Molding & Casting a Rubber tire

[bills69camaro]

Hello Shiggy. For the mold I used G T 2135 Compound RTV Silicone Clear. I don't know who makes it, it was purchased
from BCC Products , Inc.
2140 Earlywood Dr.
Franklin, IN 46131
317-736-4090

The material used for casting the tire, F-42 A/B 42 shore A polyurethane elastomer.
Purchased from BJB Enterprises, Inc. 714-734-8450 you can see all the products on their website.
Hope this helps.

[Shiggy]

Thank you for your response!

[RAT23]

Hi bill,
great tutorial!
What would you say the difference is between the styrene pins od & the tires id?

Thanks, tom

[rickparis]

I hope I can find an answer here as it has been a few years since you posted on this thread. I love what you did here. I do not understand how the silicone got into the center portion of the tire? Did you do two pours? I don't understand why you had to cut the original tire in half, did it not stretch enough to get it off the center? I do not want to make a mold of two halves, as most people do. Thanks!

[rickparis]

It also seems the piece you turned for the axel center needs to be smaller than the tire rim diameter? so you can cut it out? I see there is some white around the old tire edge, did you use some kind of spacer?
Thank you!

[MODEL A MODEL]

That's a good question!

Look at the second photo, the "Gate" is the faint off-white / grey square shape under the tire pattern. When pouring the RTV this "Gate" is the support for the pattern and is at the bottom of the mold box. It supports the pattern and the PVC pin passes through the center of the tire pattern, but does not touch it. The pin is attached to the mold box walls but not the pattern. Allowing the RTV to enter the inside of the tire.

Later the whole mold is turned upside down, with the "Gate" now at the top.

I assume that when the mold is in the vacuum, the air that had been in the mold, has to bubble-up through the resin ? The resin being in the reservoir attached to the (NOW) top of the mold. That being the case, the reservoir's walls need to accommodate the temporary rise of the resin .

Interesting!

[MODEL A MODEL]

Making a two part mold this way is the best way.

When you carefully cut through the RTV , it creates it's own "Keys", and creates a net / net fit. A perfect fit.

And when he opened the valve, allowing the ambient air to enter the vacuum chamber, the resin is drawn into the vacuum that still exists inside the tire mold, and, it is being pushed by the returning air.

He probably had to cut his pattern, because it was a rigid part. A sacrificial pattern, which had served it's purpose.

The white you see is the pattern. Some rigid plastic? Styrene or PVC? Cut in half.

[MODEL A MODEL]

Notice the pliers that he is using? These are available in auto parts stores, I own two but can't remember what they're actually designed for? When you squeeze them, they open up. Very useful when cutting into a mold like this.

[rickparis]

Thank you!!