FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction Control
DATE: Thu, 01 Jul 99 07:36:25 GMT
ORGANIZATION: A1 Internet news-server
NEWSGROUPS: rec.autos.4x4

In article <7lecj5$134$1@bgtnsc03.worldnet.att.net>,
   "Allison and Chip Orange"  wrote:
>
>Jeff Schwartz  wrote in message
>news:7ldfsk$ar8@dfw-ixnews7.ix.netcom.com...
>> I am not familiar with the Blazer but from what you describe it sounds like
>> it uses a full-time 4x4 system employing a reactive coupler in its t-case.
>> There are 2 opposing view points on this. There are those that prefer a
>> full-time 4x4 system to employ an open differential in its t-case. Assuming
>> open differentials in both axles, this system will always distribute even
>> torque to all the wheels all the time. This is beneficial in good traction
>> conditions as it is very sure footed and lends itself to pulling and towing
>> scenarios. However, it deteriorates in marginal traction conditions because
>> open differentials bias rotation to the wheels that offer the least
>> resistance - the wheels with the least traction. Hence, when you need added
>> traction control a system based on open differentials will be disappointing.
>
>Thanks for the explanation/summary.  Do you think that such an open dif
>system, when used in conjunction with a system that brakes the slipping
>wheel (thus allowing the power to go to the other wheels) is still
>"disappointing"?

It is a very nice system to restore most of the traction while still 
allowing to drive in very tight corners, as well as acting very swiftly 
(driving off onto a main road). So it gets a bonus on the foolproof 
aspect....it's always there to help you, no thinking required.

However, as the *only* system it has its downsides for serious 
offroad....it is not a very efficient way of restoring traction, engine 
power is wasted in heat, instead of foward momentum. A full center diff 
lock would be a first requirement, especially since in winter you can't 
drive very long stretches with only two chained wheels....the non-chained 
wheels would be slowed/braked down constantly, because they would spin much 
sooner as the chained ones....and there is little you can do to prevent 
them spinning.

Also note that the first vehicle having this, the Mercedes ML-series, 
really needed it because of its poor articulation....and having independant 
suspension, a full locker (like on the Mercedes Gelaendewagen) would be too 
much stress on the relatively fragile drivetrain (half shaft joints).
Actually, there are very little to no vehicles that combine independant 
suspension and a full locker....unless they have geared hubs (which reduces 
the stress on the half shafts by the same factor as the gearing).

--
Bye,

Willem-Jan Markerink


      The desire to understand
is sometimes far less intelligent than
     the inability to understand



[note: 'a-one' & 'en-el'!]















From:             "Keewai Tan" 
To:               <80_series@sgiblab.sgi.com>
Subject:          RE: Re[2]: [80] Future of Land Cruiser [SUPER chat]
Date sent:        Mon, 1 May 2000 15:30:25 +1000
Send reply to:    80_series@sgiblab.sgi.com

G'day,

This ongoing debate has drawn a couple of interesting
points from, among others, David and Zaffer. 

Zaffer has a down to earth, highly pratical experience
which he can relate easily regarding his ownership of
a HDJ100. His remark of 100s being 99.9% as good as his
80s is significant. And probably Toyota marketting dudes
will applaud that. 

I don't intent to dispute Mr. Zaffer (or others) opinion.
Infact, I genuinely believe his observation with ragards
to his HDJ100. However, having said that, I would like
to comment that (marketeers take note), Mr. Zaffer opinion
on the 100s has very high probability to reflect the general
ownership perception about the 100s. I personally haven't 
come across unhappy 100s owners.

Now, for the time being, forget about 4WD. Just think about
numbers. All the numbers we deal with whether it be volts,
dollar/cents, kpa, Nm etc. I can swear that accountants,
marketeers, most engineers, will agree that the field of
real numbers are sufficient to address all their needs.
In fact, among most of us, we can't imagine a case where
the field of real numbers fail us, be it in medicine,
machinery, mechanics, accountancy etc. To this people the
field of real numbers is trully well proven and used.
They will say it fulfils 100% of their needs.

But, I can tell you, there are groups of minority, who
will swear that the field of complex numbers is the true
numbering system. And they can't get by a single day in
their job without it. Infact, according to this people,
the universe can't even exist without the field of
complex number!

Now back to 4WD. I believe every one will agree that 
the ultimate goal of 4WD traction of any 4WD lies in
the following statement. "The vehicle progresses when
there is only one wheel or more (out of the four) has 
sufficient traction". And all traction aiding devices
(Willem comes to his elements here) aim to achieve
above statement. 

If you put an 80s, ML430 and a 100s on hoists. Have them
fully locked (electronically by microcontroller or manually
by driver). And try to grab each of the 4 wheels at all 
4 corners in turn while having some throttle input, 
starting from the 80s and end with the 100s. You will 
have the following observation.

80s
===
All 4 wheels turn at the same rate, you can't grab
any of the wheel without stopping the rest of the
3 wheels. Is either all 4 wheels stop rotating (if
you have popey hand) or all 4 rotate at the same rate
no matter what you do to the individual wheel (if you
have puny arms). There is no such thing as having the
right amout of torque to stop one wheel and the rest of 
the 3 will stop, rather you either have enough
torque to stop the combined torque of the 4 or you don't.
Which means, the only way (with a manual) to stop any
of the wheel is to overcome the torque ouput of the
engine.
Engine power output = heat dissipation on popey arm 
                      + general losses.
Fulfill "move on as long as any one of the 4 wheels 
has sufficient traction".

ML430
=====
Base on ASB. The firing rules are;
1)If left wheel angular speed is less than right, increase
  resistance on right wheel.
2)If right wheel angular speed is less than left, increase
  resistance on left wheel.
3)If front propeller shaft angular speed is less than rear,
  increase resistance on rear.
4)If rear propeller shaft angular speed is less than front,
  increase resistance on front.

If you grab one of the wheel, the other 3 wheels will have
higher angular speed, above rules will fire. Resistance will
increase on the other 3 wheels untill it matches the resistance
on the grabbed wheel. Equal torque split happens when all 4
wheels have exactly the same resistance. The stronger you grab
the wheel, higher the resistance applied on the other 3, 
higer the torque experienced by the grabbed wheel. So is also
a case of you either grab all 4 wheels or you don't. But
the differrence here is some of the engine power is converted
to heat on the discs. And the torque split is not instantaneous,
it happens only when all 4 wheels  have equal resistance and
is up to the microcontroller to match that as close as possible.
Engine power output = heat dissipation on popey arm 
                      + resistance loss + general losses.

So is sort of an "approximation" of the real thing via 
electronics means. So sort of fulfils "move on as long as 
any one of the 4 wheels has sufficient traction".


100s
====
You can grab any of the front wheels. And all power will
go to the other 3.
Engine power output = heat dissipation on loose wheels + general
                      losses.

Can't fulfil above statement. If the only wheel has traction
is from the front, the vehicle is stuffed.

So by definition (if you agree to it), the rank of traction
superiority is fully lockable 80s first, ML430 type second
and 100s last. But still, 100s is the field of real number to
majority of the world. To those who insists on complex
number will not settle for anything less than 80s.












From:             "Keewai Tan" 
To:               <80_series@sgiblab.sgi.com>
Subject:          RE: Re[2]: [80] Future of Land Cruiser [chat]
Date sent:        Wed, 3 May 2000 10:28:52 +1000
Send reply to:    80_series@sgiblab.sgi.com

Piter my mate,
Great to hear from people having great passion on his/her obsession.
I like that!

