Retrofit Bottom Stop for Arbor?

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
The school district installed a set of smoke beam detectors off the side of the high loading gallery at my sister theater. They are both VERY close to the travel path of a batten. If it's loaded causing the batten to shift or sway a little as it go up, it could easily trip the beam detector and set off the fire alarms. In my theater I have some linesets that come up under catwalks and therefore the arbor has to be stopped in a different location than the rest of the rail. These arbors have these individually located bottom stops that prevent the arbor from traveling all the way to the bottom beyond the correct stopping point.

Is it possible for me to buy these retrofit bottom stops and install them myself to prevent my friend's battens from traveling into the path of the beam detectors? What are they called? Where do I get them? Thanks!
 
  • Like
Reactions: RonHebbard

Van

CBMod
CB Mods
Premium Member
Joined
Jul 27, 2006
Location
Portland, Or.
They are literally a piece of angle with a piece of hardwood bolted to the top. The sticky downy part has holes drilled so they go through the t-bar on each side. basically set the trim height. clamp the stop to the t-bar where it's tight to the bottom of the arbor <or do that math> drill through the stop and into the t-bar PRECISELY. Then bolt in place. Ican send you a 'Drawing' when get home...
 

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
They are literally a piece of angle with a piece of hardwood bolted to the top. The sticky downy part has holes drilled so they go through the t-bar on each side. basically set the trim height. clamp the stop to the t-bar where it's tight to the bottom of the arbor <or do that math> drill through the stop and into the t-bar PRECISELY. Then bolt in place. Ican send you a 'Drawing' when get home...
Sweet! That would be awesome. I was thinking that making one myself might be a good option.
 
  • Like
Reactions: Van

Van

CBMod
CB Mods
Premium Member
Joined
Jul 27, 2006
Location
Portland, Or.
You may have to ping my to remind me. Woke up at 2:00 this morning and have been up since... Getting punchy.
 
  • Like
Reactions: RonHebbard

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
So below is the picture of the stop I'm building. I've got the angle iron and wood. But I'm not sure what kind of rubber to use. The rubber layer is 3/8" thick and very sturdy... Not soft and squishy.

I'm looking around online and I see lots of options (SBR, Gum, Hypalon, Buna) any suggestions on what type to buy? Then I learned about the hardness of the rubber on the durometer scale (never heard of this before). I see pencil rubber is about "Shore A 40" and tire treads are a little over "Shore A 60". So I'm thinking something about 60 would be about right.

Any suggestions on what type to buy would be greatly appreciated.
IMG_20210218_141431__01.jpg
 
Last edited:

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
Update: Grainger has EPDM, Neoprene, Buna, and Silicone in 2" x 3' strips rated Durometer 60A. That's the perfect size to work with for my 2“ wide wood blocks. Does this sound like a good option? Which one?

Thanks!
 
  • Like
Reactions: RonHebbard

MNicolai

Well-Known Member
Premium Member
Fight Leukemia
Joined
Mar 30, 2008
Location
Sarasota, FL
Most (all?) venues I've worked in are just wood without rubber. I think if you're doing rubber it's more for softening the impact noise than anything else. If you do go with a cushioning pad, you'll want something thick. EPDM is usually very thin.

This neoprene pad for example is 3/8" thick, which looks closer to what you have in the photo. This is a little larger than you need but you could certainly cut it up with a band saw or search around for something smaller.


@egilson1 might have better input on this.
 
  • Like
Reactions: RonHebbard

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
Most (all?) venues I've worked in are just wood without rubber. I think if you're doing rubber it's more for softening the impact noise than anything else. If you do go with a cushioning pad, you'll want something thick. EPDM is usually very thin.
This neoprene pad for example is 3/8" thick, which looks closer to what you have in the photo. This is a little larger than you need but you could certainly cut it up with a band saw or search around for something smaller.
@egilson1 might have better input on this.
Grainger has EPDM, Neoprene, Buna, and Silcone Rubber all in 3/8" thick. They come in 2" wide strips so it'll simply be one quick cut for length and I'll be set.

As for using it or not, I'm trying to duplicate what came installed in my space from the start.
 

