Hey Gear ratio guys......

I installed an XJ 1100 in my kids pulling tractor(Cub Cadet 582) and I need to know as close as can be determined what gear he will need to be in ( on the motorcycle engine)to spin the tires about 60 mph?? The rear tires have a circumference of 84 inches. Can anyone figure that out? Want to turn the engine around 8000 to 8500.
Thanks

 

What is the rear end gear ratio? A 84 inch rear tire is not much bigger than the stock one. My first estinates if your rear ratio is somewhere around 3 to 1 would be 2nd gear and 7000 rpm would give you around 60mph wheel speed.

 

They are saying a stock Cub Cadet gear ratio in high gear is 32.2 I found that on a chart Midwest Super Cub puts out. According to them a 6600 rpm input shaft speed gets you 16.4 mph. wheelspeed with the tire size I used. However I am not familiar with the final ratio of the XJ 1100 tranny in it's certain gears. I am just trying to figure out where to start or if I have to re-gear the Cub tranny. I had hped I would have enough combinations between the motorcycle tranny and the Cub tranny to get close to what I want.
Thanks

 

Wow 32 to 1 is real low. All of the gearing information I can find includes the final drive, since you din't have it any more that kind of messes things up. I have a spare engine in the garage, I'll look at it this evening and see if I can figure it out.

 

Pitmonster - you need a different rear end. The XJ1100 had about a 3.20:1 rear and the bearings and internal gears won't handle 100 HP or the multiplied torque.

The bike tops out at 150 MPH - - divide by 10, you will go 15 MPH

 

Here's my take.

First I found this: http://www.xs11.com/forum/showthread.php?t=7288

Part way down the page it lists the combined ratio for each gear. You'd divide the final ratio out to get the ratio for a given gear.

Then there's the formula here: http://www.4lo.com/calc/geartable.htm

Leave the transfer case out of it since that doesn't apply.

Crunch numbers and 8000 RPM in 5th gear the bike trans and your 32.2 on the diff and 84 inch tires is 42.339MPH.

If my math is right you could go to a 120 inch tire and get your 60mph. Or you've got some regearing work to do to get what you want.

Hope this helps. I'm not an expert.

 

I did some calculating on the spare XJ1100 I have, here are my results:
Gear ratios excluding the rear drive(just the tranny). I did this the old fationed way by turning the crank and counting the output rotations.
1 3.78 to 1
2 2.75 to 1
3 2.16 to 1
4 1.74 to 1
5 1.49 to 1

Max engine rpm(8500) in 5th gear will give you a input speed of 5704 rpm to your cub diff. A little slow for what you need. Is it possible to change the gears in the cub diff?

 

Yes I can buy overdrives for the Cub rearend. They come in various percentages up to about 30% overdrive. About what percentage of overdrive would I need to spin the tire at say 70mph if the current overdrive on the Cub rearend is zero? I Can also go with bigger tranny gears. Just searching my options, thanks for all the help guys.

 

By my calcs you'd need a 0.7 overdrive ratio to get 63 MPH. You can use the 4lo formula and input your orverdrive ratio for transfercase ratio and get MPH.

Remember though that an overdrive is going to cost you mechanical advantage. With a 1.49 gear in the trans and a 0.7 overdrive you're trying to turn those tires at pretty close to 1:1. I don't know that the engine would do it.

 

It is a fine line between too much and not enough. The big thing in pulling is wheel speed,lots of it IF you have enough power when the weight starts to transfer on the pulling machine. I think we will try it just the way it sets first. Then if we need more speed we can change things. A good pull would be physically moving at about 17 to 20 mph with the wheels spinning at 60 to 70 mph before the weight starts to slow your forward movement and slow your spinning tires. They never really hook up completely so it's kind of a black art to say the least.

 

Keep us posted on how it works out. I love to see a video of that tractor running.

 

http://www.youtube.com/watch?v=kg4MxdVurqU

Sure looks like fun !! 8)