Lock bolts missing from arbor plate?

[rm2011]

Hey everyone,

We just had our first load-in of the season at my school yesterday. Myself and the LD (also his first year) discovered something that bothered us. We went up to load weight after loading the pipes, and discovered that none of the plates on ANY of the arbors had their lock bolts (thumb screws... whatever you want to call them...) in place. I am referring to the plate that slides down the rails after you have the weight in place to keep them from moving.

What do you guys think about this? Is it normal? We both think we need to get them replaced ASAP, but really have no way to know what size bolts to buy. Is it a standard size? Any assistance or advice you can offer would be greatly appreciated.



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[Footer]

Post a picture of your arbor. Odds are it is a standard sized screw, probably a 1/4". Best bet would be to go to a hardware store and buy a few standard sized bolts and figure out what size it is.

My arbors (Late 70's install) all had allen bolts in them. Last year we went through and replaced those with thumb screws, I think it cost us about 30 bucks for 53 linesets.

 

[derekleffew]

... I am referring to the plate that slides down the rails [rods] after you have the weight in place to keep them from moving. ...

That's called a spreader plate, and the thumbscrews are missing from the locking collar /stop collar s.

http://www.sapsis-rigging.com/Images/Arbors.gif

May be a 1/4-20 or 5/16-18 thumbscrew, depending on the manufacturer.
JR Clancy Part#, Desc., Price:
099-SCS, 1/4"dog point screw, $3.56/each.

You shouldn't need justification, but if you do: http://theatresafetyblog.blogspot.com/2009/04/weight-weight-dont-tell-me.html .

http://isquint.net/wp-content/uploads/2010/04/536px-Arbor_spreader_plates-268x300.jpg
Note: Unlike as pictured, it's good practice to get into the habit of turning the collars so the thumbscrew are toward the insides of the rods.

... My arbors (Late 70's install) all had allen bolts in them. Last year we went through and replaced those with thumb screws, ...

That's crazy. Hard to imagine that it took 32+ years of using an Allen wrench for someone to say, "Enough!".

 

[rm2011]

Thanks for the information. I believe we have 20 linesets... so it should be too much to replace them. I'm just having a hard time figuring out why anyone would take them all out. The counterweight system is arguably one of the most dangerous parts of a theatre.

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[MPowers]

.....discovered that none of the plates on ANY of the arbors had their lock bolts (thumb screws... ....What do you guys think about this? Is it normal? We both think we need to get them replaced ASAP, but really have no way to know what size bolts to buy. .........

Normal?? From my many inspections each year, far too normal for many to be missing or not used (or taped or wired up etc.) but rare for ALL to be missing.

You are correct, they need to be replaced asap and put into use. You and your new LD also should try to implement a safety learning program to educate the other students and faculty/staff about the importance of using these and other safety devices and precautions. The fact that they are missing and no one has noted it, indicates that training and safety may have fallen by the wayside. This is your chance to change that.

BTW, Congrats on being observant enough and smart enough to realize there was a problem and that it needed to be addressed instead of passed over.

As for the bolt size, as others have said, 99% it is a 1/4"-20, but just grab a couple of known bolts from the tool room and try them. They should be replaced with a dog point screw that is either a thumb screw or has a knob on it. Do not replace them with bolts that require a tool to fasten down. That would lead to people not using them as "too much trouble" and they would all wind up wrenched down tight at the top of the arbor rods.

Post again after your show opens and let us Know how this works out.

 

[Footer]

That's crazy. Hard to imagine that it took 32+ years of using an Allen wrench for someone to say, "Enough!".

Well, there are a few things at play with this whole thing. First, we had two electrics that the top spreader plate was buried under about 40 lead bricks... Second, 2 plates on each arbor, so it is impossible for us to do the 2' rule with most of our sets. Even worse, the arbors are all welded so there is no way to put in new plates. All kinds of fun we have.

 

[gafftapegreenia]

Sounds like someone needs a Retrospreader!

 

[Footer]

Sounds like someone needs a Retrospreader!

Interesting. I'll look into those, looks like a decent idea and is a local product. Thanks!

 

[techieman33]

Interesting. I'll look into those, looks like a decent idea and is a local product. Thanks!

It's even reasonably priced, especially when you include the powdercoating.

 

[Footer]

It's even reasonably priced, especially when you include the powdercoating.

Until you have to buy 150!

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[techieman33]

Until you have to buy 150!

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Not really, you don't really need a full set for each arbor. If your anything like my building you only have a few line that you ever fully load, the rest only ever get a couple hundred pounds. And if you need more on a particular day you could have a few that you install for temporary use and remove them when your done using wing nuts to hold them together for the day.

 

[tprewitt]

I've done this task many times and I gotta tell ya products like the Retrospreader beat the heck out of breaking arbors apart. I have had problems with pre-made ones though. I've not specifically used the Retrospreader, but I suspect it will will have the same issue. On many older systems the arbor rods are either not 10" o.c. or with lower end manufacturers the arbor tops & bottoms were drilled by eye rather than a jig. This means the spreader plates need to be adjustable or have oblong holes or they jamb.

If your rods are welded, you may also have some that are bent a little and that will cause the same problem.

