UPS frightened of the snow?

[mark]

Is this known as 'drifting' as viewable on youtube?

mark

[Ian White]

We didn't see any post for a week but the UPS driver kept up his regular deliveries from Carlisle, 100 miles away.

[The Natural Philosopher]

Not really. Drifting is when there is no longer a 1:1 relationship between the wheels and the road. All wheels are slipping, and its the fact that the equations that giovern friction are not as simple as you might have learnt at school, that makes it work.

Classical simplistic friction says that there is a force that is equal to the pressure between two sliding surfaces times some constant, that expresses the force needed to achieve slip.

A rubber tyre on tarmac does NOT show a constancy in that relationship: It can actually generate more friction if it slips a little bit.So controlled wheelspin is the way to go as with e.g. a drag racing car, or indeed an ABS system

A drift is about throwing te car into mild slip on all wheels, to get the very best lateral forces you can, or in the case of Top Gear, to look as silly as possible. Slip on the wheels is controlled by brakes, throttle and steering angle used to make the fronts slip more or less than the rears. It is essentially a controlled skid. Depening on the exact nature of the tyres surfaces and the downforce on them, it is a way to corner faster than keeping the tyre from slipping altogether.

What I was talking about, above, is different: its a way to fool the automatic gearbox into thinking its e.g. going up hill, when in fact its actually not, so it changes up when you want it to, not when it decides to. Id you like torque to the rear axles in now not just about the right foot, the engine and the gearbox, you can use the left foot to REMOVE some torque from the road wheels. Most importantly, you can stop the differential from bleeding power from a stationary wheel to one that is spinning.

You can do this in a non auto as well..one of the better ways to get going on ice is to use the handbrake to brake the rear wheels, and then apply power to them.. Race cars use limited slip differentials to do this, but they are expensive and waste power, so road cars do not use them

On FWD you cant use the handbrake to do this, because it on the rear wheels usually. the only answer there is to manipulate three pedals simultaneously and use 'heel and toe' on the brake and clutch. That can occasionally work, if you are good enough. Probably its better to release the clutch. let the front wheels spin, and then use the brake to control the spin and transfer some power way from the spinning wheel to the stationary one.

That at least makes a FWD car into two wheel drive, not a substitute for

4WD, but better than 1WD. Which is essentially what a far with one wheel spinning madly, is.

[Bruce]

A result!

And much cheaper than getting the builders in. ;-)

[The Natural Philosopher]

it is a bloody nuisance switching from auto to non auto.

Because I left foot break the auto, or right foot, its not the actual brakes I have a problem with. Its remembering do de-clutch when slowing at a junction ;-)

judder judder Thump!

[Dave Liquorice]

Wonder if he's the same chap we have, probably not it would be a big patch to cover in a day and he's around us every working day. Little chap with a slightly disfigured face.

Pretty sure our Postie is walking down to some of the places that he would normally drive to, thus they don't have mail boxes at the top of their tracks. I see his van parked up on the main road for 20 to

30 mins and no sign of him.

The milk is delivered by 4WD pickup anyway...

[Tinkerer]

I normally drive a manual but occasionally an auto. I do the reverse of what you say and "remember" to de-clutch. Vehicle immediately attempts to stand on its nose. ;o)

[The Natural Philosopher]

yerrss..

But I've been driving both for some years now, so usually it doesnt take long to adapt.,

[Jules]

My brother-in-law used to swear by the old auto 4x4 he had that he used for snow-ploughing, too. Personally I don't like that lurch that autos seem to do as they first start trying to move (and this often seems to get them into a going-nowhere, wheel-spinning situation); I much prefer being able to 'tickle' a clutch pedal and find it gives me more feedback on what the wheels are doing.

If driving an auto when it's slippery I'll shift it like a manual - I hate having it decide to shift on me when I least want it to.

cheers

Jules

[Bruce]

I have the same problem with the clutch - I also sometimes forget to change gear when driving my partner's car.

But I don't use left foot braking even when in an automatic. My left foot goes on the footrest and stays there! It only gets used to apply the parking brake on my Mercedes.

