Crankshaft information

[gbritnell]

I didn't want to hijack the 'newbie and the crankshaft' thread so I'll post another on the same topic for those is might help. This thread was started a couple of years ago by a member of HMEM. It was a link to a build article that I did on HSM. I was building my Holt crankshaft at that time. As has been stated many times in this forum there are many ways to arrive at the same point, relative to machining. If the goal is achieved that's all that matters but sometimes there are quicker and easier ways to get to that point. I learned to make crankshafts from building Stuart steam engines. When I bought my first casting kit, and instruction book, they explained how to turn the included crank forging that came with the kit. I have tried several other methods with mixed results so I generally go back to the solid type crank. Let me stray off for just a second. When I was an apprentice patternmaker we were always machining radiused corners on patterns and coreboxes. We had access to milling machines but not the duplicator or copy mills so when we wanted to put an accurate radius on a part we would make up a sine/cosine chart. Most of the old time machinists in our shop had a little book with standard radii for the cutter and the finished boss. It was just a matter of multiplying the book number times the sine/cosine and you would have a step off chart for the desired radius. I see people making quite elaborate setups to machine their parts. Sometimes the amount of work involved in doing this is much more than stepping off the corner of a part and a little hand filling. Being as the procedure that I have mentioned is a long lost process in this day off CNC I just wanted to mention it as a viable alternative to achieving and end. With all that said here's the link that I was talking about.
http://www.homemodelenginemachinist.com/index.php?topic=559.0
gbritnell

 

[deere_x475guy]

gbritnell, thanks for the link, nice clear explanation of how you did it. I have it book marked for future reference.

 

[bearcar1]

Gbritnell, that is an absolutely amazing piece of artistry. I have read articles pertaining to crank turning but never truly understood some of the methods used. You, having actually taken photos and included them with your description makes things a whole lot clearer in this feeble mind of mine. Perhaps one day I will gather enough courage to undertake such a complex piece, but for now I am content (but restless) in the more simple procedures. Thank you for sharing your experiences.

Jim B.