"Steve" <no (AT) spam (DOT) thanks> wrote


Generally speaking it IS. Not by any great amount, but it is slightly
thicker. At least the lab tests at Texaco showed that. Maybe liquids flow
differently in YOUR lab?

Steve wrote:
eh? i don't know who you think you're talking with, but you /do/ know
that "me (AT) privacy (DOT) net" is a generic anti-spam address that /lots/ of
people use don't you?



backatcha big guy. but because i simply can't resist taunting idiots,
why don't you tell the class what you make of this:

http://i43.tinypic.com/24bq0jn.jpg

thanks.

jim beam wrote:


Oops. I owe you a very sincere apology. There is someone who just goes
by "Jim" that pops up every time a .tech thread gets cross-posted with a
..makers.honda thread, and I had you and he confused.

That was 100% my mistake, and I do apologize.


Since I mistakenly dragged you into this, I feel I owe you the
background. The last time this came up and I pulled up an oil company's
spec sheet that showed their 10w30 was slightly thicker than their own
SAE 30 even AT 100C, "Jim" dismissed it as "believing glossy
advertising" and claimed that an SAE30 weight would always be much
thicker than a 10w30,"especially" on the high side of 100C. The chart
you just linked agrees with my claim, which is that since Xw30 oils
have a viscosity index much higher than the average SAE 30 oil, they
will match SAE 30 at 100C (where the spec defines the "30" in an Xw30)
and then as temperature continues to increase the Xw30 will actually
maintain a greater thickness than the SAE 30. The viscosity lines
clearly CROSS at the 100C measurement point, so above that point (until
somewhere > 300F where the VI improvers start breaking down and the oil
itself begins to oxidize) the 0w30 becomes THICKER than the straight
SAE30. NOT thinner. Granted, that's not shown on this chart, but its
what happens.


Now, rather than just calling each other morons (which I admittedly feel
like after that mistake...), could you possibly explain your claim that
leaf spring suspensions, in general, have more lateral deflection than
other designs? I agree that *particular* implementations may have
excessive lateral movement, but in general I've always found that
panhard-rod/trailing arm axle designs are more prone to slop (due to the
large bushings involved) than most simple leaf-spring designs. And even
when the slop is eliminated (heim joints, etc.) there's a residual issue
of the fact that the axle makes a large radius arc relative to the
vehicle centerline as the suspension extends or compresses, giving rise
to the "head toss" handling quirk that coil-sprung trucks like Jeep XJs
and TJs sometimes exhibit. In fact, Dodge is rather vocal in the
automotive press about how much work went into the coil spring rear
suspension of the new Ram 1500 to enable it to match the stability and
load-carrying capacity of conventional leaf suspensions... work that was
required BECAUSE of the lateral rigidity and inherent body-roll
resistance of leaf spring stacks, which were lost in utilizing coil
springs.

Steve wrote:
no problem.


to an extent. but it's a bit more complicated than that. viscosity is
not lubricity so exclusive focus on that isn't sufficient. what you
need is an oil that is stable not just at temperature, but at high shear
rates too. from what i understand, an odd assortment of base oil
compounds with branched chains, aromatics and inconsistent compounds,
like you have with "single weight", can't be relied on to do that in a
high shear hydrodynamic situation without all kinds of oddness like
cavitation and shear thinning.


ok, we need to separate marketing spin from reality. reality is that
leaf springs are CHEAP [the primary objective of anything detroit],
simple and kind-sorta work ok with low lateral loads, low speeds, and
where unsprung weight doesn't much matter. but if any of the above are
a factor, they suck. aside from the more obvious problems with things
like axle rotation on torque, the lateral issue is the same kind of
problem you can have with a saw blade. the frame remains rigid, but the
thin blade [elastically] buckles and bucks if load, speed, angle etc.,
aren't just right. that same elastic buckling is what accommodates
lateral movement on leaf springs. add to that worn pivot points and you
have a real stability problem.

as for being "rather vocal", all this stuff about having to spend money
to "design" a suspension system is just sheer effrontery and b.s. there
is nothing new in what they're doing. if anything, it's decades behind
the times. i've been to europe many times, and over there, they've had
heavy and light trucks with independent suspension, not a leaf spring in
sight, for what seems like ever. even the last hold-out of european
backwardness, the land rover, finally got with the program in the 80's.
here /we/ are in the naughties, 30-odd years later, and we're making
out like it's new and complicated??? that dude, is ridiculous.

http://www.unimogcentre.com/unimogprinc.html

these guys know what they're doing.

jim beam wrote:

Agreed.

reality is that
Well... "suck" is relative too. Almost any leaf spring implementation
that can carry a 1/2 ton class truck or SUV will have a master leaf that
is on the order of 3" wide and 3/8" thick solid spring steel, and the
whole spring stack will be about 1.5 inches tall with the master leaf
only acting alone over a span of 3-5 inches longitudinally. So you're
really talking about "bending and buckling" something that quite frankly
is NOT going to bend or buckle under the loadings that the tires can
apply to it.

