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Misc: Everything Else 1951 Black Shadow Restoration

craig

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VOC Member
20201220_ProjectShadow51.jpg

I was offered a Black Shadow project in 2013. I purchased the project and immediately started work on it.
Took the cylinders and heads to local Vincent machinist only 3 hrs away.
Crankshaft had been completed ,prior to my purchase, by a Canadian expert and also the tank was painted and done by "Bones".
Then, another Vincent project came up, Then a buddy stopped by and said" Go buy a BMW and lets travel the USA".
Then I got a wild hair and wanted to do the Trans America Trail (TAT). So I purchased a Husqvarna 701E and proceeded to farkle it out for the off road journey. So the Shadow was boxed up for another day.

All that behind, I am now focused on this Shadow project.
The pic above shows the big stuff with a thousand other pieces and projects in boxes.

My goal is a street friendly Black Shadow to ride on a semi daily basis, couple times a week.
 
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craig

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VOC Member
Head are being checked for thread fits... exhaust, push rod tubes, cap nuts, spark plugs.
Exhaust nuts seem to be best in natural bronze, I do have patina chrome as well.



20210116_HeadExChk1.jpg
 

craig

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VOC Member
Looking at choices for C3 and see that new modern C3 are quite thinner at the tail of C3 than the earlier versions. The new C3 having a scalloped tail bore pattern due to spline broach. So this either thinner or scalloped bore makes the possibility of tapering for an o-ring questionable.

20210122_C3Lineup.jpg
 

timetraveller

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VOC Member
That is not going to help. I have not seen the later type so could you measure the internal distance between the top and bottom of the splines. It looks as though either the height of the splines must be higher or the internal diameter of the inner end must be smaller. If either is the case then it might not fit, and I assume that they do. My technique of using a valve seat grinding tool to give it a cone shape does not look as though it would work. One of them looks to have a very thick inner end and it might be possible to cut a stepped recess with a flat inner back to restrain the 'o' ring. What do you think? Even if it is possible it would certainly require better machining skills than just using a valve seat grinder in a pillar drill or mill.
 

Chris Launders

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VOC Member
I have just changed mine which was worn for one from another members stock of spares he was downsizing, it is not a recent one and both are the thin type, this is why I have been puzzled about being able to grind a groove and use an "O" ring, I certainly couldn't.
 

craig

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VOC Member
Checking the balance factor on this particular twin crank.
Setting twin crank up in a wheel truing stand , hanging weight until the crank is positionable in 360 degree without movement.
My rough weight on this crank is 220grams.
What has your twin crank balance weight been?

20210124_TwinCrankBalanceGrams1.jpg
 

timetraveller

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VOC Member
That is going to depend upon the weight of the pistons etc. It looks to me from the photograph that someone has already put the extra holes that I have found necessary into the flywheels near to the crank pin but I do not start off with the extra weight needed. I weight the small ends of the conrods, the total weight of the pistons, ring, gudgeon pins and circlips. Calculate 46% of that. Subtract the weight of the small ends and then work out what is needed to balance the flywheels. For racing some people prefer 50% balance factor.
 

greg brillus

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VOC Member
2 cranks we had recently both had Carrillo rods.......One was for a 1200 Norvin, the other for a standard Shadow........ On both we had to machine material away from the big end area of the flywheels to get the balance factors to 60% Norvin and 46% Shadow.......I'd have to go back through my worksheets to see how much material we removed, but obviously they were different from one another. The big end of the Carrillo rods seem to be heavier than stock Vincent rods.
 

craig

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VOC Member
I wasnt looking for balance factor, simply what did it take in gms to counter balance your last crank after balancing?

But here is more crude data

piston, pin, rings (in paper), clips (in plastic)

20210124_PistonRingsPinClips1.jpg
 

craig

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VOC Member
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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VOC Member
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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VOC Member
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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timetraveller

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VOC Member
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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VOC Member
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
 

timetraveller

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VOC Member
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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