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OK, so I still think the gear ratios on my car are just strange!
My first car was ancient and broken. Like all normal cars, it had 4
gears. Obviously, you start in first gear. Once your speed exceeds that
of a land snail, you need second gear. At somewhere around 30 MPH, you
need third gear. And somewhere around 45 MPH, you need to change up to
fourth gear. And that's all the gears there are - no matter how much you
keep feeling that there should be more...
My previous car was somewhat unusual, in that it has a fifth gear. As
best as I can tell, the gears work more or less the same, except that
the engine really isn't happy about exceeding 55 MPH or so unless you
change up into fifth gear - which is kinda tricky the first time you try
to do it.
My current car is completely different. For a start, it somehow has
/six/ gears. I've never seen any vehicle anywhere that has that many.
Also, the change points are just odd.
Once again, you start in first, and once the car is travelling faster
than plate tectonics, you need second gear. Then it gets weird. Round
about 20 MPH the engine runs out of power, and you need third gear. And
when you get to about 30 MPH, you need forth. At 40 MPH you need fifth,
and at 50 you need top gear.
Needing to be in forth gear just to drive around a 30 zone is just weird.
(Note that these are the speeds you need to change for cruising.
Obviously if you're trying to accelerate hard, you stay in a lower gear
for longer. But nobody wants to drive around a housing estate revving
the nuts off their engine.)
These gear settings seem very strange to me. Rather than adding more
gears up top where there's lots of empty space, they've added more down
at the bottom where there's already plenty of them...
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> OK, so I still think the gear ratios on my car are just strange!
>
> But nobody wants to drive around a housing estate revving
> the nuts off their engine.)
>
You clearly don't drive the same as my neighbor!
> These gear settings seem very strange to me. Rather than adding more
> gears up top where there's lots of empty space, they've added more down
> at the bottom where there's already plenty of them...
Gears are chosen so that your car engine remains as close as possible to
the peak of its power curve while under load, and so that the
revolutions are kept as low as possible when cruising to save on fuel.
All things being equals, the more gears, the better. This is why on
some of the hybrids, you have CVTs (Continuously variable transmissions
- or variable diameter pulleys and belt) so that you effectively have
an infinite number of gears and the power of the lawnmower engine in
those cars is always optimal.
For "normal" transmission boxes, more gears cost more money, so you only
see 7 or 8 gear transmissions on luxury german or italian cars. For the
rest of us mortals, adding gears for speeds that are illegal in most
countries is not a cost-effective measure.
--
/*Francois Labreque*/#local a=x+y;#local b=x+a;#local c=a+b;#macro P(F//
/* flabreque */L)polygon{5,F,F+z,L+z,L,F pigment{rgb 9}}#end union
/* @ */{P(0,a)P(a,b)P(b,c)P(2*a,2*b)P(2*b,b+c)P(b+c,<2,3>)
/* gmail.com */}camera{orthographic location<6,1.25,-6>look_at a }
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>> But nobody wants to drive around a housing estate revving
>> the nuts off their engine.)
>
> You clearly don't drive the same as my neighbor!
Probably not, no. ;-)
> For "normal" transmission boxes, more gears cost more money, so you only
> see 7 or 8 gear transmissions on luxury german or italian cars. For the
> rest of us mortals, adding gears for speeds that are illegal in most
> countries is not a cost-effective measure.
Sure. But there's *four* gears to get from 0 to 30, and *one* gear for
the entire range from 50 to 70. That's looking only at perfectly legal
speeds.
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Le 07/10/2011 14:54, Francois Labreque a écrit :
> Le 2011-10-07 08:12, Invisible a écrit :
>> These gear settings seem very strange to me. Rather than adding more
>> gears up top where there's lots of empty space, they've added more down
>> at the bottom where there's already plenty of them...
>
>
> Gears are chosen so that your car engine remains as close as possible to
> the peak of its power curve while under load, and so that the
> revolutions are kept as low as possible when cruising to save on fuel.
In fact, some countries have taxes based on the engine and the gear-box.
For the same engine, there could be "short" gear-box or "tall".
Tall are for large sedan-like or touring car.
Short are for sport car. (the one you encountered seems a short)
back to taxes: same engine, short gearbox was in the next higher
categories than same engine, tall gearbox.
So economic, from the car-maker, was to push more tall gearbox (it sells
better).
(That kind of tax was yearly-recurring in France... now dropped).
Nowadays, the important selling point is CO2 and this is measured at
fixed speeds (70 & 90 km/h), and time from 0 to 100.
(as advertising a maximal speed above the official limit is a very big
no-no, nobody is publishing a "can race at 254 km/h" anymore).
So, what is the best to minimize CO2 on the test: having the top gear (5
or 6..) already engaged at 70 km/h... hence short box everywhere now!
For the 0 to 100km/h time... well, a good pilot will happily jump a few
gears in its way to the record, and push on the engine too.
> All things being equals, the more gears, the better.
Well, No gearbox and no clutch at all the better.
(and no belt either!)
>
> For "normal" transmission boxes, more gears cost more money, so you only
> see 7 or 8 gear transmissions on luxury german or italian cars. For the
> rest of us mortals, adding gears for speeds that are illegal in most
> countries is not a cost-effective measure.
>
You can of course have a bus (usually 8+) or even a truck (mmm... some
reaches 16 or more, and yet they are limited to 100 km/h )
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Am 07.10.2011 14:12, schrieb Invisible:
> My previous car was somewhat unusual, in that it has a fifth gear. As
> best as I can tell, the gears work more or less the same, except that
> the engine really isn't happy about exceeding 55 MPH or so unless you
> change up into fifth gear - which is kinda tricky the first time you try
> to do it.
Unusual? Five gears (plus reverse) have been pretty standard since decades.
> My current car is completely different. For a start, it somehow has
> /six/ gears. I've never seen any vehicle anywhere that has that many.
Seen that.
> Also, the change points are just odd.
>
> Once again, you start in first, and once the car is travelling faster
> than plate tectonics, you need second gear. Then it gets weird. Round
> about 20 MPH the engine runs out of power, and you need third gear. And
> when you get to about 30 MPH, you need forth. At 40 MPH you need fifth,
> and at 50 you need top gear.
>
> Needing to be in forth gear just to drive around a 30 zone is just weird.
>
> (Note that these are the speeds you need to change for cruising.
> Obviously if you're trying to accelerate hard, you stay in a lower gear
> for longer. But nobody wants to drive around a housing estate revving
> the nuts off their engine.)
>
> These gear settings seem very strange to me. Rather than adding more
> gears up top where there's lots of empty space, they've added more down
> at the bottom where there's already plenty of them...
It's good for fuel-efficient driving in stop-and-go traffic, as you
don't have to rev up the engine that much to reach the minimum speed for
the respective next gear.
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