DrewE

Well-Known Member
Joined
Mar 18, 2019
Location
Vermont
Maybe go to your local Tractor Supply Company and get a stall liner mat (for horse stalls) and slice it up?

I suspect the precise mechanical characteristics of any rubber baby batten bumpers are pretty much non-critical here. Presumably something not overly elastic would be best so as to avoid having the battens rebound at the end of their travel.
 

What Rigger?

I'm so fly....I Neverland.
Joined
Aug 24, 2006
Location
PPT.
Update: Grainger has EPDM, Neoprene, Buna, and Silicone in 2" x 3' strips rated Durometer 60A. That's the perfect size to work with for my 2“ wide wood blocks. Does this sound like a good option? Which one?

Thanks!
60a silicone sounds like it may get tore up just under normal, conscientious use. But it may be cheap enough to replace often?
What about UHMW?
@DrewE might be onto something. I know a few people who use horse stall mats for their home gyms- these become the drop pads for when they press 300lbs overhead on an 8 foot bar!!! Good noise damping, durable as hecc.


Is this attachment helpful?
 

Attachments

RonHebbard

Well-Known Member
Premium Member
Joined
Jun 12, 2004
Location
Waterdown, ON, CA
60a silicone sounds like it may get tore up just under normal, conscientious use. But it may be cheap enough to replace often?
What about UHMW?
@DrewE might be onto something. I know a few people who use horse stall mats for their home gyms- these become the drop pads for when they press 300lbs overhead on an 8 foot bar!!! Good noise damping, durable as hecc.


Is this attachment helpful?
UHMW is available in 'tasteful' basic black for use in your (traditionally) black backstage areas (Pinch points / Hazardous be danged! [You can always apply Yellow & Black Hazard tape] akin to end users who put white masking or gaffers' on the edges of stair steps backstage, then spray them matte black to appease the set designer).
Toodleoo!
Ron Hebbard
 

gafftaper

Senior Team
Senior Team
Fight Leukemia
Joined
Jan 2, 2006
Location
Seattle, WA
60a silicone sounds like it may get tore up just under normal, conscientious use. But it may be cheap enough to replace often?
What about UHMW?
@DrewE might be onto something. I know a few people who use horse stall mats for their home gyms- these become the drop pads for when they press 300lbs overhead on an 8 foot bar!!! Good noise damping, durable as hecc.

Is this attachment helpful?
That chart is similar to the one I found that I used to come to the conclusion that something around A60-A70 (similar to tire rubber) would be about right. Seems like that's dense enough to take a hit but still a little flexible.
 

techieman33

Well-Known Member
Joined
Nov 7, 2004
Location
topeka, ks
I don't think the material matters all that much. It's not structural at all, it's just dampening the noise a little bit. You could probably go to any tire store and have them give you a used tire that you could cut up and use what's left of the tread to make pieces. Otherwise I'll 2nd the horse stall mat idea. They're usually pretty cheap if you can buy them locally. You can also use whatever is left over as one or more anti-fatigue mats. Or cut them up into squares and put them under mic stands or anything else you might want to have a little padding or isolation.
 

teqniqal

Well-Known Member
Joined
Apr 26, 2009
Location
Dallas / Fort Worth, Texas
Give a look at the bolts through the guide rails of your other arbor stops. I typically see a weaker bolt, not a strength-rated bolt, as the shearing of the bolts is what absorbs some of the energy in an arbor crash situation. Harder (higher grade) bolts may create a more abrupt stop and bend more parts on the arbor.

I'd love to hear from some of the Arbor manufacturers on their thoughts on the bolts.

Ultimately, I wouldn't rely on engineering a work-around solution to prevent a smoke detector false trip.
  • They should use a multi-criteria sensor (Smoke / Co2 / Heat -- requires 2 of the circuits to trip before sending an alarm -- see: System Sensor Corp) that is located up at the bottom fly loft roof deck - that is whre the fire code calls for for Smoke Vent release and Fire Curtain release devices. Use the correct tool for the task.
  • If they insist on the wrong solution, at least they should install it in a manner that it is NOT susceptible to false tripping. Have you / they tested this with various forms of theatrical atmospheric effects? Smoke, fog, haze, etc.
 
  • Love
Reactions: RonHebbard

Users who are viewing this thread