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Pulling Material Off Crank Taper


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#1 dotmatrix

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Posted 27 June 2020 - 10:00 PM

Hello.

I have been having problem with that when removing the flywheel off my race motor some material sticks to the flywheel boss. late last year I pulled the engine out to give it a renovation and when I pulled the flywheel off it stuck to the crank and pulled material off the taper. I ended up getting the taper redone at an engineering place and as always buying a new boss from minispares. I then lapped these together very nicely using fine valve grinding paste and I finished by applying a very light smear of cv-joint grease before putting the flywheel back on and torquing it to spec.

I then drove 2 miles in the car and then had it adjusted on a rolling road. I noticed the engine leaking from behind the flywheel (big red gasket) so I pulled the flywheel again thinking it would be easy but no. friction welded on to the crank again.

 

any suggestions?

stop using minispares hubs?

throw out the crank?

stop lapping it in?

torque as hard as possible and not to spec?



#2 nicklouse

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Posted 27 June 2020 - 10:03 PM

what crank material?

verto clutch?



#3 dotmatrix

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Posted 27 June 2020 - 10:05 PM

what crank material?

verto clutch?

 

sorry. yes verto with the removeable boss

 

http://www.minispare...el/DAM5921.aspx

 

the boss friction welds to the crank taper and when I pull it off it takes a chunk off the taper which then sits in side the boss taper

 



#4 nicklouse

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Posted 27 June 2020 - 10:12 PM

it can be an issue where the crank and the flywheel have similar materials.

 

it sounds like you are doing everything that i would suggest.

 

others might have other ideas.



#5 MiniMadRacer

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Posted 27 June 2020 - 10:36 PM

I have fitted the flywheel as you suggest but I have never done the ",,,,and I finished by applying a very light smear of cv-joint grease before putting the flywheel..."

 

The micro weld I guess is caused by the two welding or hammering together, almost "chattering" which suggests to me not a proper tight fit. I have always fitted mine to gether 100% dry...

 

But as Nick says interesting to see what others say, unless of course the crank taper is worn from too much valve grinding pastr after many re fits on and off

 



#6 dotmatrix

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Posted 27 June 2020 - 10:39 PM

I have fitted the flywheel as you suggest but I have never done the ",,,,and I finished by applying a very light smear of cv-joint grease before putting the flywheel..."

 

The micro weld I guess is caused by the two welding or hammering together, almost "chattering" which suggests to me not a proper tight fit. I have always fitted mine to gether 100% dry...

 

But as Nick says interesting to see what others say, unless of course the crank taper is worn from too much valve grinding pastr after many re fits on and off

 

I dont normally use grease or anything but I wanted to try it to see if it made a difference. it didn't

 

the two pieces was very thoroughly lapped together, the size of the touching area was not the problem in my opinion.

 

the crank taper was not worn it was brand new (material applied by an engineering company to rectify the last friction welded clutch). the boss was also new.


Edited by dotmatrix, 27 June 2020 - 10:41 PM.


#7 Ethel

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Posted 28 June 2020 - 06:36 AM

I can't imagine grease being useful. It's likely to just get expelled from where the surfaces touch and aid slipping where they don't. If you were to try anything I'd expect loctite to perform better, but I would  be worried about being able to release it or build up enough heat to destroy it.



#8 Moke Spider

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Posted 28 June 2020 - 06:40 AM

Years back when I was getting this and doing much as you had done, except fitting them dry, rather that  something as heavy as CV grease, I tried 3-in-1 Oil, with the idea that under the high pressure the Oil Film would break down. I first did this with an all steel flywheel that was proving to be troublesome in the same way as what you've found and haven't looked back. The amount of Oil I use here is just a lightest of licks. I'll add that I really do heave down hard on the flywheel bolt, I've not ever measured just how tight I've done the bolt up, but at a guesstimate, it would be a minimum of 200 ft/lb. In order to stop any fretting, the joint between the crank and the flywheel has to be very tight. It's not an ideal arrangement. I have a 12 tonne flywheel puller and these steel flywheel need just about every ounce of those 12 tonnes to get these flywheels off, however, when they come off, the tapers are totally clean.

Be warned though, that with the flywheel going on this way, it will seat deeper and so you need to check the primary gear isn't going to get pinched, which you should check as a matter of course in any case.

 

I have been fitting all flywheels, including the all steel types this way for around 25 years now and never had an issue.

 

The other thing here you may wish to try is going to a cast iron hub rather than a steel one, which is too close in material type & composition to being the same as the crank, being so similar encourages them to 'weld' when fretting. Going to a Cast Iron Hub won't stop the fretting, if it's going to occur, but they won't weld.

 

It may also be worth checking the taper in your hubs isn't getting a step in them as they are longer than the taper on the crank, If there is a step forming here, it will in a huge way stop the flywheel from seating down. As a matter of routine I actually turn the small part of that taper in the flywheel parallel for the last (roughly) 2 mm so that a step can't form in the first place.



#9 dotmatrix

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Posted 28 June 2020 - 09:01 AM

Years back when I was getting this and doing much as you had done, except fitting them dry, rather that something as heavy as CV grease, I tried 3-in-1 Oil, with the idea that under the high pressure the Oil Film would break down. I first did this with an all steel flywheel that was proving to be troublesome in the same way as what you've found and haven't looked back. The amount of Oil I use here is just a lightest of licks. I'll add that I really do heave down hard on the flywheel bolt, I've not ever measured just how tight I've done the bolt up, but at a guesstimate, it would be a minimum of 200 ft/lb. In order to stop any fretting, the joint between the crank and the flywheel has to be very tight. It's not an ideal arrangement. I have a 12 tonne flywheel puller and these steel flywheel need just about every ounce of those 12 tonnes to get these flywheels off, however, when they come off, the tapers are totally clean.

Be warned though, that with the flywheel going on this way, it will seat deeper and so you need to check the primary gear isn't going to get pinched, which you should check as a matter of course in any case.

I have been fitting all flywheels, including the all steel types this way for around 25 years now and never had an issue.

The other thing here you may wish to try is going to a cast iron hub rather than a steel one, which is too close in material type & composition to being the same as the crank, being so similar encourages them to 'weld' when fretting. Going to a Cast Iron Hub won't stop the fretting, if it's going to occur, but they won't weld.

It may also be worth checking the taper in your hubs isn't getting a step in them as they are longer than the taper on the crank, If there is a step forming here, it will in a huge way stop the flywheel from seating down. As a matter of routine I actually turn the small part of that taper in the flywheel parallel for the last (roughly) 2 mm so that a step can't form in the first place.


I will try with the light oil instead

I did actually remove some material from that part of the boss that doesnt touch the flywheel, but i dont know if it was enough.

The boss i normally use are the new ones from minispares, i can try an original rover boss, would that be what you think of which is in an other material?

Edited by dotmatrix, 28 June 2020 - 09:05 AM.


#10 Moke Spider

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Posted 28 June 2020 - 10:04 AM

One of the Parts Suppliers have or did have on offer Cast Iron Hubs. I can't recall who and I've just had a quick look but not turned much up.

 

Yes, try an old BMC Flywheel Hub from one of the early flywheels.






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