# Please help my heard hurts, Need Math help



## Dang Dawg (Jan 14, 2013)

I have an old snowmobile track and bogeys and the motor.

I want to make a "Snow Dog"










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. :


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## glenway (Mar 27, 2011)

The track must cycle 11 times per minute to go 1 mph.

The track must turn 660 times in one hour to go 1 mph.

Therefore, the track must turn 13,200 times in one hour to go 20 mph. (660x20)

It will all depend on the gears and on the horsepower, if adequate enough with the final loaded weight.

Resistance will be another hurdle, because dry land and snow will give different results.

You could use the gearing that you have and adjust ratios from there. I would do actual experiments with whatever set-up you have at slow speeds and change as necessary from there. Going only 20 mph with that motor will be no strain.

Good luck. What is a snow dog, anyway?


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## glenway (Mar 27, 2011)

Maybe this is better. Use what you have and compare revolutions of the track to the speed you want. If you are off, change gearing the same percentage.


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## kiyote (Jun 15, 2014)

I doan does head maths . I use me one o them calkilaters


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## Dang Dawg (Jan 14, 2013)

OK, I'm starting to get a picture in my mind.

If I took off the track, and if you could drive on just the cogged sprocket. the diameter of the sprocket is how many inches/feet you move in one revolution. The track would have to turn 220 times but the drive wheel will have to turn many more times to cover the distance in the allotted time.

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 make 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 backwards to get the ratios.

Ok after many online calculators I think I gave a good starting point.

I need a 2.5" pulley on the motor and a 5" on the countershaft.
That should take me from 5000 rpm on the motor to 2500 rpm on the countershaft.
Then I want chain to drive the track.
So, a 12 tooth #40 sprocket from the shaft to a 32 tooth to get to 937 RPM on the driver cog on the track.
I think


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## knapper (Feb 5, 2010)

I don't to hold on to it and walk behind at 20 mph, way too fast for me, now many years ago it would have been ok.


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## glenway (Mar 27, 2011)

I'd have to conduct a few experiments but you're on the right "track."

I figure I could look up snow dog pics somewhere, but what would be the purpose of the vehicle. Never heard of one.


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## Dang Dawg (Jan 14, 2013)




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## kiyote (Jun 15, 2014)

different but why wouldn't you just get a sled you could sit on???????


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## Dang Dawg (Jan 14, 2013)

We have two, and two 4Wheelers.

This I can put in the back of my truck, or maybe something like a bummper buddy on the front like for electric wheel chairs.


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## knapper (Feb 5, 2010)

I will stick with the machines I have and hang on on those sitting on it. I understand wanting to build something that is different but, just say so.


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## Dang Dawg (Jan 14, 2013)

YUP! I'm a RAT builder from WAY Back.

I picked up an old used VW motor and built an airboat around it.

In my garage, with a metric crescent wrench and ballpeen hammer...

I have a 12 volt trailer tug I made with a junk riding lawn mower and Harbor freight winch for a motor.

I just like doing stuff like this.

I will get something built and give it a try, Looks like great fun.

My wife says it is my thirds child onset.

Thanks for all the input.


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## glenway (Mar 27, 2011)

And, there you have it.

But, what? No doodle bug?


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## murphyranch (Dec 9, 2015)

Put 2 & 2 together, add 12 and carry 5!

Sent from my iPad using Tapatalk


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## kiyote (Jun 15, 2014)

5 wut??????????? and how fer?????????


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