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Heat shrink fitting and crankshaft balancing.

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bp:
No I think he means a shoulder.  On your 10.00mm dia shaft, at each end for a length of the web thickness (8mm?) reduce the diameter to (say) 9.80mm, in the web generate a hole 9.78/9.79mm diameter, preferably by reaming, a good finish anyway.  Think really hard to figure out EXACTLY how you will assemble everything, maintaining squareness is vital and then practise how you will assemble everything when one bit is REALLY hot, bear in mind that considerable force will be required which is why its called an interference fit.  Some sort of vice or press is really good, a hammer would be very much a last resort.  Warm up the web(domestic oven hot as possible for half an hour), cool down the shaft (domestic fridge for half an hour) and press one onto t'other using your considered and practised process.
cheers
Bill Pudney
Adelaide, Australia

Country Bubba:
If'in a dumb ole country boy can jump in on this thread,  back many years ago, I used to work on "American Indian" motorcycles and the crank pins were on a taper and had threaded ends.  You would assemble the rods with the roller bearings and then use a stand with centers to get the two crankshaft ends to line up properly. I think Harley also used this type of thing.

Country bubba

 

bp:
yup ole country boy, not only Injuns and the other one, but in the UK some of the biggish singles (350 & 500) had a similar set up.  Getting a fine taper to pull up EXACTLY where you want it too might be a challenge though, and then having enough space to use a (special) nut to stop it all falling apart.  From memory most of the UK manufacturers used a parallel pin, with a very accurately ground diameter, going into an accurately ground bore, all held together with a very fine threaded nut.  BSA on their Gold Stars even used rivets to secure the flywheels to the outer bits of the crankshaft, instead of a nut, Victorian engineering at its best!!
cheers
Bill Pudney
Adelaide, Australia

picclock:
Hi Bill

That makes much more sense. I was planning to heat the webs to 5-600C with a torch then use an old scrap drill press (once I got my mill its never been used) to push the shaft squarely into the hole.  

OK I've done some calculations that indicate that the difference in size due to expansion, at 600C is only 2.9 thou, thats 0.074mm. I think that may be achieveable. I can always make the shaft ends +2.5 thou then up the temperature to 800 for clearance.  I think its doable for a shaft into a web. But to get the webs accurately aligned with bearings on certainly sounds more challenging. I can fit two shafts into 1 web x2 for the ends with no special alignment. The centre portion of the main shaft will need two webs fitting which must be at 180 degrees and have a needle roller fitted inbetween. Then I need to fit the end assemblies with needle rollers parallel to their respective central webs.  

My main concern is the web alignment, with bearing damage or contamination next. I may have to rethink this.

Other possibilities that come to mind are a tight press fit with an 8mm csk hex screw in the end, or welding (yuk).

Many thanks

picclock

John Rudd:
When I rebuilt cranks for my motorbike many years ago, I had access to a 20 ton press...
Even with the tight tolerances it took nearly 10ton  :bugeye: to reassemble and everything was absolutely clean...


--- Quote ---Then I need to fit the end assemblies with needle rollers parallel to their respective central webs. 

--- End quote ---
Are you using thrust washers as well? You will need to allow for some side clearance....

Good luck with it.. :beer:

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