Author Topic: Pitting & Journals - Can I reuse this crankshaft?  (Read 1403 times)

Offline SimonHolyfield

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What do we think of this pitting chaps? This journal and its partner measure 1.656"...
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Offline berger

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Re: Pitting
« Reply #1 on: 22.02. 2019 00:22 »
looks nice magnified, like rain drops and a dead spider *spider*, but I would say its an A 50 or A 65 on its worn third grind, I am having a guess someone will know more than me, PUB tomorrow  *beer* *beer* *beer* put it this way it does look like oil will sit nicely in the pitting ;)

Offline Swarfcut

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Re: Pitting
« Reply #2 on: 22.02. 2019 08:56 »
 Bergs is right. Looks to be a big journal A10 or A65 Crank, with a pretty good set of drive splines. 

 The pitting is of minor consequence, as the journals are effectively smooth, rather than deeply scored or worn in ridges.

 Standard size is 1.6865"/!.6870", so it is already on its 3rd regrind at 1.656" and on the lower published tolerence.  Providing the journals are truly circular rather than worn oval, (2 thou was the limit) they should be OK with just a very light polish and a new set of shells....plus the ever popular clean of the sludge trap.

 Swarfy.

   

 

Offline SimonHolyfield

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Re: Pitting
« Reply #3 on: 22.02. 2019 09:35 »
Thanks for the reassurance guys. I've only measured in one place on each journal so far, so I'll have to go back for a proper survey.

The plugs have had it - I'll be welding a bit of thick sheet to each of them to get them out. I've got a new trap to go in.
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Offline SimonHolyfield

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Re: Pitting
« Reply #4 on: 24.02. 2019 18:28 »
Well it turns out that dimensionally these big ends are in good shape - but the t/s main measures 1.242"!

This is hugely undersized - the oil way is almost gone. I have a bush that fits it well, but I've never heard of one of these being 120 thou undersize.

Scrap I think.
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Online ironhead

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Re: Pitting
« Reply #5 on: 25.02. 2019 04:43 »
Maybe not. someone may have started setting it up for a roller conversion.
SA

Online muskrat

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Re: Pitting
« Reply #6 on: 25.02. 2019 09:42 »
G'day ironhead.
You could be right. Mine is 30mm = 1.181". They could have been using a different bearing.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline SimonHolyfield

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Re: Pitting
« Reply #7 on: 25.02. 2019 10:18 »
I guess roller conversion would be an option - I wasn't going to do it, as I have three bikes and the mileage on one probably wouldn't justify the expense.

What do you think?
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Offline Swarfcut

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Re: Pitting
« Reply #8 on: 25.02. 2019 10:44 »
Simon, If you have a bush to fit, you may as well use it.  Providing it is a solid one, even machining a circular oilway to replace the lost depth of the oilway on the crank. How the oil gets into the crank as the holes flash past beats me.  Anyone thought of drilling additional holes in the bush to feed the crank?  Or even something in the crank oilway next to the hole to act as a scoop!

 Swarfy.

Offline SimonHolyfield

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Re: Pitting
« Reply #9 on: 25.02. 2019 11:17 »
I went out to walk the dog and think.

The bush I have fits the small 1.242" journal very well. If we think the journal is big enough to carry the running loads without cracking, I will machine the oil way as an annular groove in the thick wall of the bush, not the journal - this will have the same affect as the original groove in the journal.

I guess when SRM sleeve the journal for the needle roller conversion, the shaft is a bit smaller than stock, for the roller sleeve to fit over it - and as Muskrat says, he has a 1.181" t/s journal - which I guess is performing OK, so maybe mine is not fit for scrap just yet.

I have three alternatives - my home grown approach described above; asking SRM to resleeve the journal at £107, or thirdly got for the full needle conversion at about £550.
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Offline Swarfcut

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Re: Pitting & Journals - Can I reuse this crankshaft?
« Reply #10 on: 25.02. 2019 12:33 »
Simon  Sleeving the crank will not add any appreciable strength, Muskys smaller shaft is OK.  The crank is already on its 3rd grind of a possible 4, so to my cheapskate way of thinking ....better to spend the minimum on it, give the sludge trap a clinical clearout and just build into a running unit. Unless a round the world trip is planned, most of these bikes do minimal miles and are just as reliable if treated to regular oils and not hammered. I find it hard to justify the high cost of precision engineering compared to the actual use enjoyed. But that's me.

 Swarfy.

Offline SimonHolyfield

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Re: Pitting & Journals - Can I reuse this crankshaft?
« Reply #11 on: 25.02. 2019 18:25 »
I like your thinking. I guess as the drive side journal is 1.18", with all the bending load that is subject to from the primary along with the cyclic loads from the power stroke then a 1.242" timing side journal will always be OK.
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

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Re: Pitting & Journals - Can I reuse this crankshaft?
« Reply #12 on: 25.02. 2019 19:18 »
G'day Simon.
I agree, make the bush. Make sure the bore in the case is round, it may need a skim. A light interference fit of 1-1/2 thou into the case and leave a few thou in the bore for line reaming. The thrust face may take some measuring to work out it's thickness.
Have a good look at the radius on the shaft, you don't want a sharp corner.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline SimonHolyfield

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Re: Pitting & Journals - Can I reuse this crankshaft?
« Reply #13 on: 25.02. 2019 23:09 »
Thanks guys.

As an A10 newbie, can someone explain how the end float is controlled? Shims under the drive side bearing?
cheers

Simes

'51 Square Four, '42 W/NG, '58 Huntmaster,  https://ariel-square-four.blogspot.com

Online KiwiGF

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Re: Pitting & Journals - Can I reuse this crankshaft?
« Reply #14 on: 26.02. 2019 01:01 »
Thanks guys.

As an A10 newbie, can someone explain how the end float is controlled? Shims under the drive side bearing?

Yes, and it’s better to have one thick shim (washer) not several thin ones.

New Zealand

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