OT: automatic van hire - possible?

[Steve Walker]

I presume the problem is that they keep a few (mainly manual) cars for people to test drive and eventually sell them at a discount. Automatics are a much smaller part of the market in the UK and if they were to get an automatic for each model, they'd not get many people test driving them, but they'd still have to sell them at a large discount in the end, as they'd have more than "delivery" mileage on them. Quite understandable, but you'd think that they'd have one between a number of garages and either send the person to the car or the car to the garage that the person wants to use, by pre-arrangement.

SteveW

[The Natural Philosopher]

the TD5 I had had really GOOD torque on a 5 speed box..it was a heavy bastard to change gear in tho. Heavy clutch and pretty heavy gears.

Likweise the TD4 (BMW) freelander is really good torque band.

Worst diesel I ever drove was a TD mondeo. Nothing till 2000 RPM, nothing over 3500 RPM.

[Tony Bryer]

In the sixties on smaller cars especially automatic was an expensive option which significantly reduced performance and increased fuel consumption. It took a long time for people to be persuaded otherwise and meanwhile with four and five speed transmissions (instead of the BW35 three) and electronics, the gap between manuals and autos significantly reduced.

People had the same attitude to front wheel drive - the Marina was cobbled together to humour them.

[Neil Williams]

Those do have the disadvantage that you can lose power for a short time (for a gear change) when you most need it.

Neil

[The Natural Philosopher]

that applies to any gear change.

[dennis]

That's true for any box that changes gears, with or without a torque convertor. There are some variable ratio boxes about where it may not be the case.

[Andy Burns]

In practice I've never noticed a problem, if mine has predicted the next gear correctly, a gear change only take 8ms.

If you're stationary it's already got 1st biting and 2nd lined-up, ready for a rapid take-off if necessary. 3rd will be ready before you're halfway through the rev range of 2nd, and so on.

If you're travelling at a steady speed in 7th gear it's always got 6th ready to change down to (or steady in 6th with 5th ready if it's in "sports" mode).

Other than that, I presume it aims to keep the next higher gear ready if you're generally accellerating, and the next lower gear if you're generally decellerating.

I realise that "hardcore driver's drivers" will always want a manual box, but coupled with a 3l engine a DSG makes for plenty of grins!

[Neil Williams]

With a manual, the gear change occurs when you want it, unless you're pushing right up to the end of the power band (which is not the way I drive, though that's a stylistic point and there are people who do). So if you really don't want to lose power *then*, you can delay it a short while.

With a normal automatic (epicyclic gearbox), changes are very quick.

One thing I've wondered, though. On t'railway, electric transmissions are very common, i.e. the engine drives a generator, and there are electric motors on the wheels. Why has this seemingly never applied to road vehicles? Too expensive?

Neil

[Neil Williams]

Do all of them have this second-box "prediction"? I certainly recall that the ones you get on Mercedes Sprinter vans/minibuses don't seem to have it and take far more than 8ms for a change.

Neil

[Dave Plowman (News)]

Hence now most having twin layshafts and clutches. So no actual gearchange at the time it changes ratio.

[Dave Plowman (News)]

Not so - and never was on a conventional auto. No gears change mesh.

[John Williamson]

Too heavy until they started using exotic magnetic materials. It doesn't scale down well to road use from the large sizes used on rail. Also they were too complicated to make and maintain. Some hybrids now use a similar system, though.

[Dave Plowman (News)]

Bollox. The change on a conventional auto is achieved by clutches. They can give a full power transition between one ratio and another. But most these days will reduce the engine power on a change to increase clutch life.

The ability to maintain full power on a change is why dragsters use auto boxes..

[Tony Bryer]

Denver has [expensive] buses that work this way - the best link I could find was

[fred]

=A0 London SW

My youngest son got an epiphesys fracture of the left hip in his early teens necessitating the insertion of a pin which restricts articulation of his hip which means he cannot use a clutch. When he started Uni about 10 years ago we bought him a semi auto Yaris which was simply clutchless. No clutch. Just move the gear lever. No loss of power to a slush box auto which would be killer on such a small engine. Simplest car I ever drove. Beauty of it was when he did his test it was treated as a normal, not auto, car so he got a full license

Paul Mc Cann

[Theo Markettos]

Some lorries use it... but they're the sort of huge things you find in South American mines for carting around hundreds of tonnes of ore. Though they might not count as road vehicles!

Theo

[fred]

Recently had to drive two modern diesels. BMW 320d on loan while my car was in the workshop and a Citroen C4 Picasso whilst on holiday. My own car is an auto 6 speed diesel and its excellent but I couldn't get on with the manual diesels. Low level torque my arse. Nothing seemed to happen till about 1500 rpm. Any time a gear change down to a lower gear was required it always seemed necessary to drop 2 to 3 gears to get pick up.

Paul Mc Cann

[dennis]

Bullshit. So now you have invented lossless clutches that disengage one gear and engage the next instantly. You had better patent it as nobody else has managed it yet.

Why? if there is no power loss there won't be any clutch wear.

More likely its because you can sit there, foot on brake, at high revs with the torque convertor spinning waiting for the green light. A manual clutch isn't going to like that much. brakes release much faster than engines rev up, especially with a big flywheel to store even more energy for a quick getaway.

[dennis]

Vauxhall ampera does that. Motor on each wheel, big battery, diesel engine and generator. Runs 50 miles without the engine and 300+ with. £30k though.

[Dave Plowman (News)]

Thanks for showing your ignorance to an even greater extent. On a dragster, the tyres are used as the 'clutch' from a standing start.