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Random police stop

Passion, instruction, buying, care, maintenance and more, any form of vehicle discussion is welcome here
jfgw
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Re: Random police stop

#143796

Postby jfgw » June 4th, 2018, 10:36 pm

An instructor told me that the purpose of the gearbox was to convert the revs of the engine to the torque needed to drive the wheels. I don't think physics was his strong point.

Julian F. G. W.

Itsallaguess
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Re: Random police stop

#143874

Postby Itsallaguess » June 5th, 2018, 10:22 am

redsturgeon wrote:
It's a bit like overtaking on a single carriageway road, would you signal after an overtake that you are returning to your side of the road.


No, but when I'm on a motorway I don't want to have to think about which lane I'm in when I'm deciding to indicate or not, so I tend to indicate at all times, and this then becomes automatic over time, without actually having to make a decision at all about which lane I'm in.

I don't think there's any harm in it, and I'd rather be of the 'always do it' than allow myself to think there's some occasions when I don't have to on a motorway, but then have to think about that 'which lane am I in' process instead....

Cheers,

Itsallaguess

Lootman
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Re: Random police stop

#143882

Postby Lootman » June 5th, 2018, 11:04 am

jfgw wrote:An instructor told me that the purpose of the gearbox was to convert the revs of the engine to the torque needed to drive the wheels. I don't think physics was his strong point.

He was vaguely on the right track but the word "convert" there is misleading. The purpose of gears is to compensate for the inefficiencies of IC engines outside of their optimal operating range of rpm. The gears enable the engine to be at, say 3,000 rpm to 5,000 rpm at any road speed.

If you look at the output curve of a typical IC engine it will start low and then increase as the RPM increases, until it reaches a maximum at maybe 6,000 rpm, at which point it turns down again. The "red line" on the tachometer will be around there somewhere.

It really depends on the kind of engine. The old Ford Mustang I had used a typically under-stressed, large-capacity US engine (long stroke, low compression, tons of torque). I could stick it in 4th and drive it like an automatic if I wanted. It would happily growl and trundle at 1,500 rpm.

But make a highly-tuned, small-capacity, short-stroke, high compression engine and you need those gears and have to rev it a lot to get the torque and performance you want.

Or of course you could buy an automatic and forget about it all.

UncleIan
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Re: Random police stop

#143885

Postby UncleIan » June 5th, 2018, 11:19 am

melonfool wrote:Now I happily skip from 4th to 6th, 6th to 3rd, etc. I'm not sure I've ever used 5th on this car (what's it for??).


On a voluntary minibus driving course on the practical the instructor talked about doing a "block gear change", which is what you describe. Seems it's the expected way these days. I think I use it slowing down sometimes, or when I've accelerated in, say, 3rd, but I'm in a 50 so know I'm going to be tootling along, I go straight to 5th or 6th.

Lots of reading here:

https://www.drivingtesttips.biz/block-g ... nging.html

Slarti
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Re: Random police stop

#144112

Postby Slarti » June 6th, 2018, 12:37 pm

Lootman wrote:Of course back then there were usually only four gears, and now there are 5, 6 or more, so it would be more onerous to do now. The ratios are closer together now so there is less point. And engine torques are higher now meaning that you can pull away in a lower gear and it matters less which gear you are in.


Or even only 3 gears.

And the wonderful smell, and feel, of drum brakes fading from overheating meant that you only ever got that wrong once. Assuming you survived.


Slarti

bungeejumper
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Re: Random police stop

#144122

Postby bungeejumper » June 6th, 2018, 1:26 pm

ISTR comparing notes with Redsturgeon about this subject. In 1969 I was failed in my driving test for block-changing down - something which my dad had taught me, but which the examiner highly disapproved of. (That would have been in a Mark 1 Cortina.) Only a few years later, RS said he was criticised for not doing it. You can't win. :roll:

Even today, I rarely block-change down, although I am getting more used to block-changing up from second to fourth. Fourth to sixth still doesn't feel right though. ;)

Slarti's comment about the smell of burning brake pads will ring a bell with many of us. With the added frisson of knowing that those pads were loaded with asbestos. Mind you, they lasted much longer than today's pads, and the discs hardly ever wore out.

But then, times change, and so do car components. The old ways are not always the best. And another thing. The other day I saw a group of cyclists who didn't give a waggly-arm slowing-down signal as they approached a corner, the way we were taught to do. Harrumph, where's a policeman when you need one?

BJ

panamagold
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Re: Random police stop

#144128

Postby panamagold » June 6th, 2018, 2:04 pm

One of my cars is a Ford F150 (5 gears). When descending what I consider extreme inclines, not only do I use the engine as a brake, but I automatically double de-clutch. Having driven crash gearboxes in my youth, old habits die hard.

didds
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Re: Random police stop

#144153

Postby didds » June 6th, 2018, 3:26 pm

[quote="bungeejumper"The other day I saw a group of cyclists who didn't give a waggly-arm slowing-down signal as they approached a corner, the way we were taught to do. Harrumph, where's a policeman when you need one?

BJ[/quo

Back in 2010 I was a bikeability instructor - and by then the slowing down signal was not taught. In fact when i was preliminary tested for my own cycling skills, I used it at the end of the test ride, and the trainer remarked that what I'd done hadn't been taught for a very long time, because more modern drivers (by which I took to mean "those under the age of 40!) wouldn't know what it meant anyway. A bit like the "I am progressing forwards" signal (open hand held upright beside right shoulder) had disappeared in reality by the time I took my driving test in 1980.

https://assets.digital.cabinet-office.g ... ght-on.jpg

http://road.cc/content/forum/76508-straight-hand-signal

tjh290633
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Re: Random police stop

#144184

Postby tjh290633 » June 6th, 2018, 6:02 pm

didds wrote:
bungeejumper wrote:The other day I saw a group of cyclists who didn't give a waggly-arm slowing-down signal as they approached a corner, the way we were taught to do. Harrumph, where's a policeman when you need one?

BJ


Back in 2010 I was a bikeability instructor - and by then the slowing down signal was not taught. In fact when i was preliminary tested for my own cycling skills, I used it at the end of the test ride, and the trainer remarked that what I'd done hadn't been taught for a very long time, because more modern drivers (by which I took to mean "those under the age of 40!) wouldn't know what it meant anyway. A bit like the "I am progressing forwards" signal (open hand held upright beside right shoulder) had disappeared in reality by the time I took my driving test in 1980.

https://assets.digital.cabinet-office.g ... ght-on.jpg

http://road.cc/content/forum/76508-straight-hand-signal

I don't suppose they bother about the whip signals for horses and carts, either.

TJH


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