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Discussion Starter #1
Well, to begin with, I bashed this Bachmann 4-4-0 a while back and below is a picture of the cab I made from Styrene


Well someone saw it (I'll let them remain anonymous unless they feel like speaking up) and asked me to make them one for their 4-4-0 bash.
I started doing it a couple of weeks ago, and was just about to finish up the roof, when I thought to myself,
"Well, I'm planning on bashing another 4-4-0 for the same engine at an earlier period, so why not leverage his needs and my own". So I decided to save some time and make a mold.
I started this thread for three reasons;
1. its the first time I've attempted a mold on pieces this thin and I'm not sure if I'm going to succeed. So I figured, why not share my success or failure with a step by step right here.
2. I've been so busy lately I haven't had time to contribute anything to the forum or even comment much on what I was skimming through in the morning.

3. its a chance for the person who commissioned this cab to watch my progress so he can see how far I've gotten in the months since he requested the work
I have a few last touches to the doors and then tomorrow I'll take an image of the parts unassembled and assembled and then move on to the mold making process step by

step.
:D
 

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Discussion Starter #3
PARTS

I didn't realize till I took the assembled cab shots that I neglected to fabricate the tappered rail piece that meets the roof overhang.

I ran out of styrene and my local hobby store stopped carrying it (for some crazy reason, they can't tell me). So I decided to use some scaps of ash veneer I've had hanging around my shop for about 20 years now. You can probably see from the image that I did a little bit of form lamination. To save time, I used a 3 gallon can that was just the right diameter. I cut all the laminations to size, applied glue to one side of the first 3 layers and stacked them up and covered the last layer with some wax paper and with some packing tape I taped them all together on the can as tight as I could.
I let it set for about 24 hours, well, at least till the next moring and glued it to the already assembled roof framing (sorry no pictures, I was too busy )
Its not bad, but I can see that I got a few delams going around the edge. Thats easyily fixed with a little super glue. If I wanted to spend a little more time (and if it was a real roof and not a proto I would have) I could have built a good form of plywood and a vacuum bag and vacuum form laminated the hole thing.... say, that might be a good way to go for the roof of my coach 64 (which is giving me some troubles with warping cause the stocks so thin).

As you can see from this shot, the parts are being held together by the roof, so the parts are a little mis-aligned.

This is a close up of the inside. I thought I would point out, that I see this as probably the single most problem area to cast, but if it works, it could save a lot of assembly time.
What I did was to create the channel for the window to glide in instead of doing it during assemble. To keep it looking as close to prototypical the styrene is very thin and it might ended up riddled with air pockets even though I'm casting them under pressure.
NEXT STEP
cut up some material for the mold and attached the spues(?). I have some honey do stuff to finish before I move on to that though, so it'll probably be a couple days away, unless I can sneak some time.
 

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Rick,

As soon as you finish this one and work all the bugs out of the process are you going to start cabs for 76, 98, 37, and 39? Looking very, very good buddy! Hard to believe that you've been at this for such a short time even though many skills are transferable. You're a one of a kind.

Jeff
 

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Discussion Starter #5
Thanks Jeff, but I really don't deserve the praise. The only reason they come even close to the quality of work you do is because I take 10X longer than you do to finish anything

I am definately going to do 76 if this turns or if it doesn't because I'm bashing 76 and resin is a lot more durable than styrene. I wish I could afford enough connie drives and time to do the others.
One thing, is if this works, then you shouldn't have any problems casting your coach sides like you were asking about before.
 

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Discussion Starter #6
Made my first mold on the roof and have to scrap it. I didn't seal the wooden surfaces good enough and the result was a very hair mold and almost torn up prototype. I have been busy sealing the pieces this evening. I'll cut the first mold up so at least I can save on RTV.
 

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Discussion Starter #7
Thought I would start showing some of my work on this project.

This first picture shows the parts I have cut out for the molds. The melamine is for the bottom of the molds. It is 3/4 inch. I like using melamine because it is a lot flatter than plywood and I have a lot of scap left over that can't be used for anything else ;)
 

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Discussion Starter #8

I am masking the surface of the part that will come in to contact with clay. It has been my experience that removing clay from detailed surfaces is tedious and long. When I remove the first half of the mold, I will pull the clay off in one huge chunk and then peel the tape off revealing a clean surface.
Note that the tape must be firmly adhered to the surface. To make help facilitate this, I put the parts in a vacuum chamber once the tape is on.
Sorry, but I took this images before I cleanly trimed the tape from the edges. Note the part to the left reveals some tape overhang. This must be cut flush to the edge if you want a clean edge on the mold.
 

