New Mold

[Jay Criswell]

I've been wanting to redo my 1:1 brass gearboxes for a long time. Lucky for me I have some talented friends. Jim Read did all the computer drawings, Terry Van Winkle verified they would work with his printer...and they did so he made a series of very fine resolution prints, destined to become masters. He handed off the new patterns to a shop in NY and they made a low shrink RTV mold. They shot four waxes and used them to cast four test shots in bronze. The bronze always looks mottled but when these are done in yellow brass by Valley Brass & Bronze (David Sciacca) they will look much nicer. So far, I'm very happy with the results.

Thank you for the help Jim & Terry. Obviously I couldn't have done it without you.

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Jay

[sleepmac]

Jay, beautiful!

Dan Weinhold

[E7]

I'll second Dan's comment!

Rich

[stephen neill]

Keep on keeping on Jay. They look great. We will of course want to know more as things continue to progress.
Steve

[PRR Man]

nice, nice... very nice.

[Jay Criswell]

Thanks Guys,

The way things look these are going to be far easier to prep (machine) for assembly.

Dropped the mold off at the foundry yesterday and asked David to cast up 40 or so. If they work out as well as they should I'll have him do another 100. That should last a while.

Jay

[stephen neill]

In my best Rufus imitation: You DROPPED it? I hope it didn't break.

Thanks for the update.

Merry Christmas to all.

Steve

[Jay Criswell]

It's rubber, like some checks, it will bounce.

[cole7015]

Jay do you have price figures on these yet?

Bill Basden Delta Models www.deltamodelsusa.com

[Jay Criswell]

Bill,

Same price I've been charging. $55.00 with customers choice of wheels (P:48 or O Scale, 30" to 42"). Input/output included.

The time consuming part is making the axles and input/output shafts. Actually, it's not making them that's time consuming, it's getting the correct dimensions. Axles and input/output are custom made to fit the customer's needs.

Jay

[R.K. Maroon]

Jay -- Thank you for providing the photos and an explanation of the number of steps involved in the process. It seem like quite an investment of time, effort, and (I imagine) cost.

Two questions:

1. Did you have an "old mold" to do these or were they previously hogouts?'

2. I have always been curious as to how one machines the two bores in such a gearbox. Specifically, do you establish a datum surface, such as one of the outside flat surfaces of the case, to serve as a reference for machining both shaft bores, or is there some clever way to directly locate the second bore to the first bore?

Jim

[Jay Criswell]

Jim,

The old masters were hand made buy lacking the accuracy I desired. The molds made from these masters carried the flaws right into the castings. The machining required to make them acceptable was way too time consuming. Yes there was tooling and fixtures used to hold them in place while they were drilled, milled, tapped, etc.

The new masters were made using 3d printing. No, not the Shapeways crap. The machines used for this are the high end models with very fine resolution. The resulting master require very little machining. Drilling and tapping are still needed. High speed burrs and 6 flute end mills are used for any minor clean up.

Jay

[Jay Criswell]

Jim,

I suppose that was a rather lame reply. I'll see if I can come up with something a little more in depth.

Jay

[big bad jim]

The boxes are looking good Jay. It's always nice to see things come to fruition. You should bring an example along to Chicago so that I can check them out in person.

Jim

[bob turner]

I thought it was a pretty good explanation. Lost wax can be pretty accurate if your masters are ok.