Torsional stiffness, example Klein

"Nick L Plate" wrote in message
...
On 29 Apr, 00:33, "Clive George" wrote:

And all this reminds me it's getting on time to change my cam belt
again.
Haynes suffers a serious failure here - since their first step is
"take
the
engine out", it's really easy for them - anybody else has a large bit
of
inner wing in the way :-(

Ouch, what kind of car is it? I wouldn't expect to have to take the
engine out to do that job.

BX. It's not that you have to take the engine out, but that there's not
much
room to play with on the end of the engine. There's about a belt's width
between the pulleys and the inner wing :-) If you've got the engine out,
the
entire process is really simple.


"not much room to play with on the end of the engine" -
Use a tubular spanner to remove cambelt cover screws. Cut it to
length if necessary.
If you slacken/remove engine mounts and steady bars there's the
possibility you may not torque them up correctly and your job will
certainly take longer.
While you're there make a good examination for any contamination of
the cambelt area.

Trevor, notice the "again". The cambelt cover screws aren't the pain. You
have to remove an engine mount to get to the cambelt anyway, and if I didn't
believe I couldn't put it back on properly I would'nt be doing the job. And
just how would a tubular spanner help where there's no end-on access anyway?
It's almost precisely the wrong tool for the job. Conventional spanners and
socket sets cover what's needed.

"jim beam" wrote in message
t...
Phil W Lee wrote:
jim beam considered Mon, 27 Apr 2009
20:26:10 -0700 the perfect time to write:

if you skim the cylinder head of a car, and it's overhead cam, the
distance between the cam and the crank decreases. therefore the pull on
the timing belt/chain between the crank and the cam decreases. therefore
the timing of the cam relative to the crank changes and you need to
re-time the cam.

i. for 5 points, does the cam need to advance or retard?

Retard.

ii. for 50 points, if the head is skimmed by 3mm and the cam gear is
115mm diameter, by how many degrees does the cam need to be re-timed?

3 degrees, give or take a gnat's tadger.
You made it very easy by giving a 115mm diameter for the cam sprocket.

no need to show your math - but i want correct answers.

please, nobody else help him - he needs to walk his talk on this one.

I got fed up waiting

you need to advance to compensate because bringing the cam closer to the
crank retards the timing. because the cam turns at half the speed of the
crank, you actually need to advance it 6 degrees, not 3.

3 degrees surely? The cam gear being 115mm already takes care of the
half-speed bit.

"Clive George" wrote in message
et...
"jim beam" wrote in message
t...
Phil W Lee wrote:
jim beam considered Mon, 27 Apr 2009
20:26:10 -0700 the perfect time to write:

if you skim the cylinder head of a car, and it's overhead cam, the
distance between the cam and the crank decreases. therefore the pull
on the timing belt/chain between the crank and the cam decreases.
therefore the timing of the cam relative to the crank changes and you
need to re-time the cam.

i. for 5 points, does the cam need to advance or retard?

Retard.

ii. for 50 points, if the head is skimmed by 3mm and the cam gear is
115mm diameter, by how many degrees does the cam need to be re-timed?

3 degrees, give or take a gnat's tadger.
You made it very easy by giving a 115mm diameter for the cam sprocket.

no need to show your math - but i want correct answers.

please, nobody else help him - he needs to walk his talk on this one.

I got fed up waiting

you need to advance to compensate because bringing the cam closer to the
crank retards the timing. because the cam turns at half the speed of the
crank, you actually need to advance it 6 degrees, not 3.

3 degrees surely? The cam gear being 115mm already takes care of the
half-speed bit.

Though that's 3 degrees advance WRT the cam - it is of course 6 degrees at
the crank. Which is the useful number would depend how the adjustable
sprocket was marked - the relative movement of sprocket and cam is 3
degrees, but that could be considered as 6 if WRT the crank.

On 29 Apr, 04:59, "Clive George" wrote:
"Nick L Plate" wrote in ...



On 29 Apr, 00:33, "Clive George" wrote:

And all this reminds me it's getting on time to change my cam belt
again.
Haynes suffers a serious failure here - since their first step is
"take
the
engine out", it's really easy for them - anybody else has a large bit
of
inner wing in the way :-(

Ouch, what kind of car is it? I wouldn't expect to have to take the
engine out to do that job.