What I've done that has worked well is have a local machine shop cut me spreader plates with two notches, so it looks sorta like an "E". Depending on how much play I need I adjust the measurements some, but I offset the notches about 1/2" to one end and make them 1.25" or so wide. You install them by stacking two pieces together. The offset lets you slide them back and forth to accommodate the size hole you need on that particular arbor. You can bolt, rivet, screw, or spot weld the two together to form a single spreader plate. All methods have their aggravation: Bolts holes have to be drilled in place, screws leave sharp points, rivets are soft so you need lots of them, welding is best but spot welders can be hard to rent.

Since you're doubling the plates up you can make them out of 16 ga or 18 ga material, which is cheap. Machine shops usually only charge a few dollars apiece if you clean & paint them yourself.

As a side note, I usually don't have a problem making parts for older systems where the OEM is unknown or no longer in business. On newer systems or where the OEM is available, I don't alter or add to their product without their blessing.

 

[teqniqal]

... the top spreader plate was buried under about 40 lead bricks...

If your counterweights really are LEAD, then you should seriously consider replacing them with plate steel. Lead is very toxic and when you handle it it gets on your skin and can eventually transfer into your bloodstream through various mechanisms. Using gloves can help reduce the exposure, however, lead is soft and it rubs-off onto everything you touch, so it gets on the outside of the gloves, then transfers to your skin when you handle the gloves. Non-porous gloves are recommended (leather is porous), however, they tend to tear easily when doing the type of work that is required when loading a counterweight arbor. Your school or city will usually have a lead abatement policy (much like an asbestos abatement policy), so find out about who handles that and have them survey the situation. It may be necessary to have the arbors, weight deck, and the general area around and below the weight deck all cleaned to reduce the lead residue to acceptable levels.

Lead is a neurotoxin, reproductive toxin, hematologic (blood) toxin, may cause cancer based on animal data, and can pose other significant health hazards if the material is not safely handled. Personal protective equipment such as gloves should be worn when handling lead weights or lead-contaminated items. Thoroughly wash hands, arms, and face after handling lead. Do not eat, drink, or smoke in or around areas where lead is handled or stored. Transport and store lead in secondary containers to minimize the spreading of lead dust. Health problems from exposure to lead can include profound developmental and neurological impairment in children. Lead poisoning has been linked to mental retardation, poor academic performance, and juvenile delinquency. [Wow, this answers so many questions about fly crews. . . ]

References:
http://ehs.whoi.edu/ehs/occsafety/leadweightsafety.pdfhttp://ehs.whoi.edu/ehs/occsafety/leadweightsafety.pdf
http://www.aps.anl.gov/Safety_and_Training/Notices/aps_safey_notice_lead.pdf

CDC - Lead: Information for Employers - NIOSH Workplace Safety and Health Topic
Lead Fact Sheet : The Environmental Information Association
Lead-Related Links

 

[Mutton]

Retrospreaders are also fantastic for pipe weight. My theatre installed one on each lineset at pipe weight with lock nuts. Makes it much harder to take a lineset below pipe weight.

Ninja edit: they can also act as a cigar cutter in a pinch

 

[erosing]

I've done this task many times and I gotta tell ya products like the Retrospreader beat the heck out of breaking arbors apart. I have had problems with pre-made ones though. I've not specifically used the Retrospreader, but I suspect it will will have the same issue. On many older systems the arbor rods are either not 10" o.c. or with lower end manufacturers the arbor tops & bottoms were drilled by eye rather than a jig. This means the spreader plates need to be adjustable or have oblong holes or they jamb.

If your rods are welded, you may also have some that are bent a little and that will cause the same problem.

What I've done that has worked well is have a local machine shop cut me spreader plates with two notches, so it looks sorta like an "E". Depending on how much play I need I adjust the measurements some, but I offset the notches about 1/2" to one end and make them 1.25" or so wide. You install them by stacking two pieces together. The offset lets you slide them back and forth to accommodate the size hole you need on that particular arbor. You can bolt, rivet, screw, or spot weld the two together to form a single spreader plate. All methods have their aggravation: Bolts holes have to be drilled in place, screws leave sharp points, rivets are soft so you need lots of them, welding is best but spot welders can be hard to rent.

Since you're doubling the plates up you can make them out of 16 ga or 18 ga material, which is cheap. Machine shops usually only charge a few dollars apiece if you clean & paint them yourself.

As a side note, I usually don't have a problem making parts for older systems where the OEM is unknown or no longer in business. On newer systems or where the OEM is available, I don't alter or add to their product without their blessing.

This tech expo article outlines a similar thing. View attachment 2005-exhibit31.pdf

 

[MPowers]

FWIW, Stephen Rees, a friend of mine for over 30 years, the author of the Tech Expo article, is the owner of the patent and the one who sells the Retrospreader. Same person.

 

[derekleffew]

No offense to Mr. Rees intended, but how did he get a patent for essentially the same device Tiffin Scenic Studios had in 1980? Tiffin's had the pivot in the center of the plates.


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[techieman33]

No offense to Mr. Rees intended, but how did he get a patent for essentially the same device Tiffin Scenic Studios had in 1980? Tiffin's had the pivot in the center of the plates.


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Patents are issued on a first come first served basis, if Tiffin's never tried to get a patent then it was available. That being said if they could prove prior art then they could sue to have the patent thrown out.

 

[MPowers]

....but how did he get a patent for essentially the same device Tiffin Scenic Studios had in 1980? Tiffin's had the pivot in the center of the plates.....

Because Tiffin's product had a pivot in the center and they didn't market it for the general public market. Not even sure if they applied for a patent.

 

[tprewitt]

What's the saying, "Your patent is only as good as the money you have to defend it."?