Author Topic: Crank not rotating  (Read 2465 times)

Offline Oddjob

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Re: Crank not rotating
« Reply #60 on: May 11, 2022, 09:33:46 PM »
Go for the smallest size you expect to use, as you don’t have any yellows use green.

CMS don’t have any black shells left, they had some a year ago but they’ve clearly sold them all now
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Offline alexdecker

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Re: Crank not rotating
« Reply #61 on: June 04, 2022, 01:51:42 PM »
Ok, finally got the measurements of this thing. I ended up buying a set of new green bearings to test the crank wearing with.

My crank case is BCBCB, and these are the measurements I got with plastigauge:
1: .0016
2: .0015
3: .0013
4: .0016
5: .0015

Did the same with my rod bearings (fresh pair of green shells). Got these measurements:
1: .0014
2: .0014
3: .0017
4: .0015

Now - the math is getting a bit lost on me. Can anybody help me figure out, what size shells would be the best for my particular crank case, based of above measurements?

- Alex

Offline Oddjob

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Re: Crank not rotating
« Reply #62 on: June 04, 2022, 02:31:14 PM »
Alex the standard measurements are between 0.00079 and 0.00181 for both crank and rods.

A couple are close to the max 0.0018 but are still within range, just.

According to my calculations the difference between each shell colour is roughly 0.0004.

So crank 1 is .0016, if you fitted a brown in there it would be .0012 and with a black .0008. So black would be right on the edge of giving a minimum clearance so I'd go with brown in that journal although black would probably mean within range much longer.

No2, brown again

No3, I'd leave green.

No4, brown, again you could consider black

No5, brown.

Rods.

No 1, Green are ok.

No2, green

No3, Brown or even black. Black would give 0.0009 which is tightish but acceptable.

No4, Brown.
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Offline alexdecker

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Re: Crank not rotating
« Reply #63 on: June 04, 2022, 03:22:43 PM »
Alex the standard measurements are between 0.00079 and 0.00181 for both crank and rods.

A couple are close to the max 0.0018 but are still within range, just.

According to my calculations the difference between each shell colour is roughly 0.0004.

So crank 1 is .0016, if you fitted a brown in there it would be .0012 and with a black .0008. So black would be right on the edge of giving a minimum clearance so I'd go with brown in that journal although black would probably mean within range much longer.

No2, brown again

No3, I'd leave green.

No4, brown, again you could consider black

No5, brown.

Rods.

No 1, Green are ok.

No2, green

No3, Brown or even black. Black would give 0.0009 which is tightish but acceptable.

No4, Brown.

What an absolutely magnificant explanation and answer, thank you!

Had to tighten and untighten the screws quite a few times to make this measurements. I stayed within the torque spec of the crank case though. Can threads "tire" if you do that and loosen up, or should I stop trying to see problems where there are none?

Offline Oddjob

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Re: Crank not rotating
« Reply #64 on: June 04, 2022, 06:25:38 PM »
As long as you trust you measuring skills I'd just accept that result.

The threads should be ok, they are designed to be undone etc as they are not stretch bolts.
Don't play stupid with me, I'm better at it

 

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