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Tip
Aluminium casings, including wheel hubs, can get a terrifically
firm grip on bearings, which actually drop out without any problem,
when the casing is hot. The trick is to heat the casing evenly to
avoid distortion. Blowlamps are frowned upon as providing too much
localised heat, a bucket of boiling water used to be the recommended
method. Much easier if you have one, is to use a hot air gun paintstripper.
When fitting new bearings to crankshafts, it is worthwhile after
fitting it into the engine casing, to try the bearing on the shaft
prior to trying to close the crankcase halves together. It should
slide home up the shaft easily but with some slight resistance.
If it were so tight as to need other than just a gentle tap with
a soft mallet it would be as well to 'relieve' the shaft by polishing
it with emery tape.
It should not
be necessary to "force" crankcase halves together. If
the bearings are a sliding fit on the shafts and you can't close
the joint faces, then something is out of place, (most probably
a gear or selector shaft in the case of unit construction engines).
Check and try again, don't ever do as I once saw a mechanic do,
squeeze it together in a bench vice!
| Comments |
| Sporty Steve 5th March 01 | Good articles, I was just wondering if we are going to get any that are on modern bikes rather than the old ones. (it's a bit before my time!)
| | Barry Swanson 22nd April 01 | I THINK I'VE GOOFED....the wheel bearings (tapered rollers) in my old trumpet were a bit sad, and as we couldn't find replacements, the engineer I use said "why not build a new axel that will take lateral thrust, and fit modern ball races", which we did, ...smooth as silk.
Yesterday I was telling a more experienced bike person than I this story, and he thought that ball-type bearings would not be up to the stress placed on them by a rigid frame,I had this sudden chilly feeling run up my spine as the logic of it hit home,.......your thoughts and comments?
Barry
| | Trivena 23rd April 01 | Barry, you could also post this in the Total Bike Bits Forum too, you will most likely get some good advice. Good Luck.
| | beano 13th July 01 | I don't think Barry Swanson need worry too much about using ball wheelbearings in his rigid model. Ponder this -
a)Not all rigid models used taper bearings, mainly heavyweights & sidecar models.
b)Roads are much smoother now (aren't they?) so not so many shocks
c)50+ years on we have better quality balls?
| | TonyC 12th October 02 | I recently changed a "pull-apart" roller bearing on the left side of the crank in my '70 Bonnie and found that there are different fits between inner and outer race! These are known as C1, C2, C3, CN & possibly C4. C1 being the lowest clearance, CN the normal clearance as used commercially. I read an article in the Bonneville Gold Portfolio Book by an ex Meriden engineer Harry Woolridge who strongly recommended using C1's as did the factory (avoided "mains knock" when hot). These unfortunately seem impossible to get now and I had to settle for C2's. Is this variety of fit commonly available for most bearings?
| | Beano 19th November 02 | Taper-roller head bearings. A worthwhile mod. Not available for many brits, but are for most Jap and European. Did you know that some good quality aftermarket sets are the same brands as sold for washing machine drums? Check the sizes required - the washing machine bearings sell at half the price. You could also check with your local bearing stockist - the dimensions required will be ID, OD and thickness of the original set in assembled state.
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