In article <kenjiusenet-9FAAD1.14353020102003@news.ftupet.com>,
kenji <kenjiusenet@eudoramail.com> wrote:
>In article <bn1ceg$roafv$1@ID-124897.news.uni-berlin.de>,
> "Jim Banks" <banks_jimNOSPAM@hotmail.com> wrote:
>> chuck_steak@nospam.com wrote:
>> > In article <3f93b230@news.brisbane.pipenetworks.com>,
>> > <Pooky@powerpooky.com> wrote:
>> >> Hi Guys, Iam trying to work out what the difference is between using
>> >> a large spur gear with a large pinion (like 86 spur and 23 pinion =
>> >> 3.73 etx drive ratio), compared to a small spur and small pinion
>> >> (like 78 spur and 21 pinion = 3.71 etx drive ratio) i can get nearly
>> >> the same final drive ratio with these two setups, is there any
>> >> advantage in using a large or small spur gear setup??? thanks :o)
>> >
>> > generally, the larger spur, and smaller pinion
>> > will give you more torque, even though the gear ratio is the same.
>> >
>>
>> I would be interested in knowing your basis for this statement. If the
gear
>> ratio is the same, then it appears to me that the torque has to be the
same.
>
>Maybe the reply meant that you get to maximum speed quicker with a
>smaller pinion than you would a larger pinion? Torque would be a
>constant?
Not exactly.
It's a matter of leverage. There is more mechanical advantage with
a larger spur gear.
Think of the distance between the axle centerline and the outside of the
spur as a lever. The longer that lever, the easier it is to get the car
rolling. Even though you have to run a larger pinion,
the ratio still favors more torque with the larger spur.
The other advantage is, the larger the gears, the more efficient
the mesh is.
As you mentioned. If you get to the max speed quicker,
then you had to have more torque... given identical gear ratios.
(by the way, I made a typo in the original, but it appears that
you considered that.... if you increase the spur, you have to increase
the pinion as well to achieve equal ratios).
Dan
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