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Alfredo

Milling GT6 crankshaft pulley for 36-1

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Hi to all, 

I would like to keep the original fan on my '69 GT6 and was thinking about machining the iner part of the crankshaft pullet (where the timing numbers are) with the 36-1 pattern, the idea is to be very careful not to over heat the rubber compound. What are your thoughts? Alfredo 

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Alfredo, 

The crankshaft pulley has two functions.   Its a pulley, to drive the fan and alternator, AND the solid part that has the timing scale on,  is a damper.   It can vibrate on the rubber, to absorb and damp down torsional vibration in the long crank.   The mass of the outer ring is an important part of that.   If you machine  away some of that mass it will become unbalanced.

Trigger wheels can be placed in front of the pulley,  you can go on using the fan.

John

Edited by JohnD

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I'd go with John's recomendation, you could actually take the separate nose lump that the fan bolts to, split it in half and sandwich the trigger wheel between them.

Alan

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A Mini has a short cankshaft.    So does a Spitfire, that has no damper pulley.

But Triumph reckoned that they had to fit the long cranked six-cylinder engines with one, and Triumph never spent a penny they didn't have to!

And problems have occured with faulty dampers - see my survey.    Although most were not associated with broken cranks, that is why they were fitted, to prevent the torsional vibration causing fractures.   So on a six, it may be more risky to mess with the damper than it would be on a Mini.

John

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It is very bad to fiddle with the mass of a rubber/steel damper.

Unfortunately the crank does not break immedeately and from

that people who did so feel proud for their clever idea.

 

Both TR4 and TR6 have resonant frequencies that can kill the crank

if the engine is driven longer at those revs.

 

TR4 is better because the frequency is quite high and a normal engine does

not touch that limit often.

 

TR6 needs a working damper and so I would go for triggerwheels.co.uk and buy

such a wheel

 

349732608_Viscouscoupling36-1Wheel.jpg.750acd9c8a3e5336d80bc681ea16a7e1.jpg

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3 hours ago, Triumph-V8 said:

TR6 needs a working damper and so I would go for triggerwheels.co.uk and buy

such a wheel

 

If you do a quick search here on "Trigger Wheel" you should find a recent long rambling thread on fitting a trigger wheel and associated sensor on various triumphs, but also Vitesse/GT6 where space is tight!

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7 hours ago, Triumph-V8 said:

It is very bad to fiddle with the mass of a rubber/steel damper.

Unfortunately the crank does not break immedeately and from

that people who did so feel proud for their clever idea.

 

Both TR4 and TR6 have resonant frequencies that can kill the crank

if the engine is driven longer at those revs.

 

TR4 is better because the frequency is quite high and a normal engine does

not touch that limit often.

 

TR6 needs a working damper and so I would go for triggerwheels.co.uk and buy

such a wheel

 

349732608_Viscouscoupling36-1Wheel.jpg.750acd9c8a3e5336d80bc681ea16a7e1.jpg

I am not saying it is a good idea by any means to machine a damper, on the contrary actually. Just that the Mini guys favour it. My own Ford 32-1 CAS wheel is mounted on a machined down Big T power steering pulley, interference fit. Not the damper..                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          Laurence

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