Molding tires

[Chariots of Fire]

Dominick inquired as to how I make tires for my models.  Below is one mold that was done for the tires used on the 1929 Coleman.  The description of how to do it is below the photo.  In this case front and rear tires are identical so only one mold was necessary.

The tire mold is in the left side of the above photo.  I use mold rubber that is sold by MicroMark.  It is opaque and has excellent molding qualities and picks up all details nicely. 

1.     Start with building a box to contain the mold rubber.  I use craft board but any stiff card will do.  Leave enough room completely around the tire.  Glue up 4 sides and the bottom of the mold box.  It needs to be high enough that will be mold rubber under the tire as well as above it.  A glue gun makes quick work of building up the box and it does not need to be perfect.

2.     Mix up the two part mold rubber and pour it into the bottom of the mold box about 1/3 of the height of the box and let it cure.

3.     Mix up another batch of rubber and pour a very small amount over the surface of the previously cured rubber.  Cover the face down side of the tire with a small amount of rubber so that it completely covers the bottom sidewall and all of the detail of the tire surface.  Place the tire in the mold and gently swish it around to make sure there are no air bubbles under it.  Use a weight to hold the tire in place.  You don't want it to float up after the next step.  

4.     Pour the rest of the second batch of rubber around the tire and let it cover the entire area of the box.  Continue to carefully pour the rubber around the tire until you reach the upper surface of the sidewall.  Do not let the mold rubber get on the sidewall.  Walk away from everything at this point and let the second pour cure completely.  If it has cured completely, it will not feel sticky when you touch it.  Note that there is no mold rubber inside the tire other than the thin veneer that was put there in step 3.

5.   With a sharp Xacto knife cut notches in the corners of the mold box and remove a small section of cured rubber.  The photo above shows where I cut away to corners and along one side.

6.     This next step is important.  Spray the entire interior of the mold box and the surface of the tire with mold release.  You can use petroleum jelly or a spray, which is what I prefer.  IF you forget to do this you won't be able to separate the two mold halves.

7.     Mix the final batch of mold rubber and pour it into the mold making sure to cover all exposed surfaces of the tire.  Make sure there are no air bubbles.  Continue to pour until you have completely covered the tire and bring the rubber to the top of the mold box.  Let it cure completely.

8.     After the rubber is cured, break away the sides of the mold box and remove them.  Do the same for the bottom.  Then separate the two parts of the mold.  Remove the tire master and you will be ready to pour two part resin into the mold and make a tire.  Note that I did not include an air release for the resin to escape.  

9.     Fill both sections of the mold with resin and check for air pockets.  Make sure the resin is all around the face of the mold so that the tire tread is covered.  Let the two sections of the mold with the resin gel just a little and quickly flip one half of the mold onto the other.  Square it up using the notches as a guide.  After the resin is cured, break the mold apart and remove the new casting.  There should be more than enough resin so that the excess squishes out the sides of the mold.

Below are the tires made from the mold for the Coleman.  They were white when they were removed from the mold.  Flat black was used to paint them.

 

Hope this helps in how to make tires!😎

 

Edited Friday at 11:56 PM by Chariots of Fire
adjust wording

[Rodent]

You are very talented, Sir.

[Firebuilder]

Charles,

Thank you for posting this, I  see  2 steps where my attempt failed. Step 2 where you do 1/3 layer and let it cure, and also covering the face down side of the tire and sidewalls.   I had just paced the tire flat on the foam board and pored around it!  I plan on making a second attempt sometime this week. Again I would like to thank you for  taking the time  and  providing the instructions you have given on rubber mold making. I have  many molds for parts  that I can replicate as needed now (couplings, foam cans, light bezels etc). Hopefully someday I can pass along this knowledge to someone else as you have done.

Dom