1951 T100/ TR5 Crankshaft Regrind

Hi
I need to get my 1951 TR5 crankshaft reground, problem is no one I have asked can grind the journals due to the offset of the counterweights.
The counter weights don't allow a straight sided grinding wheel to cover the journals, the offset is inwards to the flywheel.
What has been suggested is to machine the faces of the counterweights so they can then get a straight sided wheel into cover the full width of the journals.
Problem I see then is I would need to do a major rebalancing job.
I would have assumed originally they would have machined a grinding wheel with a recess to clear the counter weight of the flywheels, but the operators I have spoken to said no.
I run three grinders one a ring grinder the other two are lineal grinders, and with these two you can machine the wheels to grind any lineal profile you want.
Burgs

Burgs said:

Hi
I need to get my 1951 TR5 crankshaft reground, problem is no one I have asked can grind the journals due to the offset of the counterweights.
The counter weights don't allow a straight sided grinding wheel to cover the journals, the offset is inwards to the flywheel.
What has been suggested is to machine the faces of the counterweights so they can then get a straight sided wheel into cover the full width of the journals.
Problem I see then is I would need to do a major rebalancing job.
I would have assumed originally they would have machined a grinding wheel with a recess to clear the counter weight of the flywheels, but the operators I have spoken to said no.
I run three grinders one a ring grinder the other two are lineal grinders, and with these two you can machine the wheels to grind any lineal profile you want.
Burgs

Click to expand...

Can't you just strip the crank down remove the C/W and either grind individually , not sure if it would be rigid enough ? Could get chatter , or bolt the two halfs together with shorter bolts no counter weight , and grind journals .you need to clean it anyway .
Cheers.

HI
Just checked again, there is about 3mm clearance between the big end journal and the flywheel , so the flywheel is not the problem, on the other hand the counterweights taper in towards the flywheel on the outer edge by about 3 mm, to me this means the grinding wheel has to be relieved to clear the counter weights, probably a bit left field for modern day machinists?
Having a closer look and a bit of funny stuff has gone on many years before, as there is a step on both journals and a corresponding step in the conrod bores, and all seems to have been done to allow for the counterweight clearance issue when last ground?
The steps in the rods and journals seem to match the amount the counterweights would impede into the side of the grinding wheel?
Might just machine the counterweights to allow for clearance for the grinding wheel, and balance accordingly.
Would be interesting to see how the factory first ground them?
Burgs

Hi
Thinking about it I might just do the calcs (Phill Irving's tuning for Speed) as I did for my Manx, that turned a vibrating hammer of a machine, to a very smooth engine as all get out, in the sweet spot of cams ect. The TR5 will need a balance factor to suit how it is going to be ridden, so I can at least see out of the rear view mirrors, and up to the speeds its legally allowed to do, or maybe a bit faster.
Maybe statically balance it, and then dynamically have it balanced? The knowledge is disappearing though I think, 3 and 4 cylinders and more no problem.
Burgs

Had a 55 t 100 ( big Brg . )

As I raced it , I shouldve just chucked a 650 crank in it and had be done with it .
Id put titanium studs in the thing , Ex DC 10 or somesuch .

The RODs presumeably were Ex white Metal and ran STANDAARD 8 bearing shells ,
notched to clear the rod bolts ! . Ran 8.000 rpm , tho getting ear chewwed by telepathy
as to not blowing it up . Ran 'class C '7.5 ( 7.25 measured ) C R , with all the hot tuned
T 100 R race stuff , built prior to 1964 .

So lifing the pistons 1 millimeter ( going from 80 to 82 stroke ) wasnt going to hurt anything
and noone'd of given a toss ". in C R in 1981 .

So BULLETPROOFING it , the 67 lighter 650 crank ( Squareish chopped flywheel ) would be
a safer easier way to go about it . ( tho you may need rods too ) AND youd have the
ORIGINAL on the shelf for originality nerds / resale .

ANY idiot gets the crank CRACK TESTED before grinding on a TRIUMPH as theyre wont
to of been given a hard time , not that they cant take it . But past 2nd regrind ( .020 )
you wouldnt . Like the past .060 Barrels weakened thinned BLANG . Raced . Even if on
the street .