Re: Timing belt drives

On Mon, 2 Sep 2024 10:45:01 -0700, Bob La Londe <none@none.com99>
wrote:
 

On 9/2/2024 10:27 AM, James Waldby wrote:

Clare Snyder <clare@snyder.on.ca> wrote:

>
Any of you guys have experience with timing belt drives? I need as
compact as possible 1 1/2:1 reduction from a 600 rpm  2.5HP engine
(3600 crankshaft RPM with 6:1 reduction) then another 1 1/2:1 after
that (so lower speed higher torque) ( total reduction 13.5:1).This
will be driving a 20 inch diameter 2 inch wide tire/wheel.
>
How wide and how large do I need the small sprocket? For simplicity I
would likely like both stages identical. This simplifies everything
including tensioning

>
I've seen some timing belt power transmission calculators online,
which account for RPM, small pulley diameter, required torque, etc,
but haven't done a design.  The `AI Overview` from a google search for
`timing belt drive power sizing` has about 6 bullet points, each with
a link, that get to some design webpages or calculators.
>
I think an auto engine timing belt handles 15 to 25 HP, which you
could scale down from or get parts from.  Depending on what your app
is maybe one stage of planetary gear reduction as in drill motors
would work; and there are some inexpensive electric bike clutches that
look like 4"-diameter planetary drives but might be irrelevant -
https://www.amazon.com/AMLESO-Electric-Planetary-Clutch-Motor/dp/B09XVL1NV7
- besides having nylon gears.
>

Small sprocket on output shaft  driving large sprocket on jackshaft
turning small sprocket driving large sprocket spinning on output shaft
of the engine/gearbox  with wheel attached to that sprocket. Distance
from center of small sprocket to outside of large sprocket cannot
excede 7 inches.
>
Is this possible/feasible???

>
>
I didn't read all of that, but my problem with timing belts relates to
CNC motor drives.  If I didn't get the tension perfect they would either
exhibit backlash or they would sap power from the system at a much
higher than expected rate.
>
That being said I have seen a cog belt with cog pulleys used on a fairly
powerful pulley with good effect.  The 5hp motor on my Hurco mill uses a
1:1 cog belt to drive the spindle... and Hurco rated the mill at 4HP.
LOL.
>
I don't have the experience with them, but everything I've read
indicates a harmonic drive is the magic sauce for some applications.
>
>
-- Bob La Londe
CNC Molds N Stuff

  I've decided to just try a bigger engine - - -
 Engine has 6:1 reduction - direct driving a 20 inch wheel to move 300
to 350 lb. New enginr is 2 9/16 bore and 2 7/16 stroke