Koz wrote:



RoyJ wrote:

Correct!

Tim Wescott wrote:

Don Bruder wrote:

I've got a gearbox out of a piece of hardware. Opening it up, I find
a 6 tooth gear fixed on the input shaft driving a 48 tooth gear.
Concentric with (and fixed to) the 48 tooth gear is a 10 tooth gear,
which in turn drives a 64 tooth gear, which is fixed to the output
shaft of the gearbox.

Am I straight out of my mind to figure that I need 512 turns of the
input shaft to get one turn on the output shaft?

My figuring:
Output shaft, with fixed 64 tooth gear, needs 6.4 turns of the 10
tooth gear for one rev, which means the 48 tooth gear the 10 tooth
is attached to likewise rotate needs to 6.4 times. In turn, this
means that the 6 tooth input shaft needs to turn 48 / 6 = 8 times
for one turn of the 48 tooth gear, so to get 6.4 turns on the 48
tooth gear, the input has to spin 8 times 6.4 = .... Uh-oh ...
writing it out like that makes me realize I misplaced a decimal
point... I need 51.2 (instead of 512) turns of the 6-tooth gear to
get 6.4 turns of the 48/10 tooth pair to get one turn of the 64
tooth gear on the output shaft, don't I?

I *KNEW* 512 seemed like an awful high number of input turns...

So correction: Am I right in figuring this as a 51.2:1 reduction
gear-train? Or have I bollixed things up hopelessly, and I'm still
wrong even after recovering my missing decimal?

6 10 60 1
-- x -- = ---- = ----
48 64 3072 51.2

Looks good to me.

Just curious about something here. Along the same line as the "which
side of the car should the gas filler be on", 1:51.2 seems like a weird
and arbitrary gearing. I can assume that it was just conventiently
fitting gears that matched some existing enclosure casting or something
like that but is there some logical reason someone would need 1:51.2 vs
1:50, 1:60 or something more "round"? Assuming a 1725 RPM motor (no
slip) the output of a 1:51.2 vs a 1:50 would be less than 1 rpm (2.4%)
different .

There are a lot of "weird" ratio gearboxes out there and I'm just
curious if there was more of a purpose or in the pre-VFD days, you just
had a lot of selection for any possible strange ratio you might decide
that you need.

Koz



1, 2, 4 , 8, 16, 32, 64, 128,256, 512, an even pole stepper motor
will work out in even steps per revolution using this ratio.



John