# Casting parts from car body repair putty?



## Paulus (May 31, 2008)

In my "military modelling years" I once made parts out of 2 component resin and home made latex forms. I still have an ammount of latex, but run out of resin (to be honest; I let it dry out by opening it once, using a bit and then store it way too long...).

Now, I'm playing with the idea of casting parts again (like doors and windows or mailboxes etc.).
As resin is very expensive and 1:24 scale parts a much bigger than 1:35 (or even 1:72) parts I was looking for a good alternative. 
Recently I've read on a German site (http://www.bretzler.eu/index.php?cat=c47_Feldbahnwagen.html) you can use much cheaper car body repair putty to cast (in german it's called: Karosseriespachtel ). 

Does anybody on MLS have experience with this technique? 
Does it work? How does it react to mold latex?

Paul


----------



## SE18 (Feb 21, 2008)

I've casted parts in RTV molds using 2-part epoxy stick (the blue or green outside that you kneed). It's probably the same price as resin. They sell gallons of the smelly resin low cost in Lowe's. I'll have to give that a try. 

I'm not sure what mold latex is. 

Sorry, I know I'm not answering your question


----------



## Russell Miller (Jan 3, 2008)

Paul,
Most "Body Repair Putty" is a filled Polyester Resin; that is why there is such a strong smell. It is difficult to force the putty into small details in rubber molds because of it's thickness and viscosity. You usally distort the rubber mold and loose detail. Body Repair Putty also tends to shrink some as the solvents flash off and the material tends to curl if unsupported. After saying all of that, I have seen parts sucessfully made using the putty. Usually they were small and not too detailed. Click on the TAP Plastics banner at the top of this forum and watch the instructional videos on Mold Making. There is quite a lot of good information there and some of the mystery is takien out of the process.
Russ


----------



## Paulus (May 31, 2008)

Thanks for the replies SE18 and Russell. Nice video's on the TAB site. 
The molds I'm thinking of are not too detailed si I'll guess I just give it a try. 
I'm planning to make relitavily flat parts, like doors. I'll just try how the putty respond on the latex and how much it shrinks.
I'll be back on this


----------



## SE18 (Feb 21, 2008)

I've made rolling stock out of every stubstance that there is that can harden, well, exaggerating slightly. Here I did a tipper tub and wheel with construction adhesive in an RTV squish mold and a regular RTV mold for the wheel. I spray painted and threw dried clay on it to weather it.


----------



## Torby (Jan 2, 2008)

Who would have thought? That turned out great!


----------



## lownote (Jan 3, 2008)

I just made a pop valve out of JB Weld and modeling clay. Pressed the original into the clay in two halves, left a hole for the excess, and poured JB weld into the open mold. Closed the two halves. It worked reasonably well. A couple air bubbles. Once painted it was fine. I'll try to get a picture


----------



## SE18 (Feb 21, 2008)

nonhardening clay is great for single use molds 

I've used JB weld in RTV castings as well. 

Clay is also used to make a dam around a frog 










a crude RTV mold 










shot for strength and weight (sometimes substitute BBs) 











mix with JB weld and spray paint and presto


----------



## Ross (Jul 19, 2009)

Heck SE18..good score. 
These ideas all go to show that there is more than one way to "skin a cat"!!
Now then. Anybody used *silicone adhesive* for mold making. I understand one should dowse it is soapy water and this gets rid of the stickness so you can work with it properly without gumming up your fingers. Must try this myself. 
Latex molding needs a bit of thought for larger items AND a well supported mold. It makes good castings but needs a lot of time to get right (unless you are making rocks for indoor layouts). Six coats are the minimum plus reinforcing.
. . .and I have just had a thought.....you all knew that didn't you?


----------



## SE18 (Feb 21, 2008)

A while back I spilled a bunch of drywall paint on a brick mold. When I peeled it off (it had a rubbery consistency), it had a perfect impression. You could then glue it on a structure; don't know if it would hold out outside but outdoor paint certainly would.


----------



## Paulus (May 31, 2008)

Hey, this thread is living up again  

Brakeman, those items look great! 

shot for strength and weight (sometimes substitute BBs) 

Can you explain that? Do you use it to keep the mold parts in place? 
Or do you mix it or something? 
What is RTV exactly? 
What is JB weld? 
Can you use that turnout frog for a real operating turnout or is it just meant to be a "scenic" detail? 

Sorry for all my questions; must sound like my five years old son...


----------



## SE18 (Feb 21, 2008)

the turnout I can use (I haven't yet, however). 

I mix the shot in the JB weld (1:1 type epoxy available in HD/Lowes). Look in the glue section. It's rather expensive, however. Resin would be cheaper. I just had to add that to the many experiments I was doing. 

RTV is rubbery stuff for molds. MicroMark, smooth on Bragdon and others sell it. Experts use a vacuum chamber to remove air. 

I just mix 1:1 non-vacuum type and breathe on it. Never had a bubble form that I know of. 

It can be used with resin, epoxy and even some metal pours below 600 degrees F. I've done all. You can even patch, repair, alter RTV with other RTV. I think the only thing that sticks to RTV is other RTV 

you can spray paint the inside of the rtv and whatever you pour in it will coat it with that color. just be sure the paint is dry (don't ask me why I know)


----------



## SE18 (Feb 21, 2008)

Here's resin + BBs


----------



## SE18 (Feb 21, 2008)

Here's a tipper I made. Everything is cast except for the link and axles. The chassis is cast lead. The wheels are cast as well. Tub is from squish mold


----------



## SE18 (Feb 21, 2008)

I cast concrete as well. Here are 2 sections. Rebar is in the middle. I dumped stones on the sides of the mold 










no shortage of things you can cast. You can even recast yourself


----------



## RimfireJim (Mar 25, 2009)

Posted By Paulus on 03 Aug 2009 10:27 AM 

What is RTV exactly? 
What is JB weld? 


RTV="Room Temperature Vulcanizing" In almost all cases where the term is used, it refers to RTV silicone. There are other silicones that require additional heat to vulcanize (cure).
JB Weld is a brand of metal-filled epoxy. I've only seen it in small tubes. Another brand is PC7; I've found it in small cans, making the cost per ounce much lower than JB Weld. The PC7 seems a fair bit thicker viscosity than JB Weld, which is useful if you don't want it to run, but would make it more of a problem for casting.


----------



## chuckger (Jan 2, 2008)

A while back Garden Railways had a story on building stone buildings using auto body filler to make the stone. The building was made from plywood and covered with the stone and then grouted. The stone was made by mixing the filler, spreading it out on a cookie sheet. After it hardened you broke it up to make the stone. 

Chuck


----------



## Paulus (May 31, 2008)

Thanks for the explanations. This makes things much clearer. Never thought about using BB's that way. 
Some great castings you've got there SE18, very inspiring too. 
Thanks for showing!


----------

