more work to do

I don't believe you would have to pour the resin in a vacuum state. just pour the mold normally then stick the mold in the chamber after its poured and turn the vacuum on, it should suck all the bubbles out in its poured state. well that's what they do for lost wax casting anyhow. worth a try?

 Thank you. It sounds stupid but I didn't know what they were describing. They show a cup in a vacuum chamber?

Is that the mix? It would start to harden.

Is that just one part (of the mix)? that wouldn't make sense.

So it must be the part after pouring. It didn't seem like the vacuum would pull the trapped air all the way thru a part if it's trapped in the wrong place I thought.

Working under the time constraints of the open pot life, some of the mixes only give you a minute to do everything?

 So I figured it would be best to work inside the larger disposable chamber to speed things up. Maybe introduce some nitrogen to replace the air drawn out? Still haven't tried it.

Interesting topic Joe.  Good luck with it!

 

 It would be nice if a service tech would chime in and give us the MTH pn for the various scale wheel pilots.  

 

I've always mixed mold rubber and then placed it in a vacuum chamber to get air bubbles out. Mold resin however I pour into the mold and then put it under pressure.

 

....I've called MTH several times on this and so have a few other people to no avail...MTH will not give us a part # nor will they sell it, not even to a MTH service center.  There was even a thread on their Facebook page with ppl begging that got shut down.  I don't get it...

 I'm only guessing here:

I think they won't sell too many fixed pilots. I bet there was big demand and they don't like to sell more parts than engines. Moral: order the fixed pilot version.

 I don't mind any thing like this coming up. What really got me started was that it seemed like they went backwards with new models. They had announced moving forward with more scale versions. In reality, they didn't. I think some of the molds wouldn't have worked for fixed pilots?

 I had a GE and a EMD version of a spare fixed pilot from them. I was never able to get any more of them. Hence, my guessing.

 I'm getting better results casting pilots with a few re-design ideas that help with trapped air. Starting with a small intricate part was very difficult. I had to learn to be a little more wasteful. Exact raw material measurements don't work out when things go wrong. Leaking molds, etc. I casted a high strength product that was thicker and finally got a good cast. It still seems too brittle so it may need more time to dry or it's a stale product?

 I think I've got my mold design down and is repeatable. I have to make another master and hopefully the mold comes out perfect,..... or at least close.

 Then, I'll have to make more designs for different engines. Are there certain engines that guys would buy fixed pilots for? Would you give me exact models? If I can work it out, I may make them for others, at least popular ones.

 I would have to try a small scale test to see what others think is acceptable of my casts. There always seems to be some level of imperfection. I have sanded some that are on the back side towards the trucks for example. There are holes in the master for hoses too that may not be desired?

Enginear joe here is a video of lost wax casting tutorial that shows the vaccum idea. fast forward to about 2:30 of the video to see    http://www.youtube.com/watch?v=yFbmtJyBthg

 

also have you thought about drawing up the pilot in Sketch up and having it printed on shapeways as a alternative?

Joe, as far as I can tell, the AC4400, ES44, CW40-8, and The C40-8 all have the same pilot.  Other popular ones would be SD70aces, Sd70macs, or Ac6000.  I think the mth gp40's and Gp38's are the same pilot as well.  If you are happy with the way they come out, I am definitely interested in ordering a few!  Great work, and good luck.

 

Paul

I need a pair of the exact pilot your making there...maybe more.  I'll buy to answer your question.

 I just watched that whole video. Lots of stuff for me to learn about there. It would be cool to advance to a better material like Mike suggested before. I don't have access to some of that equipment anymore like in my ceramic days.

 One other thing would be to see how each available casting material survives in this environment. I'd pull a hundred cars or so but some times an accidental smash maybe needed to see?

 I have heard that castable plastics don't due well in sunlight unless metal powders are added. I have watched about a dozen videos trying to absorb all of this process. I didn't think vacuum was necessary with the right plastic and mold design. I did have a mold that was flawed itself from trapped air on the master. I thought this whole process was going to be easier. I will perfect it as I go.

 Stay tuned as I produce enough to get a small supply of good ones. I had needed the ACe pilot myself, so that's where I started. My GE's pilot pour came out losy and it was a less detailed version? I have not redesigned the mold yet for that.

 I'll have to check further on what fit's what. Thanks for the help there. When I bought older engines, I realized that pilots would need customizing for them. I really thought there would be more models of them. Lucky, I have a good supply of engines to compare!