The Craftmans Shop > Model Engineering
Side Valve i.c. engine from Bar stock
Brian Rupnow:
I found a mistake in the reamed hole size in the "crankshaft for side valve engine" and I have corrected it, but there doesn't seem to be any way to modify my previous post on this forum, so here is the same post with the error corrected.
So far, on this build, I have been making great speed machining the comparatively "easy" parts. I consider the hardest parts will probably be the cylinder and the combustion chamber, so I'm shying away from them so far. I guess that before I go much farther, I better have a crankshaft. It is a two piece crankshaft, which I haven't made before, with a primary half and a follower half. The fact that it is two piece lets me run a con rod with a needle bearing in the big end, which is not split.
Brian Rupnow:
Hmmmmmmm---The best laid plans of mice and men----I reamed the holes in my web plates with my 0.4985" reamer. I then went to press the 5.0005 drill rod into place. It was su7pposed to be a .002" interference fit. It didn't exactly fall through, but it sure as heck didn't press. So much for my "all press fitted" crankshaft. That will now be amended to "My silver soldered crankshaft!!!"
Brian Rupnow:
Just as I was all set up to start silver soldering, my wife called about some emergency connected with the new house. Seems that 3 year old grandson had managed to lock and close a bunch of doors that there were apparently no keys to unlock!!!--After dashing across town and applying my dormant burglary skills (which mostly involved beating on the locksets with my 3 pound hammer till the guts all fell out of the locksets) I got to thinking-----I really didn't want to solder the crankshaft. I wanted it all pressed together. Then I got to thinking, I have a lot of 5/8" cold rolled shaft ends about 10" long that some kind soul from Toronto or Orangeville brought me a couple of years ago. The simplest thing in the world would be to turn new crankshaft ends (They are only about 3" long) and bump up the end diameter to whatever size will be a hard press fit in the holes I reamed in the webs. I THINK I know why the reamed holes are larger than they were supposed to be.---Hindsight being 20/20, I think I was running the reamer too fast and that made it cut oversize. I know that the drill rod I have just re-measured is exactly 0.500, not the .5005 that I was expecting it to be, and it is a somewhat loose sliding fit in the reamed holes. This leads me to believe that if I make up a new crankshaft end that is 0.500 diameter for all of its length except the last 3/8" which I hold at .503" diameter, I should ultimately end up with what I wanted---all press fitted together. The follower end will be turned to 3/8" over its full length, again, except for the last 5/16" where I will hold the 0.503" diameter. This is holding things to closer tolerances than I am used to working to, but it will give me what I wanted.
Brian Rupnow:
It has been a rather upside down afternoon for me, and in all the excitement I forgot to post a couple of "in process" shots of the crankshaft webs. The shot where the two bars are clamped on the milling machine bed show the shaft holes being drilled and reamed, and the holes drilled which will give the 1/4" radius in the inside corners. The second shot shows where the excess material has been milled away, and both parts are almost completely separated from the parent stock. The next step, if I ever get there, is to press the webs onto the crankshaft ends, set them up in the lathe, and turn the outer diameter of the plates to the finished dimension.
Brian Rupnow:
IT WORKED!!!!! 0.503" was just the ticket. It was all I could do with my big nasty old mechanics vice to bring the shaft all the way thru the web, and then with a hollow socket backing the web up, about 3/8" more. Then I set it up in the lathe, cut the stub end off that was sticking thru, and finish machined the outer diameter of the web. Tomorrow will do the same to the follower half of the crankshaft.
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