24 replies to this topic

[minimotion]

Whats peoples thoughts on the tail end?

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[nicklouse]

lap it and see how it is.

 

very hard to comment on such a big picture for just the tail of the crank.

[minimotion]

This better?

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[cal844]

It looks pitted but lap on a good flywheel and you'll be fine

[spiguy]

Think what he meant was to take a close up picture of just the end of the crank. 

[minimotion]

Got a new med complete setup to go on so hopefully should do the trick

[Spider]

 

Really need a better and hi res photo but, I'm inclined to say on what I can see here yes, it should clean up for the most part with a lapping, but I wouldn't get at all too hung up on trying to get it 100%, - 70% or better is well enough.

[minimotion]

Theres a few odd marks which look deeper

[minimotion]

You can seem them better here just before the grove for the c washer to fit you can seen the row of putting but what you see in the photo is it it doesnt continue around the crank and the rest off the marks on the tail end is just fine pitting (feels smooth to touch)

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[Spider]

It really has seen better days and I'd say - from what I can see - that's border line.

 

I'd say either pull it and have a shop provide an opinion on it or replace it for peace of mind. Looks like it's been wet at some point. It might just clean up OK too.

[minimotion]

When I had it ground the guy said to lap the flywheel it should be fine but wanted to know what other peoples thoughts if I needed a new crank wheres the place to get a 1275a+ from? Any specifics heard of hardened ones being available I might be wrong! The engine is being built with some spirited driving in mind

[minimans]

I'd be wary of that! If you have access to a better one go with that, but that looks like a crack starting in the deeper rust pit? maybe just the picture though? If I was building this for a customer It would get a new crank. If it was mine I'd crack test it and run it knowing it might separate.

[mikal]

looks like corrosion damage?

[OzOAP]

I would say it's scrap unfortunately

Edited by OzOAP, 16 May 2018 - 09:37 AM.

[DeadSquare]

 If you can get a better one, I would. 

 

One day, when mini cranks are rare,  someone would be delighted with a crank in your condition, but then, if that rare, it would be worth having the end of the crank heavily plated to fill all the pitting, and re-machined.

 

When the " crank with a tail " was envisaged, some thought that the groove for the C washer could be an invitation for a weakness, which is one reason why a long 1.5 AF bolt was used, to hold the tail of the crank under compression past the groove.  It was also the reason why early cranks and flywheels were each balanced separately.

 

I don't think that rusty pit is a weak danger, but separate crank and flywheel balancing wouldn't be silly, if you can get it done.

 

I have never found out the exact date, but from about the introduction of the 998 Cooper, the crank and flywheel were balanced as one unit.