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Butcher
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Joined: December 05, 2015
Posts: 1285
Location: Right Here
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 Posted: Sun Dec 15, 2019 10:35 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| I have yet to meet a mechanic that could bend any crankshaft. I've seen a few ruin them. |
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jerryherb
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Joined: October 30, 2015
Posts: 205
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| Posted: Sun Dec 15, 2019 10:40 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| Butcher wrote: |
| I have yet to meet a mechanic that could bend any crankshaft. I've seen a few ruin them. |
i guess by bend i mean twist out of spec or damage the bearings, bolts, TC, flex plate. These would be all other parts involved in holding the crankshaft in place with flexplate lock while tightening the pulley bolt to spec |
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jerryherb
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Joined: October 30, 2015
Posts: 205
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| Posted: Sun Dec 15, 2019 10:53 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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OK, so found one hazet 3102 on ebay for $40, yoink 
there is one in classifieds section for twice that as well, fyi.
will post the specs once i have it in hand so that someone can fabricate one if so inclined. |
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Butcher
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Joined: December 05, 2015
Posts: 1285
Location: Right Here
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| Posted: Sun Dec 15, 2019 11:20 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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I know you meant twisting. I've heard this before. I've just never ever seen crankshaft so poorly under built that it would happen. Certainly not anything the Germans would build.
Anything can happen I guess. I would not loose sleep over it. There are enough butchers working on these engines that if bending/twisting was an issue, you certainly would of read about it. Especially here on The Samba. I would not loose sleep over it. |
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djkeev
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Joined: September 30, 2007
Posts: 32575
Location: Reading Pennsylvania
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jerryherb
Samba Member
Joined: October 30, 2015
Posts: 205
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| Posted: Sun Dec 15, 2019 4:45 pm Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| djkeev wrote: |
How many pounds of force do you reckon the flywheel is transferring to the transmission input shaft?
I'm guessing a heap more than 240 ft lbs!
Dave |
2.1 wbx at peak produces 128 lb-ft @2800 RPM, so just about half required to torque the pulley to the shaft. of course a bit of it is lost before the flywheel transmits the power from the engine through the TC/clutch to the transmission shaft. |
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Jeffrey Lee
Samba Member
Joined: February 04, 2014
Posts: 1488
Location: Wisconsin
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| Posted: Sun Dec 15, 2019 5:19 pm Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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I've never encountered it myself, but I have heard rare reports of such crankshaft and drivetrain damage in the VW diesel world, from the same technique of using the flywheel end to counterhold for pulley/sprocket removal.
I can speak from personal experience that the pain of a somewhat expensive specialty tool which I sadly will use only a handful of times is quickly forgotten when the part pops off as intended, undamaged, and with no fuss. Considering the potential cascade effects of damage caused by hamfisted techniques, the "expensive" specialty tools are often a great bargain.
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Last edited by Jeffrey Lee on Mon Dec 16, 2019 1:02 pm; edited 1 time in total |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50336
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| Posted: Sun Dec 15, 2019 7:05 pm Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| If you have looked at the crankshaft of a 1920 vintage engine it is easy to see how it could be bent if 240ft*lbs were applied to it. As for a VW WBXer engine I don't think it is an issue at all. Think of what the maximum torque much be during combustion, likely in excess of 240ft*lbs each time a cylinder fires under full load. Average torque and maximum torque are two different things. |
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jerryherb
Samba Member
Joined: October 30, 2015
Posts: 205
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| Posted: Mon Dec 16, 2019 9:37 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| Wildthings wrote: |
| If you have looked at the crankshaft of a 1920 vintage engine it is easy to see how it could be bent if 240ft*lbs were applied to it. As for a VW WBXer engine I don't think it is an issue at all. Think of what the maximum torque much be during combustion, likely in excess of 240ft*lbs each time a cylinder fires under full load. Average torque and maximum torque are two different things. |
I understand the crankshaft has to be overbuilt by an engineering safety factor of whatever standards were adopted at the time however, in case of a flywheel lock the torque required to tighten the crank pulley is being transferred into much more sensitive components than the crankshaft possibly including the transmission. All of which are built around the average torque supplied by the crankshaft of peak 128lbft. I'll take my chances with immobilizing the pulley end to tighten it up rather than dealing with the possibly destructive unknown factor in the 30+ year old drive train. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 50336
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| Posted: Mon Dec 16, 2019 11:22 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| jerryherb wrote: |
| Wildthings wrote: |
| If you have looked at the crankshaft of a 1920 vintage engine it is easy to see how it could be bent if 240ft*lbs were applied to it. As for a VW WBXer engine I don't think it is an issue at all. Think of what the maximum torque much be during combustion, likely in excess of 240ft*lbs each time a cylinder fires under full load. Average torque and maximum torque are two different things. |
I understand the crankshaft has to be overbuilt by an engineering safety factor of whatever standards were adopted at the time however, in case of a flywheel lock the torque required to tighten the crank pulley is being transferred into much more sensitive components than the crankshaft possibly including the transmission. All of which are built around the average torque supplied by the crankshaft of peak 128lbft. I'll take my chances with immobilizing the pulley end to tighten it up rather than dealing with the possibly destructive unknown factor in the 30+ year old drive train. |
The peak isn't 128ft*lbs, but much higher. Think of what the crankshaft goes through when you suddenly release the clutch or get wheel hop going up a washboarded slope. I suspect that the maximum torque the crank sees from a cylinder firing is actually around 500ft*lbs so twice what the torque on the nut is. Do some quit calculations figuring a conservative maximum cylinder pressure of 1200 psi and see what you get. |
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dabaron
Samba Member
Joined: June 21, 2018
Posts: 2559
Location: Philly, mang
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| Posted: Mon Dec 16, 2019 11:38 am Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| djkeev wrote: |
I'm thinking of ordering one just to put in my tool box! Even if I never need it! |
after using mine several times, i rate it as an invaluable tool and it belongs in your tool box. i would not have been able to torque the flex plate or the pulley without it.
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jerryherb
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Joined: October 30, 2015
Posts: 205
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| Posted: Mon Dec 16, 2019 1:54 pm Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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| Quote: |
| the peak isn't 128ft*lbs, but much higher. Think of what the crankshaft goes through when you suddenly release the clutch or get wheel hop going up a washboarded slope. I suspect that the maximum torque the crank sees from a cylinder firing is actually around 500ft*lbs so twice what the torque on the nut is. Do some quit calculations figuring a conservative maximum cylinder pressure of 1200 psi and see what you get. |
I understand what you're saying, but as I don't hold a mechanical engineering degree the calculations of combustion pressure against the cylinder walls/piston area and momentum in the wrist pin impact on the crank is beyond me as I don't even have the specs to plug into those equations. I suspect no one other than original designers of the engine have them. What I mean by peak was the average amount of torque at 2800rpm available at the crankshaft ends which is being supplied to external accessories. |
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jerryherb
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levi
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Joined: February 11, 2005
Posts: 5522
Location: Las Vegas
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| Posted: Thu Jan 09, 2020 9:26 pm Post subject: Re: Crankshaft Pulley Bolt: Why Would It Come Loose? |
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I've used an old serpentine belt on several different engine types, along with a big screwdriver to hold in one end folded into the alt, both for loosening and tightening.
Do this with a serp belt that you never want to use of course, since it puts a nice kink in it.
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