Uncle Cooperman, Voted Mr TMF 2011
Posted 24 May 2016 - 06:14 PM
When first I built my 1293 Cooper 'S' rally car I fitted a single competition diff pin. This is what happened. I thought there was a bit of a clonk towards the end of the rally, but it still did some final speed tests. I guess I was very lucky and I've never seen a diff pin this worn which hadn't snapped before.
After this I fitted a cross pin diff, but managed to shear one of the pins and had to replace even that!
Camshaft & Stage Two Head
Posted 24 May 2016 - 06:28 PM
Up Into Fourth
Posted 24 May 2016 - 06:29 PM
One Carb Or Two?
Posted 24 May 2016 - 06:59 PM
That is epic !!
Looks like whats left of a 22g2583 Tuftrided Rover pin to me as it has the flats machined for lubrication unlike the MS comp pin c-bta164.
The sheer strength of the material used is very impressive not to have snapped, shame about its wear characteristics.
The bushed planet wheels are said to do this to treated pins, was this the case ?
Edited by absx2, 24 May 2016 - 07:06 PM.
Uncle Cooperman, Voted Mr TMF 2011
Posted 24 May 2016 - 07:01 PM
I am amazed it didn't fail during the event on which I finished 4th overall.
Then I fitted a cross-pin and managed to spin the inside front wheel at a tight hairpin with a big drop off on the outside. I had to floor it in 1st to keep it from going over the edge (again!) and pulled around 7500 rpm with the inside wheel spinning. That friction-welded a planet wheel onto one of 1/4 pins and the steering went very stiff. We decided to carry on and suddenly the steering freed off and the car drove fine. The pin had sheared and was revolving in the diff housing. It carried on for the rest of the rally, a further 250 miles, and we won outright.
I thought I should see what had happened as it was clear there had been a problem. I had to put the diff in a lathe and part off the casing to get the output shafts out.
Uncle Cooperman, Voted Mr TMF 2011
Posted 24 May 2016 - 07:03 PM
That is epic !!
Looks like whats left of a 22g2583 Tuftrided Rover pin to me as it has the flats machined for lubrication.
The bushed planet wheels are said to do this to treated pins, was this the case ?
It was a long time ago, but that sounds like the what must have happened. Sure was almost a non-finish on that event, but not quite. We got a good result at the end.
I found the pin today when looking for something else in my workshop and I didn't realise I still had it.
Edited by Cooperman, 24 May 2016 - 07:04 PM.
Super Mini Mad
Posted 24 May 2016 - 09:30 PM
A close shave to say the least!
Moved Into The Garage
Posted 24 May 2016 - 09:40 PM
diff pin.
Seems an odd place to find a crankshaft down in the diff 
Nice trophy that one!
Thanks for sharing the story.
Up Into Fourth
Posted 24 May 2016 - 10:00 PM
Uncle Cooperman, Voted Mr TMF 2011
Posted 24 May 2016 - 10:26 PM
I have also had a bolt come adrift from the crown-wheel of a gearbox I didn't build myself. I bought it as a fully built SC CR box with a 3.9:1 FDR from a well-known specialist. One of the bolts had been over-torqued and the threads partly stripped. The bolt came loose during a very tough rally and, despite the locking tab, it sheared off and the bolt head went through the gearbox casing leaving a hole about 1/2" across in both directions. I took the box off and had an aircraft coded welder weld it up. We were winning the rally at the time, but I was lucky to notice the huge smoke trail as it was at night. Fortunately a spectator at a 90 degree bend turned his lights on to get our number and I saw the smoke, pushed the clutch down and stopped with oil pouring off the sump guard. Got a lift from a marshal 60 miles to get the trailer and then towed it 250 miles home. No damage to the newly refreshed engine fortunately.
Up Into Fourth
Posted 24 May 2016 - 10:27 PM
I've just posted this picture in another thread where somebody's diff seems to have gone.
Thought I'd share the photo here too at the damage that a broken diff pin can cause.
If, while I'm in the garage tomorrow, I see the other parts o will get a photo of them too. I've invested in a x pin diff for my new engine build
We had a customer have something similar happen but with the addition of a slot from the bottom to the top of the diff case.
After pressing him for details it turned out he'd been doing J turns in a car park. Apparently he got his friend to tow him home so his parents wouldn't find out what he'd been up to. 
Super Mini Mad
Posted 25 May 2016 - 05:28 AM
Uncle Cooperman, Voted Mr TMF 2011
Posted 25 May 2016 - 09:39 AM
Crazy About Mini's
Posted 25 May 2016 - 10:03 AM
Uncle Cooperman, Voted Mr TMF 2011
Posted 25 May 2016 - 03:13 PM
It didn't have the bushed planet gears as the strength of them is a bit suspect. It was a competition pin (from M.S.), but it is so long ago I can't remember what the actual specification was.
Needless to say I have always used a cross-pin since then.
Of course, rallying at National and International and later at Historic level does put a lot of load on everything and I must have broken almost everything in the transmission of a Mini over the years. I have snapped driveshafts, broken CV joints, had drop gears fail, had gearbox internals give up, broken a drive shaft UJ coupling, had the gear selector linkage rod snap (remote change type), had clutch failures, etc..
Other retirements have been through accidents including rolling the car(s), hitting banks, snapped rear radius arm putting the car into the trees in a forest, failure of the horrible hydrolastic suspension, cracked sump, plus a few things I have almost forgotten like ripping the fuel line off because it was not routed inside the car (that was in 1961).
But overall the successes have outweighed the retirements and it has all bee such great fun .
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