>True, except that most of the engine power is used to heat your discs. Note
>that the microcontroller has a limited brain. In your case, ideally it would
>block all three wheels so the one wheel that has traction can move the car. As
>soon as the car is moving, the ABS will note it has locked-up wheels, and
>reduce the braking force. No matter what happens, ABS wins (otherwise it
>could get dangerous on wet German highways). It's like that in reality you are
>slipping & sliding and you image there is something neat from Mr. Mercedes that
>makes it safe.

The electronic traction control uses the ABS channels to pulsate (or increase
resistance) on the wheels. But it doesn't share the ABS feed back control system.
ABS feed back control system is activated IF AND ONLY IF there is positive
reading from the brake pedal. If the vehicle skid without its brake pedal being
depressed, ABS will never kicks in.

Now, electronic traction control uses the ABS channels to pulsate the individual
wheel when there are sufficient angular velocity differences between them, regardless
of brake pedal. As soon as positive reading is detected from brake pedal, the
ABS channels will be under the control of ABS master controller and traction
controller releases its influence.

So if a vehicle has 3 channel 4 sensors ABS system. 2 Channel to the rear and 1 channel
to the front. That implies the rear wheels have their own separate channels and
the front share the common channel. When pulsation iniated by traction master
control, the rear wheels will be pulsated separately. Therefore the rear wheels
can react separately to different traction condition and experiece the
corresponding brake pulsation to match them. That is equivalent to having a
"rear diff locker".

Now, the front share the same channel, whenever pulsation occurs on either side,
the opposite side will HAVE to experience it regardless of traction condition. Hence
pulsating the wheel that has no traction will also resulting in pulsating the wheel
that has traction. Hence, such shared ABS channel cannot be used to symbolise "front
diff locker". Rather, it is used as the "center diff locker". By pulsating both the
front at the same rate regardless of traction condition, it diverges power distribution
from the front to the rear.

Hence, only 4 channel 4 sensors ABS system can mimic a fully lockable 105/80 by
the following.

Front wheels lose traction:
Pulsate both front wheels  => diverge power distribution to the rear.

Rear wheels lose traction:
Pulsate rear wheels        => diverge power distribution to the front.

One of the wheel loses traction:
Pulsate that wheel ONLY    => diverge power distribution to the other 3.

Two wheels lose traction from front and rear:
Pulsate that 2 wheels INDIVIDUALLY
                           => diverge power from front to rear or vice versa and
                              left to right or vice versa. So that the power goes to
                              the 2 wheels that has tractioin.

Three wheels lose traction from front and rear:
Pulsate that 3 wheels INDIVIDUALLY
                           => diverge power from front to rear or vice versa and
                              left to right or vice versa. So that the power goes to
                              the only wheel that has tractioin.

The main draw back here is power loses through heat dissipation AND non instantaneuous
"locking". Power distribution is not continuous and instantaneuous, hece, it is
a case of "too much slippage" then power redistribution.

Conclusion
==========
Electronic traction control tries to mimic the "real thing" but in actual
fact, what the vehicle gets is electronic LSD FRONT, REAR AND CENTER. ie. Locks all
three ways when there are sufficient slippages.

>So I would propose the following ranking in traction superiority (whatever that
>is):
>
>1. 105 fully lockable
>2. 80 fully lockable
>3. 100

Hence the question here is, is electronic LSD front, rear and center really
worse than a fully lock rear and center (not front) 100s? Along the line of
traction superiority definition (ie. vehicle progresses even if there is only
ONE wheel has sufficient traction), the answer is no.

But along the line of PASSIONS on all things TOYOTA, especially on all
things LAND CRUISER.
The answer is YES. ML430 is worse than 100s. So I agree with you...

105 first, and ML430 last -);

Which reminds me that this list is about PASSIONS on all things LAND CRUISER 80s
and above.

Cheers
Keewai Tan
Melbourne Aus





From:             "Norm Needham" 
To:               <80_series@sgiblab.sgi.com>
Subject:          Re: Re[2]: [80] Future of Land Cruiser [chat]
Date sent:        Wed, 3 May 2000 18:07:02 +1000
Send reply to:    80_series@sgiblab.sgi.com

From: Keewai Tan 

>Now, electronic traction control uses the ABS channels to pulsate the individual
>wheel when there are sufficient angular velocity differences between them, regardless
>of brake pedal. As soon as positive reading is detected from brake pedal, the
>ABS channels will be under the control of ABS master controller and traction
>controller
>releases its influence.

Hmmm....heard an interesting story from a Discovery driver the other
day. Apparently he was attempting to climb a sand dune previously
roughed up by other vehicles. The angular velocity difference between
various wheels at various points up the dune caused the traction
control to kick in. The on-off braking on the wheels (different ones at
different points up the dune) simply stopped his progress. ;-?
I guess he could/should have fooled the traction control by slightly
depressing the brake pedal?

NN













From:             500 UPPL Rúnar Sigurjónsson 
To:               "'80_series@sgiblab.sgi.com'" <80_series@sgiblab.sgi.com>
Subject:          [80] Traction controls, Was: Future of Land Cruiser [chat]
Date sent:        Wed, 3 May 2000 11:14:17 -0000 
Send reply to:    80_series@sgiblab.sgi.com

> Hmmm....heard an interesting story from a Discovery driver the other
> day. Apparently he was attempting to climb a sand dune previously
> roughed up by other vehicles. The angular velocity difference between
> various wheels at various points up the dune caused the traction
> control to kick in. The on-off braking on the wheels 
> (different ones at
> different points up the dune) simply stopped his progress. ;-?
> I guess he could/should have fooled the traction control by slightly
> depressing the brake pedal?
> 
> NN

The traction control is kinda stubit system to use in a 4x4 car.  Like this
Discovery guy found out, the last thing you need when climbing loose hills are
the brakes automaticly kicking in... (then of course when you stop half way up
the slippery hill, the ABS prevents your tires from locking up and you roll
brakeless back down the hill....=:-|

A friend of mine that runs a coach company likes them systems in the rwd
coaches, as long as one of the tires have traction.  Once both tires loose
traction, the system however seems to freek out...!

Consider adding a TrueTrac locker, to a veichle with traction control.  Once one
tire looses control, the traction control brakes that tire, causing the locker
to kick in and locking both tires together, totally automatically... Would
probably in effect work like that automatic 4wd by subaru...  Not a bad idea.

Cheers
Runsi.








From:             "Norm Needham" 
To:               <80_series@sgiblab.sgi.com>
Subject:          Re: Re[2]: [80] Future of Land Cruiser [chat]
Date sent:        Wed, 3 May 2000 18:07:02 +1000
Send reply to:    80_series@sgiblab.sgi.com

From: Keewai Tan 

>Now, electronic traction control uses the ABS channels to pulsate the individual
>wheel when there are sufficient angular velocity differences between them, regardless
>of brake pedal. As soon as positive reading is detected from brake pedal, the
>ABS channels will be under the control of ABS master controller and traction controller
>releases its influence.

Hmmm....heard an interesting story from a Discovery driver the other
day. Apparently he was attempting to climb a sand dune previously
roughed up by other vehicles. The angular velocity difference between
various wheels at various points up the dune caused the traction
control to kick in. The on-off braking on the wheels (different ones at
different points up the dune) simply stopped his progress. ;-?
I guess he could/should have fooled the traction control by slightly
depressing the brake pedal?

