Author Topic: Old School Barstock 2 Stroke  (Read 79341 times)

Offline ShopShoe

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Re: Old School Barstock 2 Stroke
« Reply #360 on: May 02, 2016, 01:41:28 PM »
That's running pretty well, Brian. I have followed and enjoyed the whole project, as always.

Thanks for posting the project with your reasoning for each step of the design.

ShopShoe

Offline Brian Rupnow

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Re: Old School Barstock 2 Stroke
« Reply #361 on: May 04, 2016, 11:52:51 PM »
After running the engine for about 20 minutes with the new ball bearings, I noticed that the flywheel was beginning to wobble. I shut the motor off, and sure enough, the crankshaft end with the flywheel on it was quite "wobbly" in the bearings. If I hadn't seen it myself, I would have said that was impossible. They were good quality name brand ball bearings, but after the grease shields wore in a bit, there was enough clearance in the bearings that with two bearings setting side by side like I had them, they allowed the shaft to wobble quite noticeably. So----I took a page from Jason's book. I had already determined on my first go-round with this engine that brass was simply too soft a material for a bushing, as the brass bushings wore out very rapidly. I don't know if this had anything to do with lack of lubrication or not, although I doubt it. So---this time on the crankshaft side only, I made up a new aluminum housing with an insert of 7/8" diameter #660 bronze, which I bored .001" undersize, then lapped the crankshaft into it with #600 carborundum paste. I added an oiler that I had made way back when I built my Kerzel engine, and a steel tube which supports the oiler and runs to the center of the bronze bushing. Time will tell if this was a good idea or not!!

Offline Rustkolector

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Re: Old School Barstock 2 Stroke
« Reply #362 on: May 05, 2016, 04:13:58 AM »
Brian,
I would refrain from using carborundum lapping compound in any bronze bushing that you want to last a long time. I have always been told to use a non-embedding lapping compound with soft metals as hard lapping compounds embed in the softer metal and will continue to cut the harder metal shaft during use. Also, did you fix the crankshaft to the inner races of the ball bearings you used earlier? If not, the harder inner bearing races will likely slip and wear the shaft rather quickly in an engine. It even happens on electric motors.

Jeff


Offline Jasonb

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Re: Old School Barstock 2 Stroke
« Reply #363 on: May 05, 2016, 07:37:41 AM »
The bronze is the better material and what I tend to use. Also not had poblems using lapping compound.

I don't think you will be able to do it on yours as the cylinder is part of the crankcase but the 2-stroke I'm working on has a couple of holes from the crankcase into the bearings so the crankcase pressure pushes some of the lubricant laden fuel/air mix down to the bearing surface. As well a using 2-stroke mix it also has a drip feed oiler into the carb for that added bit of oiling.

J

Offline Ian S C

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Re: Old School Barstock 2 Stroke
« Reply #364 on: May 05, 2016, 01:15:17 PM »
A bit of cast iron will make a good wearing bush.
Ian S C

Offline Brian Rupnow

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Re: Old School Barstock 2 Stroke
« Reply #365 on: May 06, 2016, 01:31:49 AM »
Everything is reassembled, and I have had a couple of good long runs with the engine. I had to remove the 3/8" thick addition I made to the engine side of the flywheel when I added the oiler pipe, and the engine absolutely would not run without it. So---I moved the added piece from inboard of the flywheel to the outside of the flywheel and that did the trick. I built this engine based on plans that came with a casting kit, and if I was doing it again, I would make the bearing housing on the flywheel side twice as long to get more separation between the bearings, and make the crankshaft longer on that side. The engine would also benefit greatly from a flywheel that was about 1/2" larger in diameter than the plan called for.

Offline Art K

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Re: Old School Barstock 2 Stroke
« Reply #366 on: May 06, 2016, 02:35:46 AM »
Brian,
I am glad to hear it run so well. I always enjoy your builds as I learn from them as well.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

 

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