BX. It's not that you have to take the engine out, but that there's not
much
room to play with on the end of the engine. There's about a belt's width
between the pulleys and the inner wing :-) If you've got the engine out,
the
entire process is really simple.

"not much room to play with on the end of the engine" -
Use a tubular spanner to remove cambelt cover screws. *Cut it to
length if necessary.
If you slacken/remove engine mounts and steady bars there's the
possibility you may not torque them up correctly and your job will
certainly take longer.
While you're there make a good examination for any contamination of
the cambelt area.

Trevor, notice the "again".

Could have been a different car.

The cambelt cover screws aren't the pain. You
have to remove an engine mount to get to the cambelt anyway,

Not to inspect it. If there are no indications of wear or age it can
be left unless its a no name job. If you did the job yourself last
time, and did it well, and have been inspecting it as per schedule
you should realise that the milage/age limits given by manufacturers
are very conservative. I think that they allow for contamination of
the belt during installation. Wiping everything down and degreasing
before removing the cover should be a matter of course.

and if I didn't
believe I couldn't put it back on properly I would'nt be doing the job. And
just how would a tubular spanner help where there's no end-on access anyway?
It's almost precisely the wrong tool for the job. Conventional spanners and
socket sets cover what's needed.

When you have the tool, you have the solution. "there's no end-on
access anyway" so how do you remove the cam cover? I've done this
job, admittedly not a BX, but similar problems persist when an engine
is squeezed between wheelarches. I could not use an open ender
because the screws were recessed, could not use a combination ring for
the same reason, could not use a socket and bar for there was
insufficient clearance to the wheelarch, a cranked ring kept slipping
in my fingers for the cramped space. The tubular spanner once in the
gap was the obvious choice, release tension with bar then spin out the
screw rotating the tube in the fingers. Took less than two minutes to
release all screws using this method. There was simply not the space
to use a handled tool with any finnesse. The tubular spanner is
conventional to some. I generally prefer to use a tubular in
combination with a combination spanner. These being the speediest to
operate. When using loose sockets I tend to use a sliding bar.

Chalo wrote:
Still Just Me wrote:
Clive George wrote:
Cam at top, crank at bottom, belt turns anti-clockwise.
Shorten cam-crank distance, keep crank fixed, cam turns a bit
anticlockwise. To put it back you have to turn the cam a bit clockwise WRT
the pulley. Isn't that advancing it?
All irrelevant since it's a theoretical problem that will never come
up in the field. Therefore it's just mental masturbation to make jb
feel like his dick is bigger than AJ's and give him an ego boost.

(Of course, if I was too stupid to find the Shift key, I'd probably
need an ego boost too).

He _is_ a metallurgical genius, you know. Maybe he can mill a
cylinder head without taking it off the engine, using just his rapier-
like wit.

I wonder if he uses CFRP heads and valves on his Honda, to avoid the
devastating effects of metal fatigue.


doubtless you regard metal fatigue as an irrelevant theoretical problem
too.

Clive George wrote:
"Clive George" wrote in message
et...
"jim beam" wrote in message
t...
Phil W Lee wrote:
jim beam considered Mon, 27 Apr 2009
20:26:10 -0700 the perfect time to write:

if you skim the cylinder head of a car, and it's overhead cam, the
distance between the cam and the crank decreases. therefore the pull
on the timing belt/chain between the crank and the cam decreases.
therefore the timing of the cam relative to the crank changes and you
need to re-time the cam.

i. for 5 points, does the cam need to advance or retard?

Retard.

ii. for 50 points, if the head is skimmed by 3mm and the cam gear is
115mm diameter, by how many degrees does the cam need to be re-timed?

3 degrees, give or take a gnat's tadger.
You made it very easy by giving a 115mm diameter for the cam sprocket.

no need to show your math - but i want correct answers.

please, nobody else help him - he needs to walk his talk on this one.
I got fed up waiting
you need to advance to compensate because bringing the cam closer to the
crank retards the timing. because the cam turns at half the speed of the
crank, you actually need to advance it 6 degrees, not 3.
3 degrees surely? The cam gear being 115mm already takes care of the
half-speed bit.

Though that's 3 degrees advance WRT the cam - it is of course 6 degrees at
the crank. Which is the useful number would depend how the adjustable
sprocket was marked - the relative movement of sprocket and cam is 3
degrees, but that could be considered as 6 if WRT the crank.



