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Scratchbuilders!: General
For general topics on scratchbuilding.
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Resin casting wheels
samkidd
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Alaska, United States
Joined: January 06, 2006
KitMaker: 519 posts
AeroScale: 4 posts
Posted: Thursday, October 11, 2018 - 07:15 AM UTC
I've done a little bit of casting myself over the years. If you're new to casting avoid pressure casting at all costs. Nearly any of the silicone mold products out there will reproduce the original down to your fingerprints so make sure the original is as perfect as can be. Use silicone mold rubbers.

Map out the gateways with a bit of forethought to avoid air entrapment issues. And speaking of air, you will need to pour the mold material in such a way as to avoid air pockets in places like mounting holes etc. Remember that any air pocket reproduced in the mold is a solid bit of plastic on the casting.

If you or anyone else gets stuck on a casting don't give up. Feel free to contact me and I'll see if I can help out. That's the benefit of experience---I've probably made nearly every casting mistake out there before so I can help you to avoid costly errors.

Jim
LSA
barkingdigger
Staff MemberAssociate Editor
ARMORAMA
#013
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England - East Anglia, United Kingdom
Joined: June 20, 2008
KitMaker: 3,260 posts
AeroScale: 0 posts
Posted: Thursday, October 04, 2018 - 09:05 PM UTC
If you can leave the vinyl tires off until all the painting is done, and the contact points on the rims are sealed with acrylic paint, there shouldn't be a problem. I don't paint my vinyl stuff with anything but acrylics (Tamiya sprayed very thin for tracks), but for tires your best bet is to rough them up with light sanding using very fine grit paper, then dust on some dry pigments so they stick in the roughened surface texture. (Apply the pigments after the tires are mounted...)

I've found that no matter how I try, any paint applied to tires will flake off eventually.
Dragon164
#226
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British Columbia, Canada
Joined: February 20, 2012
KitMaker: 1,818 posts
AeroScale: 483 posts
Posted: Wednesday, October 03, 2018 - 05:21 AM UTC
That's why I said they have some that don't need pressure casting.

Cheers Rob.
Namabiiru
#399
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Rhode Island, United States
Joined: March 05, 2014
KitMaker: 2,522 posts
AeroScale: 289 posts
Posted: Monday, October 01, 2018 - 11:04 PM UTC
@KoSprueOne: Thanks. That was my thinking: cast tires and wheels as a single piece.

@Russ: Yes, you are right; I said rubber, but really I meant vinyl. The tires themselves are nice, but I have an aversion to using anything vinyl because my experience has been that it's very difficult to get acrylic paint to adhere. I'm afraid my primer might eat them up eventually. I do have some automotive adhesion enhancer that might work. Had not considered that till just now...

@Rob: Thanks. Was not really contemplating using pressure casting; rather, just basic gravity casting.

Thanks for the tips, guys!

Dragon164
#226
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British Columbia, Canada
Joined: February 20, 2012
KitMaker: 1,818 posts
AeroScale: 483 posts
Posted: Monday, October 01, 2018 - 07:29 PM UTC
Hey Mark,
Tires can be molded in one piece, I have cast many without having to make a two part mold. Smooth On makes some nice casting silicone's that do not need to be pressure cast. Trying to use pressure on a hollow item will not work.(ask how I know )

Cheers Rob.
Kevlar06
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Washington, United States
Joined: March 15, 2009
KitMaker: 2,132 posts
AeroScale: 581 posts
Posted: Monday, October 01, 2018 - 03:24 PM UTC

Quoted Text

Awhile ago I got Takom's V2 with Meillerwagen and Hanomag SS-100. that kit includes 16 rubber tires, and I hate to use rubber tires. I figured I could spend a lot of time and effort trying to find several sets of resin wheel replacements for tires with no guarantees I'm even ordering the right ones, or I could finally take the plunge into resin casting and cast my own.

Can anyone point me toward a good tutorial on casting resin wheels? I've found a few videos on line that cover the generalities of resin casting, but I was hoping someone might know of some tutorials that discuss any specific pitfalls/solutions with doing wheels.




Aren't those tires made from a vinyl compound and not rubber? I have some vinyl tires on a Monogram Jeep and 37mm gun which was manufactured in 1959, and they are as good as the day they were made. I'd also think it would be be very difficult to mold the tread pattern in a homemade mold without some form of pressure injection-- not saying it can't be done, but it may not turn out as desired. I'll have to check the tires in my kit-- but I don't think they are traditional "rubber" as much as they are a vinyl compound.
VR, Russ
KoSprueOne
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Myanmar
Joined: March 05, 2004
KitMaker: 3,681 posts
AeroScale: 10 posts
Posted: Monday, October 01, 2018 - 12:47 PM UTC
There is also shrinkage to consider. Resin shrinks a little when it cures.
Assemble the tires onto the rims then mold that whole sub assembly. The whole wheel will slightly shrink but this method will at least allow the tire to fit the rim.
Hope that helped.









Namabiiru
#399
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Rhode Island, United States
Joined: March 05, 2014
KitMaker: 2,522 posts
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Posted: Monday, October 01, 2018 - 05:41 AM UTC
Thanks, Robert!

18Bravo
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Colorado, United States
Joined: January 20, 2005
KitMaker: 6,128 posts
AeroScale: 85 posts
Posted: Monday, October 01, 2018 - 01:38 AM UTC
Who else but the master himself? Shep Paine has a step by step tutorial with drawings in his book, Modeling Tanks and Military Vehicles. Quick summary - build a box large enough to accommodate wheel, you can use styrene or Legos. Suspend wheel horizontally in box using small rod from side of box. Fill halfway with RTV mold material (halfway up wheel all the way around) and let cure. Cut keys in mold, coat with very thin layer of petroleum jelly and pour RTV mold material over the rest of the wheel, covering it. After it cures, both halves can be separated. Cut pour channel into molds and you're ready to cast.
Namabiiru
#399
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Rhode Island, United States
Joined: March 05, 2014
KitMaker: 2,522 posts
AeroScale: 289 posts
Posted: Sunday, September 30, 2018 - 11:29 PM UTC
Awhile ago I got Takom's V2 with Meillerwagen and Hanomag SS-100. that kit includes 16 rubber tires, and I hate to use rubber tires. I figured I could spend a lot of time and effort trying to find several sets of resin wheel replacements for tires with no guarantees I'm even ordering the right ones, or I could finally take the plunge into resin casting and cast my own.

Can anyone point me toward a good tutorial on casting resin wheels? I've found a few videos on line that cover the generalities of resin casting, but I was hoping someone might know of some tutorials that discuss any specific pitfalls/solutions with doing wheels.