small engine tech...gearing?

[kodiak1232003]

CHIT-CHAT?

whatever. move it if you want to.

so here's the scenario. you have a vehicle (my lj10 ) with a motor that puts out 25hp at 4 or 5 thousand RPM. top speed is 45mph.

the 2hi gear reduction is 30:1...

the 4low gear reduction is 70:1....(diffs are 5.66's )




now, since that original motor is dead, outdated and impossible to find parts for.....


i'm toying around with the idea of a smaller 11-15hp motor(since 25hp motors are 1500.00), but can't seem to find or think of the equation needed to figure how much more gearing would be needed to get the same type of performance (or lack thereof)

keep in mind the total vehicle weight was 1200lbs w/ old motor and probably will be 1100 with this type of engine.

this will be an around town, trail-only type of vehicle so 35mph should be considered cruising speed.


consider that the setup below is a direct drive go-kart weighing in (with driver) at around 3-400lbs. these little guys get up to around 60-80mph with a 5-10hp briggs and stratton motor.

so what gearing would i need going into my tranny? is this thing gonna be screamin' just to get me moving or can i accomplish something through proper gearing.

seems to me if big kubota tractors can do what they do with 50 hp, i should be able to build a competant, light-weight crawler with 10-15hp.

that is all.

regards,
brian

[p575]

i think the deal with tractors is they have relatively low horsepower, with high torque numbers...im not sure on that though, i cant find any manufactures that post torque numbers...maybe an old motorcycle engine would be the way to go?

[MT4Runner]

x2..same thing I was thinking