Resin Casting Wheels

[844john]

I know there is a lot of information already out there about casting and mould making, but after finally getting around to trying it there are several problems that I've encountered, so I thought that I would pick your brains!

My initial attempt was to cast some rear wheels, ideally I would like to do the tyre and the rim separate, but for a first attempt I left them complete. I tried two different ways using a single mould, in one the wheel was laid flat on a short axle to keep it up off the bottom of the mould, hopefully allowing the rubber to mould all the way round. The second one I tried James's method of standing the wheel upright glued to a small sprue of plastruct.

The mixing and pouring process seemed to go well enough, but it wasn't until i came to remove the wheels from the mould that I realised my biggest mistake. The rims that i am trying to replicate have the square dish in the middle, with gaps between the dish and the rim, and i had overlooked the fact that the silicone obviously flows between the gaps, effectively encasing the rim within the mould and making it impossible to remove without cutting and damaging the pattern.

Am I right in thinking that a two part mould would be the only way to replicate these, obviously if the centre of the rim was solid it would not be a problem and the single mould would work, but with these that seems not to be an option?

The picture shows the moulds after i had to half them to extract the wheels, as expected the bottom of the wheel that was laid flat has a lot of air bubbles, but the other doesn't seem too bad, I just need to be able to remove the rims without wrecking the mould next time

[Tractorman810]

james is your man for resin wheels, and tips, i got a mf 1200 hub lookimg ok, but the tyre was a complete pain to say the least, got the black rubber resin for them and everything, but never ever got them right . its certainly not an easy thing to do 

[844john]

4 minutes ago, Tractorman810 said:

james is your man for resin wheels, and tips, i got a mf 1200 hub lookimg ok, but the tyre was a complete pain to say the least, got the black rubber resin for them and everything, but never ever got them right . its certainly not an easy thing to do 

Did you use a two part mould for the rim Sean?

[Tractorman810]

for the rim yes, took a few air bleed holes, but it works, the tyre i tried 2 peice and a single peice ,with the tyre set in at an angle,split down the middle in the cerntre of the mould where the rim sits, so in theory it would only require cutting etc on one edge, but i just couldnt get it to work properly,saw that one on a youtube vid a while back.

[bluegreen]

Any chance of you moulding a few of your MF PAVT wheels shawn

[Tractorman810]

i have a set of them from po minitures, but i aint to sure i want to really copy his stuff, kind of feels wrong, i really need to prime them up so i can see the detailing at some point, was also going to cast the uh 575 hubs, as they are much more what i saw on the 500 series, plus a few 100 series 

[SPN]

I know its not the answer to the question you are asking John, but if you are looking for a 30"  Sankey wheel for a Leyland then I'd suggest the wheels from a Britains Steyr 375 Kompakt are a pretty good alternative. The UH NH T4 is another option.

Nigel Ford also does one for his 6X 5000 but I haven't primed one yet so can't comment on it.

[Stabliofarmer]

I've only moulded a tractor rim of the same style once, the general britians tyre found on the likes of the Renault and Lamborghini which also has holes in the centre. I was still able to cast it as a one part mould, it just requires some keyhole surgery style moves with a craft knife. I cut a slit into the top of the mould, creating a space large enough to remove the rim, though obviously it is still trapped by the inner holes. I then had to get a helper to prise and hold the top of the mould open revealing the sections running through the holes. Then with a craft knife I slit through the silicone releasing the rim. Pretty much exactly as you have done but without cutting around the whole outer of the mould, what you have created is a two part mould, clamp those two parts together and you can use them as a mould.

I would get photos to show you, but the mould is slightly ruined, turns out mixing one part resin, with one part casting rubber creates and incredibly strong adhesive that sticks to everything, including RTV silicone.

[844john]

Thanks Stan, that's certainly worth thinking about for future project,  the wheels are actually for another couple of Case builds, but are a common type fitted to tractors in the 90's, so i thought being able to cast them would no doubt be useful for later builds.  I removed the rims sort of how you said James, but without any finesse after I'd realised my mistake, so the cuts around the holes in the rim are a bit rough and probably not good enough to cast from. I cut them in half afterwards just to see how the rubber had set inside the mould I think it's certainly going to be one to ponder, but it looks like i am probably going to try a two part mould next and hope for the best, after watching a video or two on YouTube it looks a bit fiddly with putty and such, but we'll give it a go!