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+--- Thread: Alternative crank bearings (/showthread.php?tid=2453)
RE: Alternative crank bearings - Zetomagneto - 28-02-2019
Hi Tony, I know at least one racer who uses 2 ordinary ball races at the front because they are readily available, a cheaper alternative, and do the job to his satisfaction.
Seems to me it comes down to personal choice.
We haven’t seen anything that won’t work, or is poorly engineered (yet!)
I think any type of ball or roller of the correct physical dimensions would allow 7000RPM
RE: Alternative crank bearings - Ruairidh Dunford - 28-02-2019
Allowing 7000rpm is the easy bit - getting there, and proving they work...
RE: Alternative crank bearings - Zetomagneto - 28-02-2019
Well you can’t get much more basic than standard rear roller, and 2 ordinary ball bearings at the front, it has been proven to work over many years by a well respected racer we all know.
RE: Alternative crank bearings - Ruairidh Dunford - 28-02-2019
Edzackerly!
RE: Alternative crank bearings - dickie65 - 28-02-2019
I am very interested in this set up, I am just about to put another engine together which will be for Hill climbs and fast road.
I suspect that this set up works best with a stiff 1 1/2" crank in which case the self aligning would not be critical as the crank will not whip much compared with an 1 5/16" one.
I have the standard bearing set up in my current engine.
So I am game to give this set up a try in my replacement engine.
I am just collecting a few bits together so this is perfect timing for me as I have not ordered any bearings yet.
RE: Alternative crank bearings - Zetomagneto - 01-03-2019
Interested to know your reasons for favouring this setup when there are numerous options available
RE: Alternative crank bearings - Zetomagneto - 01-03-2019
Has anyone tried the Hoffman P type mentioned in the companion?
RE: Alternative crank bearings - Terrytuned - 01-03-2019
Zeto I have used them they are the same outer cage as a MMRJ but the centre sleeve has a rear shoulder that butts against the crank when fitting just have to make sure the rollers are not up against the shoulder. Terry
RE: Alternative crank bearings - Zetomagneto - 01-03-2019
Yes, it did occur to me that would be a possibility and that some shims or machining would be needed.
Your usage of MMRJ1-1/4 is imho an excellent choice, thanks for sharing
RE: Alternative crank bearings - Bob Culver - 08-03-2019
Curiously I notice in the Pitman book a diagram "The Front End of the Sports Seven Crankshaft", presumably taken from an owners handbook, depicts two conventional ball races, inner rings same width as outers. Not drawn as a.c. might have been the same guy who drew the rear axle pinion in the parts books....