlist [at] theatrical.net Received: by prxy.net (CommuniGate Pro PIPE 4.2.5) with PIPE id 4824498; Thu, 28 Oct 2004 03:01:33 -0700 X-ListServer: CommuniGate Pro LIST 4.2.5 List-Unsubscribe: List-ID: Message-ID: From: "Stagecraft" Sender: "Stagecraft" To: "Stagecraft" Precedence: list Subject: Stagecraft Digest #177 Date: Thu, 28 Oct 2004 03:01:09 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Disposition: inline X-Spam-Status: No, score=-4.6 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.0.1 X-Spam-Checker-Version: SpamAssassin 3.0.1 (2004-10-22) on prxy.net X-Spam-Level: X-TFF-CGPSA-Version: 1.4f2 X-prxy-Spam-Filter: Scanned For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Stagecraft Digest, Issue #177 1. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by Bill Sapsis 2. Re: Shadow Backdrops by Jason Tollefson 3. Re: A cautionary tale by "Stephen E. Rees" 4. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by usctd [at] columbia.sc 5. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by Noah Price 6. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by Bill Sapsis 7. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Michael J. Banvard" 8. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Cyr, Dale" 9. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Paul Schreiner" 10. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Delbert Hall" 11. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Cyr, Dale" 12. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by usctd [at] columbia.sc 13. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Paul Schreiner" 14. Re: Shadow Backdrops by FrankWood95 [at] aol.com 15. Obsession II weirdness by Ed Hunter 16. Re: Obsession II weirdness by Stephen Litterst 17. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by FrankWood95 [at] aol.com 18. Re: Obsession II weirdness by Herrick Goldman 19. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by "Cyr, Dale" 20. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Delbert Hall" 21. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by Bill Sapsis 22. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by "Paul Schreiner" 23. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by Mark O'Brien 24. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Dr. Randall W.A. Davidson" 25. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by "Cyr, Dale" 26. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by Bill Sapsis 27. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by "Delbert Hall" 28. Cool audio tools? by "Cyr, Dale" 29. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by Richard Niederberg 30. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by FrankWood95 [at] aol.com 31. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by FrankWood95 [at] aol.com 32. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduc by "Cyr, Dale" 33. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by Stuart Wheaton 34. Re: Campfires on Stage by Stuart Wheaton 35. Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) by "Dr. Randall W.A. Davidson" 36. Re: Cool audio tools? by "Andy Leviss" 37. Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? by "Dr. Randall W.A. Davidson" 38. Re: Cool audio tools? by "Delbert Hall" 39. Re: Cool audio tools? by "Andy Leviss" 40. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduc by MissWisc [at] aol.com 41. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reprodu by Patrick McCreary 42. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduc by Richard Niederberg 43. Re: DMX512 Back Channel by Mitch Hefter 44. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reprodu by "Dr. Randall W.A. Davidson" 45. Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reprodu by "Chris Kennedy" *** Please update the subject line of your reply to use the subject *** line of the message you are replying to! Please only reply to *** one message subject in each reply. ---------------------------------------------------------------------- Date: Wed, 27 Oct 2004 06:35:54 -0400 Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) From: Bill Sapsis Message-ID: In-Reply-To: on 10/27/04 5:00 AM, Cyr, Dale at Dale.Cyr [at] getronics.com wrote: > For info, archives & UNSUBSCRIBE, see > --------------------------------------------------- > > this one hasn't "broken" yet, > so let's set the record straight from the start. > www.sapsis-rigging.com 800.727.7471 800.292.3851 fax 267.278.4561 mobile We stand behind, and under, our work. BIG SNIP > > the curtains were not pulled from the hampers; > they had been laid out over the seats. > it is not believed that the curtain caught on anything while flying out. > > the connector plates of the 10 foot section that, > so to speak, retained possesion of the broken 5 foot connector plates > are severly "bulged" out, but none are (visibly) broken. > > the spansets were rigged, in what I consider, an "unusual" way. > (see photo) > a bottom cord was choked, the span set passed under the other bottom > cord, > and then choked the top cord and continued up to the motor. > this had the effect of compressing the two bottom cords together, > but in a sort of "basket" fashion. > this configuration was re-created for the photo by the lead, > who had assisted in, and approved of the original rig. > (the photo shows only one side, for clarity) > > truss sections are used in several configurations, > and no attention is paid to which section is placed in which position, > (except the 5 foot sections always end up in center, if used) > or how often a particular section may be used or not used.. > > the weight of the curtains is currently being verified.. > > the motors are rigged from permanently installed stantions in the grid. > > questions / comments? > other questions that should be asked or > facts that should be acertained? > > > dale cyr > Training Supervisor > IATSE Local 93 > Spokane Wa OK. Haven't seen the photos. (Unless I missed it there were no directions on where to go to see them) But....there are several things I noticed with the rig 1) The curtain was hung on the top cord and draped over the front to hid the truss. This placed an unbalanced load on the truss. 2) The method described for attaching the spansets is inaccurate. If the sling was choked around one of the bottom cords and ended up being connected to the hoist, then it could not be choked around another, as was described. It may have been wrapped around another cord but it as long as an end of the sling was attached to the hoist there was no choke. Consequently, the slings ability to control rotation was very limited. 3) This procedure had been done a number of times. my theory..... the truss was hung improperly and, after having done so a number of times, it simply got tired of doing it and failed. The truss should have been hung point down. The truss should have been supported by two slings at each hoist. Each sling should have been choked around the bottom cord and wrapped around the opposing top cord. There should have been a third hoist. This accident shows why the excuse "Hey. It hasn't broken yet." doesn't hold water. OK. Now I gotta get the kids ready for school. Bill S. www.sapsis-rigging.com 800.727.7471 800.292.3851 fax 267.278.4561 mobile We stand behind, and under, our work. ------------------------------ Message-ID: <20041027104652.59974.qmail [at] web54701.mail.yahoo.com> Date: Wed, 27 Oct 2004 03:46:52 -0700 (PDT) From: Jason Tollefson Subject: Re: Shadow Backdrops In-Reply-To: I've had pretty good luck with a Lensless 1Kw Fresnel. It helps if the light source (whatever it is) is below the level of the performer. Jason Tollefson > I want to use shadow as backdrops in my theater play. The problem is > that the light remains on in the performance; meantime off course I need > shadow in the background. > > I have two questions; > > 1: Which light I should use? > 2: are there any specific suggestions from you? ------------------------------ Message-ID: <417F90AB.2010707 [at] fredonia.edu> Date: Wed, 27 Oct 2004 08:12:27 -0400 From: "Stephen E. Rees" Subject: Re: A cautionary tale References: Fred, From curiosity, do you provide your renters with WRITTEN policy information about what can and can not be done and do they have to sign off on it in a contractual manner? I see a lot of exposure for you unless you do. Mayhaps doing so would alleviate some of the confusion and demonstrate to your front office types that you are not being obstructive. Regards, Steve Rees, TD SUNY-Fredonia Fred Fisher wrote: > [presnipped] I'm always surprised at user groups who come into > our facility assuming that because they are paying rent they can do > anything they want to the place. I spend a lot of time explaining to > the heads of the tech staff well before they arrive what we will do for > them and what we expect from them. There are times when it would be > more productive for me to talk to a brick wall. > > Fred Fisher ------------------------------ Message-ID: <4582.129.252.241.105.1098888118.squirrel [at] webmail.columbia.sc> In-Reply-To: References: Date: Wed, 27 Oct 2004 10:41:58 -0400 (EDT) Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) From: usctd [at] columbia.sc First, I am glad everyone is OK. A couple questions/comments: 1. Are the hoists directly above the points on the truss? If they are not, you could have been producing extra forces that the truss could no longer contend with. 2. Is there a lot of stop and go hoist action going on to set trim? Without a third motor on this rig, this would be of great concern to me. 3. This is a hindsite 20/20 thing, but if the manufacturer says spans up to 50' with what I am assuming they are saying should be a uniform load, then this particular truss should not have been used at a 65' span. However, like you say in the post, you understood that the manufacturer had been consulted. 