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+--- Thread: Alternative crank bearings (/showthread.php?tid=2453)
Alternative crank bearings - Terrytuned - 27-02-2019
Photos of the alternative crank bearing I use for high revving engines, the triple front bearing set up gives a free spinning crank with no preload
but plenty of thrust capability, the single track front bearing helps keep the timing gears in mesh. At the rear the separate centre sleeve of the
bearing can be pressed on the crank before fitting into the c/case which makes assembly or removal much easier (although I have never had
to replace one) or use a standard MRJ 1 1/4 preferably with a brass cage.
Terry.
RE: Alternative crank bearings - Zetomagneto - 27-02-2019
Great info Terry, thanks very much.
A real advantage using that rear main if the crank goes in with it already in place particularly with a Phoenix crank which don't give good access to get the track off.
RE: Alternative crank bearings - Ritchie Wilson - 27-02-2019
Thanks Terry I fond that most useful. Do you always use the same brands of bearings?
RE: Alternative crank bearings - Alan - 27-02-2019
I’ve used MMRJ bearings for the rear main, always. They seem to have a much longer life than the standard item, although they are a bit more expensive. I think the grooved outer track retains oil and lubricates the first few seconds after start up. Maybe the standard bearing runs dry and wears more quickly.
RE: Alternative crank bearings - Ruairidh Dunford - 27-02-2019
(27-02-2019, 10:39 PM)Alan Wrote: I think the grooved outer track retains oil and lubricates the first few seconds after start up. Maybe the standard bearing runs dry and wears more quickly.
That makes a lot of sense and I too like the look of that particular design.
RE: Alternative crank bearings - Mark McKibbin - 27-02-2019
I am about to replace my crank so this interests me, however with the preloaded bearings there would be no end play at all but surely a single track ball race would have some, and over time would this could effect the timing gears?
RE: Alternative crank bearings - Tony Press - 28-02-2019
I cannot see the benefit of fitting a single row deep groove ball bearing and a double row self aligning bearing on the front of an Austin Seven crankshaft.
The self aligning capability is negated by the ball bearing although the drsa bearing rolls a little more easily than say a roller bearing.
The original ball and roller bearing combination gave a radial load capacity and axial capacity which with similar internal radial clearances the bearing loads would be shared reasonably well.
The axial movement due to radial clearance in the single row deep groove ball bearing would be somewhere about 3 to 4 times the radial clearance - around 2-3 thou mounted and the engine survived on this end float until the pair of angular contact ball bearings were introduced, probably giving about 0 to 1 thou end float with standard bearings nowadays.
The suggestion about the flanged outer ring rear roller bearing retaining oil could be correct but it would seem to be difficult to remove the plain inner ring from the crankshaft.
RE: Alternative crank bearings - Ruairidh Dunford - 28-02-2019
And yet, it works - very well indeed.
Thank you for sharing Terry.
RE: Alternative crank bearings - Zetomagneto - 28-02-2019
Tony, I can't see how it would be difficult to get the inner track off the crank, especially as the crank can be removed from the case with the track still fitted so removal can take place on the bench.
I definitely like the idea and will use it.
I couldn't see the reason for the self aligning bearing at the front together with the deep ball bearing
but it obviously works, and Terry will have good reason to use it.I can't see any reason not to use it.
Bear in mind this is a race engine so not subject to the mileage of a road car.
RE: Alternative crank bearings - Hedd_Jones - 28-02-2019
(27-02-2019, 11:23 PM)Mark McKibbin Wrote: I am about to replace my crank so this interests me, however with the preloaded bearings there would be no end play at all but surely a single track ball race would have some, and over time would this could effect the timing gears?
I bought a 'used' engine from the late Mick Kirkland for my Saloon. It was fairly worn but a runner (and mick was 100% honest as you would expect and the price reflected it). It went in my saloon after some TLC which included loctiting the loose inner rear race on the crank. Decoke, some studs etc. At the time I was young (17) and whilst I noticed a lot of end float in the crank (approx 1/16 inch) but went with it in anycase.
The engine went like a rocket, was smooth and quiet, yet it burnt a lot of oil, and made lots of smoke out of the valve chest cover. I did lots of miles in it.
Eventually, say 5000 miles later, it developed an intermittent knock arriving at Kemble near Cirencester having driven there from Whichurch (Salop) via my work in Birmingham. I nevertheless drove it home after the event, via Birdlip, Hope Under Dinmore A49 etc.
When I eventually took the engine out and dismantled it, I found nearly 1/8 of end float on the crank which allowed the crank to touch the cam centre bearing, the source of the intermittent knock. There was also about 50 tho end float on the cam. There was no visible issues with the timing gears, and I think they are currently on the engine in my chummy. It was a earlyish coil engine, so a ball and a roller front.
So in My experience, suggests not.