Mark VII speed control

richardrouse · Post by **richardrouse** » Fri Oct 09, 2015 9:13 am

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3d Printed speed control cam...

Needs to undergo testing, but it looks promising.

nothungry3 · Post by **nothungry3** » Fri Oct 09, 2015 8:04 pm

Wow!
What is the material? Do you know any physical properties?
What do you think of the feasibility of making a rack? How long would the segments be?
Jack

richardrouse · Post by **richardrouse** » Fri Oct 09, 2015 8:21 pm

It's an abs thermo plastic. As soon as I get my motor bearings, I'll put the cam through its paces. I expect it to perform as well as the original plastic piece.

As for the racks, I'm limited by an 8" bed..

But I was thinking about that .

Has anyone ever tried to cast them with a poly resin?

We could create a mold by vacuum forming a plastic sheet around a good section of rack .. Then pour the poly resin into the mold. We would have to allow it to cure with a way tube (or something of comparable od) on the back part of the mold.

They wouldn't be as cheap as a 3d printed part, but they wouldn't be as expensive as say machining them out of vinyl or poly carbonate bars either.

JPG · Post by **JPG** » Sat Oct 10, 2015 12:53 am

The original racks are two 15" pieces with 3 rivets each.

4 7 1/2" pieces with two rivets each should work.

richardrouse · Post by **richardrouse** » Sat Oct 10, 2015 12:59 pm

I'm game to try it. Let's get the cam good, and then work out the gears.

lwmccord · Post by **lwmccord** » Sat Oct 10, 2015 9:27 pm

I would be interested in one of these when you think it is a go.

richardrouse · Post by **richardrouse** » Mon Oct 12, 2015 11:23 am

I'll know here in another couple of days.

I got my motor bearings, I just need to get those pressed on and get everything reassembled.

Geometrically speaking this cam is pretty good. It fits the speed changer shaft and the roll pin hole is in the right spot.

It'll just be a matter of trying it out.

JPG · Post by **JPG** » Wed Oct 14, 2015 12:40 am

...

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BuckeyeDennis · Post by **BuckeyeDennis** » Wed Oct 14, 2015 7:48 am

I suppose that one could buy this rack and then machine it to size. A bit pricy, though. Molded racks are more reasonable, at about 10 bucks per foot, but I couldn't find any in 12 pitch -- 16 pitch was the coarsest.

richardrouse · Post by **richardrouse** » Wed Oct 14, 2015 1:09 pm

Thanks to JPG for the drawing.

If we do this with the 3d printer, we are looking at 10 bucks per cubic inch. Using JPG's drawings I'm guestimating the cost for 4 7.5" sections to be around 60 bucks.

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