Casting black rubber like tires

[Psychographic]

I've had good luck casting resin parts using the silicone and resin from Aluminlite. I would like to try casting some black rubber like tires such as the ones Modelhaus used to sell. Do I need a special silicone to make the molds? What resin do I need to get to cast them?

 

Thanks for any help.

 

[RAT-T]

I/VE NEVER DONE IT, BUT I THINK YOU HAVE TO USE PLATINUM CURED RTV, I THINK THE TIN CURED WILL INTERACT WITH THE CASTING RUBBER. 

[JollySipper]

The member here "Lovefordgalaxie" makes these for his models..... He even casts a separate white wall insert. Maybe a PM to him will get your answers.........

[Snake45]

At my last job, we used to cast things out of a resin called 75-80. It was black, and pretty rigid but a little flexible. I'm sure there are softer variants available. (We bought the stuff in 5-gallon buckets. It was NOT fun to work with IMHO.) 

ETA: Now that I think about it, the stuff might have been a clear/amber color and we'd add the black coloring to it. 

Edited May 11, 2018 by Snake45

[Ace-Garageguy]

At one point in my career, I owned an engineering consulting company that worked with inventors, patent attorneys, and made presentation models for marketing and product development.

During that time, I had the opportunity to work with a vast array of materials and procedures.

It's been more than 20 years since I've done much of that kind of work, but THIS company's products and technical advice have always been outstanding.

https://www.polytek.com/product-type/polyurethane-liquid-casting-rubbers

 

[ScottH454]

I gave it a shot an made some tires. The hardest part for me was understanding how to set up the mold. I get them to cast fine it is finding away to let the air bubbles vent. Here is a video of me opening a tire mold. 

https://youtu.be/e2ZSsUOfWu0

I am using Task 14 from Smooth-On an seems like a great choice. Does cure to a hard urethane rubber pretty much like kit tire. 

https://shop.smooth-on.com/task-14

[Snake45]

2 hours ago, Ace-Garageguy said:

At one point in my career, I owned an engineering consulting company that worked with inventors, patent attorneys, and made presentation models for marketing and product development.

During that time, I had the opportunity to work with a vast array of materials and procedures.

It's been more than 20 years since I've done much of that kind of work, but THIS company's products and technical advice have always been outstanding.

https://www.polytek.com/product-type/polyurethane-liquid-casting-rubbers

 

Yeah, the product I was talking about was made by Polytek. I recognize the name. 

And I remember the hardest part about using it was, we'd inject the stuff using some giant syringes. It wouldn't be bad to work with if you could just pour it. 

Also, I eventually developed an allergy to it. Working with it would give me asthma-like symptoms for the rest of the day. I wouldn't sneeze or break out in hives, but it made my breathing very labored and my heart race for hours.  It took me several such incidents to recognize what was causing it. From that time on,  I was the only one there who had to wear a respirator using the stuff. 

[Ace-Garageguy]

39 minutes ago, Snake45 said:

Yeah, the product I was talking about was made by Polytek. I recognize the name. 

And I remember the hardest part about using it was, we'd inject the stuff using some giant syringes. It wouldn't be bad to work with if you could just pour it. 

Also, I eventually developed an allergy to it. Working with it would give me asthma-like symptoms for the rest of the day. I wouldn't sneeze or break out in hives, but it made my breathing very labored and my heart race for hours.  It took me several such incidents to recognize what was causing it. From that time on,  I was the only one there who had to wear a respirator using the stuff. 

All the products listed in the link I provided are polyurethane. That means they'll have isocyanates as a component. Some people become "sensitized" to isocyanates and exhibit the reaction you had.

The thing is, just about ALL casting "resins" you're going to use for model parts will be urethanes these days.

The great majority of auto-body paints are too. It's just necessary to ALWAYS take proper safety and health precautions.

ALSO: These Polytek products are 2-component goo that HAS to be mixed, and they are POURABLE.

Most mix in a simple 1:1 ratio.

They come in an array of hardnesses (most are measured on the Shore A scale).

They are also compatible with a wide range of mold materials:

PT Flex rubbers can be cast in PlatSil^® silicone molds without any release agent and can be cast in polyurethane rubber molds, polyurethane plastic molds and latex molds with the proper release agent (e.g., Pol-Ease^® 2300 Release Agent).

 

[Psychographic]

12 hours ago, Ace-Garageguy said:

At one point in my career, I owned an engineering consulting company that worked with inventors, patent attorneys, and made presentation models for marketing and product development.

During that time, I had the opportunity to work with a vast array of materials and procedures.

It's been more than 20 years since I've done much of that kind of work, but THIS company's products and technical advice have always been outstanding.

https://www.polytek.com/product-type/polyurethane-liquid-casting-rubbers

 

I forgot about them, Polytek is about 15 minutes from me.I've been there before and they were very helpfull.

Edited May 12, 2018 by Psychographic

[JollySipper]

Here's a link to Tulio's thread on how he makes them......