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This is a layup of the front end. I apologize that these shots are out of sync, but I sometimes forget to take pictures and so you will see various stages of the process, but on different parts.
The first thing I do, not shown here, is to trace an outline of the part on the melamine. I apply the clay to the inside of the outline, then I squeeze if flat with another piece of melamine with wax paper on it. When I'm sure the surface of the clay is flat, I heat it up with a blow dryer so that it looks a little glazed, then I place the piece on the clay with the unmasked side up.
I forgot to mention this most important part in the masking; always mask the least detailed side of the part. This makes masking much easier and metigates destortion to detailed parts that might occur after you gently press the part into the clay using a wooden straight edge.
After the part has been pressed into the clay, I use a combination of dental tools and pallet knifes to trim the clay away from the part and the vents and sprus.
 

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Discussion Starter #10

This is just a shot of the second half of the mold. I forgot to take pics of the first half.
There are two steps for the first half. The first step of course is to pour the rtv into the mold, which also has two steps for me; one I mix the rtv and while its still in the mixing bowl, I extract all the air. That takes about 15 minutes. The second part is to pour it in the mold and then submit it to a vacuum for an additional 17 minutes or more depending on the amount and type of air bubbles I see on the surface of the RTV after the elapsed time.
Once the RTV sets, I poor a backer straight into the unbroken mold right on top of the RTV. The backer makes sure the mold retains its original shape. Once the backer has harden (about 1 hour) I flip the mold over, break out two sides and remove the melamine, the clay and the masking tape.
Sometimes the tape bleeds so you need a razor knife and some detal picks to clean up leaks.
Once the part is cleaned I put the sides back on then I coat the first half of the mold with my solution of vasaline and paint thinner. I do 3 coats of this letting the solution dry before each and before finally pouring the second half of the mold.
 

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Discussion Starter #11

This is a shot of the first two castings while still in the first part of the mold. If you look close you can see the backer. For these parts the backer is casting resin. I did this because the figure business has been slow and the resin is about to go. Resin does not last a long time on the shelfs and I bought a gallon expecting a lot of figure sales this summer. The economy went south and now I am left with using the resin before it goes south. Normally I would use plain old board resin because it is a lot cheaper. It important to note that when using the boat resin, do not, do not mix it too hot.
Anyway what you are seeing in this image is what I refer to is my cleanout piece. This is usually discarded but this piece turned out pretty good, I will probably use it on my own 4-4-0. The cleanout piece does a couple of things. It removes the small smears of clay that are hard to get off the rtv and it shows me where the venting problems are so that I can cut them out with a razor knife. I had a couple of them on this part, nothing great big and you can probably spot them.
 

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Richard, I tried to email you via the 'send message' link, but got this:

undeliverable to xxxxx
Body of message generated response:
550 Error: Possible Spam peculiar Subject line

Maybe you could add MLS to your email contacts so it accepts messages?
 

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Thanks Pete, but could you edit out my email address from your post. It makes that address vulnerable to phishing programs that scour web pages looking for email addresses to spam. I got your email through MLS and sent back a response, again thanks for the interest. As far as adding MLS, it is already on there. The problem looks to be with the subject line. If you send message me right here on mls I will be able to determine what words, or combinations of words got the email rejected.
 

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Discussion Starter #15

Was cleaning up my shop area today and I came across this clean out piece. I thought this would be a perfect example of why you want to make sure you put the most detail side of the part up for the first pore. Its a poor image but if you look at the top door stop you can see evidence of a distortion. This occured because the detail of the door stop on the mold was too thin. Had I setup the part correctly with the door stop facing up for the first pour, then the stop would have had more backing and would not have warped.
If you look at the windows you can see a lot of flash that is covering those window stops too. Again if I had poured this side first I could have avoided that too.
 

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Oh,,, I had to remake this mold too. So far I've learned a couple of things on this project. REALY REALY seal wooden surfaces and make sure you put the most detailed side of a part up for the first pour.
 

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Discussion Starter #19

I poured my first piece for the roof today and assembled some of the cleanout pieces so I could check the fit on the Windows, Doors, and that tappered rail piece.
Everything seems to fit ok with minimal filing as long as all the parts are trimmed well.
 

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Discussion Starter #20

As you can see, I didn't calculate the amount of resin I would need to pour for the roof, so its kind of fragile because of the big air bubble running down the center.
 
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