4. I would have recommended highly against flying that truss again, even minus the broken section, without it having been thoroughly inspected. Especialy since the crew was not sure what made it break in the first place. -- Eric Rouse TD-University of SC, Columbia Freelance Foyboy > For info, archives & UNSUBSCRIBE, see > --------------------------------------------------- > > this one hasn't "broken" yet, > so let's set the record straight from the start. > > at the spokane arena Sunday (october 24, 2004) morning an experienced IA > crew > assembled a 65 foot span of 20 inch truss consisting of 3 sections 10 > feet long, > one 5 foot section, then 3 more 10 foot sections. > > they then hung several sections of curtain on this truss. > > this operation has been performed (estimated) 20-30 times > over the last 4 years or so, > and is done to create a more intimate space inside the larger arena. > > two tapered sections are hung, > one over the stage left seating area, > one over the stage right seating area, > and another one on a separate truss > to create an upstage curtain / back stage area. > > the curtain is tapered to accomadate the slope of the seats. > the longest (tallest?) section is about 45 feet, > the shortest about 15 feet. (these are rough estimates for now.) > > the truss is hung point up > and the manufacturers website says this is an acceptable configuration. > > the truss is picked at each end, > about 18 inches from the end, > at the first (inverted) "V". > > the curtain is attached to the top of the truss, > and hung on the downstage side, > thereby hiding the truss itself. > > the stage left truss was flown to almost trim height, > and both motors were in motion, > when it failed. > > apparently the curtain itself held and the lead on the crew > requested the motor control operator fly the > broken truss in, while attempting to maintain a constant > relationship between the broken pieces. > > the curtain held for a few seconds, > then it failed also, > ripping from top to bottom, > leaving each half of the broken 65 foot span > hanging from it's spanset, > with half of the torn curtain attached. > > at that point, the lead on the crew requested that the motor control > operator > immediately fly the broken pieces in. > > it was not known what caused the failure. > > after a cursory inspection, the lead requested a seamstress to repair > the curtain, > with an intention to possibly attempt to fly the truss again, minus the > broken section. > > moving to the stage right truss, and assembling it in the normal manner, > it was flown to about 3 feet short of trim, > and the lead (who had taken over the motor control operation) > moved to a better vantage point to establish a reference for level, > when that truss also failed, ripping the curtain from top to bottom. > > the attempt to hang the "side" curtains was then abandoned altogether, > and only the back curtain was hung (uneventfully). > > noah has graciously agreed to host several high resolution photos > of the broken pieces, and hopefully he will respond to this thread > with a url. > > ************************************************************* > this post is also a request for comment relevant to the failure > analysis. > > these are the potential relevant facts as they are currently known: > > both truss failed at the same point, ie, at a 5 foot / 10 foot boundry. > both truss failed in the same way; all three connector plates of the 5 > foot section > were ripped from the 5 foot section and stayed attached to the adjacent > 10 foot section. > > both truss were assembled with the 5 foot section in the middle of the > 65 foot truss. > > the load is not "uniformly distributed" in the strictest sense, > because the onstage end carries longer pieces of curtain. > > alledgedly the manufacturer was consulted on the load distribution and > pick > points (this is being confirmed). > > the spec plate (see photo) references spans up to 50 feet. > their web site also mentions "spans up to 50 feet". > > looking at the damaged end of the truss (see photo): > the top connector plate ripped some of the truss member away from both > truss members. > both bottom connector plates ripped some of the bottom truss member away > BUT both bottom plates had the weld only fail on the "vertical" truss > members. > > the weather recently has been humid. > > the curtain are stored in normal hampers, > in a warehouse area. > > the curtains were not pulled from the hampers; > they had been laid out over the seats. > it is not believed that the curtain caught on anything while flying out. > > the connector plates of the 10 foot section that, > so to speak, retained possesion of the broken 5 foot connector plates > are severly "bulged" out, but none are (visibly) broken. > > the spansets were rigged, in what I consider, an "unusual" way. > (see photo) > a bottom cord was choked, the span set passed under the other bottom > cord, > and then choked the top cord and continued up to the motor. > this had the effect of compressing the two bottom cords together, > but in a sort of "basket" fashion. > this configuration was re-created for the photo by the lead, > who had assisted in, and approved of the original rig. > (the photo shows only one side, for clarity) > > truss sections are used in several configurations, > and no attention is paid to which section is placed in which position, > (except the 5 foot sections always end up in center, if used) > or how often a particular section may be used or not used.. > > the weight of the curtains is currently being verified.. > > the motors are rigged from permanently installed stantions in the grid. > > questions / comments? > other questions that should be asked or > facts that should be acertained? > > > dale cyr > Training Supervisor > IATSE Local 93 > Spokane Wa > ------------------------------ In-Reply-To: References: Message-Id: <22F78A5F-282A-11D9-84A4-000A958ABBF8 [at] theprices.net> From: Noah Price Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 08:09:02 -0700 On Oct 27, 2004, at 2:00 AM, Cyr, Dale wrote: > noah has graciously agreed to host several high resolution photos > of the broken pieces, and hopefully he will respond to this thread > with a url. That's using a new gallery system that I'm planning to integrate into the site to replace the existing manually created gallery, and give list members a place to upload photos. Thanks, Noah ------------------------------ Date: Wed, 27 Oct 2004 11:22:24 -0400 Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) From: Bill Sapsis Message-ID: In-Reply-To: on 10/27/04 11:09 AM, Noah Price at stagecraft-web [at] theprices.net wrote: > For info, archives & UNSUBSCRIBE, see > --------------------------------------------------- > > > On Oct 27, 2004, at 2:00 AM, Cyr, Dale wrote: > >> noah has graciously agreed to host several high resolution photos >> of the broken pieces, and hopefully he will respond to this thread >> with a url. > > > > Thanks Noah. Yeah. Looks like the truss wasn't supported against rotation and that's what it did. a 65' span is a long way to go without pick up points. This is why I always use 2 slings. You maintain much better control that way. And yeah, 65' is a long way to go. That much fabric weighs a lot more than some folks anticipate. A center motor would have helped a lot. Bill S. www.sapsis-rigging.com 800.727.7471 800.292.3851 fax 267.278.4561 mobile We stand behind, and under, our work. ------------------------------ From: "Michael J. Banvard" Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 10:31:58 -0500 In-Reply-To: Message-Id: > Okay, now that I have looked at the pictures... 1. The choke, and orientation of the truss (point up), is as Unka Bill says: All Wrong! I've never seen a choke in this arrangement. 