Roland Perry wrote:
In message
, at 11:38:16 on Sun, 26 Oct 2014, Recliner remarked:
ABS-style braking is the opposite of traction control. The former
automates the stopping of vehicles, that latter the acceleration.

Yes, but they work in the same way using the same physical features of
the car, taking advantage of how the differential works to deliver the
former, which is why adding the latter is mainly a software thing.

I would hope that proper traction control fed the power the most suitable
wheels, without having to rely upon brakes on the least suitable wheels
absorbing 100HP that the electronics says should be suppressed.

If you had a car with independent direct power transmission to each wheel,
your solution would work. But in the near 100% of cars with differentials,
you just have to stop the wheel with no traction from spinning the power
away from the other wheel that may have some limited traction. But the
brake certainly won't be absorbing 100bhp: very little power is being
transmitted when the wheels are spinning without traction.

I'd do that by locking the differential, rather than braking the errant
wheel, but I can see how the two activities could be conflated.

Independently and momentarily applying the individual brakes probably is
more effective for regaining traction than locking the diff, not that many
two-wheel drive cars have locking diffs.

"Recliner" wrote in message
...
Roland Perry wrote:
Really? Traction control is all about putting the power down to the
wheels with the best grip. Do cars really implement this by applying the
brakes to those wheels which you don't want power transferred to?

Yes, and they cut the power, too. See
http://www.bbc.co.uk/news/business-13609388


Slightly scary is that some systems will *apply* power to maintain
directional control, even though the driver is requesting full braking.

--
DAS

In message

, at 11:57:56 on Sun, 26 Oct 2014, Recliner
remarked:
ABS-style braking is the opposite of traction control. The former
automates the stopping of vehicles, that latter the acceleration.

Yes, but they work in the same way using the same physical features of
the car, taking advantage of how the differential works to deliver the
former, which is why adding the latter is mainly a software thing.

I would hope that proper traction control fed the power the most suitable
wheels, without having to rely upon brakes on the least suitable wheels
absorbing 100HP that the electronics says should be suppressed.

If you had a car with independent direct power transmission to each wheel,
your solution would work. But in the near 100% of cars with differentials,
you just have to stop the wheel with no traction from spinning the power
away from the other wheel that may have some limited traction. But the
brake certainly won't be absorbing 100bhp: very little power is being
transmitted when the wheels are spinning without traction.

I'd do that by locking the differential, rather than braking the errant
wheel, but I can see how the two activities could be conflated.

Independently and momentarily applying the individual brakes probably is
more effective for regaining traction than locking the diff, not that many
two-wheel drive cars have locking diffs.

Not permanently locked ones, but a brake in the diff (rather that at the
wheel).
--
Roland Perry

In message , at 17:06:40 on Sun, 26 Oct
2014, D A Stocks remarked:
Really? Traction control is all about putting the power down to the
wheels with the best grip. Do cars really implement this by applying the
brakes to those wheels which you don't want power transferred to?

Yes, and they cut the power, too. See
http://www.bbc.co.uk/news/business-13609388

Slightly scary is that some systems will *apply* power to maintain
directional control, even though the driver is requesting full braking.

One of the attractions of a high-end car is that the accelerator is a
"speed pedal", but the quid pro quo is that the brake is a "stop pedal".
--
Roland Perry

On 2014-10-26 16:20:14 +0000, John Levine said:

The obvious approach would be to put motors in the wheels, like they
do on electric streetcars.

In the *wheels*? Never heard of that. They'd usually be on the bogie, surely?

But apparently motors are heavy, and that
would make the unsprung weight of the car undesirably high, so they'd
have to put the motors in the body, with fiddly universal joints to
connect them to the wheels.

No more fiddly than the same universal joints/CV joints required to
connect the internal combustion engine in a regular car to the wheels.

But unless they are a lot more fuel
efficient than current hybrids I wouldn't bother.

The gains are different - lower complexity as there is no traditional
gearbox, and a better ability to run electric-only for short periods
e.g. when in and around a city, where avoiding pollution at the point
of use is a key feature. Not necessarily raw MPG.

Do electric trolly buses have motors in the wheels like streetcars?

I'd expect body mounted and connected via a propshaft with a CV joint
on each end.

Neil
--
Neil Williams
Put my first name before the @ to reply.

On 2014-10-26 16:20:57 +0000, Roland Perry said:

I would hope that proper traction control fed the power the most
suitable wheels, without having to rely upon brakes on the least
suitable wheels absorbing 100HP that the electronics says should be
suppressed.

Your hope would be misplaced. But do some reading on how a
differential works - it has exactly the same effect with a massive
reduction in complexity over what you propose. Essentially the brake
is not having to absorb anything.

Neil
--
Neil Williams
Put my first name before the @ to reply.

On 2014-10-26 16:47:22 +0000, Roland Perry said:

I'd do that by locking the differential, rather than braking the errant
wheel, but I can see how the two activities could be conflated.

That's rather more expensive as it adds another component to the system
(another thing to build, and another thing to break, as well as more
weight added to the car) - all cars built since the early-mid 2000s
have individually controllable brakes and all cars even older than that
have a differential. All you need is a bit of software to make it
work. The braking solution is incredibly elegant in its efficient and
safe use of existing components.

Neil
--
Neil Williams
Put my first name before the @ to reply.

On 2014-10-26 17:15:20 +0000, Roland Perry said:

Not permanently locked ones, but a brake in the diff (rather that at
the wheel).

What would be gained by duplicating the function?

Neil
--
Neil Williams
Put my first name before the @ to reply.

Roland Perry wrote:
In message
, at 11:57:56 on Sun, 26 Oct 2014, Recliner remarked:
ABS-style braking is the opposite of traction control. The former
automates the stopping of vehicles, that latter the acceleration.

Yes, but they work in the same way using the same physical features of
the car, taking advantage of how the differential works to deliver the
former, which is why adding the latter is mainly a software thing.

I would hope that proper traction control fed the power the most suitable
wheels, without having to rely upon brakes on the least suitable wheels
absorbing 100HP that the electronics says should be suppressed.

If you had a car with independent direct power transmission to each wheel,
your solution would work. But in the near 100% of cars with differentials,
you just have to stop the wheel with no traction from spinning the power
away from the other wheel that may have some limited traction. But the
brake certainly won't be absorbing 100bhp: very little power is being
transmitted when the wheels are spinning without traction.

I'd do that by locking the differential, rather than braking the errant
wheel, but I can see how the two activities could be conflated.

Independently and momentarily applying the individual brakes probably is
more effective for regaining traction than locking the diff, not that many
two-wheel drive cars have locking diffs.

Not permanently locked ones, but a brake in the diff (rather that at the wheel).

A permanently locked differential isn't a differential at all, but a solid
axle. A locking diff is one where there is resistance to the turning of one
wheel vis a vis the other, which can be either mechanically or electrically
controlled. But ASC (including traction control) are much more capable and
sophisticated, which is one reason why so few two-wheel drive cars now have
locking diffs.

In message , at 18:42:49 on Sun, 26
Oct 2014, Neil Williams remarked:

Not permanently locked ones, but a brake in the diff (rather that at
the wheel).

What would be gained by duplicating the function?

Braking a wheel isn't the same as locking a diff. Apart from anything
else, the locked diff still powers both wheels.
--
Roland Perry