NN





From:             "Willem-Jan Markerink" 
To:               80_series@sgiblab.sgi.com
Date sent:        Sat, 20 May 2000 20:22:13 +0100
Subject:          Electronic Traction Control is crap (was: [80] Future of Land Cr
Send reply to:    80_series@sgiblab.sgi.com

On  3 May 00 at 10:28, Keewai Tan wrote:

> >So I would propose the following ranking in traction superiority (whatever
> >that is):
> >
> >1. 105 fully lockable
> >2. 80 fully lockable
> >3. 100
> 
> Hence the question here is, is electronic LSD front, rear and center really
> worse than a fully lock rear and center (not front) 100s? Along the line of
> traction superiority definition (ie. vehicle progresses even if there is only
> ONE wheel has sufficient traction), the answer is no.
> 
> But along the line of PASSIONS on all things TOYOTA, especially on all
> things LAND CRUISER.
> The answer is YES. ML430 is worse than 100s. So I agree with you...
> 
> 105 first, and ML430 last -);

Well, the German mag OffRoad has tested both an old-style Defender with 
aftermarket lockers, and a new-style one with ETC....guess which one 
got stuck where the other one kept going....

Also, *all* reports thusfar stress the fact that one must give full
throttle, otherwise you will come to a grinding halt in a worst case
scenario....this means a) goodbye to careful terrain 'negotating',
b) tearing up the trail where a full locker wouldn't (and dig
deeper), and c) any hill one can barely make in a certain gear,
powerwise, will be an impossible hill with ETC....you either loose 
torque or speed.

--                 
Bye,

Willem-Jan Markerink

      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]











From:             "Willem-Jan Markerink" 
To:               80_series@sgiblab.sgi.com
Date sent:        Sat, 24 Jun 2000 12:30:08 +0100
Subject:          Re: Electronic Traction Control is crap (was: [80] Future of La
Send reply to:    80_series@sgiblab.sgi.com

On 20 May 00 at 20:22, Willem-Jan Markerink wrote:

> On  3 May 00 at 10:28, Keewai Tan wrote:
> 
> > >So I would propose the following ranking in traction superiority (whatever
> > >that is):
> > >
> > >1. 105 fully lockable
> > >2. 80 fully lockable
> > >3. 100
> > 
> > Hence the question here is, is electronic LSD front, rear and center really
> > worse than a fully lock rear and center (not front) 100s? Along the line of
> > traction superiority definition (ie. vehicle progresses even if there is
> > only ONE wheel has sufficient traction), the answer is no.
> > 
> > But along the line of PASSIONS on all things TOYOTA, especially on all
> > things LAND CRUISER.
> > The answer is YES. ML430 is worse than 100s. So I agree with you...
> > 
> > 105 first, and ML430 last -);
> 
> Well, the German mag OffRoad has tested both an old-style Defender with 
> aftermarket lockers, and a new-style one with ETC....guess which one 
> got stuck where the other one kept going....
> 
> Also, *all* reports thusfar stress the fact that one must give full
> throttle, otherwise you will come to a grinding halt in a worst case
> scenario....this means a) goodbye to careful terrain 'negotating',
> b) tearing up the trail where a full locker wouldn't (and dig
> deeper), and c) any hill one can barely make in a certain gear,
> powerwise, will be an impossible hill with ETC....you either loose 
> torque or speed.
xxxxxxxxxxxxxxxxxxxxxx

Remember these old notes?

While sitting on the toilet, and reading this mag report again, it 
suddenly dawned upon me (not the toilet) that the matter of torque vs 
speed is even far worse than anyone thusfar has considered with these 
traction control systems (including each and every magazine). 

While the math is amazingly simple (Keewai, watch this!):

- imagine one wheel in the air, the other on firm ground
- imagine full braking power applied to that wheel, to maximize 
torque on the grip-wheel on the other side....theoretically this 
means the airborn-wheel will be standing still, while the grip-wheel 
rotates (hopefully).
- the grip wheel now has to rotate at TWICE the speed as the 
airborn-wheel....that's what any differential will do....grab one 
side, and the other wheel will rotate at twice the speed.
- twice the wheel-speed with same rpm at the drive-shaft, means half the 
torque....here is where any traction control will meet its 
Waterloo....

Now the optimists might argue that the airborn-wheel will be kept 
spinning at the same rpm as the other wheels, ie never stand still 
completely....however, from a standstill-stuck situation, it will 
have to at least *try* to reduce the airborn-rpm to zero, since 
that's what the rest of the wheels are doing too....and for every 
grab-release-grab-release sequence of that brake, the above 'twice 
the speed means half the torque' is valid....and what happens in such 
split-seconds is also what happens in average....

Note that *any* diff-internal device is better in this regard 
than a brake-traction-control, with best performance of course by a 
full locker (either manual or auto variety)....but LSD's (be it 
viscous, hydraulic or mechanic) also lack this torque-halving 
effect....

--                 
Bye,

Willem-Jan Markerink

      The desire to understand 
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]















From:             Keewai Tan 
To:               "'80_series@sgiblab.sgi.com'" <80_series@sgiblab.sgi.com>
Subject:          [80] RE: Electronic Traction Control is crap [CHAT]
Date sent:        Mon, 26 Jun 2000 17:34:37 +1000
Send reply to:    80_series@sgiblab.sgi.com

Greeting,

>While sitting on the toilet, and reading this mag report again, it 
>suddenly dawned upon me (not the toilet) that the matter of torque vs 
>speed is even far worse than anyone thusfar has considered with these 
>traction control systems (including each and every magazine). 

William you amaze me. Your analysis is thorough. Your
thought modelling have demonstrated that you are indeed a 'diff
head'!

>
>While the math is amazingly simple (Keewai, watch this!):
>
>- imagine one wheel in the air, the other on firm ground
>- imagine full braking power applied to that wheel, to maximize 
>torque on the grip-wheel on the other side....theoretically this 
>means the airborn-wheel will be standing still, while the grip-wheel 
>rotates (hopefully).
>- the grip wheel now has to rotate at TWICE the speed as the 
>airborn-wheel....that's what any differential will do....grab one 
>side, and the other wheel will rotate at twice the speed.
>- twice the wheel-speed with same rpm at the drive-shaft, means half the 
>torque....here is where any traction control will meet its 
>Waterloo....

Here is my throught;
Sum(front left(power), front right(power)) + losses = 
              power(front propeller shaft). Must hold at all time.

Now power is product of torque and rps (revolution per second).

Assuming at an instantaneous time t1, at t1, left wheel up in the
air, halted by the ETC brake pulsation. At the same time, right
wheel is firmly planted in the ground. Also assume that throttle
input is positive.
Now, there is no rotational power dissipates on the left. 
But there are heat power dissipation.Hence we have

Sum(front right(power) + front left(heat)) + losses =
     power(front propeller shaft)
If both wheels are rotating. The power from the front propeller
shaft will be distributed to both sides. As soon as you grab
one wheel. The other wheel will rotate at twice the velocity
this is because all power now goes to the free wheel. Intead
of sharing it with its immediate neighbour, the free wheel dissipates
it all. Hence, the speed doubles without torque reduction. If
torque reduce at the same rate as the rps increases, there will be
no increase in power. But this is not the case. There is increase
in power because the free wheel is now experiencing the 'diverged'
power from the grabbed wheel.

But then in the ETC case, the torque on the free wheel does reduce
not due to the fact that it is now ratating twice the speed. Rather
there is actual power losses happenning in the pulsated wheel.
Hence not ALL power is diverged to the the wheel that has grip.
Hence the torque must reduce to compensate the loss in power.

