Re: to change a Honda Accord 1988 model timing belt

jim beam wrote:
TeGGeR® wrote: 
jim beam <nospam@xxxxxxxxxxx> wrote in
news:R-SdncMSAoVPtPneRVn-oQ@xxxxxxxxxxxxx:

TeGGeR® wrote:

jim beam <nospam@xxxxxxxxxxx> wrote in
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<snip>


in this instance, it /can/ tighten because of crank rotation
direction. the pulley /is/ keyed as you say, but it still has a small degree
of lash, and the pulley/bolt still have momentum. and crank rotation velocity spikes with each cylinder combustion. 




Sorry, but this is dead wrong. Once tightened to spec, that bolt does
not move.


dude, it can and it does.  that's why drive shaft nuts are peened -
same thing.  one will tighten, the other loosen.





Do you havre any references to this?




the amount of
movement is restricted to the lash on each side of the key, but it
doesn't even need a thou to slowly rotate.  just because it doesn't
/look/ like it's moving, doesn't mean it won't!




Then explain why the exact same thing happens to Toyotas, Fords and other vehicles that turn the engine such as to LOOSEN the bolt.

I have been unable to find any references to your alleged phenomenon in Google searches.


My personal theory is that with heat and vibration, the bolt and its threads "settle in" and thus increase their static friction.



bolts can loosen on side loads - as is the case with l/h wheel nuts on
cars where r/h threads are used.  or they can tighten - as is the case
with pedal spindles on bikes.  bikes have r/h thread on the right and
l/h thread on the left to prevent loosening, and often these continue to
tighten with use.  side loads cause what's called "precession" and that
works both ways.

we don't have much side load here, so the only movement is angular.  an
example of angular tightening is the locking ring on a fixed gear bike.
 it's l/h thread vs. the drive cog which is normal r/h thread.  the
drive cog can move back & forth slightly in use [resistive braking] and
this tightens the locking ring.  in fact, because soft alloy hubs are
used, it's not uncommon for the locking ring to strip after a time, even
though the initial tightening torque of the cog & ring are well within
normal spec.

regarding citations for the honda pulley bolt, i don't have anything
immediately to hand.  you have to go back to basic engineering
principles.  if you can accept that there is some angular lash in the
pulley, you can figure out the inertial predominance of that lash as the
crank rotates.

i absolutely agree, other factors such as rust do undoubtedly have a
significant impact on tightness of fasteners, but that's not the case
with my crx and messing about with the pulley bolt on two seperate
disassemblies on consecutive days with only one run in between.
[initially to replace the locked water pump and determine whether the
motor worked at all, and the second day, having decided that the motor
ran like a champ, deciding to re-do the job properly and put in a new
pump, not the junker i'd used before.]

i'll also say that having worked on a number of other "right way" motors
and loosened their pulley bolts as well, i've never come across anything
as tight as the honda bolt.  the difficulty with an ordinary pulley bolt
is simply holding the wheel so the bolt can be undone.  once the pulley
wheel is held, it's not that much of a problem.  and you'll note that
most of them have locking washers under them [the honda doesn't].  the
starter motor trick is a great quick convenience if you don't want to
bother with a holding tool or have an impact driver.  but even if the
motor turned the right way for the starter motor to try unscrewing this
bolt, i'm not sure it would work in this case.  starter motor cranking
torque i believe to be in the range ~200 ft.lbs, [which /would/ shift an
unstuck bolt] but i think estimates of these honda bolts being stuck at
over 400 ft.lbs completely reasonable based on me needing to bounce my
full weight on an 18" [3/4"] breaker bar.

Wow the replies are overwhelming. Thanks Dudes... Its like bing in Honda knowledge heaven..
.

Relevant Pages

  • Re: to change a Honda Accord 1988 model timing belt
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  • Re: to change a Honda Accord 1988 model timing belt
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