Smarter then an old retired bread guy, I need some math help

jetman

New member
I have an old snowmobile track and bogeys and the motor.
I want to make a "Snow Dog"

snowdog.jpg


What I'm wondering is.
Here we go.
I want it to go about 20 mph full out.
The track is a little over 8 feet long/ around.
What is the RPM to do 20 miles in an hour?
Then I need to do two reductions
One from a belt than one to the track with a chain.
5000 rpm on the motor.
My head hurts.
ohmy.gif

 
OK.
The drive wheel is 23" around.
There is 63360" in a mile.
It would take the drive wheel 2755 revelations to cover a mile.
That makes it turn 55,096 times for 20 miles then divide that by 60 minutes.
That is 920 rpm, to get it to 20 mph.
Same thing but Now I know the final RPM needed I can work backward to get the ratios.
 
I'm about as far from a mathematician as you can get, but, wouldn't this work?

Motor w/3" pulley @ 5000 RPM -> 7" pulley = 43% reduction or 2150 shaft speed driving 10" sprocket (@ 2150 rpm) ->23" sprocket = another 43% reduction or 925 RPM @ drive shaft.

I'm sure there is an algebra formula that would get ya there a lot quicker, but unless I'm missing something........

Regards,
hm
 
Any red neck boy knows the answer. A 350 small block Chevy should handle the chore about right.
smile.gif
 
[FINALlY! I'm ready for a real-world field test.
Still needs paint.
I started this to use in mixed road/trail conditions. Big drifts of snow that a 4wheeler will not go over, I have skis that strap on to the wheels, and blown clear gravel and dirt a snowmobile is not mad to go over for miles. But, I wanted to be able to put a 4wheeler in the back of the truck and not have a trailer. I made an extra heave duty Bumper buddy, I made the trailer to stack on top of the dog, the Handles all come off so nothing is wider than the truck. All in with the Buddy strapped on and lifted it is just under 600 pounds. Should be within the limits of the truck even with the 4wheeler in the back. I do think I want airbags in the back of the truck it deflects about 3'' and raises the headlights a lot.
Easy on easy off.
PS it does 23.5 MPH full out.


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