Cheers
Keewai Tan














From:             "Brian" 
To:               
Subject:          Discovery Series 2 Traction Control System - The best 4x4 by Tar??
Date sent:        Thu, 7 Jun 2001 14:48:27 +0100

Greetings from South Africa,

I purchased a  Landrover Discovery series 2 TD5 with Traction Control in June 2000 and I
am not happy at all with it's off road performance.This vehicle is probably the best
in it's price range and class when quality, technology, comfort, articulation, power and all
other aspects(apart from offroad) are considered.Compared to my previous Landy, a '96 Defender
 110 with standard center diff-lock, traction control fails miserably.

With no load on a steep uphill gradient the cars' center of gravity shifts back and lightens
the load on the front wheels causing all that power/torque to be transferred to one or both
with the least traction.Traction control is not instantaneous and so during those split seconds
when wheels are spinning, before the ABS system reacts and transfers power, you lose
momentum - the system then attempts to transfer the power to the other three or two rear
wheels whilst holding the wheel(s) that are slipping, but it is not intelligent and only holds the
slipping wheel(s) for +/- 2-3 seconds after which it is assumed you will have regained traction.
Wrong! By now, as a result of the car almost at standstill, there is no traction available to the
other wheels and so one at a time they spin, are braked by traction control and are unable to
move the car forward.
The Landrover people will call it driver error/tyre problems - I have been on their course to learn specifically
how to drive this car - basically you are supposed to use a more aggressive approach and maintain
momentum by increasing power when you lose traction - environmentally this is a disaster as
you tend to destroy a lot more than standard diff lock equipped cars.I also consider myself an
accomplished and sensible driver off-road and never experienced this frustration before with the
old '96 Defender.
Also on a recent outing with a whole range of 4x4's  from 2001 Jeep Grand Cherokee's,
 1996 Toyota Land Cruiser Station Wagon's, Defenders, Jeep Wranglers, Ford and Colt light
commercial 4x4 trucks, the Disco was last overall on performance. We had 3 Disco's all
of similar age and mileage so this is a flaw in theory/design not just a factory fault on one.
On one particular hill, that was not that steep anyway, all the above 4x4's idled up in 1st or
second gear low range - not one got stuck. All the Disco's battled and stopped amid plumes
of dust,grit and stones spewing forth from the wheels, as Traction control decided when it should
or shouldn't apply itself. I tried several approaches - 1st gear low range fast and slow ; second
gear low range fast and slow until eventually with a very aggressive approach, risking damage
to the car, I and the other Disco's got up.
In another instance, coming off a beach up a slope +/-25-30 deg, the Disco with traction control
struggled 6 times to get up using different tactics/speeds and simply dug itself in or stopped climbing.
An older Disco Series 1 with standard center diff lock simply idled up, no fuss first time!

Also another serious flaw - if over rocks/boulders in slippery conditions and you are stuck,
you have to rev the motor to get the wheels that have no traction to spin and make the traction control
effective.So suddenly, all that power and torque go to one wheel causing it to spin and you have no
control over your steering causing the front end to wash out sideways.Don't forget though that all of this
needs to happen very precisely as after +/- 2-3 seconds the traction control lets go and then
brakes again, in-between losing the very power it is supposed to be sending to the wheel with traction!

In cross-axle situations and on flattish land/obstacles the system works pretty well, but overall this
vehicle is not ready/suitable for serious offroad/expedition work.

I intend taking this up with the dealership that sold me the Disco as I was lead to believe and had
offroad tests done (suited to Disco 2 ??) to prove that the traction control system was more
effective than center diff-lock.

Fortunately the transfer box is the same one used on previous Disco's and still has the diff lock hardware.
All that is required is the linkages to the high/low transfer lever. Once done I will have the best of both
technologies - will follow up once test done.

Regards,

Brian Cunniffe.













FROM: "Giorgio Rossi" 
SUBJECT: Traction control?
DATE: Sun, 06 Jan 2002 12:17:43 GMT
ORGANIZATION: [Infostrada]
NEWSGROUPS: aus.cars.offroad

Does anyone know how wheels' traction control acts ( in terms of forces,
physics & dynamics)?
Any links where can I find material?

Thanks in advance.













FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Sun, 06 Jan 02 17:37:35 GMT
NEWSGROUPS: aus.cars.offroad

In article ,
   "Giorgio Rossi"  wrote:
>Does anyone know how wheels' traction control acts ( in terms of forces,
>physics & dynamics)?
>Any links where can I find material?

Some physics, details and ponderings (in particular some which no 
car-salesman wants to hear):

http://www.a1.nl/phomepag/markerink/tad_elec.htm

Bottom line: in a worst-case scenario, you will be wasting 50% of your 
available power, compared to a full mechanical locker (either auto or 
manual operated).

As an additional/supplemental system (on top of a mechanical locker), it's 
very nice; but as the only traction aid, it's a scary compromise not meant 
for serious offroad.

(posted & mailed)

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]














FROM: "JD" 
SUBJECT: Re: Traction control?
DATE: Mon, 7 Jan 2002 07:05:15 +1100
ORGANIZATION: JJD
NEWSGROUPS: aus.cars.offroad

Willem-Jan Markerink  wrote in message
news:a1a1hc$pau1i$6@ID-34205.news.dfncis.de...

> In article ,
>    "Giorgio Rossi"  wrote:
> >Does anyone know how wheels' traction control acts ( in terms of forces,
> >physics & dynamics)?
> >Any links where can I find material?
>
> Some physics, details and ponderings (in particular some which no
> car-salesman wants to hear):
>
> http://www.a1.nl/phomepag/markerink/tad_elec.htm
>
> Bottom line: in a worst-case scenario, you will be wasting 50% of your
> available power, compared to a full mechanical locker (either auto or
> manual operated).
>
> As an additional/supplemental system (on top of a mechanical locker), it's
> very nice; but as the only traction aid, it's a scary compromise not meant
> for serious offroad.

Without going into how it is applied in practice, at least in theory,
traction control has one major advantage over a locking or limited slip
diff. This is that with TC, unlike a locking diff, it is impossible to apply
full torque to a single half axle or diff. This means that the vehicle
designer has the advantage of not having to make the choice of either over
designing the system to allow for full engine torque multiplied by first
gear low range, or crossing their fingers and hoping no driver is silly
enough to use full throttle in first/low with everything locked.  In other
words, avoiding damage is less the driver's responsibility. Beefing up
everything to cover the use of lockers results in penalties in cost and
unsprung weight, and I doubt any manufacturer has fully covered it.
JD












FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Sun, 06 Jan 02 20:31:41 GMT
NEWSGROUPS: aus.cars.offroad

In article <3c389f7b@dnews.tpgi.com.au>,
   "JD"  wrote:
>Without going into how it is applied in practice, at least in theory,
>traction control has one major advantage over a locking or limited slip
>diff. This is that with TC, unlike a locking diff, it is impossible to apply
>full torque to a single half axle or diff. This means that the vehicle
>designer has the advantage of not having to make the choice of either over
>designing the system to allow for full engine torque multiplied by first
>gear low range, or crossing their fingers and hoping no driver is silly
>enough to use full throttle in first/low with everything locked.  In other
>words, avoiding damage is less the driver's responsibility. Beefing up
>everything to cover the use of lockers results in penalties in cost and
>unsprung weight, and I doubt any manufacturer has fully covered it.
>JD

You better think twice about what you just said.
You basically state that your halfshaft cannot take the full force, even if 
that would be the only way to get unstuck.

As I said, nice onroad or as an additional system, otherwise a Bad 
Thing(tm) offroad.

Or: why would you want a T-case if you waste half of the available power 
anyway?....to overcome the drag, and basically get even with a non-T-case 
4wd with mechanical locks?....;))


Also, for those living in snow/ice regions: with traction control, you need 
4 chains, otherwise the continuous braking on slippery slopes will eat 
brakepads like there is no tomorrow, and the continous rattling will annoy 
the hell out of you....