[Jules]

Unless you have a shitty US vehicle with a "parking brake" - a ratcheting pedal that you push down in the footwell, with a lever that you pull out by hand to release :-(

For some reason all the US vehicles with slushboxes that I've seen are like that, but US cars with manual 'boxes still have a handbrake between the two front seats like a real car.

[The Natural Philosopher]

I found it the only way to make a jaguar handle like a sports car.. Id been used to heeling and toeing old sports cars with crappy synchromesh..so left foot braking was just an extension. The key thing is you CAN use it to prevent that nasty lurch as the torque converter cuts in. rev up in gear with with foot on brake, and use BRAKE to control the start.

[The Natural Philosopher]

Golly. are the still some like that?

Still a lot of them are RWD still, so you can use the footbrake.

It's worth a bit of practice anyway, to exploit whatever control they have in fact left you...

I love autos for taking the effort out of 'normal' driving stop start creep etc etc. But I hate them for taking ultimate control away when I want it. So basically one learns to make them do what YOU want.

[dennis]

And lock up your front, steering, wheels at the same time, very useful!

Its a smart.. they don't kick down.

At least that one won't lock the front wheels.

[Bruce]

I've never found that a problem. I take my foot off the brake, gently accelerate and the car moves smoothly away.

[Huge]

Your problem is the "occasionally". I routinely switch between manual & auto vehicles and have no problems these days. I used to forget to depress the clutch when coming to a halt, in the early days.

[dennis]

Sorry but all that is BS.

A tyre that is slipping does not generate more friction than one that is not. Drag racers don't like the wheel spin and go to great lengths to minimise it. ABS increases stopping distances as it doesn't achieve the same grip as having a heel balanced on the edge of slipping.

The reality is that drifting relies on breaking the friction grip between the road and the tyre so that they can slide around, they don't do it to increase grip.

Drag racers like as much friction as they can get, hence the warming of the tyres and putting down the sticky tracks before a run.

ABS is designed to keep the wheels rotating as a tyre that is not rotating behaves exactly as school physics says and the car slides in the original direction as there is no force to change its direction if the tyres aren't rotating.

ITYM down.

Doesn't appear to work for BMWs. ;-)

A car with one wheel spinning is a no wheel drive unless it has a limited slip clutch. You might make it into a one wheel drive by braking the spinning wheel which is what I assume you meant to say.

The smart makes horrible bleeping noises when you do that BTW, unless its in reverse that is. I can see the logic.. handbrake on and being driven, sound alarm, in reverse isn't being driven so silence.

[dennis]

I have no trouble with that, I can never remember where reverse is though. The fiat van makes funny noises when you try and put it in reverse at 50mph.

[The Natural Philosopher]

That works fine in 'lazy' situations. But in fast starting or where you want very precise control of torque, there is a delay between engine revs and axle torque.

If you ant to get a really fast start in a Jag, you rev it up with the foot on the brake, and release the brake.

[The Natural Philosopher]

It does.

But NOT to eliminate in entirely.

Wrong. Google cadence braking.

Oh yes they do. Any motor race you care to actually watch will reveal that the car is not moving in the direction its pointing, when cornering.

They dont do that for style points, they do it for lateral grip. About

15% is typical slip where the actual force generated peaks. Rally drivers use a lot more, on loose surfaces.

Indeed, but they still use a little wheelspin. Typically the first 50 meters or so. before the acceleration become power rather than grip limited.

Believe what you like. ABS is designed to stop wheels COMPLETELY locking, for two reasons. A completely locked wheel generates LESS retardation than one that is slightly locked, and to retain steering control

You should read up on race and rally technology and engineering.

The actual performance of tyres and the effects of slip are one of the most highly studied areas of race engineering.

in practice, the force you can apply through the tyre contact patch increases up to a maximum at about 15% slip in terms of RPM over 'free rolling' and then declines.

Down in number, up in ratio

I change up from 4th to 3rd.

well since you don't seem to understand the principles, I am not surprised.

semantics. You understood what I emant, anyway.

one more reason not to drive one.