2. The combination of the choke and the tie the curtain to the top of the truss add together to create a twisting moment on the truss as it is raised and lowered. Aluminum truss is not the most forgiving of compound stress, and the welds are the hardest, most brittle points in the system. The possibility is that the 5' section, being the shortest member and stiffest, became the focal point for the twisting moment, focusing all the stress on the welds, every time the truss was moved, as well as with the eccentric load of the curtains on the top chord. And, officially, the curtain was not a uniform load, since it was cut to fit the seating. There should have been some algebra involved in design the truss for the load, at some point. I'm sure Bill S. will have things to say about it, when he sees the pics. - Michael Michael J. Banvard SRI Midwest Saint Louis, Missouri (866) 773-1174 (314) 629-3644 (314) 773-1174 fax http://www.sapsis-rigging.com ____________ Virus checked by Guardian Worm Killer && AntiVirus Version: AVK 15.0.675 from 26.10.2004 Virus news: www.guardianproducts.com ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 09:11:59 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E232 [at] excuswa100.americas.unity> From: "Cyr, Dale" thanks for your comments bill and eric. I need to clarify a few things... from bill: "1) The curtain was hung on the top cord and draped over the front to hid the truss. This placed an unbalanced load on the truss." I'm not sure that I see this one. do you mean a torsional load due to the uneven load the tapered curtain puts on the truss? "2) The method described for attaching the spansets is inaccurate.=20 you are correct. the top cord was *wrapped* not choked." my bad. "my theory..... the truss was hung improperly and, after having done so a number of times, it simply got tired of doing it and failed." one of our thoughts too. but the fact that *both* stage left and stage right failed within one hour of each other in the same place in the same way is *extremely* coincidental... especially considering the fact that truss sections are always mixed up during=20 disassembly / assembly. "The truss should have been hung point down." the manufacturers website specifically allows a point up configuration, but does not proceed to address how the load should be attached. "The truss should have been supported by two slings at each hoist." it was. I didn't explain that very well. "There should have been a third hoist." I agree. but the truss manufacturer (alledgely) signed off on this config. (this is being confirmed.) "This accident shows why the excuse "Hey. It hasn't broken yet." doesn't hold water." agree again. this will be used to correct other potential problems in other houses. from eric: "1. Are the hoists directly above the points on the truss? If they are not, you could have been producing extra forces that the truss could no longer contend with." yes, the motors are directly above the pick points. "2. Is there a lot of stop and go hoist action going on to set trim? " no more than is normal for trimming any other truss. ie: there are no special issues with the house that would require multiple adjustments of each side, or anything like that. both side curtain trusses are flown straight up to approx trim height and then bumped to level. "4. I would have recommended highly against flying that truss again, even minus the broken section, without it having been thoroughly inspected.=20 Especialy since the crew was not sure what made it break in the first place." I agree. and in fact, as noted, they didn't. (I wasn't on the call) and when the broken pieces were brought down to the floor, it was noted that the truss sustained torsional forces as evidenced by the fact that the truss would not sit level on the floor. it had a twist along its length. but it is not known if this happened as part of the failure, or if this happened on the way down with the curtain acting as a giant sail producing a twisting motion. and finally from bill: "Thanks Noah. Yeah. Looks like the truss wasn't supported against rotation and that's what it did. a 65' span is a long way to go without pick up points. =20 This is why I always use 2 slings. You maintain much better control that way. " as noted above, two slings were used at each motor. the pix I uploaded was staged after the fact by one of the riggers who had participated in the original rig. only one spanset was shown for clarity. (apparently causing confusion... guess *that* didn't work :) but I'm starting to like the torsional load idea... can anyone on the list support or dispute this theory by observing the=20 failure patterns of the connector plates? (specifically noting that two of the welds (only) failed, like they were pulled straight out, but the other 4 areas of contact of connector plate to truss=20 shows that the truss members were torn) for others that havent seen the pix yet, they are at: dale cyr Training Supervisor IATSE Local 93 Spokane Wa ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 12:12:09 -0400 Message-ID: <6E497ADB607656479C24E6D7BF6B505A74AD2E [at] exchange.rmwc.edu> From: "Paul Schreiner" > The possibility is that the 5' section, being the shortest=20 > member and stiffest, became the focal point for the twisting=20 > moment, focusing all the stress on the welds, every time the=20 > truss was moved, as well as with the eccentric load of the=20 > curtains on the top chord. That would make sense, since the loads on the two 30' (3 [at] 10') sections were seriously unequal IIRC. One would have been subject to more twisting than the other, and the 5' piece failed because it was not flexible enough to handle the difference between the two...Plus, with no center pick, the two lower connector plates would have been subjected to more tension (while the top plate was in compression), which may have contributed to the pattern of ripping failure seen... One other thing...is it just me, or do those welds look a little flimsy? The broken one looks like the weld was just laid on top of the joint...the flat edges inside the weld are almost too even to appear to have been welded properly. But then I don't have a lot of experience with aluminum... ------------------------------ From: "Delbert Hall" Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 12:13:39 -0400 Organization: ETSU Message-ID: <000001c4bc3f$ec2c8a40$6400a8c0 [at] delbert> In-Reply-To: I think Michael B. is right on target. I have never seen this type of bridle either. It was just wrong. I believe that torque and the exceptionally long distance of the span resulted in the failure. I also agree with Michael that the stiffness of the 5' sections probably focused more stress on these points. There is a great story on in the book STRUCTURES on Germany's early attempts to build a single wing plane and how the wing kept tearing off. They kept making the wings stronger (and stiffer) and the problem kept getting worse. I am amazed that the trusses held up this long. -Delbert ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 09:18:40 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E233 [at] excuswa100.americas.unity> From: "Cyr, Dale" Paul Schreiner wrote: "One other thing...is it just me, or do those welds look a little flimsy? The broken one looks like the weld was just laid on top of the joint...the flat edges inside the weld are almost too even to appear to have been welded properly. But then I don't have a lot of experience with aluminum..." I purposely didn't bring that up, although others onsite noticed the same thing. this doesn't excuse an incorrect loading of the truss, but might explain how the failure began... dale cyr Training Supervisor IATSE Local 93 Spokane Wa ------------------------------ Message-ID: <4787.129.252.241.105.1098895074.squirrel [at] webmail.columbia.sc> In-Reply-To: References: Date: Wed, 27 Oct 2004 12:37:54 -0400 (EDT) Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) From: usctd [at] columbia.sc I would agree that the welds don't look that great inside, but diagnosing aluminum welds in a photo like this is tricky. If you look at the last photo it seems to me that the welds could be cold. Not much penetration. But I am not sure what is where in that photo. -- Eric Rouse TD-University of SC, Columbia Freelance Foyboy > For info, archives & UNSUBSCRIBE, see > --------------------------------------------------- > >> The possibility is that the 5' section, being the shortest >> member and stiffest, became the focal point for the twisting >> moment, focusing all the stress on the welds, every time the >> truss was moved, as well as with the eccentric load of the >> curtains on the top chord. > > That would make sense, since the loads on the two 30' (3 [at] 10') sections > were seriously unequal IIRC. One would have been subject to more > twisting than the other, and the 5' piece failed because it was not > flexible enough to handle the difference between the two...Plus, with no > center pick, the two lower connector plates would have been subjected to > more tension (while the top plate was in compression), which may have > contributed to the pattern of ripping failure seen... > > One other thing...is it just me, or do those welds look a little flimsy? > The broken one looks like the weld was just laid on top of the > joint...the flat edges inside the weld are almost too even to appear to > have been welded properly. But then I don't have a lot of experience > with aluminum... > ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 12:39:10 -0400 Message-ID: <6E497ADB607656479C24E6D7BF6B505A74AD2F [at] exchange.rmwc.edu> From: "Paul Schreiner" > I would agree that the welds don't look that great inside,=20 > but diagnosing aluminum welds in a photo like this is tricky.=20 > If you look at the last photo it seems to me that the welds=20 > could be cold. Not much penetration.