[EVDL List]

Can someone explain the terms "shorter" and "taller" that keep getting
mentioned in relation to gear ratios? They seem to be the opposite of
what I'd intuitively think (i.e., 3.25 is "taller" than 4.25--which is
opposite of how the numbers would seem to indicate). Is it because the
driving gear is "taller" in relation to the driven gear at 3.25?

Thanks.

Bill Dennis

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Bill Dennis wrote:
> Can someone explain the terms "shorter" and "taller" that keep getting
> mentioned in relation to gear ratios? They seem to be the opposite of
> what I'd intuitively think (i.e., 3.25 is "taller" than 4.25--which is
> opposite of how the numbers would seem to indicate). Is it because the
> driving gear is "taller" in relation to the driven gear at 3.25?

"Taller" simply means a "higher gear" if you were thinking of it in
terms of a gearshift on a transmission. This means less torque
multiplication, and higher travel speed for a given input RPM. It's one
of those terms that perhaps doesn't make logical linguistic sense, but
feels like the right word when you get a sense for it.

Assuming we're talking about rear end differentials... since 3.25
driveshaft revolutions per wheel revolution is effectively a "higher
gear" than 4.25-to-1, folks frequently call it a "taller" ratio. Torque
is only multiplied by 3.25 instead of 4.25 (less torque), and wheel
speed is not reduced as much (and is therefore faster) for the same
motor (or transmission output) RPM.


--
Christopher Robison
[email protected]
http://ohmbre.org <-- 1999 Isuzu Hombre + Z2K + Warp13!

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Hello Bill,

The lower gearing is actually a higher ratio like a 5.57:1 like I have than
a higher gearing with a low ratio like a 3.01:1.

If you place the low ring gear next to the high ring gear, the low ring gear
will be higher then the high ring gear, because the low ring gear has more
teeth on it and is a larger diameter than the high speed ring gear.

Low and high gearing is related to low and high speed.

The high ratio is related to low speed at a high rpm.

The low ratio is related to high speed at a low rpm.

Roland


----- Original Message -----
From: "Bill Dennis" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, August 24, 2007 12:01 PM
Subject: [EVDL] The Short and Tall of it


> Can someone explain the terms "shorter" and "taller" that keep getting
> mentioned in relation to gear ratios? They seem to be the opposite of
> what I'd intuitively think (i.e., 3.25 is "taller" than 4.25--which is
> opposite of how the numbers would seem to indicate). Is it because the
> driving gear is "taller" in relation to the driven gear at 3.25?
>
> Thanks.
>
> Bill Dennis
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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[EVDL List]

In the US established notations, many things like that are backwards
vs what you'd intuitively think. If something is bigger, naturally
you'd assign a bigger number to it, sort of 3 mm is bigger than 1mm.
(or something of 3 feet is bigger than of 1 feet).

Yet, consider wire diameter - more gauge number - less diameter.
Instead of simply specifying diameter (or crossection area),
AWG system was established where wire diameter associated with
a number. larger number - smaller diameter. Now you got to remember
which number is want diameter.

Similar - for sand paper. You'd think more number - larger grain
(the number just represents size of grain), but it's opposite.

Similar for bolt/nut sizes.

If you grew in the US and and don't know any better, you're accustom to
it and it's comfortable system then. That is unless you try what whole
rest of the world is using, but too many die hards to try seriously.

Have you heard expression "Don't ask fish what the water is like"?

Its like braking old habit, say, quitting smocking - you're far better
off at the end, but the process is painful and discomforting for
human nature, (and, in case of industry - expensive) so instead
people come up with all sort of excuses justifying doing nothing.

Funny thing is that's the people who qualified to compare the least
(never experienced any alternatives themselves) defend it the most

So you're stuck with "taller" gear even though reduction ratio is lower.
Don't apply logic here, there isn't any (or rather, backwards to
intuitive understanding), just established and settled
conventions. It is very American thing.

Sorry, got too far OT.

Victor

Bill Dennis wrote:
> Can someone explain the terms "shorter" and "taller" that keep getting
> mentioned in relation to gear ratios? They seem to be the opposite of
> what I'd intuitively think (i.e., 3.25 is "taller" than 4.25--which is
> opposite of how the numbers would seem to indicate). Is it because the
> driving gear is "taller" in relation to the driven gear at 3.25?
>
> Thanks.
>
> Bill Dennis
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>

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>From: Victor Tikhonov <[email protected]>
>Reply-To: Electric Vehicle Discussion List <[email protected]>
>To: Electric Vehicle Discussion List <[email protected]>
>Subject: Re: [EVDL] The Short and Tall of it
>Date: Sat, 25 Aug 2007 10:52:04 -0700
>
>In the US established notations, many things like that are backwards
>vs what you'd intuitively think. If something is bigger, naturally
>you'd assign a bigger number to it, sort of 3 mm is bigger than 1mm.
>(or something of 3 feet is bigger than of 1 feet).
>
>Yet, consider wire diameter - more gauge number - less diameter.
>Instead of simply specifying diameter (or crossection area),
>AWG system was established where wire diameter associated with
>a number. larger number - smaller diameter. Now you got to remember
>which number is want diameter.
>
>Similar - for sand paper. You'd think more number - larger grain
>(the number just represents size of grain), but it's opposite.
>
>Similar for bolt/nut sizes.

Victor - larger screw sizes DO have larger numbers. a number 10 screw is
larger than a number 6.
As for threads per inch, that is quite logical and easy to understand. A
10-32 screw has 32 threads per inch. That is both easy to understand and
very easy to measure. ( counts the threads in one inch)

>
>
..
..
..

>
>So you're stuck with "taller" gear even though reduction ratio is lower.
>Don't apply logic here, there isn't any (or rather, backwards to
>intuitive understanding), just established and settled
>conventions. It is very American thing.

"Taller gearing" has become common usage simply because it IS so intuitive
and easy to understand. A taller person ( with longer legs) goes faster for
the same pace ( steps per minute) . A "taller" ratio gear means the car
goes faster for the same engine speed.

The first time I heard "taller gear" I knew what it meant. That would not
be true for the term "higher" gear. That would be ambiguous, because it
could mean numerically higher, or that the car went faster for the same
engine speed.


Phil

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