Wheel balancer pressure cup questions

[ckeboss]

Hello all, just picked up a Coats 1001 wheel balancer for home use. It came with 4 cones, a hub nut, and a few other misc. spacers. It was missing the back cone spring, and the pressure cup for the front.

I was able to order the spring and the small pressure cup, but it does not looks like there is a good source for a larger pressure cup for light truck wheels.

The issue is that these old coats and snap on machines used a 28mm shaft, and current machines use a 40mm shaft. For cones, I understand it is imperative that they are dead center on the shaft. But for the pressure cup, does it really matter if it's perfectly centered on the shaft?

The goal of the hub nut is to simulate the force of the lug nuts clamping the wheel to the hub. I am thinking if the cone is centered and the wheels hub is inside the cone, and the wing nut is centered on the shaft, the cup, pushing on the wheel, really doesn't need to be centered on the shaft exactly.

The reason I bring this up is you can buy many different pressure cups for 40mm machines, that have a 53.5mm ID for the wing nut, but my wing nut has a 40mm OD shoulder, but a larger flat that would support the 53.5mm face of the cup.

Has anyone tried this?

 

[rlitman]

If it were me, I'd cut a square from aluminum stock, locate its center and use a hole drill to make it fit my hub nut, and rivet it in place on the cup centered over the hole. Alternatively, making a bushing/washer would be a good lathe project.

On that note, I wonder if a steel conduit knockout filler blank would fit in the hole. If so, you could drill that.

 

[ckeboss]

I agree that this is an ideal project for a lathe if I wanted to get the pressure cup centered on the shaft. A lathe is on the tool wishlist when I build a shed.

Thoughts on the actual need for the pressure cup to be centered on the shaft? The way I see it, with back cone mounting, the need is the cone is centered, and the pressure cup needs to be square with the shaft, but I don't see why it needs to be centered.

 

[rlitman]

I agree that this is an ideal project for a lathe if I wanted to get the pressure cup centered on the shaft. A lathe is on the tool wishlist when I build a shed.

Thoughts on the actual need for the pressure cup to be centered on the shaft? The way I see it, with back cone mounting, the need is the cone is centered, and the pressure cup needs to be square with the shaft, but I don't see why it needs to be centered.

It doesn't need to be perfect, but if it's off too much it might throw off the balance a little. That's less of an issue with a lightweight plastic cup to be fair.

I do see 28mm hardware on ebay FYI, but it is pretty expensive.

 

[ckeboss]

It doesn't need to be perfect, but if it's off too much it might throw off the balance a little. That's less of an issue with a lightweight plastic cup to be fair.

I do see 28mm hardware on ebay FYI, but it is pretty expensive.

Correct, I have seen some $80-100 pressure cups. There are also kits to convert the shaft to 40mm, which opens up a lot of options for tooling, but exceed the cost of the machine.

I didn't think about the actual weight of the cup factoring in to the actual balancing of the wheel. Makes more sense on how they are designed now.

But I agree that the plastic cup, assuming it's close, shouldn't affect the balance that much, as there is quite a bit of tolerance in these machines. They are only balancing to .25 of an ounce, and even the newer machines will try to calculate different weight positions to minimize wheel weights, so getting a "perfect" balance seems to not be very important, they are just looking at getting it close.

This is the "correct" part: https://www.tooldiscounter.com/product/coats-drum-large-pressure-coa8110544

But a hard sell at $120 when you can get the 40mm version for $30

 

[rlitman]

Yeah, I see the small cup at $45 on ebay, but not the large one. And the prices are indeed outrageous. Really, you could saw these out of a couple of layers of plywood and have something good enough. You're already all set with the cones, and those I can understand why they're expensive.

 

[ckeboss]

Yeah, I see the small cup at $45 on ebay, but not the large one. And the prices are indeed outrageous. Really, you could saw these out of a couple of layers of plywood and have something good enough. You're already all set with the cones, and those I can understand why they're expensive.

Are you thinking to make the "wall" of the cone out of circle cut ply, then circle cut at a smaller diameter?. E.g 6" and 5" saw?

I also wonder if modern 3d printer material would be strong enough. Seems very easy to model.

 

[rlitman]

Are you thinking to make the "wall" of the cone out of circle cut ply, then circle cut at a smaller diameter?. E.g 6" and 5" saw?

I also wonder if modern 3d printer material would be strong enough. Seems very easy to model.

Well, I own a 6" hole saw for ceiling light cans that would work on ply, so yeah, I'd use that to cut two or three circles out of ply. Then stick a piece of 1/4" rod in where the pilot bit goes, and use other hole saws to make the bushing hole in one and turn the others into donuts.

But if you have a scroll saw and a compass, that would also be more than accurate enough for this job, without a complete set of hole saws and a drill press. It's not like you need to be buying hole saws to make this. I'd suggest using what you have, as it's a pretty simple part with not very demanding tolerances.

I think you probably could 3D print this. It's just a bowl that sees a lot of compression. But it sure will use a lot of filament.