A= bXz /12 ???? Any math students out there?

[BrentD]

I say just build it and see how fast it goes.

I say, just get a dog sled and have 10x more fun...

 

[Dave N]

I still want to know how you're going to steer it.

 

[DouglasR]

Fixing up the old super twin, eh?

 

[Wildabeest]

 

[D4570]

"I still want to know how you're going to steer it."

Handlebars

 

[kevinfoerster]

This is a great thread. Learned a lot here.

 

[ImBillT]

Off the top of my head, you have plenty of HP, BUT there is a lot more to figuring out if you can go 20mph than motor RPM and how fast the drive sprocket moving the track needs to be spinning. If you’ve settled on the motor, then you need to be more concerned with its torque and hp curve than with your target speed. Those will tell you what your gear reductions must be, and the speed of your machine will simply be the result.

On the other hand, if you are building to achieve specific performance, then start with the reductions(as you have) and end with WHAT MOTOR CAN DRIVE THAT LOAD.

 

[Fullquiver]

There is a Co that makes them and they claim twenty MPH plus.
The Pic is just one off the computer, I have not made anything yet.
I Have the motor that came off the snowmobile, a 71 Johnson skee horse 30 HP, and red lines at 5500 rpm.

The drive system that is on your snowmobile will tell you the tail of what your ratios need to be. The shaft with the sprockets driving the belt should have a sprocket on it as well as the shaft coming out of the driven pulley in your centrifugal clutch setup. Figure out what the top speed of the sled was as made then change the ratio of the 2 sprockets accordingly.. (Likely changing only one sprocket. Making one of these "snowdogs" out of an already existing sled should be pretty straight forward. I'm thinking perhaps just changing the position of the engine and size of the drive/driven sprockets in the final drive system accordingly.

 

[F250]

Bolens's made these back in the late 60's.

 

[D4570]

The drive system that is on your snowmobile will tell you the tail of what your ratios need to be. The shaft with the sprockets driving the belt should have a sprocket on it as well as the shaft coming out of the driven pulley in your centrifugal clutch setup. Figure out what the top speed of the sled was as made then change the ratio of the 2 sprockets accordingly.. (Likely changing only one sprocket. Making one of these "snowdogs" out of an already existing sled should be pretty straight forward. I'm thinking perhaps just changing the position of the engine and size of the drive/driven sprockets in the final drive system accordingly.

The snowmobile is LONG gone along with the drive set up. All I have is the running motor, the track, the boogies, and the drive cogs.

 

[Fullquiver]

The snowmobile is LONG gone along with the drive set up. All I have is the running motor, the track, the boogies, and the drive cogs.

I would find another snowmobile for parts of the same make and model and go from there. The drive system from your sled would be much easier to piece together from there moving forward in your design.

 

[Gerald Martin]

I’ll take, “Good Ideas That Get Out of Control” for a $1000, Alex.

 

[Panda Bear]

I say, just get a dog sled and have 10x more fun...

I’ll take, “Good Ideas That Get Out of Control” for a $1000, Alex.

 

[D4570]

I would find another snowmobile for parts of the same make and model and go from there. The drive system from your sled would be much easier to piece together from there moving forward in your design.

That's really not an option.

 

[Fullquiver]

When I was a boy we had a sled just like that.

Here in Michigan it wouldn't be too difficult to find parts for that sled. I'm not sure where you are located... There are several tutorials on building these on YT. I watched a couple. Pretty straight forward and kind of cool..

 

[RobG]

Sounds like a good Red Green project.

RPM of the engine will depend on gear ratios

Here’s some fun stuff: the front of the track is in contact with the wheel so it goes the same speed. That speed depends what part of the track (or wheel) you are looking at. The part of the track in contact with the ground is going the same speed as the ground: zero MPH. (If I recall correctly the top of the track is traveling 2x the speed of the vehicle.).

 

[D4570]

Fun facts indeed....