Wheel tyre moulding compounds etc


I’ve currently got 3d printed TPU wheels on my Featherweight prototype, but I am sure they won’t give enough grip, possibly even if I coat them with latex or similar.

Has anyone done moulding of wheels for Featherweights, and if so,

  • What kind of compound do you use? RTV Silicone, Urethane etc?
  • What shore hardness (or other hardness) do you think is about right?
  • Do you need any fancy equipment like vacuum chambers? Or can I just 3d print a mould and hope for the best?

I’m thinking of doing a metal hub, 3d printed middle section, then overmoulded tyre. I see videos (e.g. Seth Schaffer’s one) about doing this for Beetles. I’ve made my own tyres from bathroom sealant for my 150g robots, they worked pretty well.

I did try some siliconey tape stuff on the tyres but it fell off just driving the robot around the room a little (I guess Featherweight-ish forces are really a lot higher than the little robots).

I love making wheels so here’s my two pence.

My absolute foolproof way of batching out wheels is printing the wheel profile you want, with whatever geometry both locates the hub and includes whatever tread you want and cast that in silicone to give you a negative mould.

Then I use polyurethane poured into this silicone moulding for a hassle free demould.

I use 60a polyurethane with a touch of pigment for colour which adds a little hardness too. I have used a printed mould for these, just you need to use a liberal application of mould release agent (or a very thin film of something like Vaseline) Flatpacks wheels were cast like this. If I was doing it again I’ll do it with a silicone mould. If you have a smooth tyre it probably matters less about it sticking to the mould as there’s less to grab.

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I love cast wheels - mostly been doing them at beetleweight - I use polyurethane - a brand called duroflex. Tend to do either 30A or 40A - but would probably go higher on a feather.

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Agree with all the above, 50 or 60A shore sounds good for feathers. I did 70A on mine and found I’d basically never need to change them but they were lacking in grip vs trusty bike tyre (which does wear down after a few events!)

Update: it’s now Christmas Eve and I finally got around to trying out the wheel moulding.

I’ve 3d printed two parts - a hub designed to be overmoulded, and an outer part (printed in “vase mode” with thin wall")

So I used PolyTek Poly PT Flex 60 rubber (from here: Polytek Poly PT Flex 60 Liquid Casting Rubber - mbfg.co.uk ) which is a shore 60A.

I also mixed in some green pigment from the same seller. I used 5% by weight pigment, which might be too much, but anyway it looks pretty nice.

As I mostly expected, the outer mould was not possible to remove without breaking it into tiny pieces; this is no big deal as it’s only a few grams of 3d printed part and new ones can be made easily.

The result is very solid feeling, very grippy feeling and looks quite nice

Happy so far. Apologies for lousy photo, and Happy Christmas.