=20 > But I am not sure what is where in that photo. Photo 4 was the one that caught my eye, for the exact reason you describe...much easier to tell what went where on that one. ------------------------------ From: FrankWood95 [at] aol.com Message-ID: <1e5.2db01e4a.2eb12b83 [at] aol.com> Date: Wed, 27 Oct 2004 12:49:07 EDT Subject: Re: Shadow Backdrops In a message dated 27/10/04 11:47:40 GMT Daylight Time, jason [at] tollefsondesigns.com writes: > I've had pretty good luck with a Lensless 1Kw Fresnel. It helps if the light > source (whatever it > is) is below the level of the performer. If you take the mirror out as well, this will work even better. You will then have a Linnebach Projector. Strand once sold a 1KW fresnel with neither lens nor mirror, with an extension on the front to take a 2' square colour frame. This was the Patt. 223L Frank Wood ------------------------------ Date: Wed, 27 Oct 2004 09:56:05 -0700 (PDT) From: Ed Hunter Subject: Obsession II weirdness Message-id: <0I69006NM5TEEJ30 [at] ha14sca-mail1.sfbay.sun.com> I've now seen this problem twice on two different boards so now I'm either crazy or there's something about the operation I'm confused about. I record a cue with split fade times ( time 3/8 for instance). When it runs the channels which are going down fade out on a 3 or 4 count and not an 8 count. If I just do straight time then then whole cue will run on an 8 count. Unfortunately, that's not what I want. As I've said I've seen this on two different boards. It doesn't appear to happen with all cues which is the weird part. I'm going back into the theater tonight to do some experiments and try to collect some more data to go to ETC with but I thought if anyone out there had seen this behavior and had any insight they could share that would be great. Thanks. -edh ------------------------------ Date: Wed, 27 Oct 2004 13:04:50 -0400 From: Stephen Litterst Subject: Re: Obsession II weirdness Message-id: <417FD532.AA859A8D [at] ithaca.edu> Organization: IC-Dept. of Theatre Arts References: Ed Hunter wrote: > --------------------------------------------------- > I've now seen this problem twice on two different boards so now I'm either crazy > or there's something about the operation I'm confused about. > > I record a cue with split fade times ( time 3/8 for instance). When it runs the > channels which are going down fade out on a 3 or 4 count and not an 8 count. If > I just do straight time then then whole cue will run on an 8 count. > Unfortunately, that's not what I want. I've had a similar problem with our Obs II. 3/0 split fades would happen without the split. The reccommendation from ETC was to save the show, reboot the console and reload the show. This seemed to solve the problem for us -- temporarily. What I was told is that the memory gets cluttered, and a simple reload of the show will usually clear out the clutter. In an extreme case you might need to do a deep clean of the memory from the dos level. Steve L. -- Stephen C. Litterst Technical Supervisor Ithaca College Dept. of Theatre Arts 607/274-3947 slitterst [at] ithaca.edu ------------------------------ From: FrankWood95 [at] aol.com Message-ID: Date: Wed, 27 Oct 2004 13:05:46 EDT Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) In a message dated 27/10/04 17:14:35 GMT Daylight Time, halld [at] etsu.edu writes: > There is a great story on in the > book STRUCTURES on Germany's early attempts to build a single wing plane > and how the wing kept tearing off. They kept making the wings stronger > (and stiffer) and the problem kept getting worse. There is indeed. The book in question is "Structures, or why things don't fall down" by J. E. Gordon. ISBN 0-14-021961-7. What you haven't revealed is how they solved the problem. The dynamic loads on the wings were distorting the wing structure in such a way as to increase these loads. The solution was to make one of the wing spars WEAKER so as to avoid this. Frank Wood ------------------------------ Date: Wed, 27 Oct 2004 13:16:59 -0400 Subject: Re: Obsession II weirdness From: Herrick Goldman Message-ID: In-Reply-To: I believe I was told at LDI that this is a known bug and that they are working to fix it. Do call ETC tech support and let them know. I think it is difficult to repeat so they are looking for more data. -Herrick -- Herrick Goldman Lighting Designer, NYC www.HGLightingDesign.com "To the scores of silent alchemists who wreak their joy in darkness and in light bringing magic to life, we bow most humbly. "-CDS ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 11:02:56 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E236 [at] excuswa100.americas.unity> From: "Cyr, Dale" after thinking this thru a little more, I'm not sure the twisting moment, or torsional force, is the culprit. although the spansets were rigged in an unusual manner (to reduce the length from the motor to the truss) the net result of rigging two opposing spansets per motor point in this way is essentially a basket. the curtain was hung on the top cord and draped over the downstage cord, and thus applying a force on the downstage cord in the upstage direction. because the curtain is tapered to fit the seats, the force on the bottom cord is not uniform. but it differs only by the weight of about 20 feet of curtain. (the difference between the shortest and longest lengths of curtain.) I cant remember the equation for rotational force right now, (something like: weight times distance from center?) but it doesn't *seem* (dangerous word) like 20 feet of curtain on a 10 inch horizontal arm would create enough of a force to tear apart a truss... (10 inches =3D the horizontal distance from center of top cord to = outside edge of bottom cord) perhaps others can help out with the math here... dale cyr Training Supervisor IATSE Local 93 Spokane Wa -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of usctd [at] columbia.sc Sent: Wednesday, October 27, 2004 9:38 AM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) > >> The possibility is that the 5' section, being the shortest >> member and stiffest, became the focal point for the twisting >> moment, focusing all the stress on the welds, every time the >> truss was moved, as well as with the eccentric load of the >> curtains on the top chord. > > That would make sense, since the loads on the two 30' (3 [at] 10') sections > were seriously unequal IIRC. One would have been subject to more > twisting than the other, and the 5' piece failed because it was not > flexible enough to handle the difference between the two...Plus, with no > center pick, the two lower connector plates would have been subjected to > more tension (while the top plate was in compression), which may have > contributed to the pattern of ripping failure seen... > ------------------------------ From: "Delbert Hall" Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 14:26:55 -0400 Organization: ETSU Message-ID: <000001c4bc52$8a275470$6400a8c0 [at] delbert> In-Reply-To: Thanks Frank. My copy of this book is in the office, and I am at home today, so I did not have all of the bibliographical information handy. It has been many years since I read this book, but it was certainly a very enlightening book on structural engineering that is presented in a non-technical manner. I highly recommend it to anyone interested in structural design applications (I think that is just about everyone in technical theatre). -Delbert -----Original Message----- There is indeed. The book in question is "Structures, or why things don't fall down" by J. E. Gordon. ISBN 0-14-021961-7. What you haven't revealed is how they solved the problem. The dynamic loads on the wings were distorting the wing structure in such a way as to increase these loads. The solution was to make one of the wing spars WEAKER so as to avoid this. Frank Wood ------------------------------ Date: Wed, 27 Oct 2004 14:49:07 -0400 Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? From: Bill Sapsis Message-ID: In-Reply-To: on 10/27/04 2:02 PM, Cyr, Dale at Dale.Cyr [at] getronics.com wrote: > I cant remember the equation for rotational force right now, > (something like: weight times distance from center?) > but it doesn't *seem* (dangerous word) like 20 feet of curtain > on a 10 inch horizontal arm would create enough of a force to tear apart > a truss... > (10 inches = the horizontal distance from center of top cord to outside > edge of bottom cord) > perhaps others can help out with the math here... Yes, but you forgot the 65' span. I certainly can't say for certain what caused the accident but, with the info I have, I'm putting my money on a rotational problem. bill s. www.sapsis-rigging.com 800.727.7471 800.292.3851 fax 267.278.4561 mobile We stand behind, and under, our work. ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 15:02:57 -0400 Message-ID: <6E497ADB607656479C24E6D7BF6B505A74AD30 [at] exchange.rmwc.edu> From: "Paul Schreiner" Just a thought (or two) on the tortional force theory... Considering the original post mentioned this particular arrangment being used about a hundred times over the past four years, did any of the 10' spans show any signs of having been permanently twisted BEFORE being used on the day in question? It would be my suspicion that something would have had to been building up over time until it reached the breaking point, and if anyone had noticed any twisting, this would tend to support the theory... Especially if (as the original post also mentioned) there was no rhyme (or rime...can you tell what I've got opening tomorrow?) or reason to the system of designating which 10' section went where from time to time. IOW, one piece may have randomly ended up carrying the most extreme load (say, farthest onstage right, resulting in a counterclockwise twist if viewed from stage) and then been used the next time in the mirrored position, where the heaviest portion of the curtain would have been pulling it into a clockwise twist. If the welds are as cold and unpenetrating as they appear from that picture, this repeated miniscule twisting in first one direction and then the other could have worked the welds loose over time. Continuing to speculate...I love detective work! :) ------------------------------ In-Reply-To: References: Message-Id: <3184EB67-2850-11D9-A022-000393897332 [at] email.arizona.edu> Cc: marko [at] email.arizona.edu (Mark O'Brien) From: Mark O'Brien Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 12:41:27 -0700 On Oct 27, 2004, at 12:02 PM, Paul Schreiner wrote: > Considering the original post mentioned this particular arrangment > being > used about a hundred times over the past four years, did any of the 10' > spans show any signs of having been permanently twisted BEFORE being > used on the day in question? It would be my suspicion that something > would have had to been building up over time until it reached the > breaking point, and if anyone had noticed any twisting, this would tend > to support the theory... The funny thing about aluminum is that metal fatigue can be unnoticed, until it is too late. This lesson was learned very early on in jet aviation with the "Comet" airliner. It flew VERY well for a time, and then it just started dropping out of the sky. Many important lessons were learned there. Mark O'Brien Opera Technical Director University of Arizona, School of Music Tucson, AZ 520/621-7025 520/591-1803 Mobile ------------------------------ From: "Dr. Randall W.A. Davidson" Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 12:47:07 -0700 Message-ID: <00d001c4bc5d$bea0dbd0$726dfea9 [at] DrDoomsComputer> In-Reply-To: Yes. Frank, a great book. I have used it and all of Gordon's books for my Risk Management Master Classes in Rigging since 1986. He is certainly a master of what he writes about. Dr. doom ==================================================== A Masters Workshop for Entertainment Technicians, Riggers, Public Assembly Technicians, and Educational Performing Arts Personnel - Sponsored by Risk International & Associates, Inc. April 4, 5, 6, 2005 at ELCO Performing Arts Center, Elkhart, Indiana Brochure & Registration Form available at: www.riskit.com/workshops ==================================================== Risk International & Associates, Inc. - Dedicated to making the world a healthier & safer place. Website: www.riskit.com E-mail: rdavidson [at] riskit.com ==================================================== International Secondary Education Theater Safety Association (ISETSA) - Dedicated to the protection of every student in the performing arts. Website: www.isetsa.org E-mail: info [at] isetsa.org ==================================================== 960 E. Bonita #158, Pomona, CA 91767 Phone/Fax: (909) 625-5961 ==================================================== -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of FrankWood95 [at] aol.com Sent: Wednesday, October 27, 2004 10:06 AM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) For info, archives & UNSUBSCRIBE, see --------------------------------------------------- In a message dated 27/10/04 17:14:35 GMT Daylight Time, halld [at] etsu.edu writes: > There is a great story on in the > book STRUCTURES on Germany's early attempts to build a single wing plane > and how the wing kept tearing off. They kept making the wings stronger > (and stiffer) and the problem kept getting worse. There is indeed. The book in question is "Structures, or why things don't fall down" by J. E. Gordon. ISBN 0-14-021961-7. What you haven't revealed is how they solved the problem. The dynamic loads on the wings were distorting the wing structure in such a way as to increase these loads. The solution was to make one of the wing spars WEAKER so as to avoid this. Frank Wood ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 12:53:36 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E237 [at] excuswa100.americas.unity> From: "Cyr, Dale" from bill sapsis: "Yes, but you forgot the 65' span. I certainly can't say for certain what caused the accident but, with the info I have, I'm putting my money on a rotational problem." from paul schreiner: "did any of the 10' spans show any signs of having been permanently=20 twisted BEFORE being used on the day in question?" "If the welds are as cold and unpenetrating as they appear from that picture, this repeated miniscule twisting in first one direction and then the other could have worked the welds loose over time." tonight I will layout the remaining truss=20 (it was used for the upstage curtain and was uneffected by this incident) and extremely closely examine them for twist and connector plate weld cracks. I'll let you know late tonight or early tomorrow my findings. dale cyr Training Supervisor IATSE Local 93 Spokane Wa ------------------------------ Date: Wed, 27 Oct 2004 15:56:03 -0400 Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? From: Bill Sapsis Message-ID: In-Reply-To: on 10/27/04 3:41 PM, Mark O'Brien at marko [at] email.arizona.edu wrote: > For info, archives & UNSUBSCRIBE, see > --------------------------------------------------- > The funny thing about aluminum is that metal fatigue can be unnoticed, > until it is too late. This lesson was learned very early on in jet > aviation with the "Comet" airliner. It flew VERY well for a time, and > then it just started dropping out of the sky. Many important lessons > were learned there. > > Mark O'Brien > Opera Technical Director > University of Arizona, School of Music > Tucson, AZ > 520/621-7025 > 520/591-1803 Mobile > Yeah. Note to self. Don't fly on plane named after a ball of ice hurtling threw space. www.sapsis-rigging.com 800.727.7471 800.292.3851 fax 267.278.4561 mobile We stand behind, and under, our work. ------------------------------ From: "Delbert Hall" Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 17:20:31 -0400 Organization: ETSU Message-ID: <000001c4bc6a$caadce80$6400a8c0 [at] delbert> In-Reply-To: First, I think there was a lot of twisting force in this truss, weather it is noticeable in the other sections or not. It is just difficult for me to believe that a 62' span of truss, loaded the way this one was, would not have a significant amount to torque placed on it. Second, thanks for clarifying that two spansets were used on each point. This makes a lot more sense. Third, I think we really have to applaud Dale for his diligence in investigating the cause of this failure. It seems to me that he is looking at every possible cause and not rushing to any conclusions. He is discussing everything openly, correctly misperceptions, acknowledging known problems, and not being defensive about the accident. Lots of people are going to learn two things from this discussion: 1) (eventually) what caused this failure, and 2) the proper way to investigate a problem. Thanks for the lesson Dale. -Delbert ------------------------------ Subject: Cool audio tools? Date: Wed, 27 Oct 2004 14:46:29 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E238 [at] excuswa100.americas.unity> From: "Cyr, Dale" has anyone seen any "cool" tools relevant to the audio (or video) world, perhaps at the recent ldi show? during our classes we hand out "give aways" in the form of=20 tools, charts, books, equipment, etc as an enticement to members to attend. (we charge non members $15 to attend) the next class is Audio / Visual, which includes sound system setup, video projection setup (with laptop), and video camera setup, with limited operation of each system. cost should be in the under $15 range. dale cyr Training Supervisor IATSE Local 93 Spokane WA ------------------------------ Date: Wed, 27 Oct 2004 14:29:05 -0700 Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Message-ID: <20041027.144617.2480.0.ladesigners [at] juno.com> From: Richard Niederberg Dear Dale, Permission to reproduce the photographs is hereby requested. Dr. Davidson may wish the same permission. Did you personally take the pictures and arrange them to be placed on the website? Thank you for your diligent reporting. /s/ Richard ________________________________________________________________ Speed up your surfing with Juno SpeedBand. Now includes pop-up blocker! Only $14.95/ month - visit http://www.juno.com/surf to sign up today! ------------------------------ From: FrankWood95 [at] aol.com Message-ID: <15c.41eef976.2eb1781f [at] aol.com> Date: Wed, 27 Oct 2004 18:15:59 EDT Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) In a message dated 27/10/04 19:27:35 GMT Daylight Time, halld [at] etsu.edu writes: > Thanks Frank. My copy of this book is in the office, and I am at home > today, so I did not have all of the bibliographical information handy. > It has been many years since I read this book, but it was certainly a > very enlightening book on structural engineering that is presented in a > non-technical manner. I highly recommend it to anyone interested in > structural design applications (I think that is just about everyone in > technical theatre So do I. It provides an illuminating and non-technical introduction to the theory of structures. The maths is available in appendices. Sad to say, but he died earlier this year. Frank Wood ------------------------------ From: FrankWood95 [at] aol.com Message-ID: <1e1.2de97cc4.2eb179a1 [at] aol.com> Date: Wed, 27 Oct 2004 18:22:25 EDT Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? In a message dated 27/10/04 20:55:20 GMT Daylight Time, bill [at] sapsis-rigging.com writes: > Yeah. Note to self. Don't fly on plane named after a ball of ice hurtling > threw space. I have news for you. They're still flying. The RAF Nimrod is a modified Comet. Not as versatile as an AWACS, but it still does a fair job. Frank Wood ------------------------------ Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce Date: Wed, 27 Oct 2004 15:25:36 -0700 Message-ID: <407DF7D68DD30440B5CEB70ED234D1CF0316E239 [at] excuswa100.americas.unity> From: "Cyr, Dale" richard: permission is granted specifically to, and only to, the members of this list, to reproduce the photos of the truss failure that have been placed on the website with the url of: PROVIDED that they are used for educational purposes only; that no money or other item of value is exchanged, in any form,=20 for transmission, receipt or use of these photos; that the words "Copyright dalecyr [at] hotmail.com" are included as part and parcel of the photos, of which being a part of a caption is acceptable; that this list server, the administrator of this list server, the members of this list, and the opinions of the members of this list are held harmless in regards to=20 any and all litigation which may directly or indirectly result from this incident. any commercial use is expressly prohibited, but may be negotiated at a later time between the photographer (myself) and interested parties. any use by those who are not members of this list,=20 or use of the photos other than covered above, must be specifically granted by me. good grief! ... and I'm not even a lawyer! dale cyr Training Supervisor IATSE Local 93 Spokane Wa -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Richard Niederberg Sent: Wednesday, October 27, 2004 2:29 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Dear Dale, Permission to reproduce the photographs is hereby requested. Dr. Davidson may wish the same permission. Did you personally take the pictures and arrange them to be placed on the website? Thank you for your diligent reporting. /s/ Richard ------------------------------ Message-ID: <41802887.3050901 [at] fuse.net> Date: Wed, 27 Oct 2004 19:00:23 -0400 From: Stuart Wheaton Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) References: In-Reply-To: Cyr, Dale wrote: > Paul Schreiner wrote: > "One other thing...is it just me, or do those welds look a little > flimsy? > The broken one looks like the weld was just laid on top of the > joint...the flat edges inside the weld are almost too even to appear to > have been welded properly. But then I don't have a lot of experience > with aluminum..." > > I purposely didn't bring that up, > although others onsite noticed the same thing. > this doesn't excuse an incorrect loading of the truss, > but might explain how the failure began... Dale, I suggest you might want to forward the weld photos to Ernie Leimkuhler ernie [at] stagesmith.com He used to be lead metals guy for Seattle opera, now does high end architectural stuff, also teaches welding. He used to play on RATS but mostly he's one of the most gifted guys on the welding groups now. This kind of thing would probably interest him and he has a good background in both fields. Stuart ------------------------------ Message-ID: <418029BC.6070005 [at] fuse.net> Date: Wed, 27 Oct 2004 19:05:32 -0400 From: Stuart Wheaton Subject: Re: Campfires on Stage References: In-Reply-To: CB wrote: > Dang! You guys cursed me1 I just found out that I have to make a > campfire, ala the flowing-silks-and-fan-and-light type. Someone mentioned > the FS-2 starters for the lamps, and I was wondering if those could be used > for the pin spots I'm planning on using. You know, the 6V 30W with the > little transformer in the can? I'm guessing that the starter and the txfmr > won't play nice, but I don't have the brainpower left over to do the math > in my head. As far as I know, the FS-2 starter has a small heater and a small bi-metal strip inside, it does not seem to dim the light just make and break randomly. It ought to work fine with the transformer. But the load might be too much (or not enough) probably worth the effort to try it! Stuart ------------------------------ From: "Dr. Randall W.A. Davidson" Subject: RE: Bizarre Multiple Catastrophic Truss Failure / rfc (long) Date: Wed, 27 Oct 2004 16:31:24 -0700 Message-ID: <01c601c4bc7d$1353cf10$726dfea9 [at] DrDoomsComputer> In-Reply-To: Interesting photos. Not as exact as we would like, but thank you. I seem to recall during my one year in Walt Disney Engineering Quality Control, with the mouse, examining and observing what seemed like zillions of welds for materials and stuctures used for all the theme parks Disney had around the world. There was an exacting test to become a welder and only for very specific welds, and the certification by authorized inspectors both in house and from the state and cities. And then all of the workshops we conducted over a period of twenty years looking at trusses from many countries. Interesting. Scary to see some of them. I was always pleased to have a bone fide registered structural engineer with me at the time. I seem to have learned a lot, and it has held me in good stead. Again, thanks for the pictures. They will certainly be useful. Dr. Doom ==================================================== A Masters Workshop for Entertainment Technicians, Riggers, Public Assembly Technicians, and Educational Performing Arts Personnel - Sponsored by Risk International & Associates, Inc. April 4, 5, 6, 2005 at ELCO Performing Arts Center, Elkhart, Indiana Brochure & Registration Form available at: www.riskit.com/workshops ==================================================== Risk International & Associates, Inc. - Dedicated to making the world a healthier & safer place. Website: www.riskit.com E-mail: rdavidson [at] riskit.com ==================================================== International Secondary Education Theater Safety Association (ISETSA) - Dedicated to the protection of every student in the performing arts. Website: www.isetsa.org E-mail: info [at] isetsa.org ==================================================== 960 E. Bonita #158, Pomona, CA 91767 Phone/Fax: (909) 625-5961 ==================================================== -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Richard Niederberg Sent: Wednesday, October 27, 2004 2:29 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure / rfc (long) For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Dear Dale, Permission to reproduce the photographs is hereby requested. Dr. Davidson may wish the same permission. Did you personally take the pictures and arrange them to be placed on the website? Thank you for your diligent reporting. /s/ Richard ________________________________________________________________ Speed up your surfing with Juno SpeedBand. Now includes pop-up blocker! Only $14.95/ month - visit http://www.juno.com/surf to sign up today! ------------------------------ From: "Andy Leviss" Subject: RE: Cool audio tools? Date: Wed, 27 Oct 2004 19:34:19 -0400 Organization: Duck's Echo Sound Message-ID: <00ec01c4bc7d$7b8b5800$a19afea9 [at] AndyLeviss> In-Reply-To: > has anyone seen any "cool" tools relevant to the audio (or=20 > video) world, perhaps at the recent ldi show? Hmm, most of the "cool toys" I have (or have lusted over) have been in the $30-50 range, rather than $15, so they won't necessarily help Dale, but I figure I'll post them anyway in case others are interested: -The Rat Sniffer/Rat Sender This is the coolest XLR cable tester I have ever used. Designed by Dave Rat, the sound engineer for (among other groups) the Red Hot Chili Peppers, the Sniffer is a small XLR male barrel with three green/red LEDs at the end of it. It runs of phantom power or power from the Sender, and not only tells you if the cable is good or bad, but what is wrong with it based on the color code shown by the LEDs (similar to those neon light Edison power testers). The Sender is a slightly longer XLR female barrel (about 3-1/2" I'd guess) that takes a 12V battery and lets you use the Sniffer without phantom power. The pair makes it a breeze to run down a snake line even after it's been run (or if it's an installed line running through conduits and patchbays) and check it out, and the fault indicator telling you what's miswired is a huge timesaver. The Sniffer alone is $25, the pair runs $50, they're available direct from