TRANSMISSION GEAR RATIOS .

greetings new member here !

I am interested in transmission gear ratios .

I`ll tell you what I am after ;

I need a gear box that will reduce high rpm to low rpm.

I need a final wheel rpm of between 50-60 rpm .

I want the maximum H.P. , but need the low wheel rpm .

any idea what transmission I should use ?

I will detail this at a later time .

thanks AL.

Probably should know how much horsepower
and engine rpm's. Are you just trying for
a gearbox or a multiple gear transmission?

That's kind of like asking what horsepower to
tractors have? Need a few more specifics.

I put a 2nd aux trans in my Oliver HG crawler.
Used a Ford Model A trans for the job. Oliver
did the same when they sold factory aux trans
kits.

Keep in mind that many if not most automotive
transmissions lack proper support in front to
be used since they are designed to be plugged
into a pilot bearing somewhere. Ford Model A
is a common choice for an aux trans because it
has full support in front and is very rugged.

With the Ford Model A 3 speed transmission
installed as an auxillary unit, ground speeds
at full throttle in my Oliver are as follows:

Original: 1st - 2.01 m.p.h., 2nd - 3.19
m.p.h., 3rd - 5.24 m.p.h., Rev. - 2.33 m.p.h.

Range 1: 1st - .64 m.p.h., 2nd - 1.02
m.p.h., 3rd - 1.68 m.p.h., Rev. - .74 m.p.h.

Range 2: 1st - 1.08 m.p.h., 2nd - 1.72
m.p.h., 3rd - 2.83 m.p.h., Rev. - 1.26 m.p.h.

Range 3: 1st - 2.01 m.p.h., 2nd - 3.19
m.p.h., 3rd - 5.24 m.p.h., Rev. - 2.33 m.p.h.

Range Rev.: 1st - .53 rev. m.p.h., 2nd - .85
rev. m.p.h., 3rd - 1.4 rev. m.p.h., Rev. - .62
froward m.p.h.

Actual reduction is 2.6 in 1st, 1.6 in 2nd. and
2.2 in reverse.

Compared to a John Deere 420 crawler:
1st - 7/8, 2nd - 2 1/4, 3rd - 3, 4th - 5 ¼

OC-4 (with hi/lo in high range) 1st - 1.5
m.p.h. 2nd - 2.4 m.p.h. 3rd - 3.3 m.p.h. 4th -
5.2 m.p.h. rev. 1.8 m.p.h.

OC-4(with hi/lo in low range) 1st - .8 m.p.h.
2nd - 1.2 m.p.h. 3rd - 1.7 m.p.h. 4th - 2.7
m.p.h. rev.-.9 m.p.h.

I would look to the world of "doodlebugs" for guidance here.

It was very common at one time for farmers to build tractors out of old cars/trucks. They would install multiple automotive transmissions, one after the other, to get the right gearing for field speeds while keeping the engine running fast enough to produce adequate power for the job.

You should be able to couple two or maybe three automotive style manual transmissions together and then find a gear combination that gives you the output RPM you're looking for.

The question is very vague, so I hope this is helpful.

What RPM will your engine produce max HP? What is
the max HP?
What type differential are you using and what is
its ratio?
Does ground speed matter? If so what size tires
are you using?
How many gears do you want? Do you need variable
ratios or would a fixed ratio box be needed? Or
are you looking for a single speed?
How much $$$ do you want to spend?
Lots of questions need to be answered for an
answer to this.

Well. the old Fordson tractors did it with worm drive finals. Of course that means the driven shaft will be 90 degrees or perpendicular to the driving shaft. I never drove or was around one, but they tell me they got quite hot and growled pretty bad when they were used continuously pulling heavy loads...and it was hard to start the engine by pulling the tractor. You couldn't just pull start 'em with the horses if they wouldn't start. Incidently, that's how they drive the rotary tables on most precision machine tools too.

You need to provide a lot more information than that if you want any kind of useful answer... One would need to know the application, the power requirement, layout, etc to be of much use. I would say with that kind of reduction you're pretty well going to be into the realm of reduction boxes behind a transmission...


Rod