OT: Digital Speedometer

[The Natural Philosopher]

No, its a jaguar.

and mine except when accelerating very hard

Sure tim. Electric would be lovely except I cant afford one and I do make long trips

[The Natural Philosopher]

No. They will effectively change the voltage though.

[The Natural Philosopher]

because he is not completely right Flat tyres don't put more tread in contact really under *cornering* - the tyre is designed for a particular contact area and if the pressure sis too low the sidewalls flex too much and lift the whole tread off the road under cornering. For pure straight line traction though it cam be good. If you get stick in mud or sand or snow, dropping the tyre pressures can get you out

Take a look at drag racers. They run practically flat for maximum traction (dont go round corners) and rely in centrifugal force to 'inflate' the tyre.

Also wide low profile tyres can be useless on wet grass or snow - you want a tyre with tread that digs into snow and mud So a higher contact pressure helps

[Tim+]

No ?gear changing? noises in mine (or any electric train type acceleration surges).

Tim

[Tim+]

I had a V6 Jaguar XF a few years back. Very smooth and fairly quiet, but not EV smooth and quiet.

I?m not suggesting you buy a car unsuited to your needs, but you might find a free test drive an interesting experience.

Tim

[Tim+]

Only the more expensive ones. I think most use a single motor and differential.

Tim

[Andrew]

In my village, the roads without street lights pay slightly less parish council 'rates' too.

[Andrew]

M25 in the rush hour ?

[Andrew]

The BMW i3 was noticibly different with narrow tyres though, presumably to reduce rolling resistance and more aerodynamic

[NY]

Ah, so still all the disadvantages of a gearbox (discrete ratios; vague final-drive ratio and lag because of torque converter). If I went for an EV, I'd want one which used the motor in a single ratio (preferably direct drive with no gears to cause gear-whine) and made use of its torque at zero rpm. But that probably needs a more powerful battery because there's no low ratio to scale up the motor's torque when setting off.

[nothanks]

The gearbox is very good and, for all reasonable driving, changes are imperceptible in auto mode; there's none of the old kick-down delay that my previous autos had. In manual mode it protects the engine by forcing a change if the revs are getting too high or low. My only experience is of PHEVs (an EV isn't viable in the sticks - yet). As I said, I believe Volvo have direct edrive to a pair of wheels. I believe Teslas are also direct e-drive but I've only got a passing acquaintance with them.

[The Natural Philosopher]

No, you simply limit the current. The limit to staring torque is essentially the I²R limit on the windings. Provided that is enough to get the car moving on the steepest hill with the highest load you dont need to a box to start.

It is all really about efficiency. You can get a leccy motor to be pretty efficient over a wide range or RPM but it does vary

[Dave Plowman (News]

True. But that's not what the post I replied to said. Implied there was a magic way of knowing the speed limit without signs.

And you need to say just what frequency those repeater signs must be by law. And try and get London to abide by this. It is now near impossible to tell the speed limit on London roads with the recent changes.

Really? All motorways today?

Again, needs speed limit signs.

[Dave Plowman (News]

Good to know. Could it be I actually understand what thrashing means?

Virtually. A magic car that thrusts through the air silently. Apart from noisy tyres.

[Dave Plowman (News]

How do you achieve heating and AC, then? ABS? Keep the screen clear of rain?

No shit, Sherlock. ;-)

[alan_m]

Top fuel drag racing tyres

[nightjar]

Strictly, it has to be a system of street lights. That means three or more at no more than 200 yards (183m) apart IIRC 185m in Scotland.

The difference is whether or not the light falls on the carriageway.

[The Natural Philosopher]

same stupid myth about 'reduction of diameter'.

you can see the sidewall deforming to show that that is what is happening, not a circumference reduction

[Dave Plowman (News]

I very much doubt it would have a torque convertor. At one time they were needed to bridge the gap between wide ratios of say a three speed transmission. Autos have many more gears these days. And with an electric motor, you'd not need a TC or clutch for moving off from rest.

[Robin]

The way councils describe lights has no bearing on what is and is not "street lighting" for the purposes of the 30 mph limit. Some councils use the term "footway lights" based on the definition in the Highways Act 1980* but using that would leave an awful lot of residential roads unrestricted (with 60 mph limits).

• Section 270 Transfer of lighting systems.

"(1) In this section-

?footway lighting system? means a system of lighting, provided for a highway, which satisfies the following conditions, namely, that either?

(a)no lamp is mounted more than 13 feet above ground level, or

(b)no lamp is mounted more than 20 feet above ground level and there is at least one interval of more than 50 yards between adjacent lamps in the system.

or such other conditions as may be prescribed by order of the Minister in substitution for the above-mentioned conditions;

?road lighting system? means a lighting system that is not a footway lighting system;

and...