Timing belts

i fully admit to being rusty on this stuff, by why would you have a glass-
filled aramid fiber??? there is no benefit that i can see unless you want
to reduce elasticity of pure aramid, but the fatigue properties would
suck. glass is plenty stiff and virtually fatigue proof if the surface is
sufficiently protected. in which case, maybe you mean aramid /coated/
glass fiber?

 

I have no argument there, but it is common practice. Somebody has to pay the
big depreciation, I guess.

A mechanic who had a radio show in Phoenix a while back (maybe still does)
had an interesting formula for deciding whether it is cost effective to
repair an old car or to replace it. As a basis for comparison, learn the
lease payment of a car that would fulfill the requirements you have for the
vehicle you currently own. Amortize the costs of repair at that rate (say,
$300 per month) to determine when you would break even on the cost. If you
don't foresee putting money into the old car at that rate for the indefinite
future - and most owners have a pretty good idea what they can expect, as
opposed to what they fear - then it makes economic sense to do the repair.
This formula neglects the added cost of comprehensive insurance for a new
car or the higher costs of registration in many states, but it puts people
in the ballpark.

Mike

 

"Might" is the operative word. It assumes several catastrophic problems and
a flurry of lesser problems. Consider the handful of potential problems that
could comprise the $12,000: transmission failure (about $3000), driveshaft
replacements, a timing belt (since it is a predictable expense it would be
correct to put 4/7 the cost into four years). That's still a very, very long
way from $12K... and it assumes terrible luck. I would think if somebody was
having that kind of record with a car they would unload it, even at a huge
loss to a DIYer like me, long before the four year mark came around. If a
car is that bad when a few years old you know it was that bad when it was
new. The difference is that when new nobody knew how bad it was before it
was sold.

It's amazing how many costs are not covered by warranty. My daughter-in-law
lamented that the non-warranty costs on her Kia, counting the mandatory 3000
mile oil changes to keep the warranty in force, were more than her car
payments. You mention "all those oil changes plus new tires, shocks, brake
job and battery" (here in Arizona you can add windshield replacement)...
none of those are warranty items. New cars need those at the exact same rate
used ones do. In the end, a warranty is only as good as the service you can
get. Even if you get past the problems of denials - a very common complaint
in auto forums - good luck finding somebody who actually knows how to find
and fix your problem.

New cars demand repairs, while used ones do not. That statement is easy
enough to illustrate. My son-in-law is a new driver and tried to take his
'86 Taurus to Phoenix as its first freeway trip in many years. On the long
climb out of the Verde Valley the engine lost coolant, overheated and ended
up with two warped heads. If the car had been worth it he would have been
looking at a repair he couldn't afford. Instead he is out the $300 he paid
for the car. $2000 vs $300 - not a hard decision.

Personally, I am relieved when the warranty runs out on just about anything
I own. I get no pleasure from anything that I have to convince somebody else
needs to be fixed, and I am easily frustrated by poor troubleshooting skills
in techs I have to rely on to complete the repair.

BTW - I don't think you should be touting the unalloyed advantages of "new
technology" to Elle or me - we've been in high tech too long to believe
that. But maybe I can interest you in a Windows ME update to your old
Windows 98?

Mike

 

I was amiss in calling it "welding in place" when the problem is actually
galling, like stainless steel does. According to the guy at work who learned
about it a little late, when he removed his plugs even according to the
procedure they bound and screeched all the way out. Not a good thing in an
aluminum head.

 

ISTM the last statement above is wisdom borne of years of
experience, honed by the laying on of hands often on
engines. It is something I had not considered, maybe because
I have not owned nearly as many cars as JT, the OP or you,
or because I have always owned a Japanese-make car.

snip; please look back for context

Wisdom beams through this post like sunshine in Arizona.

This drives my happy Honda DIY efforts. It is not that the
dealer's or other import shop's techs are not good; it is
that they are not allowed the time to do a repair or
maintenance really well.

Ha, but to explain to others, I trust you mean that Windows
ME turned out to be terrible and many reverted to the older
Windows 98 where possible?

Elle
Former Win ME user; now Win XP user, and whose dad is still
happily using Win 98 on one of his computers, partly because
of the principles Michael Pardee states here.

 

There are many applications for glass filled polymers. Depending on the
glass partical size and aspect ratios, it can greatly increase the
Young's/Flex modulus (stiffer) without greatly losing the material
properties (though there will be some loss). This will reduce part
elongation and increase tensile strength, as long as one doesn't go too far
and displace too much of the resin.

Glass filled polyamides and polycarbonates are used in a wide variety of
applications (mostly industrial).

As an example (fictitious in so much as I don't have the actual numbers in
front of me. I'd have to do some research to get real numbers as it's been
quite a few years since I've looked into this for an application), one can
use 10% glass fill in aramid fiber and reduce the elongation by a factor of
15%-25% and increase the tensile value by an almost equal amount, but add in
25% glass fiber, and these can values can be greatly reduced. Fatigue
properties would be dependent on each application as well, depending on the
expected bend radii needed, velocity, service temperature, glass particle
size/aspect ratio and other factors.

Carbon fibers and nano-clays are also used, though I believe glass is the
least costly.

 

absolutely, understand all that. but small particle reinforcing, to my
incomplete understanding, doesn't serve well in a fatigue environment.
that is the kind of mechanism by which plastic radiators crack - great low
cycle mechanical properties, but when the load cycle gets up there,
fatigue romps away. i would therefore expect timing belt fiber, given
that it's subject to considerable repetitive strain many times that of
traditional small particle reinforced plastics, to have the most coherent
microstructure possible - no fillers. but i'm guessing.