the manufacturer at http://audiocontrolindustrial.com -The SoundPlug This is a pretty simple gadget, a female XLR plug that has a very sensitive transducer wired across pins 2 and 3 inside it. While that sounds pretty boring, what it does is way cool, which is to allow you to plug it into any XLR line receiving line level signal, and hold the end of the cable up to your ear and hear what is going down it. It runs $40 from David Smith's VizEar.com, and a clip with a key ring to clip it into is another $5. He also sells a DMX version that lets you hear the DMX chirps, and an adapter to turn the standard one into a DMX one. The one warning I will give is that, as sold, if you clip the SoundPlug into the KeyClip and carry it around on your belt/in your bag for a while, it will work its way loose. I've had it happen to me twice, and the first time I never found the Plug and ended up having to order a new one (had I known at the time that it was a design flaw of the clip, I would have asked David to replace it at cost if not better, but I didn't discover that until the second one showed up). It's a really simple device, and one that if you know what you're doing you can probably make up your own fairly easily. That said, David deserves the business* for having come up with it, and for making a very well manufactured product. -Tone Plug GTC Industries makes this cute little male XLR plug with a little pushbutton out the side of it and a red LED at the top end (sticking out of the strain relief). The LED acts as a phantom power tester (which is what the TP runs off of, it doesn=92t need batteries), and then the = button lets you select from the following test tones, all sent as balanced mic level signals: 5 Calibrated Sine Waves, Multi-frequency pluse, 20db Amplitude Sweep, Frequency Sweep Tone, 40Hz VLF System Test. Very, very cool and useful gadget, and only $50 (actually, it may be available cheaper; Full Compass has it listed in their catalog with a $50 list price and a note to call for current price, which means it's sold at less than the MAP). -Noise Plug The brother to the Tone Plug, this puppy runs off of phantom as well, and looks identical to the Tone Plug save for the lack of a button. It pumps out pink noise from 20 Hz-20 kHz. List price is $50, same as for the Tone Plug. My "test kit" in my toolbox, consists of everything above except for the Noise Plug, and a pair of XLR turnarounds (for checking return lines on snakes with the Rat Pack), and a Neutrik MR-1 MiniRator tone/noise generator, which I'll probably eventually replace with a Noise Plug (which, paired with the Tone Plug, does most everything I ever used the MR-1 for, although it does have some additional features, at a lower price; it just happens that I got a great deal on a used MR-1 before I'd heard of the two Plugs). I don't leave home without it. I'm always on the hunt for other similar gadgets/toys that make my life easier (and more fun!) out on the road, so I'd love to open this thread up to other stuff, even if it's not necessarily in the price range Dale is looking for, if anybody's got anything.=20 Best, Andy Leviss Sound Engineer, "Sesame Street Live: Elmo's Coloring Book" Currently in: Hartford, CT Next week: Norfolk, VA --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.778 / Virus Database: 525 - Release Date: 10/15/2004 =20 ------------------------------ From: "Dr. Randall W.A. Davidson" Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Twisting force? Date: Wed, 27 Oct 2004 16:36:45 -0700 Message-ID: <01ca01c4bc7d$d2eda4e0$726dfea9 [at] DrDoomsComputer> In-Reply-To: Yes, very helpful and even more interesting from the point of view of failure analysis methods. Thanks. Doom ==================================================== A Masters Workshop for Entertainment Technicians, Riggers, Public Assembly Technicians, and Educational Performing Arts Personnel - Sponsored by Risk International & Associates, Inc. April 4, 5, 6, 2005 at ELCO Performing Arts Center, Elkhart, Indiana Brochure & Registration Form available at: www.riskit.com/workshops ==================================================== Risk International & Associates, Inc. - Dedicated to making the world a healthier & safer place. Website: www.riskit.com E-mail: rdavidson [at] riskit.com ==================================================== International Secondary Education Theater Safety Association (ISETSA) - Dedicated to the protection of every student in the performing arts. Website: www.isetsa.org E-mail: info [at] isetsa.org ==================================================== 960 E. Bonita #158, Pomona, CA 91767 Phone/Fax: (909) 625-5961 ==================================================== -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Delbert Hall Sent: Wednesday, October 27, 2004 2:21 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Twisting force? For info, archives & UNSUBSCRIBE, see --------------------------------------------------- First, I think there was a lot of twisting force in this truss, weather it is noticeable in the other sections or not. It is just difficult for me to believe that a 62' span of truss, loaded the way this one was, would not have a significant amount to torque placed on it. Second, thanks for clarifying that two spansets were used on each point. This makes a lot more sense. Third, I think we really have to applaud Dale for his diligence in investigating the cause of this failure. It seems to me that he is looking at every possible cause and not rushing to any conclusions. He is discussing everything openly, correctly misperceptions, acknowledging known problems, and not being defensive about the accident. Lots of people are going to learn two things from this discussion: 1) (eventually) what caused this failure, and 2) the proper way to investigate a problem. Thanks for the lesson Dale. -Delbert ------------------------------ From: "Delbert Hall" Subject: RE: Cool audio tools? Date: Wed, 27 Oct 2004 19:42:03 -0400 Organization: ETSU Message-ID: <000001c4bc7e$900822d0$6400a8c0 [at] delbert> In-Reply-To: Dale, I don't have any audio or video tools to share, but if you have not seen LD Calculator Lite http://www.paul-pelletier.com/ I suggest that you give it a look. The rigging module is very nice. -Delbert ------------------------------ From: "Andy Leviss" Subject: RE: Cool audio tools? Date: Wed, 27 Oct 2004 19:46:33 -0400 Organization: Duck's Echo Sound Message-ID: <00ee01c4bc7f$31303d50$a19afea9 [at] AndyLeviss> In-Reply-To: I was just checking, and if you buy the Rat Pack testers directly from Rat Sound, rather than from ACI, they're actually only $45.95, not $49.95. http://www.ratsound.com And they also usually throw in some cool Rat stickers for your toolbox or other road cases :o) --Andy --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.778 / Virus Database: 525 - Release Date: 10/15/2004 ------------------------------ From: MissWisc [at] aol.com Message-ID: Date: Wed, 27 Oct 2004 20:22:59 EDT Subject: Re: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce Cc: Dale.Cyr [at] getronics.com In a message dated 10/27/4 5:26:23 PM, Dale.Cyr [at] getronics.com wrote: <> With your attention to detail, you would be a credit to that profession, just as you are to ours. May I ditto what Delbert said? I applaud you for your willingness to photograph, share, discuss, gently debate potential causes, and disseminate the findings. You're making the theatre world safer for ALL of us. Kudos to you! Kristi ------------------------------ Message-Id: <6.1.2.0.1.20041027203429.019d8ad0 [at] incoming.verizon.net> Date: Wed, 27 Oct 2004 20:46:21 -0500 From: Patrick McCreary Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce In-Reply-To: References: Two things - 1. According to the first posting from Dale, the motor points were 18" from the ends of the truss, putting them about 62' from each other. If it's not possible to get a middle point for lack of motors, is it possible to put the two motors closer to the 'quarter-points' (the two points approximately 1/4 of the length of the truss in from the ends)? Wouldn't be better, Bill S. and Delbert, for an evenly distributed load? Or, Dale, are your pick points in the roof(?) that far apart? It would lessen the span to about 30' - 35'. (I could be all wrong on this - Bill? Delbert? - I don't do many trusses, but I DO do a lot of beams.) 2. When I look at figure 4, the connector plate corner and edge at the bottom center of the picture seem to still have quite clean and sharp edges, as though there was no real weld penetration at all; I would definately have an expert look at those welds. 