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"Old Porcupine"


Art Anderson

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Very cool, Art. Did you drill all of the holes before attaching the rods? Did you wear out your dividing head? :) Will you be doing the rest of the car? :blink:

Andy,

Yeah, I drilled every single hole. For those who don't know, I finally sprung for a Sherline vertical mill, with about $700 worth of toys to go with it, one of which is the rotary milling table, which is screw-driven, indexible to 1/10 of a degree. Each hole required two drilling operations, as I was too chicken to buy carbide center drills longer than their diameters (those things break almost by looking at them!). So, each .020" hole was deepened to .040" with an ordinary #76 drill bit, using the same setup. Just drilling the holes took a total of about 8 hours. Each brass pin is a light press-fit into its hole, needle nose pliers, and my sprue nippers got a workout. Truing up the ends took a lot of thought, get them all to the same length, and nice and flat on the ends. Finally, I came up with the idea of using a pad of 400-grit sandpaper, held against the side of a tool post on my Sherline lathe (which I've had for nearly 30 years), and GENTLY advancing that tool post against the pins, which I rotated at a fairly slow speed in the lathe. As you can see, that worked perfectly!

The crankshaft was also simple. It's made with 1/8" square brass bar stock, milled down on one side to .080", then drilled for 1/16" rod stock, to make the crank throws. The crankshaft itself is 3/32" round stock, actually K&S tubing over 1/16" rod (that made for easier drilling of the crank throws). The connecting rod was milled out of the same quarter-inch bar stock, fishmouthed at one end, for the big end of the rod, the other end crossdrilled for a wrist pin, and inserted into a dummy piston, for proper alignment in the cylinder bore--all this for looks, the crank won't rotate, and the piston is in a very short bore, but I think I captured the look I want.

These engines, like most early internal combustion engines, was lubed pretty much like industrial/agricultural steam engines, with mechanical lubricators where needed, the rest by either drip or splash. The crankcase you see will remain open, as those early engines were "total loss' oil system units--again, steam engine technology.

Oh and yes, this one will be a complete vehicle--a 3/4 ton canopy delivery truck. Stay tuned!

Art

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Hey Art!

I am always impressed with your problem solving and methodology. I always learn something from every one of your started modeling efforts. I only hope I live long enough to see another one finished.... :lol::lol:B)

Well Dave, this one will progress rather quickly. With the Knox, the engine was going to be the tough part going in, the rest of the truck is no more complex than a hammer and a 10-penny nail. The only real challenge left is laying out the fore-and-aft leaf springs, making sure that they have exactly the same arch side-to-side, and allow for the correct wheelbase.

Art

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Some progress:

I finished the carburetor today. I've heard of "cotton wick" carburetors, sorta understood the principle of them, but hadn't ever seen pics of one until I started researching the Knox. Basically, they were very simple, primitive by modern standards, using a large cotton "wick" inside a pipe that was perforated with many holes to admit air. Gasoline flowed onto that wick, and with each intake stroke, the rush of air through the perforations evaporated the gasoline, then the piston drew the vapor into the cylinder through an atmospheric pressure operated intake valve (still to be added). While unsuitable for multi-cylinder engines, it probably worked quite well for a single cylinder unit, turning perhaps between 500 and 1000 rpms.

enginewithcarburetorinstalled1-vi.jpg

Also added are the flywheel, and the basic transmission drums, turned from clear acrylic plastic bar stock.

enginewithcarburetorinstalled2-vi.jpg

More to come, so stay tuned!

Art

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