 

engine clearance of a hot engine at 6,000rpm is somewhat different to that
of a cold engine hand turned on the bench. if the manufacturer says it's
interference, i'd believe them.

 

yes. penetrant allows lube all the way down the tread. if it's galling
and dry, forcing the plug to turn can drag the whole thread out with it.
trust me on that.

 

i think frod's desire to save a few cents by not having a compression
washer on their spark plugs is one of the most fundamentally retarded
design decisions of the 20th century. it's cost the consumer millions and
millions of dollars in munged heads and excess labor. and the thing is,
they knew it would be that way too! the pinto fiasco, the exploder
fiasco, red rear turn signals... frod management deserves a good hard
kicking in the balls.

 

The engine (B230F) is claimed by Volvo to be non-interference. See also
http://www.volvoclub.org.uk/faq/EngineSealsBeltsVent.html#InterferenceEngines
"The B230 series is non-interference with the exception of the B230E
[(high-compression B230 sold outside of North America)]."

 

Usually, glass re-enforcement is within a binding matrix of a polymer.
Depending on the actual additive, percent used and the polymer, it may
not have a great negative affect on fatigue. I am not sure if plastic
radiators are a thermoplastic or a thermoset based structure, but the
aramids used are thermoset and do have different properties from a
thermoplastic.

I would think that without the binding polymer, 100% glass fiber would
be more prone to fatigue failure than with the binding polymer (think
of glass fiber optic cable vs. polymer fiber optic cable and bend
radius).

Of course (as I mentioned), it has been awhile since I have looked
into this application, and there may have been advancements made in
the use of long glass fiber with or without a binding polymer matrix.

 

but glass pretty much doesn't fatigue afaik. it fractures if the
surface degrades, but that's not a fatigue mechanism as such.

just looked at the bosch automotive handbook - for positive drive belts,
they say "the tension member consists of twisted glass fibers". no
other materials details. under friction drive, they discuss nylon,
polyester and aramids - i think elasticity is a benefit in friction
drive, but not in toothed belts as it affects pitch and thus, wear.

 

my argument is with the "provably" statement. cold bench != hot running.

 

It is dependent on how much elasticity is allowable and the load needed. If
you go to www.matweb.com and enter a search term of "nylon 66" (I would hope
that you would get the same results as I did)...

If you look at item 13, this is general nylon 66 properties. For this, the
averages

ultimate tensile 99MPA
elongation at yield 9%
ultimate yield 51%.

If you look at item 19 (10% glass filled), the average values are

ultimate tensile 96.3MPA
elongation at yield 4.39%
ultimate elongation 5.08%

So the ultimate elongation is limited with only a minor impact to overall
tensile. If you look at item 20 (20% glass filled), the ultimate tensile is
reduced to 58%, which is a major impact to the overall strength, while
elongation at yield is 4% and at break is 4.32%, which further limits
elongation.

It would be faily easy to calcualte how much overall fiber is needed if the
tensile requirements are known and 4.39% elongation at yield and 5.08%
ultimate elongation meets the need of the application. The natural material
may even meet the a specific need as long as tensile at yield is high enough
(I probably should have included those values for comparison as well).

As far as fatigue is concerned, that may or may not be affected, depending
on use. Usually (but not always), fatigue is not greatly affected unless
tensile properties are greatly affected.

Once again, that's not to say that this is the case as far as a Honda timing
belt is concerned, they may be using something different.
I do know this is the case for the extruder drive belts that I use on my
equipment, which are timing belts, and they last much longer today then they
did 20 years ago.

 

There were plenty of instances of timing belt failure when I was active in
the alt.autos.volvo forum - about like we see here. Those in the multi-valve
engines invariably resulted in engine damage while those in the earlier B230
engines never did. Over the decade or so I was active there that seems
pretty solid. It makes sense; with the standard cam the clearances were very
large. With the high lift cam (available in the UK as the "K" cam) you might
have a point, but not with anything available in North America.

Mike

 

Not really. This year we (Austin, TX) had consistent highs of 100 or
more. And it's supposed to hit the low 30s/ high 20s tonight (it's 70
something at noon).

I think the phrase "complete engine rebuild" sums it up nicely
(badly?)

Kevlar is wonderful in both tension and compression. But once a
construction like a belt (or body armor) starts to fail, there's a
cascade effect.
--
- dillon I am not invalid

When you wish upon a falling star, your dreams come true.
Unless it's really a meteorite hurtling to the Earth which
will destroy all life. Then you're pretty much hosed no
matter what you wish for. Unless it's death by meteor.

 

Wait a minute, "red rear turn signals" .... that's how they are supposed to
be. If God wanted them amber he would have given us better night vision. I
can remember when anything other than red in the rear was illegal. OOOps
...showing my age again.

 

Actually, I think the point isn't weather or not you can see amber or red,
but which one destroys you ability to see anything else after having it
flash in your eyes while behind it. I really hate those vans with the huge
ambers mounted about two thirds the way up the back. A few seconds behind
one of those at night, is like staring at the sun and then walking into a
darkened movie theatre and trying to find a seat.

 

Wide range here as well, but the extremes at both ends are limited in
time. I would think extended exposure to the extremes would be a
worst case scenario. I always use the change interval listed for
"normal" conditions, and it hasn't failed me yet (knock on wood).

Yep, I guess there is no way to soften the blow....I probably should
have said failure is usually catastophic....!

Try standing next to a 3 1/2" plasticating extruder with a 60 HP drive
running at 1750 RPM applying untold amounts of tourque through a huge
gearbox when one of those belts fail and gets tangled in the drive
sheave and rattles around for awhile......(usually a belt that is 10ft
or more in length by about 6" wide)....it can take years off of ones
life.