6 at the cam.

to be honest, i wasn't completely sure on this until i checked different
honda cams on a project. i was putting an imported zc cam from a "d16"
honda engine onto a d15 block. the deck height difference is 2.75mm and
the cam gear is ~57.5mm. i figured out the math at 5.5 degrees, then
started second-guessing, so figured i'd better measure.

first check is the "2ner" guys - using dynos they end up advancing the
cam "about half a tooth", which is nearly 5 degrees. [interestingly, i
note that recently, you can now buy adjustable cam timing gears that
have this offset pre-marked.]

second check is putting the cams in a jig and measuring the angles
relative to the distributor drive - the woodruff keyway offset
difference is 5.5 degrees.

"Clive George" wrote in message
et...
"Kerry Montgomery" wrote in message
news
Am not sure it's so easy to work out unless you know the diameter of the
crank gear and what angle a line between the gear centers makes with the
top of the block. That is, if the center line of the cam is offset
horizontally with respect to the center line of the crank, a 3mm
reduction in the height of the cylinder head will not be a 3mm reduction
in the cam - crank distance.

Two points : you do know the diameter of the crank gear, since it's almost
certainly a 4-stroke engine, and the other one is that the small angle
approximation is probably good enough. To be utterly precise though, yes,
you would need to know the crank/cam distance.

(jim's 115mm pulley is a carefully chosen size for the problem though
:-) )


Clive,
I don't know the diameter of the crank gear, since I have no idea if jim's
made-up example is a 4-stroke, 2-stroke, or some other thing entirely.
Not that any of this is worth talking about, given the origin.
Kerry

On 2009-04-29, Clive George wrote:
"Clive George" wrote in message
et...
"jim beam" wrote in message
[...]
you need to advance to compensate because bringing the cam closer to the
crank retards the timing. because the cam turns at half the speed of the
crank, you actually need to advance it 6 degrees, not 3.

3 degrees surely? The cam gear being 115mm already takes care of the
half-speed bit.


Though that's 3 degrees advance WRT the cam - it is of course 6 degrees at
the crank. Which is the useful number would depend how the adjustable
sprocket was marked - the relative movement of sprocket and cam is 3
degrees, but that could be considered as 6 if WRT the crank.

Usually timing is measured and quoted in degrees "before top dead
centre" of one of the pistons-- i.e. with respect to the crank.

I would expect timing markings, whatever component they're actually
stamped on, to refer to crank timing.

On Apr 28, 8:55*pm, jim beam retard... wrote:

having the cam gear radius equal to one radian's worth of mm's makes the
math real easy and i love honda for that.

I like how legends in USGS maps show arrows toward true north,
magnetic north, and UTM grid north-- and list the angular offsets
in milliradians.

To walk one kilometer true north:
walk one kilometer of UTM northing
and x meters of UTM easting (where x
is the angular offset between UTM grid
north and true north, in milliradians).

This is an approximation based on cos(x) being nearly 1
and sin(x) being nearly x for small values of x.

Tom Ace

Tom Ace

Clive George wrote:
"Ben C" wrote in message
...

I guess this does assume the tensioner is on the non-pulling side,
rather like the derailleur cage on a bicycle. But it probably is.

Wouldn't work, would it? Well, without having a tensioner exerting more
force than the camshaft can provide as resistance, which would almost
certainly be bad for the belt.

And all this reminds me it's getting on time to change my cam belt again.
Haynes suffers a serious failure here - since their first step is "take
the
engine out", it's really easy for them - anybody else has a large bit of
inner wing in the way :-(
Ouch, what kind of car is it? I wouldn't expect to have to take the
engine out to do that job.

BX. It's not that you have to take the engine out, but that there's not much
room to play with on the end of the engine. There's about a belt's width
between the pulleys and the inner wing :-) If you've got the engine out, the
entire process is really simple.

Now a 20v Fiat engine reputedly really doesn't fit in some of their cars -
that is engine out to change the belt.



Been there, done that, water pump R&R on a transverse V-6, had to jack
the motor up 3". I find that while most manuals are cribbed from the OEM
shop manual, some of them offer unique approaches to difficult problems.
News group archives are another valuable source, but like this one, lots
of bad information.