# Wheels



## GaryR (Feb 6, 2010)

This seemed a better place to put this than in public. > Scratch building pics < This where I stick all of the train pics.


Scratch building is only cheaper if you already have the tools, or you want something they don't sell. In my case it's the later. 


Today, it's the wheels. 


I start with a pattern made in TurboCad. I export this as A jpg image. In photo editing software I make a "negative" from the jpg image and print it on transparent film . The negative is used to make a "rubber stamp" using a photo polymer and black light. With the 
"rubber stamp", I make a silicone mold. With the silicone mold, I cast a polyurethane wheel and fit a tire onto it that I turned on the lathe. At some point I'll try a wax wheel from the mold and try to cast a metal wheel with the lost wax process. List of suppliers on request. 

GaryR


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## SE18 (Feb 21, 2008)

Very creative and fine craftsmanship. Bravo! 

Dave V


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## lownote (Jan 3, 2008)

That sounds very interesting--is that process described anywhere in more detail?


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## TonyWalsham (Jan 2, 2008)

Thank you Gary. 

I would be delighted to see your lost wax masters.


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## GaryR (Feb 6, 2010)

This is a merging of 2 or 3 or more different hobbies. > Rubber stamp instructions < They show pouring the polymer on top of the negative.....I lay the negative on top of the polymer after I pour it. Likely either way will work.

Instructions for using silicone to make molds comes with the silicone from > MicroMark <



Polyurethane> Epoxies Ect < Ask for item number 70-2170 This is a manufacture , not a hobby suppler. I got a free sample under my company name. They will sell retail. Be warned though the price is about $28.50 for the quart kit, the shipping was $14. They don't shipp till a week after they get the order. They bill your card at the end of the month. 

While no parting agent is needed using a silicone mold, I've yet to find one that would work if needed. They all bubbled up and ruined the part. 
It sets up fast in warm weather. When it starts to turn white, it's too late. 



Tony, truth is, I've always sand cast. I haven't as yet used the lost wax process. Though when I do, I expect no more issues than I've had with any of this other stuff. 


I know for a fact that there are several others around these forums that do the same kind of stuff. Let's hear from you. 



GaryR


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## Totalwrecker (Feb 26, 2009)

You can use unscented talcum powder for your parting agent. Dust it on and blow off the excess. Keep it out of the part impression. 

Porosity may be your biggest headache when casting, as you will need a rapid pour and a method to replace the air in the flask with metal, ie; centrifical or vacuum. 
You can also use the plastic wheels in lost wax casting, the plastic should burn out cleanly too. 
Also you should allow for an aproximate 10% shrinkage from master to cast object. This was true for silver and gold, my experience. 

Your burnout oven may be the most expensive machine you'll need, the better ones are computer controlled as they ramp up to 1400+ degrees and then down to 900 for casting. Part of the process is firing the plaster so it withstands the impact of molten metal. 
Simple wind up casting arms are relatively inexpensive and work well, but can throw hot metal, so we put ours into a steel tub with a fold down lid. 
I prefer vacuum assist casting as it pulls the metal in. My vacuum table also helps when pouring the investment (plaster) by de-bubblising it under a dome and then the flask, after firing, fits in a sleeve and the metal is poured. For years I torch melted (there's a fine line between just right and too hot!), but after going to vacuum assist, I'm sold on an electromelt crucible. 

What metal are you going to use? 

John


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## ralphbrades (Jan 3, 2008)

Errmmmm... All I can say is -why are you using such a complex process? Surely Stereo Lithography would be faster, cheaper and simpler to produce your masters from? 

regards 

ralph


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## pagosarr (Jan 5, 2008)

In the sequence of steps, how do you get from a "rubber stamp" to a silicone mold? 

Thanks, Roger Bush


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## GaryR (Feb 6, 2010)

Talcum powder works fine for casting metals not in plastic resins. It just mixes with the resin. Other wise, very helpful. Thought I mite try gravity with an 8" riser for head pressure. Probably try it in zinc as that is what I have the most of, other than aluminum. Brass is nice, but have a hard time getting it up to pouring temps. Have the stuff for a second furnace, but haven't gotten around to making it. Few things I'd have to buy, so it will be a while. 

Ralph: If I was rich I'd just buy a 3D printer and be done with it. However, I live on $1100 a month social security and have to use what I have on hand. Donations accepted.  


Roger: Put the "stamp" in the bottom of a frame and pour the silicone on top of it. I set the frame and stamp on aluminum sheet cause it won't stick to it. Not a good idea to set it on glass, the silicone will stick to that. 

