Force needed for rotating platform

[derekleffew]

[Seconding what [USER]Van[/USER] said in post#16 above...]

The only way a ball transfer
(Notice McMaster doesn't call them casters? They're intended to be mounted ball up, fairly close together on assembly lines/freight handling: )
with a diameter of 11/16" could ever work is if you had a stage deck of seamless 1/4" steel plate (and even then it's dubious).

Try this when they come in:
"Caster" up one of your stock 4x8 platforms, one caster in each corner and one in the center of each long side. Flip it over and load 200 pounds of pig weight on it. Watch the six gouges on your nice tempered hardboard stage as you attempt to drag, not roll, the "wagon" around.

There's just no substitute for high-quality casters, talking minimum $25-30 each. Since they're 100% re-usable, it's a lifelong investment with proper periodic maintenance.

From the thread http://www.controlbooth.com/forums/scenery-props-rigging/16227-caster-psa.html :

I just remember what my Old Uncle Footer used to tell me;
"Son, Life's too short for cheap casters."
Then he'd spit, turn, and waddle off, Festus-like into the sunset. ...

 

[IntimeTD]

ouch. I had not thought of these things. This is why I ask you guys

so just to clarify, I should use neither ball casters (transfers, if McMaster insists) nor smart casters? That basically leaves the zero-throw casters that are just massively out of budget for us. Or is there a middle option?

 

[derekleffew]

Smart (swivel) casters will work, as long as you always turn the revolve the same direction. Ideally you'd want to use fixed, and mount them wheel up, for a revolve, but that's obviously problematic for a non-circular shape or where there's no fixed pivot point.

Years ago in college I built a set similar to yours and used 4" Darnell swivels. Although we had a fixed pivot, we didn't always go the same direction. Four guys could turn it, but the masonite was ruined where we reversed direction after just a few rehearsals. Had to paint touch up all spots before every show.

 

[Footer]

ouch. I had not thought of these things. This is why I ask you guys

so just to clarify, I should use neither ball casters (transfers, if McMaster insists) nor smart casters? That basically leaves the zero-throw casters that are just massively out of budget for us. Or is there a middle option?

Yes, there is. A good smart caster. These are what I use: McMaster-Carr

In fact, they are the exact same caster that Production Advantage sells for more. Yes, it takes some muscle to get them to go in the direction you want but these things move really well. They work as well as any comparable Colson. At my last gig I bought about 50 over a period of 2 years and they held up great show after show.

 

[IntimeTD]

Brilliant. Those casters are totally within our budget. Derek, Footer, you guys are awesome, thanks so much.

 

[Footer]

Brilliant. Those casters are totally within our budget. Derek, Footer, you guys are awesome, thanks so much.

Another quick tip that will help with speed. When the unit is placed pre-show, make sure the casters are already in the direction that they need to be for the next shift. Same thing goes for the intermission shift. Always think about which way the casters are facing and it will help a ton. Let us know how it turns out.

 

[shiben]

[Seconding what Van said in post#16 above...]

The only way a ball transfer
(Notice McMaster doesn't call them casters? They're intended to be mounted ball up, fairly close together on assembly lines/freight handling: View attachment 5502)
with a diameter of 11/16" could ever work is if you had a stage deck of seamless 1/4" steel plate (and even then it's dubious).

Try this when they come in:
"Caster" up one of your stock 4x8 platforms, one caster in each corner and one in the center of each long side. Flip it over and load 200 pounds of pig weight on it. Watch the six gouges on your nice tempered hardboard stage as you attempt to drag, not roll, the "wagon" around.

There's just no substitute for high-quality casters, talking minimum $25-30 each. Since they're 100% re-usable, it's a lifelong investment with proper periodic maintenance.

From the thread http://www.controlbooth.com/forums/scenery-props-rigging/16227-caster-psa.html :

You dont build your stages out of 1" steel plates, welded and ground seamless already? I thought that was industry standard...

 

[Van]

Thanks for following up , guys. I had to go do my " Job" so I could get paid and couldn't get back to finish my thoughts. Once again, however, you have eloquently crystallized my thoughts. Another point pertaining to Ball casters as opposed to wheel casters is sort of what Footer mentioned when he talked about the ball surface area being the weight bearing surface of a ball caster. Even in a cheap wheeled caster the weight is carried along the contact point of the axle and the inner raceway of the caster bearing suraface. Compare that area to the total area of contat between the hemisphere of a ball caster and it capturing surface. As well, a caster has a torsional torque advantage; the distance between the center of the wheel and point of contact of the axle acts as a force multiplier:
If you push sideways on a platform with 50 pounds of force, and you have a 4" caster, then you can take 2 ( the radius of the caster) X 50 ( amount of force being exterted) = 100 foot inches of rotational torque at the axle. you have no such advantage with a Ball caster.
mstaylor, I'm going to assume you read these other posts after mine, and can see what I was talking about as re point load on a ball caster. If not Please let me know. I want to make sure I'm clear about this. I think it's a very good learning experience for folks on here.