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#31 pete l

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Posted Yesterday, 04:51 PM

There is no longer any need to hold the flywheel. He just needs to pull that tapered part off the crank.

#32 hhhh

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Posted Yesterday, 05:13 PM

There is no longer any need to hold the flywheel. He just needs to pull that tapered part off the crank.

But don't you need to hold the flywheel against turning the puller's center bolt?



#33 dotmatrix

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Posted Yesterday, 08:36 PM

I once had a flywheel that had friction welded it self to the end of the crank. couldn't pull it off no matter what we tried. we ended up cutting off the pressure plate and removing that, then cutting a slit in the boss. that enabled us to pull it off leaving two missing "welds" on the tapered end of the crank.



#34 Rorf

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Posted Today, 05:30 AM

Anyone have any theories on how these weld spots occur on the crankshaft taper, possibly something to do with the starter motor earth current?

 

One would assume if the flywheel turned on the taper then it would damage the key washer.



#35 dotmatrix

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Posted Today, 07:30 AM

Anyone have any theories on how these weld spots occur on the crankshaft taper, possibly something to do with the starter motor earth current?
 
One would assume if the flywheel turned on the taper then it would damage the key washer.


I don't think it turns, I think it is just slightly loose enabling the flywheel to slightly wiggle because the two tapers does not fit perfectly well to gether and they weren't properly "lapped in".

#36 Retroman

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Posted Today, 10:28 AM

Its partly to do with the properties of the metals

 

En24 steel flywheels are less prone to doing it as its harder than many steels

 

New flywheels should be lapped on using fine valve grinding paste. The whole taper should end up with that nice fine grey finish.

By lapping the flywheel on it sits with full contact on the whole area of the taper not on a few high spots so the power transfer is by the full area

 

If they are not lapped in fully my theory is the fretting comes from the high spots which have to transmit all the engine power from the crankshaft to the flywheel. With all the pressure concentrated on such a small spot it has not enough grip, so it will move a fraction maybe backwards and forwards 'fretting' which as its 'tight' will create a very localised heat hence the welding / blistering effect.

 

Guess its a friction burn in metal, like train wheels which are friction welded to the axle as an engineering process.



#37 dotmatrix

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Posted Today, 10:54 AM

Its partly to do with the properties of the metals
 
En24 steel flywheels are less prone to doing it as its harder than many steels
 
New flywheels should be lapped on using fine valve grinding paste. The whole taper should end up with that nice fine grey finish.
By lapping the flywheel on it sits with full contact on the whole area of the taper not on a few high spots so the power transfer is by the full area
 
If they are not lapped in fully my theory is the fretting comes from the high spots which have to transmit all the engine power from the crankshaft to the flywheel. With all the pressure concentrated on such a small spot it has not enough grip, so it will move a fraction maybe backwards and forwards 'fretting' which as its 'tight' will create a very localised heat hence the welding / blistering effect.
 
Guess its a friction burn in metal, like train wheels which are friction welded to the axle as an engineering process.


I have heard mini people say that they apply a bit of grease to the tapered part before fitting the flywheel to avoid this. is this normal? a good idea?

#38 Moke Spider

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Posted Today, 11:18 AM

 

Its partly to do with the properties of the metals
 
En24 steel flywheels are less prone to doing it as its harder than many steels
 
New flywheels should be lapped on using fine valve grinding paste. The whole taper should end up with that nice fine grey finish.
By lapping the flywheel on it sits with full contact on the whole area of the taper not on a few high spots so the power transfer is by the full area
 
If they are not lapped in fully my theory is the fretting comes from the high spots which have to transmit all the engine power from the crankshaft to the flywheel. With all the pressure concentrated on such a small spot it has not enough grip, so it will move a fraction maybe backwards and forwards 'fretting' which as its 'tight' will create a very localised heat hence the welding / blistering effect.
 
Guess its a friction burn in metal, like train wheels which are friction welded to the axle as an engineering process.


I have heard mini people say that they apply a bit of grease to the tapered part before fitting the flywheel to avoid this. is this normal? a good idea?

 

 

 

I'm not sure on that as in why someone would do that ???

 

I lapp in the flywheels & cranks together and then use a very very light machine oil, just the lightest licks, on the taper when assembling. This allows the flywheel to seat deeper and tighter on the crank, so that fretting doesn't occur. Also, being such a light Oil, under the extreme pressure of the fit between the flywheel & crank taper, the Oil Film breaks down so that there is contact between these parts.

 

If using a Lubricant, like engine oil or grease, then this oil film break down won't occur and the flywheel will likely spin on the tail of the crank.

 

When the Flywheel & Crank fret, then they become really hard to get apart again as they 'weld' to each other and when they do eventually separate, the Flywheel pulls 'chunks' from the crank.






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