Practical physics question: casters and wagons and weight.

I second gafftapegreenia's recommendation for using straight wheels. However, if it is not tracked, then be sure to allow space for it to wonder a bit, over the multiple trips back and forth. Making sure the wheels are all mounted parallel is important.

Locking casters are more prone to wonder, because that lock may permit some wiggle to the caster's direction when it is traveling backwards.

As an aside, the word Caster refers to how much a wheel is offset from its swivel. So, it really can only be properly used to refer to swiveling wheels. Thus, the phrase "swivel caster" is redundant.

-Joe
 
We did Wonka a few years back and used low profile casters from Lee Valley with no problems whasoever - they are our go-to caster for our theatre, other than using Air Pux for more specific applications. Each caster is rated for 220 pounds (100 kilograms). So six casters would more than satisfy weight requirement. Two youth would have no problem moving this and these casters are so smooth that controlling direction is extremely manageable.
http://www.leevalley.com/en/hardware/page.aspx?p=70055&cat=3,51976
 
2 thoughts:

1. In general, larger diameter wheels have lower rolling resistance than smaller diameter wheels, all other things being equal.

2. Remember that inertia works both ways - objects at rest tend to remain at rest and objects in motion tend to remain in motion. Building a wagon to start rolling more easily also makes it harder to stop. A 1000 lb wagon moving at a decent clip could easily steamroll a couple of kids. It might be wise to build in some kind of mechanical limits to the movement of this wagon.
 
I would not assume that the total weight is distributed evenly over the casters, and suggest maybe plan for 150% at least, 200% possible.
 
This is simply a job for air casters. No rumbling noises, but maybe some hissing. Omni-directional. Frictionless (platform easily moved by one youth). Practically unlimited weight, 1000's of pounds (depends on size of air caster) .Platform rests solidly on the floor when pressure released.
Yes it involves some thought and engineering, but many of the air caster manufacturers will provide guidance. Not that costly when you consider it's an investment that can be used over and over like buying rolling casters.

Unfortunately if you need to whip this up in a hurry, it's probably not the best solution for now.
 
If weight is the concern, do your best to make sure the weight is evenly distributed. We did a production of "Pirates of Penzance" a few years ago. We had a 30' pirate ship with as many as a dozen or so actors on it. We used a bunch of large poly casters, maybe eight or ten. With four of us inside we were able to maneuver the ship around the stage relatively easily. The only problem was one of the casters seemed to be taking more of the weight than the others, and after a few trips around the stage, the poly just came apart. So we kept a small floor jack, tools and extra casters in the "engine room" of our ship. When a caster broke during a performance we had plenty of time to replace while we were on stage. The actors had no idea we were jacking up part of the ship and changing the caster, and the audience was completely oblivious. We also learned to work the tools in time with the score so that any sound we made would just blend in. Ah, the things we do for our art!
 
Here's the rolling resistance page from Hamilton castor <www.hamiltoncaster.com/Portals/0/.../White%20Paper%20Rolling%20Resistance.pdf >
The larger the wheel diameter, harder the tire and better the bearing the easier the pushing. If you don't need to steer use ridgid castors if you need to steer I agree with the above, use a tri castor if you can afford it over swivels. The recommendations from the manufacturers generally are for industrial applications, so you should up the specifications a bit for the stage I reckon.
Nick
 
BillConnerFASTC said:
The zero throw cost more but it's a great investment. Definitely more applications but definitely expensive.
Click to expand...

I love zero throw casters. I hate their price. I did research on them a few years ago when I had a set that was going to require 40 of them... not economically feasible. I found a paper online from a student at MIT which included plans on making your own out of scrap plywood, hardware store casters, and a lazy susan bearing. I have been following this thread for a few days now, and have not been able to find that paper online anymore, but as my pack-ratting skills have manifested into the digital world, I found the file saved onto my google drive. I have uploaded it to this post, with the disclaimer that I do not claim to have any ownership over this material, but can attest to its functionality. I have used the 40 zero throw casters that I made several years ago many times. I have thrown out or rebuilt and added to my collection many times, and find new uses for them every year. I hope this is as helpful for you all as it has been for me. Plus, added bonus for teachers out there, it's a great resource for your classroom.
 

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lightingtek said:
I love zero throw casters. I hate their price. I did research on them a few years ago when I had a set that was going to require 40 of them... not economically feasible. I found a paper online from a student at MIT which included plans on making your own out of scrap plywood, hardware store casters, and a lazy susan bearing. I have been following this thread for a few days now, and have not been able to find that paper online anymore, but as my pack-ratting skills have manifested into the digital world, I found the file saved onto my google drive. I have uploaded it to this post, with the disclaimer that I do not claim to have any ownership over this material, but can attest to its functionality. I have used the 40 zero throw casters that I made several years ago many times. I have thrown out or rebuilt and added to my collection many times, and find new uses for them every year. I hope this is as helpful for you all as it has been for me. Plus, added bonus for teachers out there, it's a great resource for your classroom.
Click to expand...
I like it. Thanks!
 
The fisrtvones i saw were made at Yale. Used a swivel caster base with a plate and three casters welded to it. Its always a question of jow much is your time worth.
 
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