How strong is a hydro transmission

[alabama mike]

Originally Posted by Matt G.

Get him an 1872 or 2072. Problem solved

that would make things easier for me, LOL. now to see if I can talk him into it!

[Matt G.]

Originally Posted by jbollis

I am going to have to disagree with the above concerns. If you were to run those 38 inch tires with out the bull gears, I am sure you would have problems. But with them I don't believe you will. The bull gears are essentially a gear reduction. Could also be looked at as a permanent low range. And the top speed of a cub with the 28 inch tire is 6.5 mph with an engine speed of 1800 rpms in 3rd gear. (http://www.farmallcub.com/cms/index....pacities-specs)

Now, true you would double that engine rpm and also double the ground speed. But I could not find the gear ratio's for the farmall trany. I would have to bet that the 3rd gear ratio is the same or real close to the cub cadets 1:1. The hydro is not stuck in a gear, so you do not have to go 13 mph if you don't want. And I don't know what the drive ratio is on the hydro pump, but it can't be 1:1 it has to less or it would not work. The engine (input) side has to spin faster than the drive (output) side, or else there would be no pumping action to make pressure to drive the drive rotaries.

I don't think axles will be a problem either, as you will probably have to use and modify some farmall cub axles and they handle that size tire and more power with out problems.

I do agree that you would need to take extra caution when changing directions of travel though. It would be best to come to a complete stop before changing direction, to keep the unneeded stress out of the pump.

The way you're wording your post I'm not sure you understand the reduction on both tractors.

The F-cubs do not have a gear reduction before the trans like the Cub Cadets do (7:1 for the gear drives). The extra reduction is in the axles. The hydro Cubs have a similar reduction between the hydro and the pinion shaft. I imagine the gear ratios in the F-cub trans are probably about the same as those in the Cub Cadet. The drive ratio on the hydro is probably close to 1, the speed of the output cylinder block is probably 85% or so of the pump block at 3600 rpm. So just to clarify, just putting F-cub wheels on a CC with no other changes will increase the speed by about 60%. The F-cub final drives are probably in the neighborhood of 4:1 or something like that based on the numbers you posted, which, if added to a CC rear, would cut the speed down to 2 mph or less.

The F-Cub actually has less power than most Cub Cadets. The F-cub only had 8 or 9 drawbar hp, and only the numbered Lo-Boys had 15-18 hp. There is less stress on the trans itself on those because the engine is a smooth 4 cylinder engine directly coupled to the transmission. The gear reduction in front of the trans on the CC rear means that the transmission internals are experiencing higher torque loads than the F-cub because the reduction is before the trans and not after it. It's also harder on the rear because of the torque impulses of the single-cylinder engine.

[jbollis]

I understand the gear reductions completely on both machines, And the point was that they both are probably about the same final ratio at the wheel. This is purely guessing because I could not find any info on it. In addition the f-cubs are gear drives and the 3rd gear is 1:1 that = 6.5 mph at full throttle on 28 inch tires. The cub cadets hydro pump is going to drive the output at at least 15% less rpm than the input. Then it will be reduced again at what you say is probably 7:1 in the reduction housing. Then if he uses the bull gears it will be reduced again at least 4:1 before it gets to the wheels.

So the way I see it the f-cubs engine rpms are being reduced in this order, engine at 1800 rpms, through the tranny at 1:1,then through the ring and pinion into the bull gears at 4:1 then to the wheel

The cub cadet with hydro and bull gears, engine at 4000 rpms into the hydro reduced by a minimum of 15%,then to the reduction housing at an 7:1 reduction, then to the ring and pinion, then to the bull gears for another 4:1 reduction then to the wheels.

A person does not need to know the exact numbers to see that the cub with bull gears added will have allot more (end point) reduction then the f-cub has.

I agree with the 60% increase in speed by adding the 28 inch wheels with no other modification. But the OP said he plans on using the bull gears, so that would reduce everything 4:1 give or take.

And I would have to say that any torque pulses made from the engine would be absorbed in the transition of drive shaft power to fluid power and back to shaft power in the hydro.

I do not intend to make an argument out of this, The addition of the f-cub bull gears to the hydro cub is the key point to this having any chance of working.

[hillbilly]

f-cub bull gears are around 6.8:1 F-cub and F-cub loboy and loboy 154 and cub cadet all have the same gearsets in the main tranny With there being different 2nd gears depending on the years. all the above have the same carrier and differential gears. Cub cadet has a 7:1 reduction in the front. cub cub loboys have on reduction in the front of the trans.

[hillbilly]

I will try to get some pics of my project up and maybe some numbers. a hydro with bull gears definately too slow. As for your dads tractor I would say you might get away with a 30 or 31" tire if you were not going to use it as a worker. Parades and shows even mowing I think you would be ok.

[alabama mike]

Originally Posted by hillbilly

I will try to get some pics of my project up and maybe some numbers. a hydro with bull gears definately too slow. As for your dads tractor I would say you might get away with a 30 or 31" tire if you were not going to use it as a worker. Parades and shows even mowing I think you would be ok.

well the problem is that knowing him like I do, there is no telling what he would use it for, he just got a zero turn mower, so I know he wouldn't mow with it. and the problem for me is if I built it and it breaks, then I have go in and redo it, I would like to build him something that would last.