Crank Bolt Tightening Debate, what is the issue?

you have the correct original title for the original thread it all started with "jim bean" then "tegger' and then the posse's joined

someone has a website dscribing the finer points of bolts

HTH

"robm" wrote in news:ejMbf.6029$ snipped-for-privacy@newsread1.news.atl.earthlink.net:

To robm: Go back to the original message and start from there.

Sure is.

Go to Advanced Search, and search in rec.autos.makers.honda for the title of the thread (not including the "Re" part).

Oh, I'll do it for you...

And by the way, it's not a good idea to start new threads regarding another cross-posted thread without cross-posting your new one. Most of the posts in the thread above were posted in rec.autos.makers.honda and only ended up here on account of the cross-posting.

Not everybody checks alt.autos.honda.

The debate grows out of the observation that crank bolts require several times as much torque to break loose as the specified tightening torque at timing belt changing time. One theory has it that the bolt actually creeps CW with engine operation, while another has it that the bolt doesn't turn and the increase in break-loose torque comes from other phenomena.

It has been the subject of conjecture for some time and only recently flared into active discussion.

Mike

"Michael Pardee" wrote in news:V7KdnXoibs8Ji-3enZ2dnUVZ snipped-for-privacy@sedona.net:

That theory has been decisively debunked by a representative of Bolt Science, Ltd. in Great Britain.

The theory also does not explain its opposite in engines that turn so as to LOOSEN the bolt. NObody can explain why, if "creep" exists, those bolts do not come loose in operation. Every time I bring this up, it gets ignored.

This is a well-known and established fact. To deny its existence in favor of discredited conjecture is not wise.

er, what's the context? "debunked" requires somewhat more analysis than "i got this email". have your bolt science guy post to this group.

no it doesn't! /you/ are ignoring the fact that /other/ bolts use loctite and/or locking washers!!!

other phenomena /do/ exist. we've already discussed them: rust, localized adhesion, etc., but they do /not/ account for an increase in torque within a period of 24 hours as per my crx! and proven galling is as plain an evidence of lash as you will /ever/ see. and once we've estblished that lash exists, there is no "discredited conjecture".

the fact that you mistook bolt washers for pulley wheels doesn't strengthen any argument that you can interpret the evidence correctly.

"Michael Pardee" wrote

/My/ theory ;-) emphasizes the crankshaft turning faster than the bolt turns (at times, possibly consistent with what Burt has written about impulses acting upon the pulley due to inertial/centrifugal forces, which then imposes forces upon the bolt head, etc.), with the result that the bolt advances deeper into the crankshaft. But bolts can advance without actually turning.

In other words, there is at times some relative motion between crankshaft female threads and bolt male threads.

I think, but am not sure, that Jim calls this "precession." I call it simply 'male and female threads working per their design when sufficiently loosened.'

Ha good choice of words.

It appears that the threads don't bind and free to move. But I can see that the face of the bolt takes on a lot of stress, sometimes scratched beyond recognition on some cars. I also believe that the pulley is expanding, caused by the centrifugal force which squeezes the face of the bolt. I can't explain this without a drawing. See this same page again but scroll to the bottom.

Okay, not saying either theory is accurate, but there's a simple explanation for this *If* "creep exists": since rotation of the pulley is limited by the splines/key, and it only tweaks a tiny amount under rotation, the bolt would only loosen as long as it's tight enough that the friction between the bolt and the pulley overcomes the rotational torque. Once the bolt is loose enough that it "slips" against the pulley, it won't loosen any more.

"Burt S." wrote

You say at the above site:

"This image shows what the power of centrifugal force can do. It can squeeze the bolt to the point where the bolt can get pretty tight."

I am not sure what you're saying. My view: The pulley has centrifugal forces acting on it. If the bolt were absent, the pulley would fly off the crankshaft. With the bolt present and reasonably tight, the pulley is pushing against the underside of the bolt head. This pushing doesn't "squeeze" the bolt. It stretches it. The stretching reduces the bolt diameter a bit. The smaller diameter makes it "looser." Hence with, say, momentary impulses, the crankshaft will turn a bit faster than the bolt, resulting in relative motion between the two.

The boltscience.com guy first said "the screwing in theory is somehat improbable." I don't know if he was talking about the notion that precession was behind this alleged rotation, or something else. (Again, I completely reject the precession theory. Tegger had by accident assumed it was part of my theory when he wrote boltscience.com.) In his second email, the boltscience.com guy said, "There is no net rotational movement."

I am not sure he is correct. He might be. Physics-engineering wise, I think it's valid to hypothesize, using simply Newton's laws, that high enough pulley rotational speeds and sudden changes in them could certainly tear that bolt head right off or rip the bolt right out, destroying the male and female threads. Not that the RPM ever gets /that/ high. Also, there are other limiting factors. I am only attempting to indicate the forces at work here. I don't know if they are large enough to do what I propose.

He didn't debunk it. He said there was no net rotational movement and did not explain it or rebut the theory. That's his opinion. He is, on the other hand, drawing from some experience, so I don't disregard what he said.

Rotation of the pulley /around the crankshaft/ is so limited to the angular lash in the key or splines.

Rotation of the bolt is not so limited. If it's loose, and the friction between its threads and the crankshaft's female threads is small enough, it can turn freely and without limit from the key or splines.

The crankshaft/pulley/bolt assembly move as one only as long as the axial load in the bolt is high enough to maintain clamping.

tegger kindly forwarded me the email, and the boltscience guy says no NET rotation movement - which is true for the pulley because the woodruff. but it still lashes and those lashes create impuse, which in this case happens to be in the tightening direction.

it's also worth noting that, apart from the bolt locking methods commonly used in "loosening" applications, most pulley wheels on "loosening" engines incorporate rubber insulators - ostensively for harmonic balancing - but these also substantially mitigate lash momentum.

That's not centrifugal force causing the pulley to come off...

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Thank you; this tells very nicely what the issue is.