First off, I realize there are already well engineered products already out there, this project is mostly just for rips and giggles…and science
I was wandering through a thrift store last weekend and couldn’t resist buying a $7 monster truck that had some pretty awesome rubber tires on it. My goal is to make a relatively small(for torque) and lightweight wheel that would work well in packed dirt situations like a bmx pump track. Enemy #1 of a pneumatic tire seems to be rolling resistance caused by elastic hysterisis. So my thought was to either line or completely fill the inside of a rubber tire with a material that has better rebound and thus less energy loss.
Here’s where i’m at with the wheels. I’ve cut out the center portion of the wheel and machined a new hub insert out of UHMW to fit bearings
I’ve got myself a liter of shore 80 two part urethane and am trying to decide if I should completely fill the inside of the tire cavity. Or if I should attempt to pour a liner, effectively thickening the tire walls. I am leaning towards the latter option first but if anyone has thoughts or experience with this kind of thing, the 2 cents would be greatly appreciated!
This is a fascinating idea. I would be concerned about filling them because it would be very difficult to get a balanced wheel because it would be pretty easy to end up with air bubbles. Just my thoughts of the top of my head.
Balance is an issue I will have to figure out either way…I was thinking i might have to mount the wheels on a lathe while the urethane is setting up…like a centrifuge. I’m not 100% sure that this will solve the problem though, I may just have to keep the rotational mass to a minimum to limit the effect. I do have a vacuum pump to draw out air bubbles if necessary.
I had the same idea for a long time but never had the energy to try.
I still don’t get why we use urethane wheels when we could develop small tire wheels like a 100 mm one with a rubber tire… You still have street wheels but it’s way more confortable
At least it was working in my head hah
Since getting in to all of this a few months ago I’ve been looking for exactly this, a 110ish mm rubber wheel. I don’t mind wear or replacements, the comfort would be great
For sure! I’ll have to machine my own hubs to fit 608 bearings anyway so I can beef things up a bit. All of this is proof of concept. I think the end goal would be to have a 3 piece aluminum wheel, with some kind of beadlock and replaceable rubber tires.
You could drill some holes in the inner sidewall of the tire, and inject the PU until it’s full, periodically spinning the tire on a perfectly vertical truck axle to evenly distribute and hopefully balance the tire along the way.
Have you seen these wheels by SRC? They are belted and suitable for high speeds. If you broke the bead and built a new wheel with the same fitment and bead in a beadlock style setup, you could totally run some non-corrosive oil inside the tire. Put two elastic vanes opposing to seperate the two halves inside the tire should cause the oil to rotate with the tire to act as a solid mass while still providing sufficient rebound…
Those wheels look sick! You’re right belted tires would be necessary or they’ll just ballon right off the rim. Even then though rc tires feel kinda like jello…I think they might be too soft of a compound to fill with any kind of fluid that could leak out (puncture city) But that is an an interesting idea and would eliminate the need to run crazy psi in a pneumatic setup. Most of the rc tires I’ve encountered have a foam insert inside so vanes wouldn’t really be necessary. Guess you never really know until you try…might have to give it a go and see!
The road wheel hubs have breather holes so I don’t even have to drill. The head scratcher is the foam insert inside the tire and trying to get even distribution around it. My current thought is to make a mandrel for the wheel out of a 8mm bolt, run it in a drill press and hold another wheel against the outside of the tire to “squish” the liquid urethane evenly into the foam insert. The foam insert will either be brilliant, or a catastrophe, I’ll keep y’all posted.
