Explaining and developing gear selection with a 'student'.

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Adamxck
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Explaining and developing gear selection with a 'student'.

Postby Adamxck » Thu Nov 10, 2016 3:14 pm

I'm teaching somebody to 'advanced' drive and next time we drive we're going to discuss appropriate gear selection.
She read something in roadcraft about gearing and quoted the following which reads like a misquote, or I grossly misunderstand what is going on. (highly likely.)

"If you are in too high a gear, the engine will not respond because the load from the wheels is too great."

Wheels? Bit weird and I cant check because she has my copy... Unless its using wheels as they are the final component to rotate?

I tried a pushbike analogy (peddling in gear 1 vs 10 up a hill) which she understood but Im not convinced my explanation was good enough. I understand why you need an appropriate gear to make use of both engine braking and acceleration and to prevent the engine bogging down or blowing up etc etc, but if anybody can offer some sort of metaphor or analogy I could use to better explain the principal, I'd appreciate it.

I will have her play about with gears when it doesn't matter to feel what is going on which i hope will help, but how does one work on getting a sense for what gear is suitable for a given situation? Trial, error and practice?
Adam.

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Mr Cholmondeley-Warner
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Re: Explaining and developing gear selection with a 'student'.

Postby Mr Cholmondeley-Warner » Thu Nov 10, 2016 4:10 pm

I generally use responsiveness of the car as the illustration. Just pick a speed on a nice empty bit of road and try it in different gears. For each gear:

- If the student understands the purpose of their rev counter, note the RPM.
- does the engine feel "happy"? (is it screaming, buzzing, chugging?)
- Is there a lot of noise? (does that diminish with a higher gear?)
- If you squeeze the throttle firmly, does the car respond immediately? (if no, does that work better with a lower gear? If yes, try a higher gear. Does it still respond?)
- Now note the engine RPM again once you've found the "sweet spot". For petrol, this will be 2000-2500 RPM. For diesel, perhaps 1500-2000 (just a rule of thumb, find the right revs in her car).
- Now do the same going uphill / downhill. What's the difference? Once the sweet spot has been found on the flat, this should be a much shorter exercise.

Then suggest the old chestnut mnemonic - 3rd for 30, 4th for 40, etc. and see if that works. It usually does.

Her quote is not wrong. The torque required to turn the wheels increases as the wheel speed decreases. It might not be verbatim from Roadcraft, but it's a fair point. Which edition of Roadcraft is she using? I couldn't find wording like this in the 2013 edition.
Nick

gannet
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Re: Explaining and developing gear selection with a 'student'.

Postby gannet » Thu Nov 10, 2016 4:12 pm

Wheels are what helps the engine overcome the inertia of the car and gain the momentum that gets us places...

so the slower the speed, the slower the wheels and the more momentum you need to gain, thus higher load...

dunno if that helps?

The bicycle analogy is good one though.

and of course everything what ^ he said :D

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Adamxck
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Re: Explaining and developing gear selection with a 'student'.

Postby Adamxck » Thu Nov 10, 2016 4:30 pm

Its the 2013 edition. It'll be somewhere in chapter 5 as that was her homework. For the other questions she asked she sent me a picture of the page which would have been useful in this case.

I will do all of the things you suggested, thanks Nick. It's one of those things where I can do it, but cant explain it properly.

I understand the wheel/torque/load. Makes more sense reading it like that and I shall repeat your words as if they were mine and take all the credit.
Adam.

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GTR1400MAN
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Re: Explaining and developing gear selection with a 'student'.

Postby GTR1400MAN » Thu Nov 10, 2016 4:48 pm

I just get them to ride a suitably variable quiet stretch of road in 6th, then 5th, then 4th, then 3rd. Then get them to drive along at 40 and switch between 3rd, 4th, 5th and 6th without changing speed.

Practical vs explanation.

For a description of a responsive gear I explain it as a gear that won't go 'bleughhhhh' if you open the throttle and will slow you if you come off the throttle, while not throwing you forward (applies to cars or bikes).
Last edited by GTR1400MAN on Thu Nov 10, 2016 5:27 pm, edited 1 time in total.
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Adamxck
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Re: Explaining and developing gear selection with a 'student'.

Postby Adamxck » Thu Nov 10, 2016 5:18 pm

Sounds like a plan. Which is another discussion we'll be having.
Adam.

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Mr Cholmondeley-Warner
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Re: Explaining and developing gear selection with a 'student'.

Postby Mr Cholmondeley-Warner » Thu Nov 10, 2016 5:26 pm

Adamxck wrote:Sounds like a plan. Which is another discussion we'll be having.

When?
Nick

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Adamxck
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Re: Explaining and developing gear selection with a 'student'.

Postby Adamxck » Thu Nov 10, 2016 7:37 pm

I tried to write something witty but gave up.

I've only been out with her once, so likely next time, early on. I thought I'd let roadcraft do the hard work and I will do a working example or 10 with her.

She's only had the book 2 days.
Adam.

Smeeagain
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Re: Explaining and developing gear selection with a 'student'.

Postby Smeeagain » Fri Nov 11, 2016 12:10 am

Apologies if Im missing the point or misunderstanding .... when you say you are teaching someone to advanced drive do you mean they can drive already but are preparing to take an advanced test or do you mean they are learning to drive and youre teaching an advanced style? If it is the former then surely they are nowhere near the required standard if they dont understand this already ???
Smee

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Mr Cholmondeley-Warner
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Re: Explaining and developing gear selection with a 'student'.

Postby Mr Cholmondeley-Warner » Fri Nov 11, 2016 7:46 am

Smeeagain wrote:Apologies if Im missing the point or misunderstanding ... do you mean ... they can drive already ... or ... they are learning to drive ... If it is the former then surely they are nowhere near the required standard if they dont understand this already ???

The former. Adam isn't an ADI.
Adamxck wrote:She's only had the book 2 days.

I think this answers your question :D
Nick


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