But my real disagreement here is that we have to compare leafs and their
shortcomings to real-world alternative rear suspensions made with
oversized bushings, sub-optimal geometry to avoid impinging on interior
space, and rather flexible stamped steel or cast aluminum members that
compare rather poorly to the leaf spring stack in terms of rigidity. FOR
THE MONEY, leaf springs quite often suck LESS than alternatives, which
was my point. IMO that was a big part of why the Honda Ridgeline hit the
market with a dull wet thump- it was all road manners and no hauling
ability. Were there some horrible leaf spring designs? SURE! Look at any
GM midsize car of the 70s that used leaf springs with long single-leaf
sections and not enough asymmetry to overcome axle torque (Nova, for
example). Those are the springs that gave rise to a whole aftermarket of
traction bars and other band-aids to try to get them to work as well as
better designs.

Of course leafs don't play with independent rear suspensions which are
becoming more common even on trucks, but that too is fuelled largely by
marketing hype. Solid axles actually have some favorable handling
characteristics (such as roll center) that get ignored because they're
considered "ancient" by the advertising types. If you want a truck with
an acceptable combination of weight hauling capability, drivetrain
strength, low cost, and acceptable handling, then solid axles (with or
without leaf springs) are actually near the top of the list of candidates.

Can they ever achieve the ultimate handling of a good independent rear
suspension? Of course not, or we'd see solid-axle Ferraris. Can an
independent rear suspension ever equal solid axle load carrying ability
and longevity under heavy loading? No, not at any reasonable cost (or
else we'd be seeing IRS on cement mixers. The pickup market falls in the
middle where either solution can be made to work with some compromises.


The innovation here is combining leaf springs with a solid axle in this
application, not IRS. Its the first non-leaf-sprung solid axle truck
since the '72 GM pickups, which were notoriously poor handlers when
loaded, although much better than leaf-sprung trucks when empty. Its the
combination of load carrying ability and stability with unloaded manners
that is new here. IRS ala Unimog or Humvee would be cost prohibitive
and unnecessary. I agree they're just crowing about what someone should
have looked into about 15 years ago, but as you said- COST is an
engineering driver as much as function in many cases.

At any rate, thanks for the discussion.

Wonder if he ever found out what the problem was????

krp wrote:
What was the question again??? :-p

jim beam wrote:

If you are referring to petroleum based oil your understanding is not
correct. The fact is that a single weight (monograde) oil is well
suited to handle the high temp high shear requirements of modern oil
standards. In fact if you research the origins of the current standard
for high temp high shear you will find the standards for multigrade oils
were arrived at by sampling all the monograde oils being sold and the
standard for high temp viscosity was set at the 95 percentile of what
tests found for monogrades at that point in time. That is, almost every
single weight oil (95% of them) they tested was better then the minimum
standard set (Viscosity at 150C and 10^6 s^-1 shear rate) for that
particular weight range. Very few of the multigrades exceed the standard
for high temp viscosity by much but almost all monograde oils do. And
this only applies to 20 and 30 weight oils . A 5w40 or 10w40 is even
required to meet the same standard that the straight 40 wt must meet. A
10w40 is only required to have the same viscosity as any common
monograde 30 wt to meet the the high-temp-high-shear test standard. Look
it up if you don't believe me.


The problem of the petroleum based oil becoming very thin and weak at
high temp and high load conditions is and always has been a problem
related to the viscosity improvers used in multigrade oils. The polymers
that are used to improve viscosity start to break down at temperatures
above the standard 100C temperature at which viscosity is measured for
establishing the grade. What that means in simple layman's term is that
lots of engines were being damaged when drivers attempted to haul their
boat up a hill on a hot day or when their cooling system failed for some
reason at highway speeds. This was a known problem with petroleum based
multigrade oils. But since the oil companies and automakers had no known
chemical solution for the problem with petroleum based oil (other than
the unacceptable one of using straight weight oils) the problem was kept
very quiet for many years after multigrade oil was first introduced.
Then about 15-20 years ago when the technology was sufficiently advanced
the problem was finally addressed by changing the standards. That change
is one of the main reasons why you now hear so many claims on how modern
oils are so so much better than they used to be. That is because what
was in most cars on the road 30 years ago was really crap if your engine
ran hot for some reason. Even today they have no means to economically
make the viscosity of 10w40 a good as straight 40 wt. oil (at the 150C
temp and 10^6 s^-1 shear test) and that is why the standard for
viscosity for those multigrades are less than it is for the 40 wt.
monograde. It is not until you get to the 15w40 oils that the high temp
viscosity requirement for multigrade is the same as it is for straight
40 wt.

The irony of all this is that the oil companies have used this as an
advertising ploy. Nowadays, they claim that their multigrade oil is
specially formulated for high temp high load operating conditions. The
implication is that because the straight weight oils are not specially
formulated for high temp high load they must not be as good under those
conditions. Apparently through this sort of advertising they have been
successful at leading many people to leap to this false conclusion.

-jim

"Steve" <no (AT) spam (DOT) thanks> wrote

The tranny QUIT on him. No-go... I wonder IF he found out why.

Steve wrote:
but they don't. really.


that's completely untrue. think about it - there is no way a "boxed"
structure is as rigid as a triangulated structure. it simply cannot be.


i don't think it's about "reasonable" cost - earth movers don't use leaf
springs and they're /way/ bigger than cement mixers. if you want my
opinion, based on my having traveled a lot and seen other peoples
solutions, i think it's simply that we have a kind of bizarre cultural
inertia here that simply doesn't /believe/, hence we don't even try.


but it's not cost prohibitive. and what cost is safety? the exploder,
leaf sprung, is a classic example. how many people do we have to kill
before we start looking at the big picture?