Ideas for copying a foundry pattern

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UnkaJesse
Posts: 4090
Joined: Sat Jan 04, 2003 10:29 pm
Location: Tennessee, Obion County, Town of Troy

Re: Your best bet is to make a reverse mold ...

Post by UnkaJesse »

Jack, that tread plate is beautimus, but then you already knew that didn't you? [img]/ubb/images/graemlins/cool.gif"%20alt="[/img] The stuff you recommend sounds like the same resin I used for the driver patterns for the Filer and Stowell, gray when it cures out?? [img]/ubb/images/graemlins/confused.gif"%20alt="[/img] I machined a reverse pattern in dental wax with a 2 degree tapered end mill I got from the late Fred Ellis (may he rest in peace) at Power Model Supply and poured the resin in it four times. The resin patterns were fastened to a standard mold board and gated at the foundry.

Unka ( I need to crank up my little foundry this summer) Jesse
"The same hammer that breaks the glass, forges the steel" Russian proverb
alaskajack
Posts: 45
Joined: Sun Jan 12, 2003 11:06 pm

Re: Your best bet is to make a reverse mold ...

Post by alaskajack »

Thanks for the compliment. Probably Not. This stuff comes out a creamy tan color and has a tensile strength of 2500 to 3500 lbs psi. I am making couplers out of it right now and am going to run a test. I made some knuckles and pins and they required a substantial amount to break the knuckle at the joint. I will have to go out to the shop and get the absolutly correct name for this stuff. The deck plate is .54 thick and holds up well. I have poured up to 6 ounces of resin. after that the rubber mold expands and requires a holder of some kind. Like I say I use leggos a lot. Cheap cheap. Here is the latest out of my shop Lots of Resin here. JAck
Mikado14
Posts: 77
Joined: Sat Jan 04, 2003 6:47 pm
Location: Pughtown, Pa

Re: Your most economical bet......

Post by Mikado14 »

Kelly,
Here's my two cents. What everyone has posted is all good info. However, if I understand you correctly, you have a number plate pattern made of wood. Now, if what you want to do is to make some castings of it and not a production project, here is what I would do.

I would go to a foundry and have them make one casting. After I had that castings, I would use that as what is called a loose pattern and have all subsequent castings from that one casting.

You are not looking at a lot of shrinkage. The original wooden pattern will give the original size. When you use the casting as the pattern, shrinkage most likely will not exceed 5% and probably less but then shrinkage is determined by what you have it cast from. Yellow brass, bronze (85-5-5-5), aluminum, etc, all have different shrink rates and the wooden pattern is built upon what material the cast will be made from.

Your only talking a number plate and not a critical part where shrinkage is a major concern. You said you do not want shrinkage, well, if you are talking about 4mm/100mm(roughly 4mm/4 inches) that is not a lot. Anyway, why is it so critical, after all, they are a repro unless you are replacing an original. Geez, I have rambled enough. Good luck on any decision you make.

Just my two cents.

Ron
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Dick_Morris
Posts: 2842
Joined: Sat Jan 04, 2003 2:09 pm
Location: Anchorage, AK

Re: Your best bet is to make a reverse mold ...

Post by Dick_Morris »

Last weekend I saw Jack's locomotive for the first time since he's finished it. It was on display at the ARR Anchorage station for the Fur Rondy, our winter carnival. It's a real work of art with lots and lots for details. Nice job, Jack.
alaskajack
Posts: 45
Joined: Sun Jan 12, 2003 11:06 pm

Re: Your best bet is to make a reverse mold ...

Post by alaskajack »

Aw Shucks Dick: Wait until I get the other one done(4008 Spirit of Wasilla). I'm gonna runnem back to back. 21 feet long both powered. Thanks for the compliment. They both should be ready to go about the same time as the wye gets finished. They wont be able to fit on the turntable thats for sure. JAck [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]
UnkaJesse
Posts: 4090
Joined: Sat Jan 04, 2003 10:29 pm
Location: Tennessee, Obion County, Town of Troy

Re: Your best bet is to make a reverse mold ...

Post by UnkaJesse »

Beautimus jpb on the Alaska RR Lokie Jack. Looks like you have all the detail work in there. Perhaps you know the bloke in the attached photo? Patrick Durand from somewhere up in cold, cold Alaska. [img]/ubb/images/graemlins/crazy.gif"%20alt="[/img] He also has a beautiful locomotive and brought it to Mid-South meet a couple of years ago. Really nice guy even if he do live in the North! You do know how us Rebs feel about Yankees, don't you? [img]/ubb/images/graemlins/cool.gif"%20alt="[/img]

Unka ( gonna stay here where it is warm most of the year) Jesse
"The same hammer that breaks the glass, forges the steel" Russian proverb
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