G'dday From The Sunny South,
Does anyone know what the tolerance is for aligning the CC Model crankshaft big end journals with the cylinder bores?
My notes just say "accurately aligned" -- delightfully vague!
I would suggest plus or minus 0.005" but don't know if that is achievable.
Regards to all,
Mike Allfrey.
Crankshaft Positioning Within Crankcase
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Mike Allfrey
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Crankshaft Positioning Within Crankcase
E0 SA 42R; Rover 75
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PAUL BEAUMONT
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Mike Allfrey
- Posts: 491
- Joined: Thu Apr 06, 2006 10:14 am
- Your interest in the forum: It is a good vehicle for getting Jowett information to others.
- Given Name: Michael
- Location: Melbourne, AUSTRALIA.
Dear Paul,
No, I don't think you have missed a point. My reasoning for the 0.005" tolerance was that it should be possible, with shimming to have one of the crankpins within 0.005" of central alignment with the cylinder bore. I think it would be extremely naive of me to expect that both crankpins could be aligned with the bore centres with such a tolerance.
As you say, there is a good amount of clearance between the gudgeon bosses and the connecting rod small end and, provided the rods are straight, there should be no concern about working with 1/32"s and 1/16"s here.
My main query was, if anyone knew what the tolerance would be when adjusting the crankshaft "accurately" to centre the crankpins with the bores.
From memory, the CC model has separate thrusts, so, assuming wear has taken place at the crankshaft and flywheel, the position of the crank could be adjusted using differing thickness thrust bearings. I have done that on my Jupiter back in 1963 when it had an alarming amount of end float!
Best wishes to all,
Mike A.
No, I don't think you have missed a point. My reasoning for the 0.005" tolerance was that it should be possible, with shimming to have one of the crankpins within 0.005" of central alignment with the cylinder bore. I think it would be extremely naive of me to expect that both crankpins could be aligned with the bore centres with such a tolerance.
As you say, there is a good amount of clearance between the gudgeon bosses and the connecting rod small end and, provided the rods are straight, there should be no concern about working with 1/32"s and 1/16"s here.
My main query was, if anyone knew what the tolerance would be when adjusting the crankshaft "accurately" to centre the crankpins with the bores.
From memory, the CC model has separate thrusts, so, assuming wear has taken place at the crankshaft and flywheel, the position of the crank could be adjusted using differing thickness thrust bearings. I have done that on my Jupiter back in 1963 when it had an alarming amount of end float!
Best wishes to all,
Mike A.
E0 SA 42R; Rover 75
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PAUL BEAUMONT
- Posts: 452
- Joined: Wed Feb 08, 2006 1:57 pm
- Your interest in the forum: Bradford Registrar and club Chairman
- Given Name: Paul
- Location: South Yorkshire
Hi Mike. You make a fair point about the crank shaft thrusts, but these are at the rear end of the crank shaft only, ie they can only bias the crank forwards or backwards (can't remember exactly where they are fitted!). I suggest that this maybe to control crank endfloat when the clutch is used - and maybe because the Borg and Beck clutch is less tolerant of crank float than was the old Jowett Clutch. I can certainly agree that aspiring to less than 0.005" crank shaft end float must be a good thing.
What do you think?
What do you think?
Paul Beaumont