Sad story from Wales about a unlicenced and uninsured driver responsible for the death of a little lad.

tinyurl.com/nxsk5u

Should you have to show you've a licence when you buy a car? There could be a space in the V5 to be completed with the purchaser's licence details if the car is used or passed straight on to DVLA by the dealer if the car is new.

Read more

Any ideas as to why the wipers juder across the screen & some times stop half way on the way back down?. They also dont park properley sometimes. This seems to happen when I use them on intermitant. Read more

Sorry about the rambling nature of this post - it's arisen from a conversation with a friend who drives but knows nothing at all about car engines and transmissions, but who is also used to riding a multi-geared pushbike.
Thinking about things, I seemed to have tied my own brain in knots. Perhaps Number Cruncher will come along and define it all in black and white!


A car will accelerate in top gear if it is already doing say 30 mph.
A cyclist can accelerate in top gear if he's already doing say 10mph.

But a cyclist will struggle to set off from rest in top gear, even if the pedal crank is at its most favourable angle (horizontal).

I can understand a petrol/diesel car will struggle to set off in top gear because of insufficient torque developed at the low revs that would be forced upon it by the gearing. But given a sufficiently thick clutch plate or sufficiently-cooled fluid clutch, would it set off provided the engine revs can be held at the speed of maximum torque?

It's all about starting torque, because typical electric cars will set off from rest with no gearing at all.
Does the human leg also develop less force when pushing against a static pedal than when it is already rotating?

The mass of the vehicle is the same, so if the force/torque is the same, in the same gear would a car or bicycle not add 10mph to its speed in the same amount of time starting from 30 mph as from zero mph?

F = m a suggests it would, but subjectively it doesn't feel as though it would.

Is this purely due to the outside factors like torque not being able to be developed at low speeds / slippage in the clutch etc? Or is starting from rest a special case?

I presume that a (theoretical) motor with utterly constant torque from zero (no clutch) to 6000 rpm would give a vehicle a constant rate of acceleration (assuming there was no wheelspin) until wind resistance became an ever-increasing restriction?

Momentum actually plays no part?

So is it that the bottom line is indeed that a cyclist's leg cannot develop as much force when pushing against a static pedal as when everything is in motion?

Read more

I'm looking to see if anyone could give me some advice regarding upgrading of my driving licence.
I currently restricted due to medical reasons to categories B and BE, but need to upgrade to C1.
I have an application form on the way from DVLA, but would like to know if a new driving test is required and how long the process typically takes.
A trawl through the DVLA web site didn't provide any answers.

Thanks in advance

S6 1SW Read more

I have a Jeep Garnd Cherokee 3.0 CRD purchased 2 years ago from a Jeep dealer, Old of Yeovil, and which has always been srviced on time at that dealer. The car has been excellent, particularly for towing a two horse trailer. Until now at 60,000 miles when the steering rack has about 1/4" of play and needs replacing to pass the MOT. A quote of £1,200 to do this seemed high but I accepted it. I am now told the engine needs to come out to get at the rack and so a further £800 of labour. This seems excessive to me. Do you think Chrysler should make some contribution to this cost? Surely a steering rack should be good for 200,000 miles? Your advice would be much appreciated.

Gideon Sumption 19/06/09 Read more