Crank Bolt Tightening Debate, what is the issue?

I just joined this group, and I see a heated "crank bolt
tightening debate." This debate has forked into several
branches and it is difficult to see what the issue is. It
started before I joined this group, and it is not clear
to me what the issue is. Is there a summary?

 

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

 

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

Sure is.
www.googlegroups.com

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...

www.boltscience.com


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

 

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.

 

/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.'

flared

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.

http://square.cjb.cc/bolts.htm#centrifugal

 

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.

 

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...

 

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