Misc: Everything Else 1951 Black Shadow Restoration

craig

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463+463=926
191+191=382
recip weight=926+382=1308gms
Guess the factor is 46%
46% of 1308=602
subtract pin ends - 602-382=220 is the expected counter balance weight

So the balance factor for this Vincent Black Shadow crank is 46%
 

timetraveller

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So you now know that you can use it and if it vibrates it will not be the balance which is wrong. Your method is just the same as the one I use and if you compare your flywheels, with any standard ones you can find, then you will see what I mean by the extra holes. Have you checked the run out of the main shafts? It is good to try to get down to about one thou per side. Not always possible but sometimes it is possible to do better.
 

Vincent Brake

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mainshafts better be within say 0,015mm, run out.
And more: one who has done a rebuild without checking the alignment of main bearings in the casings: oh, oh, oh.....
(not saying it happend here)

balancefactor i have by experience 52-54% but more important is the weight of the conrods to be the same, when doing my B crank i milled 0,8 mm form a to thick conrod, to make them both the same, its the most vibrationless bike i have now.:).
I saw the formula in Tuning For Speet

and when weighing the smallends, a big difference is seen measured when one does not have the centers LEVEL.
and even than; two ways: fist one read out when yust laying it on.
than when laying it on with bit presure and read when released.

cheers
 
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craig

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The only way I can vary this balance factor to a higher percentage is to lighten the pistons,
Holes in the pistons?

PitonHoles1.jpg
 

timetraveller

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Remember that you could always tap some of the holes near the crank pin and screw in some extra steel if that side is too light, Alternatively you could drill holes opposite the crank pin if that was what was needed. On the ones I have done (tens) I have always found that it needed the extra holes at the crank pin end and that has been done on your flywheels
 

craig

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Thank you, I am going with my current 46% balance factor.
I will report on vibration when road tested.

Moving on to using Loctite 638 (exp 10/22) on ET92 roller races and centering crankshaft in cases.
I have honed out ET92 inner races without rollers to allow mock assembly of crank/cases.
Where do you place shims to shift crank?


TwinMainViewColor2.jpg
 

Bill Thomas

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Next to the flywheel, Before the bearing, There should be a raised boss,
But sometimes it's worn I think it's the same washer as in the gearbox E76 ????
 

timetraveller

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I don't think it is a washer Bill. Assuming that the flywheel boss is still in good order then the shim, if needed, has to go between the inner of the inside drive side main bearing and the boss on the flywheel. It might need a washer if the boss has gone. It is one of those jobs one does not want to do too often. Assemble the whole thing, linished bearings are a good idea, and then measure from one side of the little end to the side of the mouth of the crank case. Both sides on both front and rear cylinders. They might not be exactly the same front and rear although they should be. Then work out what thickness of shim one needs to get the little ends near enough to the centre of both bores. Patience is your friend here.
 
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