QUESTION about resin casting wheels/tires

[Nells98Vic]

Hello all

I'm new to these boards, so bear with me...

I have a question regarding resin casting wheels and tires.

I am building an old JoHan kit of a AMC Javelin AMX. It's actually a test-build, since I hope to eventually learn from it and build a replica of my boyfriend's '74 AMX. Anyhoo, his car has what are called "Rebel Machine" wheels. I managed to make a good mold of a 1/24 wheel from an old kit with the correct ones, and have made some nice resin copies. Problem is, I only have one set of correct tires, Goodyear Polyglass ones. Soooo, I made a mold of the tires, wheels, and backings. I thought I was home-free... until I detail painted the finished products. There are air bubbles in the resin that ruined the surface of the part. I am not happy with the result at all, and do not want to use the only set of rubber tires I have.

If any of this makes sense, and anyone has a possible solution for me, PLEASE let me know! I have NO ONE to talk modeling with, even after more than 10 years of building cars, so this is the first time I've asked anyone for help.

HEEEEEELP!!

Nells
www.crownvicsetc.com/carmodels.html

[tonioseven]

Try SATCO They have a nice selection of rubber tires. Welcome to AF!

[Nells98Vic]

The only thing is, how can you be sure the wheels will fit aftermarket tires? I have yet to figure that one out... If they give a size, it's sort of hard to use a ruler and figure out if the wheel will be the right size for the wheel...

Any further tips on choosing the right size tire?

Nells

[Jay!]

a. Shake the hell out of the casting as soon as the resin is poured to loosen out those bubbles.

b. "paint on" a first thin layer of resin in the mold

c. try another casting medium, even if it's not ideal... (black wax, water-based glue + acrylic paint, etc...)


And if you do keep looking for replacement rubber tyres, remember that to do have a bit of stretching room, so you can use tires slightly smaller than the wheel size.

And welcome to AF!! Your models are fantastic! I really like your XKSS!!

[Ragnarok043]

ive had trouble with bubbles too when i cast parts, but first you need to determine how the bubble was formed. if its traped air from pouring the resin into the mold then you can just chase the bubble away with a stick (dont use a tooth pick ill explain later) or pour along side of the mold. the other way is when bubbles form in the resin during the curing process(commonly know as pin holes) which is caused by moisture. polyurathane resin is very sensative to moisture so you shouldnt use any thing wooden(which has a little moisture in it) to mix it, and dont do it on humid days.

other than having the perfect condition to create bubbleless cast the best method is to cast in layer by brushing on the first few layers.

[Dave ESPI]

I do profesional molding and casting. Vigerious shaking with some resins is very bad and can make for more bubbles.
try a high viscosity resin. what manufactuer are you using..? (PLEASE DONT SAY SMOOTH-ON) that sh*t sux.
try Sil cast from Silpac resins in California.
Also try to use some baby powder very lightly applied to the mold surface. it will "suck" the resin up and eleminate 99 % of surface blemishes, BUT BEWARE as this can/will also reduce the longjevity of the mold materials.
try a "bronzing powder" this when shaken inside of the mold and then later excess is dumped out, will also do the same but with it mixed in the resin will make a very heavy plastic that will literaly force the air - micro-bubbles off the surface.

OTHER NOTE, use yer laundry clothers dryer. set it on NO-low heat, and run it while the resin cures it will shake the bubbles loose.
Hope this helps.

[Nells98Vic]

I have been using the molding agent and resin sold by Micro Mark. I am still new to resin casting, so I don't know much about other manufacturers products. It could be that Micro Mark's stuff is made by another company.

The comment about mixing the resin with anything wooden is interesting. I have been using the popsicle-stick style mixers that came with the mixing cups I have. Wood. I have tried mixing different ways, and I still can't not make bubbles! I just don't know... I also only mix a small batch at a time, if that matters.

It's a shame, really, because making copies of parts has the potential of solving a lot of future problems with other kits.

That XKSS was a problem kit at first. I tried some MCW British Racing Green paint for the first time, and it orange peeled. I was just a bit mad, since it's hard to find that kit. But I managed to save the paint, and now it sits in my "museum", one of my best models! :flash:

Nells

[Dave ESPI]

you could always send me the parts and I could make them, or at least a better mold. lemme know.