Author Topic: New crankshaft  (Read 1148 times)

Offline AlexS

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New crankshaft
« on: August 23, 2018, 08:51:32 PM »
Been busy around with other hobby's, work etc etc!

For my single-cylinder engine (55cc), I am working on making a new crankshaft (ehm crankwebs). The whole is carried out in material C45. As shown in the picture, the whole is pressed. This according to the same method as my previous crankshaft (see picture).

I want to turn and mill the crankwebs first. And then one of the crankweb realize the fit of the drive shaft. This first cheek I want to squeeze in one of the drive shaft.


Then I mount the crankpin for the bigend. Where then the second crankweb is compressed linear as possible.
To get the both driveshafts concentric, I had to turn the fit for the second drive shaft of the second crank cheek.
This I also applied for the previous crankshaft, this worked out well. However, the crankwebs were made of aluminum. Which caused a not so good fit between the crank cheeks and drive shafts. But were strong enough.

Given this reason, I am now going to use C45. And it also ensures an even stronger / stiffer crankshaft (Supercharge ready?? :-X). I want to secure the mounted axle in addition to the press fit. I am thinking to give the light a weld (TIG) or to braze.

My question is, what is sensible? Only apply a press fit? Or welding / soldering? The material could possibly deform and introduce additional stresses in the material.

Thanks in advance for thinking along!

Offline Roger B

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Re: New crankshaft
« Reply #1 on: August 24, 2018, 09:15:15 AM »
So far I have only machined crankshafts from solid bar but others have had good results with Loctite or similar. You would need to machine a clearance space for the Loctite as there is a defined thickness range that they work in.
Brazing or silver soldering would also work but again you would have to have clearance for the filler metal and be aware of possible distortion due to heat. I have no experience of TIG (but it's on my list of skills to learn  :headscratch: ).
Best regards

Roger

Offline gbritnell

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Re: New crankshaft
« Reply #2 on: August 24, 2018, 12:31:13 PM »
You could pin them or just lightly file several flats (a couple of thousands) and silver solder. The small flats would be enough for the solder to wick into.
gbritnell
Talent unshared is talent wasted.

Online b.lindsey

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Re: New crankshaft
« Reply #3 on: August 24, 2018, 04:56:52 PM »
Is there a hub on the outer part of each web that you can pin through. Not a big issue for the crankpin, but if there isn't a hub, that is a relatinely long distance to pin through the two shafts. I have had good luck using loctite and then pinning. I wouldn't rely on loctite alone.

Bill

Offline Tjark

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Re: New crankshaft
« Reply #4 on: August 24, 2018, 07:25:45 PM »
Hello Alex,

In the time i modified racing engines i tigged some crankshafts.
You can make a small weld on the inside off the web for the shafts and on the outside on the big endpin.
You do not fil with extra metal, but use the shaft and web metal.
You put very little head in the crank this way.

Regards Tjark.

Offline AlexS

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Re: New crankshaft
« Reply #5 on: August 25, 2018, 11:30:06 AM »
Thanks for all comments guys.

It would try to tigged the crankshaft after press it together. It is good to read that the application of heat should not be a big problem.