GaryR


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## GaryR (Feb 6, 2010)

Uploaded a few images this morning to my> train folder< showing how you get from a stamp to a silicone mold. 


GaryR


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## SteveC (Jan 2, 2008)

Gary

Just curious, but what thickness of finished part are you limited to, and how is that controlled in the process of making the stamp?


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## Jack - Freshwater Models (Feb 17, 2008)

Gary, 

What kind of wheel are you making? 

Jack


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## GaryR (Feb 6, 2010)

As for length and width, it's however big the black light source is. I'm working at what is probably the max of 1/4" in depth. More than that and the black light won't penetrate to the bottom. Also, The lines of the pattern cast a "shadow". That is to say the line will be much thicker at the bottom than it is at the top. Looks like this /\ . 
What i do is do ahead and cast a urethane part with the "first" silicone mold and carve/file the excess and make a second silicone mold from it. 
The first usable wheel from this process will cost the same as one you'd buy. Each successive wheel cost about $1.00. Obviously if you only need a few wheels just like a thousand others, just buy them. If you need 10, 20 or more or it's a wheel they don't sell, this is practical. 
I haven't tryed the sides and ends of a box car.....yet. Oh, and yes, the urethane is highly machinable. Stands up well to drilling and turning on the lathe. 

Jack: It's a ten spoke wheel, about 1" dia at the tread . 

You guys ready for this? The wife wants a few of them for buttons. LOL 

GaryR


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## SteveC (Jan 2, 2008)

Gary thanks for the explanation on the depth/thickness part.


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## Jack - Freshwater Models (Feb 17, 2008)

Gary, 

A few years back I played with the photo resin process for making relief lettering on a model. At the time I wasn't 3D CAD proficient. The results I got were less than expected. The lettering was sort of low durometer and resolution was a bit fuzzy/lumpy. I suspect a lot had to do with my light source. I think that the results would have been better with a much stronger focused light source. Luckily the lettering was good enough for the project. 

Since then I have changed over to strictly CAD and 3D printing. 3D printing is outstanding for patternmaking for spoked wheels but requires the use of 3D CAD and cost of the printed pattern. 

Jack


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## GaryR (Feb 6, 2010)

Jack,
In this case I used 2d cad (TurboCad V8). I'm using 18" florescent tubes. Yes, I agree a more focused light source would help a lot. The "shadow" would be much less of a problem. It's on my list of things to do. 

Oh BTW: I just up loaded pics of mixing and pouring the urethane into the molds on> My train folder.< 

My budget is shot for the month. Ran out of silicone. Sigh......back to cutting ties and mounting rail. 



GaryR


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## Jack - Freshwater Models (Feb 17, 2008)

I also used 18" tubes about 4" away from the resin. I wonder what the commercial rubberstamp companies use for a light source. 

Is there a reason you don't just fabricate the pattern from wood or styrene? 

Jack


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## GaryR (Feb 6, 2010)

Jack,
Saw a segment on one of those "how they do it" shows. They don't use a photo-reactive process. The place I get the photo polymer from, sells what looks like a "tanning bulb". > http://www.art-rubberstamps.com/<

Wood wouldn't work too well. Styrene on the other hand is a real possibility. And I have a good bit of it on hand. Next time I get silicone, I'll try it. I do know silicone won't stick to styrene. 

GaryR


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## Jack - Freshwater Models (Feb 17, 2008)

Gary, 

I smiled when I saw that you sand cast! Few modelers realize the possibilities of making parts using sand castings. Once in a while I make a sand casting using oil bonded sand using a wood pattern. For wheels I usually make the pattern with 5deg+ draft on the spokes and 3deg+ on the inside/outside of the rim. 

Jack


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## GaryR (Feb 6, 2010)

Jack, 
We'er a dieing breed. I have about a 100 lbs. of the oil bond. Thanks to a local foundry, I have over 300 lbs. of the old fashioned stuff. 
The draft sounds right for the wheel. 
The metal casting is on hold cause of time and space limits. Some folks ask how I'm keeping myself busy in retirement, I just laugh. Sigh........so much stuff to mess with.....so little time. 

GaryR


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## Jack - Freshwater Models (Feb 17, 2008)

Gary, 

Most of what I cast is done by rubber mold spincasting but for larger scale stuff I like the look of a sand casting. I have actually made a pattern by sand casting and used it to make a rubber spincasting mold just to get the texture on the finished part. Sadly spincasting wheels is a tough one. 

Jack


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