# Wagon casters



## bobgaggle (Jan 22, 2008)

I just saw the most recent tour of My Fair Lady at the Kennedy Center in DC. I got to go on a backstage tour of the show and noticed the wagons they use to move scenes on and off. Naturally they used a tracked deck with a cable system to move the wagons, but I couldn't figure out what kind of wheels they were using. Of course we weren't supposed to touch anything, but as the group moved forward I couldn't resist. I lagged behind and gave the thing a shove. Needless to say it sailed like a ghost 7 or 8 feet across the stage before the cable jerked it to a stop (and I probably fouled it up in the motor too 

But I have no idea how they got that thing to be so silent and so low to the ground (it was 2" max off the deck) Anyone know how to do this?

Air cushion?
Uber soft rubber wheels?
Mag Lev?
The Force?


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## Van (Jan 22, 2008)

Hmmm Good question. Don't think it would have been air casters, as they require a constant supply of air when lifting, and you certainly don't leave big wagons lifted when tours are comming through. Were the wagons tracked with a rail on the stage? In that case I say it was probably dual or right angle roller ball casters. Or maybe, since it's a big show they have the money to buy really good ball bearing casters, unlike us schmucks in the Non-Profit world who get by on rollerskate wheels and 1/4" bolts.


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## soundman (Jan 22, 2008)

Just come in during preshow and ask the tech that is rewraping the winch system what kind of casters are on it. 

Was the clearance two inches or the total height? If it was total hight and the units were light weight they could have used shop built nylon rollers or just stuck UHMWPE on the bottom of the unit http://en.wikipedia.org/wiki/Ultra_high_molecular_weight_polyethylene


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## derekleffew (Jan 22, 2008)

It's been 25 years since I've spec'd casters, are Darnells still the Rolls Royce of the industry?


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## bobgaggle (Jan 23, 2008)

Total height (not clearance) of the wagon was 2". I've been googling like mad and I can't find anything. The wagons just had two knives in the track (on in front and one in back) to which the cable was attached.

Doing a bit o' research on UHMWPE...is it really low friction?


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## soundlight (Jan 23, 2008)

derekleffew said:


> It's been 25 years since I've spec'd casters, are Darnells still the Rolls Royce of the industry?



Yes, they are. Dunno if the name has changed since you spec'd though, the full name is now Darnell-Rose but I just call the casters Darnells.

Ooohh...2" total thickness...now I really want to know what the deal is here!


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## soundman (Jan 23, 2008)

bobgaggle said:


> Doing a bit o' research on UHMWPE...is it really low friction?



Yup to most surfaces in low weight applications it will glide quite nicely.


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## bobgaggle (Jan 23, 2008)

so what defines low weight? would it glide with a desk on the wagon? a few people? only a folding chair?


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## soundman (Jan 23, 2008)

If you don't have a copy of Technical Design Solutions for Theatre buy volume one and look pages 210-214 because there is a very well written write up of several different plastics that can be used as guides. 

Using the Formula F=UN where F is the amount of force to start movement, U is the coefficient of static friction and N is the weight of the object being tested 

UHMWPE has a U value of .17

you can do the rest of the math to figure out how much weight you can apply and still only need to give it a good shove.


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## themuzicman (Jan 23, 2008)

soundman said:


> If you don't have a copy of Technical Design Solutions for Theatre buy volume one and look pages 210-214 because there is a very well written write up of several different plastics that can be used as guides.



would that be the book you mentioned?

http://books.google.com/books?id=5zuA1SSDvIsC&dq=technical+design+solutioins+for+theater&pg=PP1&ots=guWlp87rBD&sig=OXZM-j6tM07nZqneJQgkhagx_rc&hl=en&prev=http://www.google.com/search?client=safari&rls=en&q=technical+design+solutioins+for+theater&ie=UTF-8&oe=UTF-8&sa=X&oi=print&ct=title&cad=one-book-with-thumbnail


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## soundman (Jan 23, 2008)

Yup, one and the same


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## gafftaper (Jan 24, 2008)

I just got it for Christmas. It's Excellent so far.


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## Van (Jan 24, 2008)

The big issue with UHMW or UHMD PE< Ultra High Molecular Weight or Ultra High Molecular Density, Poly-Ethyline> is Expense! The stuff should be should as a High value commodity on the stock market, or maybe used as a currency base like gold. It is very cool stuff, and fun to work with as you can route, cut, Lathe, and machine it just like Wood and Metal combined.


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## superdoo (Jan 24, 2008)

It's funny you mentioned that book!I just ordered both volumes and rigging book, they should be here in a week


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## Charc (Jan 25, 2008)

gafftaper said:


> I just got it for Christmas. It's Excellent so far.



Mind PMing me with some more detailed opinions? From a glance it seems a tad dated.


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## avkid (Jan 25, 2008)

charcoaldabs said:


> Mind PMing me with some more detailed opinions? From a glance it seems a tad dated.


A 5 year old book is "dated" now?
Horse hockey.:neutral:


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## Van (Jan 25, 2008)

avkid said:


> ...........Horse hockey.:neutral:


 
How do you keep the skates on? Do they hold the stick in their mouths?


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## punktech (Jan 29, 2008)

nah i've seen it in canada...it's like polo but with blades attatched to the hooves


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## bobgaggle (Jan 29, 2008)

you all have an uncanny knack for getting off topic...isnt' there a area for that somewhere on this site?!!?!?!?!


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## thelightingmancan (Jan 30, 2008)

Sorry Aaron, but I had to say this, I saw a license plate today that sayed 
"horse hcky"


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