The Project Pad

Anybody ever so bored they calculated the crank pulley bolt clamp force?

I would assume based on the way the stock sintered crank pulleys seem to fail on high horsepower cars, it's ALMOST enough to overcome the torsional harmonics of joining the crank damper to the front of the engine...

Thats a good point. The unknown history motor I had to shotgun-rebuild was the only pulley of three where the outer portion of the pulley hadn't walked around the damping material. I may just be bored enough someday to calculate this myself

I think I misunderstood what you were saying but I got it now. I'll just leave my anecdote up there anyway

Welp, I had a moment (lol) and my machine design book handy, so I took a crack at it.



Tl;dr 30,000 lbf, give or take. Probably a little less, since I just assumed the friction coefficient for the diamond washer is standard steel on steel, since I don't have that info handy.

Lol that's awesome thanks Sven
I haven't seen this kind of math in about 6 years (out of college for MET). Good work!

Glad you did it so I didn't have to Kevin LOL

I would have needed my book though anyway.

proud...

I still think I could do 30k lbs with a 3/8th with enough anger....

Hahaha reminds me of the first time I pulled the crank bolt. I only had 3/8" extensions at the time, so I popped one on there and immediately sheared it.

Fun fact: Clamp force can be roughly approximated in most cases by F = 4.75*T/d, where T is the torque, and d is the thread diameter. This is because the coefficients of d in the denominator can be factored out and remain almost entirely constant regardless of the bolt, due to the similar proportions of different-sized bolts. Using this approximation, the clamp force comes out to 28,150 lbs.

And don't you worry, Chris, I needed my book too

Wha... wait a second! The only diamond washer I'm aware of is on the later AAN motors and goes between the damper and the nose of the crankshaft. So it wouldn't have any effect on the bolt's torquing and the clamping force.

Is there another one I'm not aware of?

elaw wrote:Wha... wait a second! The only diamond washer I'm aware of is on the later AAN motors and goes between the damper and the nose of the crankshaft. So it wouldn't have any effect on the bolt's torquing and the clamping force.

Is there another one I'm not aware of?

Yeah, I'm gonna be honest, I'm just going off memory here, and I just assumed that the diamond washer that people had talked about was the one that goes with the crank bolt. It never occured to me that they might be two different things. Wait, there is a washer with the crank bolt, right?

In any case, I just assumed the collar had the same friction coefficient as the threads

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Lol this really took off. On the 3B I didn't come across any washers on the crank.