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]













FROM: "JD" 
SUBJECT: Re: Traction control?
DATE: Mon, 7 Jan 2002 17:56:01 +1100
ORGANIZATION: JJD
NEWSGROUPS: aus.cars.offroad

Willem-Jan Markerink  wrote in message
news:a1abnm$pb8sl$2@ID-34205.news.dfncis.de...
> In article <3c389f7b@dnews.tpgi.com.au>,
>    "JD"  wrote:
> >Without going into how it is applied in practice, at least in theory,
> >traction control has one major advantage over a locking or limited slip
> >diff. This is that with TC, unlike a locking diff, it is impossible to apply
> >full torque to a single half axle or diff. This means that the vehicle
> >designer has the advantage of not having to make the choice of either over
> >designing the system to allow for full engine torque multiplied by first
> >gear low range, or crossing their fingers and hoping no driver is silly
> >enough to use full throttle in first/low with everything locked.  In other
> >words, avoiding damage is less the driver's responsibility. Beefing up
> >everything to cover the use of lockers results in penalties in cost and
> >unsprung weight, and I doubt any manufacturer has fully covered it.
> >JD
>
> You better think twice about what you just said.

I have  - still stand by it

> You basically state that your halfshaft cannot take the full force, even if
> that would be the only way to get unstuck.

The half shaft will not handle the maximum torque - fortunately, it rarely
has to, even with lockers, as in most circumstances, way less than maximum
torque (low/first) will break tyre adhesion on the one wheel gripping, even
where the loss of traction is not slippery surface but lack of axle
articulation.  (Dynamic loading can, however, provide much more grip than
normal, and there will be cases where the axle will go first unless it is
designed to handle the full torque.)
With TC, no wheel is allowed to spin, so shock loading by spin then grip is
not possible.
There will be circumstances where lockers will outperform TC, but it will be
in a fairly narrow range of conditions, and will not be due to more power
available, but because it allows this spin/grip scenario.

> As I said, nice onroad or as an additional system, otherwise a Bad
> Thing(tm) offroad.
>
> Or: why would you want a T-case if you waste half of the available power
> anyway?....to overcome the drag, and basically get even with a non-T-case
> 4wd with mechanical locks?....;))

The transfer case's primary purpose is to split drive to front and rear, but
I assume you mean why have low range? Low range has two purposes, one is to
multiply torque, the other is to provide low speeds for rough surfaces. Low
range is normally (or at any rate should be) sufficiently low to meet the
"creeper" requirement that it can, in the lowest gear, give far more torque
than can be coupled to the ground by the tyres.
As a result, I stick by my view that the "waste of power " is irrelevant, so
that your argument against traction control loses force. And this is
especially the case where traction control/lockers are required primarily
because of a slippery surface.
Traction control, as applied by a particular manufacturer may well be
totally useless, but this will be because of the particular design rather
than any basic shortcoming.  ABS brakes present similar problems, and it is
noticeable that systems designed for snow, ice and wet bitumen are worse
than useless on loose gravel (much more common round here)
A completely separate consideration is whether an off road vehicle intended
to be used in remote areas should depend on a complex computer controlled
system or on a relatively simple mechanical system. The answer depends on
both the reliability and the failure mode of both systems - and I for one do
not know the answer. I doubt if any of the manufacturers do either. They
will always prefer traction control, since it is a trivial addition to ABS
(which is probably either already fitted or is an option), whereas using a
locking or limited slip diff will require redesign of the entire drive train
and probably suspension modifications, if reliability is to be maintained.

>
> Also, for those living in snow/ice regions: with traction control, you need
> 4 chains, otherwise the continuous braking on slippery slopes will eat
> brakepads like there is no tomorrow, and the continous rattling will annoy
> the hell out of you....

If you have four wheel drive, and you need chains, you need them on all four
wheels regardless of whether you have traction control or not!

Note that the above discussion is purely theoretical, and practical results
depend entirely on how the manufacturer implements the system, and how it is
driven. I have no personal experience with traction control, and do not
currently use locking or limited slip diffs. In any case, the tyres are
probably more important.
regards
JD













FROM: "Brendan Southey" 
SUBJECT: Re: Traction control?
DATE: Mon, 07 Jan 2002 09:39:33 GMT
ORGANIZATION: BigPond Internet Services (http://www.bigpond.net.au)
NEWSGROUPS: aus.cars.offroad

"JD"  wrote in message
news:3c393798@dnews.tpgi.com.au...
>
> Willem-Jan Markerink  wrote in message
> news:a1abnm$pb8sl$2@ID-34205.news.dfncis.de...
> > In article <3c389f7b@dnews.tpgi.com.au>,
> >    "JD"  wrote:
> > >Without going into how it is applied in practice, at least in theory,
> > >traction control has one major advantage over a locking or limited slip
> > >diff. This is that with TC, unlike a locking diff, it is impossible to apply
> > >full torque to a single half axle or diff. This means that the vehicle
> > >designer has the advantage of not having to make the choice of either over
> > >designing the system to allow for full engine torque multiplied by first
> > >gear low range, or crossing their fingers and hoping no driver is silly
> > >enough to use full throttle in first/low with everything locked.  In other
> > >words, avoiding damage is less the driver's responsibility. Beefing up
> > >everything to cover the use of lockers results in penalties in cost and
> > >unsprung weight, and I doubt any manufacturer has fully covered it.
> > >JD
> >
> > You better think twice about what you just said.
>
> I have  - still stand by it
>
> > You basically state that your halfshaft cannot take the full force, even if
> > that would be the only way to get unstuck.
>
> The half shaft will not handle the maximum torque - fortunately, it rarely
> has to, even with lockers, as in most circumstances, way less than maximum
> torque (low/first) will break tyre adhesion on the one wheel gripping, even
> where the loss of traction is not slippery surface but lack of axle
> articulation.  (Dynamic loading can, however, provide much more grip than
> normal, and there will be cases where the axle will go first unless it is
> designed to handle the full torque.)
> With TC, no wheel is allowed to spin, so shock loading by spin then grip is
> not possible.
> There will be circumstances where lockers will outperform TC, but it will be
> in a fairly narrow range of conditions, and will not be due to more power
> available, but because it allows this spin/grip scenario.
>
> > As I said, nice onroad or as an additional system, otherwise a Bad
> > Thing(tm) offroad.
> >
> > Or: why would you want a T-case if you waste half of the available power
> > anyway?....to overcome the drag, and basically get even with a non-T-case
> > 4wd with mechanical locks?....;))
>
> The transfer case's primary purpose is to split drive to front and rear, but
> I assume you mean why have low range? Low range has two purposes, one is to
> multiply torque, the other is to provide low speeds for rough surfaces. Low
> range is normally (or at any rate should be) sufficiently low to meet the
> "creeper" requirement that it can, in the lowest gear, give far more torque
> than can be coupled to the ground by the tyres.
> As a result, I stick by my view that the "waste of power " is irrelevant, so
> that your argument against traction control loses force. And this is
> especially the case where traction control/lockers are required primarily
> because of a slippery surface.
> Traction control, as applied by a particular manufacturer may well be
> totally useless, but this will be because of the particular design rather
> than any basic shortcoming.  ABS brakes present similar problems, and it is
> noticeable that systems designed for snow, ice and wet bitumen are worse
> than useless on loose gravel (much more common round here)
> A completely separate consideration is whether an off road vehicle intended
> to be used in remote areas should depend on a complex computer controlled
> system or on a relatively simple mechanical system. The answer depends on
> both the reliability and the failure mode of both systems - and I for one do
> not know the answer. I doubt if any of the manufacturers do either. They
> will always prefer traction control, since it is a trivial addition to ABS
> (which is probably either already fitted or is an option), whereas using a
> locking or limited slip diff will require redesign of the entire drive train
> and probably suspension modifications, if reliability is to be maintained.
> 
>
> > Also, for those living in snow/ice regions: with traction control, you need
> > 4 chains, otherwise the continuous braking on slippery slopes will eat
> > brakepads like there is no tomorrow, and the continous rattling will annoy
> > the hell out of you....
>
> If you have four wheel drive, and you need chains, you need them on all four
> wheels regardless of whether you have traction control or not!
>
> Note that the above discussion is purely theoretical, and practical results
> depend entirely on how the manufacturer implements the system, and how it is
> driven. I have no personal experience with traction control, and do not
> currently use locking or limited slip diffs. In any case, the tyres are
> probably more important.
> regards
> JD

This is interesting reading.

