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MG Midget and Sprite Technical - Engine out - roller release bearing in

Engine coming out soon to replace yet another failed carbon thrust release bearing.
A Peter May RRB will be fitted to hopefully save having to do this every 3-4000 miles. Has anyone any tips for fitting the RRB - it seems very straight forward?
Looking through the archives it seems fairly evenly split between engine & gearbox or just engine removal, so for a change I'm going for just removing the engine this time. I'll be working with an electric hoist (Aldi) slung from a, yet to be installed, beam.

Thanks Jeremy
Jeremy 3

the RRB is much heavier than the carbon one, and longer too. As a result unless the design has changed, they often dangle and make contact with the input shaft. This is not a problem on a race car which maybe only does 400-500 miles a year but on a road car can lead to premature failure. I hope you've researched this well.
Also I'd be diagnosing the problem that is causing your carbon thrusts to fail so quickly when it's not unusual for them to last 75000 miles and many years.
David Smith

The way to stop the dangle is to make sure it is constant contact with the forks on the clutch cage. Ours has the centre section removed (the bit where the carbon thrust bearing would touch). We have to make sure the RRB is touching the forks without compressing them, then we measure the distance between the slave rod fully retracted to where the hole is in the fork and make a specific rod to suit so that the RRB cannot dangle.

We still, however, suffer from the brass bush wearing along with the lugs on the carrier of the RRB wearing oval, so they still have to be changed frequently.

HTH
Andrew McGee

Andrew

Adjusting the pushrod length to keep the bearing in contact with the pressure plate is not a good idea.

As wear occurs in the friction plate, the pressure plate pad - or fingers, in your case - gets further away from the flywheel, only it won't be able to, so you will have less clamping pressure.
Dave O'Neill2

Thanks Dave. live and learn. What do you advise then as that's the only thing I've been advised to do so far.

A
Andrew McGee

If using a standard type clutch, I would use a good quality carbon bearing. The only problem is finding one.

When I used an F3 clutch in the racer, I tried various roller bearings, as supplied by David Gathercole, who built the engine.

I ended up with a specially made steel carrier (heavy) which was a sliding fit on the first motion shaft and the fork modified to operate it. The fork also had to be strengthened as it kept bending - the F3 clutch was seriously strong and unforgiving.

In the end, I reverted to standard type clutch with a carbon bearing.

Dave O'Neill2

Weld a pipe of suitable length and diameter over the input shaft.
The RRB can now lean on this pipe so no rattels or wear
Onno K

Thanks for your responses.
Dave (O'Neill) has hit the problem on the head - I'd gladly use a carbon replacement but the quality of the new replacements is astonishingly poor. The original did over 80k. I now never stop in gear so if stationary am always in neutral as I'm parpanoid about the bearing wearing. It's started to make the familiar graunching noises and so I know it won't be long before it fails all together.
I think I'll ring Peter May in the morning and see what he suggests - thanks again.

Jeremy
Jeremy 3

I'm with Onno on this one. Mine has a tube covering the input shaft to prevent contact. The tube is supported by a plate that bolts onto the front gearbox cover using longer studs and spacers.
Is the concentric slave cyl another way around this problem?
Mike
M H Allen

I have had a PM Roller Bearing for about 10000 miles now, and its been no problem at all. The last Carbon Bearing lasted about 500 miles.

Dave
Dave Barrow

Keep your foot of the pedal when driving 8^P
Alex G Matla

This thread was discussed between 29/04/2012 and 30/04/2012

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