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Old Mar 01, 2012, 10:00 PM
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Idea
Machine shop project 4 cylinder cox?

In machine shop, I though about me and my friends making a inline 4 cylinder cox motor, from a bunch of old .049 engines we got at a garage sale. We would separately fabricate a little engine block, crank shaft and a head design that is able to be made on a small cnc machine. Could a tiny carburetor be shanghai'd onto the cylinders with a miniature manifold thing? Or does any body have a better plan? Thanks

~ charlie
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Old Mar 01, 2012, 11:55 PM
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Quote:
Originally Posted by Charlie ricker View Post
In machine shop, I though about me and my friends making a inline 4 cylinder cox motor, from a bunch of old .049 engines we got at a garage sale. We would separately fabricate a little engine block, crank shaft and a head design that is able to be made on a small cnc machine. Could a tiny carburetor be shanghai'd onto the cylinders with a miniature manifold thing? Or does any body have a better plan? Thanks

~ charlie
Here is a 4 inline, not entirely finished yet, built from a Model Engine Builder magazinewith plan inside. I believe you can still get the back issues.
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Old Mar 02, 2012, 08:52 AM
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cox 4 cylinder (0 min 14 sec)
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Old Mar 02, 2012, 10:59 AM
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I bought the plans for the engine from the designer of it.
Model Engine News Referenced it too. http://modelenginenews.org/ed.2006.11.html#9
He had a website for it, along with free plans for the two cylinder Hex engine too.
It is the Hex-2 and Hex-4 model engines. He also sells the special tap needed for the cylinder threads.
He was working on a V-twin and V-four when I last looked too.
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Old Mar 03, 2012, 06:13 AM
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I forgot, but here is the URL to his website http://www.jamesengine.com/index_files/Page486.htm
This is for the Hex-2 and Hex-4 plus the V-4 he is tinkering with.
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Old Mar 03, 2012, 02:17 PM
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Aaah!! The drawings clear up a lot. At first, I couldn't figure out how he was managing his mixture induction and crankcase compression. I wonder how much drag the induction/crankpin journal adds to the system?
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Old Mar 03, 2012, 07:53 PM
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There is some drag and a loss of efficiency of course. The 4 cylinder engine of which four .049's makes it about a .20 displacement, turns a 8x6 prop at around 7,200 RPMs. But that could be improved on with better intake port timing maybe. The engine might work better with a larger prop as it may develop better lower RPM power than high speed. The main thing one needs to make the engine is the 17/32-40 Tap for threading each of the cylinder holes. He used to sell the tap, I don't know if he does anymore now. You could do it on a lathe, but you are talking some serious jig and fixture work to do all four holes.
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Old Mar 04, 2012, 10:03 AM
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On the Hex 2, does the stroke setup negate the crankcase pressure? If not, how is it prevented from blowing out of the venturi?
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Old Mar 04, 2012, 02:17 PM
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Godsey --

The center section of the crankshaft serves as an induction valve for timing intake to each cylinder and as a partition, separating the crankcases from each other. Think of the center section as working much like the induction valving on a Tee Dee .049, except that it has two slots, one feeding the forward cylinder and one feeding the rear cylinder.
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Old Mar 05, 2012, 01:53 AM
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Quote:
Originally Posted by earlwb View Post
I bought the plans for the engine from the designer of it.
Model Engine News Referenced it too. http://modelenginenews.org/ed.2006.11.html#9
He had a website for it, along with free plans for the two cylinder Hex engine too.
It is the Hex-2 and Hex-4 model engines. He also sells the special tap needed for the cylinder threads.
He was working on a V-twin and V-four when I last looked too.
Here are my tap and dies for the Cox 049 and the Cox 020. The maker is Widell-USA the 020 tap made by Courvelle-Gavelle in France. That last one cost me 342$ to have special made !!! I believe the others were made to special order as well, costly in any case. And soon after I did find out someone on ebay did have these for sale, probably the guy you mentionned.
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Old Mar 05, 2012, 02:04 AM
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Cox 4

Two pictures of the internal parts
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Old Mar 05, 2012, 06:28 AM
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Cool pics, thanks for sharing Reginald.
Yeah, I think JamesEngines was selling the 17/32-40 taps at the time I bought mine from him as well as the plans. I think he had a batch made as the cost was quite reasonable at the time (albeit still more expensive than regular common taps). I don't see anyone selling the smaller 25/64-48 taps at this time. So one would have to have it custom made.
I think the cost has gone up a lot since I bought my tap, one place wanted US $109.99 for one, but it was out of stock. The die was like US $160 too. I just looked back at my old emails and I paid US $48 for the 17/32-40 tap that I bought from James Engines back a couple of years ago. He only had 5 left at the time though.
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Old Mar 05, 2012, 09:03 AM
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Taps and dies for the cylinder are only one way to make the crankcase. A thread cutting lathe will cut both internal and external threads for these parts. Sometimes you have to be creative with holding parts like crankcases. While the James engine is simple, I don't think it's very useful. I like the Schroeder twin.

I picked up this picture of the net somewhere. I don't know who made these.

Greg
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Old Mar 05, 2012, 01:42 PM
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gkamysz, yes you are correct. But it will be arguably more tricky doing it like that with a thread cutting attachment on a lathe.
Now those are some pretty neat multi-cylinder engines there in those pics too.
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Old Mar 05, 2012, 04:34 PM
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Earl, I wouldn't know. I thread a lot on the lathe and large diameter fine pitch threads like this would be done in my cnc mill.

I'm sort of like the boxer idea for my cox cylinder project. Haven't decided yet.

Greg
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