3. (I lied) J. E. Gordon wrote another wonderful book - "The New Science of Strong Materials (or Why You Don't Fall Through The Floor)" - both it and "Structures (or Why Things Don't Fall Down)" are required reading in my Advanced Stagecraft classes. Patrick G. Patrick McCreary Ass't. Professor - Technical Director Department of Theater and Dance Indiana University of Pennsylvania Indiana, PA 15701 (Office) 724-357-2644 (Home) 724-349-4309 ------------------------------ Cc: Dale.Cyr [at] getronics.com Date: Wed, 27 Oct 2004 18:55:44 -0700 Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce Message-ID: <20041027.185820.2480.2.ladesigners [at] juno.com> From: Richard Niederberg I agree, and I am a lawyer... /s/ Richard > In a message dated 10/27/4 5:26:23 PM, Dale.Cyr [at] getronics.com > wrote: <> > With your attention to detail, you would be a credit to that > profession, just as you are to ours. > May I ditto what Delbert said? I applaud you for your willingness to > photograph, share, discuss, gently debate potential causes, and > disseminate the findings. You're making the theatre world safer for > ALL of us. Kudos to you! > Kristi ________________________________________________________________ Speed up your surfing with Juno SpeedBand. Now includes pop-up blocker! Only $14.95/ month - visit http://www.juno.com/surf to sign up today! ------------------------------ Message-Id: <6.1.0.6.2.20041027224155.01eec0a8 [at] mail.DesignRelief.com> Date: Wed, 27 Oct 2004 22:42:12 -0500 From: Mitch Hefter Subject: Re: DMX512 Back Channel On 10/21/2004, several listers wrote on the "DMX512 Back Channel" Sorry for the late response - I was at LDI. See http://www.usitt.org/standards/DMX512.html Of particular interest is the Hazard Warning about Power on the Data Line link down on the page. We have had equipment damaged by such power. Karl Ruling's responses are, of course, correct. Note that there may not be DMX512 police, but willful violators have experienced some bad press and market pressures. >. . . trying to get a feel for what can be expected on pins 4 & 5, in case >our future products could do something useful with it (like support >equipment that uses it). The general feeling I get is it isn't worth >supporting ANYTHING on those two pins. Several companies do use the second pair for various legitimate functions which may be proprietary, but are not always. Some companies do not wire pins 4 & 5 at all, some wire them through. You will have to check with the manufacturer directly or through their documentation. This ambiguity is addressed in the new ANSI version of the standard developed though the ESTA Technical Standards Program. It is expected to be published soon. Compliant legacy equipment should have no problem working with products compliant with the new version and vice-versa. Again - see the link above. It should answer most questions. . . . ------------------------------------------------------------------------ Mitch Hefter mitch.hefter [at] DesignRelief.com ESTA / USITT DMX512 Revision (ANSI E1.11) Task Group Chair USITT Engineering Vice-Commissioner, DMX512 Subcommittee Chair Office: Entertainment Technology / a Division of the Genlyte Group mhefter [at] genlyte.com +1-214/ 647-7880 x 7967 (Direct Line 214/ 647-7967) +1-214/ 647-4738 Fax http://www.etdimming.com http://www.lolcontrols.com http://www.vari-lite.com http://www.genlyte.com ------------------------------ From: "Dr. Randall W.A. Davidson" Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce Date: Wed, 27 Oct 2004 23:56:51 -0700 Message-ID: <02a201c4bcbb$4db636f0$726dfea9 [at] DrDoomsComputer> In-Reply-To: Good for you. Keep using Gordon. I have all his books and use them in my work regularly for years. Excellent. Doom ==================================================== A Masters Workshop for Entertainment Technicians, Riggers, Public Assembly Technicians, and Educational Performing Arts Personnel - Sponsored by Risk International & Associates, Inc. April 4, 5, 6, 2005 at ELCO Performing Arts Center, Elkhart, Indiana Brochure & Registration Form available at: www.riskit.com/workshops ==================================================== Risk International & Associates, Inc. - Dedicated to making the world a healthier & safer place. Website: www.riskit.com E-mail: rdavidson [at] riskit.com ==================================================== International Secondary Education Theater Safety Association (ISETSA) - Dedicated to the protection of every student in the performing arts. Website: www.isetsa.org E-mail: info [at] isetsa.org ==================================================== 960 E. Bonita #158, Pomona, CA 91767 Phone/Fax: (909) 625-5961 ==================================================== -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Patrick McCreary Sent: Wednesday, October 27, 2004 6:46 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Two things - 1. According to the first posting from Dale, the motor points were 18" from the ends of the truss, putting them about 62' from each other. If it's not possible to get a middle point for lack of motors, is it possible to put the two motors closer to the 'quarter-points' (the two points approximately 1/4 of the length of the truss in from the ends)? Wouldn't be better, Bill S. and Delbert, for an evenly distributed load? Or, Dale, are your pick points in the roof(?) that far apart? It would lessen the span to about 30' - 35'. (I could be all wrong on this - Bill? Delbert? - I don't do many trusses, but I DO do a lot of beams.) 2. When I look at figure 4, the connector plate corner and edge at the bottom center of the picture seem to still have quite clean and sharp edges, as though there was no real weld penetration at all; I would definately have an expert look at those welds. 3. (I lied) J. E. Gordon wrote another wonderful book - "The New Science of Strong Materials (or Why You Don't Fall Through The Floor)" - both it and "Structures (or Why Things Don't Fall Down)" are required reading in my Advanced Stagecraft classes. Patrick G. Patrick McCreary Ass't. Professor - Technical Director Department of Theater and Dance Indiana University of Pennsylvania Indiana, PA 15701 (Office) 724-357-2644 (Home) 724-349-4309 ------------------------------ Message-Id: <200410280714.i9S7EtVE079464 [at] popmail.ucsd.edu> From: "Chris Kennedy" Subject: RE: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce Date: Thu, 28 Oct 2004 00:16:48 -0700 In-Reply-To: Patrick, As per point #1, Alys Holdens, Structural Design for the Stage points out that closer to a "fifth point" as you might call it (one fifth of the total length overhung, 3/5ths in between points) is most efficient in a double overhanging evenly distributed load. Just a handy rule of thumb I like to use. Chris -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Dr. Randall W.A. Davidson Sent: Wednesday, October 27, 2004 11:57 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Good for you. Keep using Gordon. I have all his books and use them in my work regularly for years. Excellent. Doom ==================================================== A Masters Workshop for Entertainment Technicians, Riggers, Public Assembly Technicians, and Educational Performing Arts Personnel - Sponsored by Risk International & Associates, Inc. April 4, 5, 6, 2005 at ELCO Performing Arts Center, Elkhart, Indiana Brochure & Registration Form available at: www.riskit.com/workshops ==================================================== Risk International & Associates, Inc. - Dedicated to making the world a healthier & safer place. Website: www.riskit.com E-mail: rdavidson [at] riskit.com ==================================================== International Secondary Education Theater Safety Association (ISETSA) - Dedicated to the protection of every student in the performing arts. Website: www.isetsa.org E-mail: info [at] isetsa.org ==================================================== 960 E. Bonita #158, Pomona, CA 91767 Phone/Fax: (909) 625-5961 ==================================================== -----Original Message----- From: Stagecraft [mailto:stagecraft [at] theatrical.net] On Behalf Of Patrick McCreary Sent: Wednesday, October 27, 2004 6:46 PM To: Stagecraft Subject: Re: Bizarre Multiple Catastrophic Truss Failure - Limited Permission to reproduce For info, archives & UNSUBSCRIBE, see --------------------------------------------------- Two things - 1. According to the first posting from Dale, the motor points were 18" from the ends of the truss, putting them about 62' from each other. If it's not possible to get a middle point for lack of motors, is it possible to put the two motors closer to the 'quarter-points' (the two points approximately 1/4 of the length of the truss in from the ends)? Wouldn't be better, Bill S. and Delbert, for an evenly distributed load? Or, Dale, are your pick points in the roof(?) that far apart? It would lessen the span to about 30' - 35'. (I could be all wrong on this - Bill? Delbert? - I don't do many trusses, but I DO do a lot of beams.) 2. When I look at figure 4, the connector plate corner and edge at the bottom center of the picture seem to still have quite clean and sharp edges, as though there was no real weld penetration at all; I would definately have an expert look at those welds. 3. (I lied) J. E. Gordon wrote another wonderful book - "The New Science of Strong Materials (or Why You Don't Fall Through The Floor)" - both it and "Structures (or Why Things Don't Fall Down)" are required reading in my Advanced Stagecraft classes. Patrick G. Patrick McCreary Ass't. Professor - Technical Director Department of Theater and Dance Indiana University of Pennsylvania Indiana, PA 15701 (Office) 724-357-2644 (Home) 724-349-4309 ------------------------------ End of Stagecraft Digest #177 *****************************