However, I cannot see that the distribution of torque between wheels on a
vehicle with locked diffs; front centre (or locked 4wd) and rear is all that
different to the distribution of torque on a vehicle with TC (given similar
traction conditions).

FULLY LOCKED DRIVETRAIN
When any given wheel looses traction, that particular wheel absorbs much
less torque because of bad tyre adhesion.  The drivetrain is still absorbing
the same amount of torque from the motor, and hence it is now being
distributed to the other wheels.  When that wheel regains traction, it
accepts its share of torque back from the drivetrain.

TC EQUIPPED VEHICLE
When in similar conditions a TC equipped vehicle looses traction at that one
wheel, the brake is applied to that wheel and the open diffs distribute this
torque to the other wheels.  When that wheel regains traction, the brakes
are released and the wheel accepts is share of torque again from the
drivetrain.

Assuming I have not come unstuck anywhere, I conclude that the two vehicles
distribution of torque under low traction conditions is very similar not
considering dynamic loading.  Now the important difference is that the fully
locked drivetrain is digging holes with tyres that have poor adhesion where
the TC vehicle is not.  But then, the locked drivetrain is not dependant on
microchips to operate.

Someone steer me in the right direction pls!!

Brendan












FROM: "JD" 
SUBJECT: Re: Traction control?
DATE: Mon, 7 Jan 2002 22:00:01 +1100
ORGANIZATION: JJD
NEWSGROUPS: aus.cars.offroad

Brendan Southey  wrote in message
news:p1e_7.1981$9u6.11015@news-server.bigpond.net.au...
> This is interesting reading.
>
> However, I cannot see that the distribution of torque between wheels on a
> vehicle with locked diffs; front centre (or locked 4wd) and rear is all that
> different to the distribution of torque on a vehicle with TC (given similar
> traction conditions).
>
> FULLY LOCKED DRIVETRAIN
> When any given wheel looses traction, that particular wheel absorbs much
> less torque because of bad tyre adhesion.  The drivetrain is still absorbing
> the same amount of torque from the motor, and hence it is now being
> distributed to the other wheels.  When that wheel regains traction, it
> accepts its share of torque back from the drivetrain.

Correct - but since the total torque output from the engine/gearbox is
unchanged the torque to the other wheels (down to a minimum of only one
wheel gripping) is increased - 4 wheels gripping, each wheel 25% of torque,
1 wheel gripping, that wheel gets 100% of torque.


> TC EQUIPPED VEHICLE
> When in similar conditions a TC equipped vehicle looses traction at that one
> wheel, the brake is applied to that wheel and the open diffs distribute this
> torque to the other wheels.  When that wheel regains traction, the brakes
> are released and the wheel accepts is share of torque again from the
> drivetrain.

No - the torque is still distributed equally to all wheels, but at the wheel
that has lost traction is now being absorbed by the brake applied by the
Traction Control. The TC periodically (typically a number of times each
second) releases the brake and only reapplies it if the wheel slips again

> Assuming I have not come unstuck anywhere, I conclude that the two vehicles
> distribution of torque under low traction conditions is very similar not
> considering dynamic loading.  Now the important difference is that the fully
> locked drivetrain is digging holes with tyres that have poor adhesion where
> the TC vehicle is not.  But then, the locked drivetrain is not dependanton
> microchips to operate.

But the microchips usually fail safe -i.e. revert to no TC, whereas a
failure of a locking diff is more likely to result in no drive at all from
that axle. The question is, what is the failure rate of either in real life?
Actually I would worry more about the other components of the TC system such
as hydraulic pump and electrohydraulic control valves.

> Someone steer me in the right direction pls!!
>
> Brendan

Hope this is clear. Ultimately, when grip is lost by all wheels, both
systems will spin all wheels, in the all locked case at a rapidly increasing
rate until the driver eases up. I think most Traction Control Systems
prevent sudden acceleration by all wheels when the final wheel slips, but as
they depend on comparing differences in speed between wheels, once all
wheels are slipping the system has no way of knnowing when (or if) traction
is regained. How the software handles this situation may well make the
difference between a useful and non-useful system.
JD











FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Mon, 07 Jan 02 18:17:27 GMT
NEWSGROUPS: aus.cars.offroad

In article <3c397083@dnews.tpgi.com.au>,
   "JD"  wrote:
>> TC EQUIPPED VEHICLE
>> When in similar conditions a TC equipped vehicle looses traction at that one
>> wheel, the brake is applied to that wheel and the open diffs distribute this
>> torque to the other wheels.  When that wheel regains traction, the brakes
>> are released and the wheel accepts is share of torque again from the
>> drivetrain.
>No - the torque is still distributed equally to all wheels, but at the wheel
>that has lost traction is now being absorbed by the brake applied by the
>Traction Control. The TC periodically (typically a number of times each
>second) releases the brake and only reapplies it if the wheel slips again

And the brake absorbs half the torque that went to the entire axle....or, 
if it brakes down the spinning wheel completely (which it temporarily 
does), the other wheel must spin at twice the speed, hence half the 
torque....

>> Assuming I have not come unstuck anywhere, I conclude that the two vehicles
>> distribution of torque under low traction conditions is very similar not
>> considering dynamic loading.  Now the important difference is that the fully
>> locked drivetrain is digging holes with tyres that have poor adhesion where
>> the TC vehicle is not.  But then, the locked drivetrain is not dependant on
>> microchips to operate.
>But the microchips usually fail safe -i.e. revert to no TC, whereas a
>failure of a locking diff is more likely to result in no drive at all from
>that axle. The question is, what is the failure rate of either in real life?

Actually, the only NATO-approved mechanical locker is one which can still 
be operated by hand, at the axle-housing. Only a few brands offer this 
(Mercedes G, KAM-Differentials, Pinzgauer).

>Actually I would worry more about the other components of the TC system such
>as hydraulic pump and electrohydraulic control valves.
>>
>> Someone steer me in the right direction pls!!
>>
>> Brendan
>>
>Hope this is clear. Ultimately, when grip is lost by all wheels, both
>systems will spin all wheels, in the all locked case at a rapidly increasing
>rate until the driver eases up. I think most Traction Control Systems
>prevent sudden acceleration by all wheels when the final wheel slips, but as
>they depend on comparing differences in speed between wheels, once all
>wheels are slipping the system has no way of knnowing when (or if) traction
>is regained. How the software handles this situation may well make the
>difference between a useful and non-useful system.
>JD

At very slick surfaces you get a continous rattling that drives you 
crazy....a comment present in the more serious tests-reports (once started 
with the Mercedes ML, still one of the few with T-case, yet open center 
diff....there is nothing you can do to make life easier for the traction 
control, hence also the problem of needing 4 chains instead of 2)

Also, this problem of knowing when traction is present or not is inherent 
to all reactive traction systems, be it reactive-4wd, or traction 
control....they all can only act when, after, and as long as slip is 
present....which means they *must* allow a certain amount of wheel spin to 
detect a lack of grip in the first place.

