Crankshaft bearings

[John Cornforth]

Hi derekn

Not wishing to add to your workload, but you say "I have purchased the standard 2 bearings for the front". The front bearing inner and outer race thicknesses must be such as to give an acceptable amount of preload. Off the shelf bearings may need a little grinding or shimming to achieve this.

More information is available here on the forum for the asking. If you already know all about preload, ignore my comments.

[derekn]

Thanks everybody for your contributions when I asked for help regarding the back end bearing on the crankshaft of my RP. On closer inspection, it is obvious that the end of the shaft has been ground down to a slightly smaller diameter than the standard bearing size. I have found a local engineer who says it is a common problem when reconditioning engines and has the equipment to put a collar on the end of the shaft and grind it to fit the standard Austin 7 bearing. However, before we go down that road, with his help, we will see if we can find a modern metric sized bearing which will fit on the shaft as it is. If we can’t find one we will put the collar on the end of the shaft. Hopefully we’ll solve the problem one way or another. Thanks again, it’s good to know the knowledge is out there. Regards, Derek.

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Hi derekn

Not wishing to add to your workload, but you say "I have purchased the standard 2 bearings for the front".  The front bearing inner and outer race thicknesses must be such as to give an acceptable amount of preload.  Off the shelf bearings may need a little grinding or shimming to achieve this. 

More information is available here on the forum for the asking.  If you already know all about preload, ignore my comments.

Many thanks John, I’ll follow up on that.  Derek

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I had a similar problem with my RP's rear crankshaft bearing, although I know that the old one had spun on the rear journal. My new bearing was no more than a good push fit on the crank, so I used some Loctite bearing fit to secure it.No problems is the 8K or so miles since this was done.

I know that there are some members who don't like Loctite as it can make the rear main difficult to remove again. However, Loctite is destroyed by heating to about 300 degrees centigrade, so warming the bearing inner race with a blow torch should release it.

I used a 'crowded roller' replacement bearing from Seven Workshops (See my thread from April 2019 entitled "Rear Main Bearing") so, when the outer track is removed, all the rollers will fall out enabling the crank with the neer track to be removed and dismantled on the bench.

Thanks David, I think we have found a solution - putting a collar on the shaft and and grinding it to fit a standard Austin 7 bearing. Derek

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what markings did the old bearing have on the edges of the outer race.

it may at least have a company stamp, rm rhp etc.

it may even be stamped with a size?

tony.

Hi Tony, the outer race had 1.1/4 inches stamped on it. The manufacturer seems to be ‘R & M made in England’.  The inner race is 8 thou undersize on its inner diameter onto the shaft.  It was probably put on in the 1960s.  Unless I can find a modern metric one which will fit, it looks like I’m going to have to have a collar fitted on the shaft and have it ground to fit the new Austin 7 bearing I have got. Derek

[Bob Culver]

Has anyone ever encounterd this before? Could have been a good market for!
has the inner ring been internally hard chrome plated?
(Eons ago when I was very green I found the clutch splines were very worn, male and female. I had rebuilt the gearbox splitting the cluster to avoid mismatching gears (as old books advised) and could not face rebuilding the gearbox again. Had the clutch splines built up. Has done many miles. I did not then know about the fatigue effect of chrome! Incidentally when I started work some of the young guys could not fathom the m and f terminology applied to plugs and sockets. Times have changed!)

[Tony Betts]

hi bob, derek.

if my memory serves me right. there are bearings available with added letters after the C & H i think.

these were explained to me by the local bearing companies as being overlap bearings.

you need to talk to a proper supplier like BSL, i think now braemar bearings. about this.

they can explain better than me.

thanks tony

[Chris KC]

Derek, in order to sleeve the shaft they will have to take more material off, in order for the sleeve to have adequate strength/ thickness - you can't just make a 4 thou thick sleeve. 

What I can say is that I have at least one engine in which this has been done - on the front bearing, which is a smaller diameter, but doesn't support a flywheel - without any troubles; so you can take some comfort from that. Care will be needed not to foul the end of the taper, which might result in the flywheel not seating properly.

That said, if you sleeved up to the next metric size - 35mm perhaps - you would preserve more of the shaft's strength. 

I must say for only 4 thou I would look at plating options as Robert suggested.

[dickie65]

I have got a crankshaft which had a bit of shimstock wrapped around for the rear main bearing. It is in the box of curious spare parts.
( Charlie.Romeo.Alpha.Papa Box ) along with a set of white metalled front and rear bearings / Housings.