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]










FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Mon, 07 Jan 02 18:02:01 GMT
NEWSGROUPS: aus.cars.offroad

In article ,
   "Brendan Southey"  wrote:
>This is interesting reading.
>
>However, I cannot see that the distribution of torque between wheels on a
>vehicle with locked diffs; front centre (or locked 4wd) and rear is all that
>different to the distribution of torque on a vehicle with TC (given similar
>traction conditions).
>
>FULLY LOCKED DRIVETRAIN
>When any given wheel looses traction, that particular wheel absorbs much
>less torque because of bad tyre adhesion.  The drivetrain is still absorbing
>the same amount of torque from the motor, and hence it is now being
>distributed to the other wheels.  When that wheel regains traction, it
>accepts its share of torque back from the drivetrain.
>
>TC EQUIPPED VEHICLE
>When in similar conditions a TC equipped vehicle looses traction at that one
>wheel, the brake is applied to that wheel and the open diffs distribute this
>torque to the other wheels.  When that wheel regains traction, the brakes
>are released and the wheel accepts is share of torque again from the
>drivetrain.

You have to take a closer look at what a diff does....if you grab one side 
solid (as a brake temporarily tries to do), the other side must spin at 
twice the speed....or half the torque....and that is your core 
problem....it's much worse than just preventing wheel spin on one 
side....it's definately not a clean 'zero-sum' concept.
It couldn't be either, since that brake simply wastes energy....and that 
has to come from somewhere....

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]








FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Mon, 07 Jan 02 17:57:14 GMT
NEWSGROUPS: aus.cars.offroad

In article <3c393798@dnews.tpgi.com.au>,
   "JD"  wrote:
>
>Willem-Jan Markerink  wrote in message
>news:a1abnm$pb8sl$2@ID-34205.news.dfncis.de...
>> In article <3c389f7b@dnews.tpgi.com.au>,
>>    "JD"  wrote:
>> >Without going into how it is applied in practice, at least in theory,
>> >traction control has one major advantage over a locking or limited slip
>> >diff. This is that with TC, unlike a locking diff, it is impossible to
>> apply
>> >full torque to a single half axle or diff. This means that the vehicle
>> >designer has the advantage of not having to make the choice of either over
>> >designing the system to allow for full engine torque multiplied by first
>> >gear low range, or crossing their fingers and hoping no driver is silly
>> >enough to use full throttle in first/low with everything locked.  In other
>> >words, avoiding damage is less the driver's responsibility. Beefing up
>> >everything to cover the use of lockers results in penalties in cost and
>> >unsprung weight, and I doubt any manufacturer has fully covered it.
>> >JD
>>
>> You better think twice about what you just said.
>
>I have  - still stand by it
>
>> You basically state that your halfshaft cannot take the full force, even if
>> that would be the only way to get unstuck.
>The half shaft will not handle the maximum torque 

A Land Cruiser half shaft *will*.
That is why Toyota even interfered electronically with the 1HD-FTE, so that 
1st and 2nd gear won't see full throttle....until 360Nm times a 40:1 ratio 
was okay, 430Nm made the engineers nervous (even though the IFS-front 
doesn't have a factory locker).

>- fortunately, it rarely
>has to, even with lockers, as in most circumstances, way less than maximum
>torque (low/first) will break tyre adhesion on the one wheel gripping, even
>where the loss of traction is not slippery surface but lack of axle
>articulation.  (Dynamic loading can, however, provide much more grip than
>normal, and there will be cases where the axle will go first unless it is
>designed to handle the full torque.)
>With TC, no wheel is allowed to spin, so shock loading by spin then grip is
>not possible.

And what about a fully loaded truck, making a tight turn on grippy 
pavement, with the locker enaged? Let's assume 100% grip, with a load of 
2000kg, hence a force between road and tire of 20000N, times 0.35m arm of 
leverage, is 60000Nm. That is way more than even an 1HD-FTE, with 430Nm and 
a 40:1 ratio (=+16000Nm) would be capable off....

>There will be circumstances where lockers will outperform TC, but it will be
>in a fairly narrow range of conditions, and will not be due to more power
>available, but because it allows this spin/grip scenario.

It will be in ALL conditions where the *combination* (read compromise) of 
power and speed is barely enough to make it up/through an obstacle.

>> As I said, nice onroad or as an additional system, otherwise a Bad
>> Thing(tm) offroad.
>>
>> Or: why would you want a T-case if you waste half of the available power
>> anyway?....to overcome the drag, and basically get even with a non-T-case
>> 4wd with mechanical locks?....;))
>The transfer case's primary purpose is to split drive to front and rear, but
>I assume you mean why have low range? Low range has two purposes, one is to
>multiply torque, the other is to provide low speeds for rough surfaces. 

With the interesting side note that many reports about traction control 
clearly state that they need MORE speed to get over an obstacle....it's the 
full-throttle scenario you wanted to avoid with low range in the first 
place....8-))

>Low
>range is normally (or at any rate should be) sufficiently low to meet the
>"creeper" requirement that it can, in the lowest gear, give far more torque
>than can be coupled to the ground by the tyres.

At idle, or at full throttle?

>As a result, I stick by my view that the "waste of power " is irrelevant, so
>that your argument against traction control loses force. And this is
>especially the case where traction control/lockers are required primarily
>because of a slippery surface.

Yet other surfaces are only bumpy....yet also very steep, hence you don't 
want to waste any power, or speed.

>Traction control, as applied by a particular manufacturer may well be
>totally useless, but this will be because of the particular design rather
>than any basic shortcoming.  ABS brakes present similar problems, and it is
>noticeable that systems designed for snow, ice and wet bitumen are worse
>than useless on loose gravel (much more common round here)
>A completely separate consideration is whether an off road vehicle intended
>to be used in remote areas should depend on a complex computer controlled
>system or on a relatively simple mechanical system. 

Anyone who has read the never ending problems about faulty ABS-sensors 
(yes, including Land Cruisers!), knows the answer.

>The answer depends on
>both the reliability and the failure mode of both systems - and I for one do
>not know the answer. I doubt if any of the manufacturers do either. They
>will always prefer traction control, since it is a trivial addition to ABS
>(which is probably either already fitted or is an option), whereas using a
>locking or limited slip diff will require redesign of the entire drive train
>and probably suspension modifications, if reliability is to be maintained.
>>
>>
>> Also, for those living in snow/ice regions: with traction control, you need
>> 4 chains, otherwise the continuous braking on slippery slopes will eat
>> brakepads like there is no tomorrow, and the continous rattling will annoy
>> the hell out of you....
>If you have four wheel drive, and you need chains, you need them on all four
>wheels regardless of whether you have traction control or not!

No you don't. Definately not onroad, to reach the average skiing resort.
It might be good to have 4 instead of 2, but it ain't necessary....as long 
as you can block the center diff that is.

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]














FROM: "JD" 
SUBJECT: Re: Traction control?
DATE: Tue, 8 Jan 2002 07:04:31 +1100
ORGANIZATION: JJD
NEWSGROUPS: aus.cars.offroad

Snipped
> >are released and the wheel accepts is share of torque again from the
> >drivetrain.
>
> You have to take a closer look at what a diff does....if you grab one side

But the TC does not lock the wheel - it brakes enough to keep the wheel
speeds approximately the same.

> solid (as a brake temporarily tries to do), the other side must spin at
> twice the speed....or half the torque....and that is your core
> problem....it's much worse than just preventing wheel spin on one
> side....it's definately not a clean 'zero-sum' concept.
> It couldn't be either, since that brake simply wastes energy....and that
> has to come from somewhere....

My point is that it is only in unusual conditions that all the available
energy is required, or even usable in off road conditions.
To write off TC as only useful on road is to assume all offroad use is in
these conditions. After all, probably over 90% of four wheel drives in use
for actual off road (farming, mining etc) have neither locking diffs nor TC.
Sure they get stuck occasionally - done it myself - but mostly they don't.
JD














FROM: w.j.markerink@a1.nl (Willem-Jan Markerink)
SUBJECT: Re: Traction control?
DATE: Mon, 07 Jan 02 20:56:48 GMT
NEWSGROUPS: aus.cars.offroad

In article <3c39ef6c@dnews.tpgi.com.au>,
   "JD"  wrote:
>
>Snipped
>> >are released and the wheel accepts is share of torque again from the
>> >drivetrain.
>>
>> You have to take a closer look at what a diff does....if you grab one 
side
>But the TC does not lock the wheel - it brakes enough to keep the wheel
>speeds approximately the same.

No, it stutters, so at least temporarily the situation is 'speed 
zero'....*especially* when accelerating/spinning from a 
standstill....applying throttle slowly, until traction is lost.
The slower the speed, the more this effect applies, and the more torque you 
actually wanted to have....at higher speeds the effect would be less, yet 
that's where loosing a bit of torque is also far less problematic.

>> solid (as a brake temporarily tries to do), the other side must spin at
>> twice the speed....or half the torque....and that is your core
>> problem....it's much worse than just preventing wheel spin on one
>> side....it's definately not a clean 'zero-sum' concept.
>> It couldn't be either, since that brake simply wastes energy....and that
>> has to come from somewhere....
>My point is that it is only in unusual conditions that all the available
>energy is required, or even usable in off road conditions.

It takes only one big pothole at a steep incline....and a fully loaded rig 
plus trailer. 'Enough power' is a luxury only roadgoing vehicles have, on 
a flat surface.

>To write off TC as only useful on road is to assume all offroad use is in
>these conditions. 

I never wrote it off, I would love it as a *supplemental* system....but not 
as the only system knowing that 100% of torque in 1st low is sometimes 
barely enough. Mind you, I also rather idle over obstacles than having to 
floor the pedal....the word traction 'control' is a bit misleading in that 
context....the need for speed/throttle actually impless *less* control....

>After all, probably over 90% of four wheel drives in use
>for actual off road (farming, mining etc) have neither locking diffs nor TC.
>Sure they get stuck occasionally - done it myself - but mostly they don't.
>JD

One argument not yet mentioned: some surfaces are too fragile to allow any 
wheelspin at all....bottomless sand is one, but so are most icy 
surfaces....wheelspin means either sinking, or a lot less traction 
(friction vs stiction)....there are times where wheel spin should be kept 
to an absolute minimum....

--
Bye,

Willem-Jan Markerink

      The desire to understand
is sometimes far less intelligent than
     the inability to understand


[note: 'a-one' & 'en-el'!]
















 From: Mark Brodis [mailto:fj40rockcrawler@y...]
Sent: Wednesday, June 18, 2003 11:20 AM
To: 100scool@yahoogroups.com
Subject: [100scool] Re: rear diff lock in US-spec 100's

>It seems like those traction control methods that uses braking to
>reduce wheel spin is basically a software tweak. After all, you
>already have the ABS sensors. Just program in a few more lines of
>code, burn the PLA, and the automaker can charge thousands more for
>it!
>
>--Jim


Bingo!!

You have all the sensors you need, so it's just software, which any
capable embedded programmer could solve in a few days.

I am very shy of a system which uses brakes to help you go forward,
since applying the brakes (even pulsing them) is defeating the whole
purpose of getting up a trail.

I have not seen the Cruiser setup in action, maybe it's better
(hopefully), but I have seen several glaring examples of the system
used on newer Hummers (Original Hummer, not the 'tahoe' H2), we met up
with 5 of them on a trail here in Colorado called Spring Creek. There
is a rock garden, fairly big rocks, nothing all that bad though, many
vehicles walk right through with only 33" tires, some have more
trouble, descent driveing and lockers will let you walk through usually
very easily, unless you try a glory line like I usually do.. :)

The 5 Hummers took very easy lines, but were all completely stuck, the
traction control was applying the brakes because the tires were
spinning, however, it was doing this to ALL 4 WHEELS! Since they were
slightly high-centered, all 4 tires could spin at some times, not
because it was high centered that bad but the ground was soft/wet and
the rocks were smooth.

So these 'poor' guys with brand new Hummers were floored, black smoke
pouring out of the thing and couldn't even spin one tire, they tried to
spin, but the computer stopped the tire from spinning. If they could
have spun all 4 tires at once they would have made it through just
fine, but the computer kept applying the brakes, since it won't let
them spin.

That was the most glaring example I have seen of how a system like that
is fundamentally flawed. In this example if the computer could have
sensed that all 4 tires were trying spin then letting them all spin,
kinda like a override, if only two are trying to spin then go into it's
control, but if all 4 will spin, then let them spin...

The example of having two tires completely in the air and the other
tires with traction, just needing power, that would be a great
situation for the traction-control system, but around here usually any
tire WILL spin, they all have some traction, just not enough by
themselves...

The Hummer owners were somewhat pissed when they finally got out of the
trail and 2 Toy trucks with 33" tires and no lockers walked right
through what just took them 2 hours, the trucks didn't even slow
down... :)

Later..
Mark Brodis
Castle Rock, CO
'97 LX450, OME, ARB, Slee-sliders..

















From:   "Shotts Family" 
Date:  Wed Jun 18, 2003  11:49 am
Subject:  RE: [100scool] Re: rear diff lock in US-spec 100's

Mark: What you have seen is VERY normal for vehicles with traction systems.
To date, all experience this sort of problem except the Cruiser. Even
Toyota in the Sequoia has a system that slows and stops the truck making it
worthless. The new 4Runner/GX470 is about half good half bad. The only
other vehicles that have traction systems that I've seen "help" but wouldn't
say "work" are in the recent Land Rover Disco and Range Rover (though the
vehicles are not that capable).

In the 100, there are no ActiveTrac problems like you saw in the Hummers.
Nor does the 100's system stop you in the sand or mud. If you apply the gas
in those situations you will spin out sand and mud from all 4 wheels just as
if you did not have a system.

Lastly in those rocky and steep section as you describe below, I have
followed many locked 80's up and over these same sections and with great
finesse. The key is learning your truck just like you need to learn using
lockers. At first I would give it the gas thinking if I stop progress I'm
stuck. This is wrong. I would hit deep holes and begin to spin. When I
learned how the system worked I was amazed at the ease of driving. You just
point the thing, keep light throttle and the truck climbs the obstacle by
itself. Yes, it literally crawls up just my locked up 80. Lastly, there
have been NUMEROUS times where I have followed a F&R locked 80 spinning all
tires looking for traction and I have zipped right up in the 100 making it
look easy.

Only at times in loose gravel will it jerk here and there looking for
traction. This is what Doron points out about trail wear and tear. This
doesn't occur much though.

So yes, all traction systems I have seen or read about suck......except the
Cruiser's.

If you have any question, remark, comment, want to share some philosophy or just want to express your opinion about these pages, feel free to send email to: w.j.markerink @ a1.nl