Check my logic, please

[NCMau]

I have two hydraulic motors to choose for a side-deck (21") mower, tractor driven project.
(1) Eaton, 101-1704, 1021 RPM, 10 GPM, 497 lb-in, 8 HP
(2) Eaton, 101-1026, 760 RPM, 18 GPM, 1044 lb-in, 12.5 HP

Formula used to figure HP= Torque x RPM : 63025
Tractor, 35 HP with a 7 GPM PTO pump
I am considering a 5:1 pulley ratio to increase blade speed.

Which motor you think would be a better choice, or is it viable at all?
I am thinking that motor No.2 would be a better choice. With my tractor 7 GPM pump, the final blade speed would be about right, but I am still wondering if the 7 GPM pump would be strong enough.

 

[oldnslo]

Is there a reason you are not considering a gear motor and direct drive to the spindle? I believe this is how the majority of the hydraulic mowers are driven.

 

[mikester]

Take a look at your hydraulic motor speed torque curves and match it with your tractor flow rate and operating pressure. Motor #1 requires about 1.5x your tractor's flow rate and #2 requires about 3x. You won't get near the speed and torque you are looking for or are expecting.

Your better choice would be a 20GPM PTO pump to start with. I think you will be disappointed.

Are you building a whipper snipper to hang off the bucket or run cantilevered off the side? 21" is a pretty small mower

 

[CincyFlyer]

I have two hydraulic motors to choose for a side-deck (21") mower, tractor driven project.
(1) Eaton, 101-1704, 1021 RPM, 10 GPM, 497 lb-in, 8 HP
(2) Eaton, 101-1026, 760 RPM, 18 GPM, 1044 lb-in, 12.5 HP

Formula used to figure HP= Torque x RPM : 63025
Tractor, 35 HP with a 7 GPM PTO pump
I am considering a 5:1 pulley ratio to increase blade speed.

Which motor you think would be a better choice, or is it viable at all?
I am thinking that motor No.2 would be a better choice. With my tractor 7 GPM pump, the final blade speed would be about right, but I am still wondering if the 7 GPM pump would be strong enough.

If you get 7 GPM, and, say, 2200 PSI, you have about nine horsepower to play with. Anything above about half of that will likely run your 21" blade, but you'd need a 7 GPM motor "just in case". I wouldn't go with more than that (certainly no more than your 10 GPM), and you'll need a belt or gearing to get your blade speed. Probably something with 2.5 to 3.0 CID would work. Surplus Center has a bunch in that range for $150 more or less.

 

[flingwing1969]

Take a look at your hydraulic motor speed torque curves and match it with your tractor flow rate and operating pressure. Motor #1 requires about 1.5x your tractor's flow rate and #2 requires about 3x. You won't get near the speed and torque you are looking for or are expecting.

Your better choice would be a 20GPM PTO pump to start with. I think you will be disappointed.

Are you building a whipper snipper to hang off the bucket or run cantilevered off the side? 21" is a pretty small mower

Can you effectively run a PTO pump from your tractor's hydraulic fluid tank or would you need to add or should you add a dedicated tank to run the pump on its own? There are a couple of projects for which I would like to use hydraulic motors for but the CUTs simply don't have the necessary flow.

 

[farm boy00]

Can you effectively run a PTO pump from your tractor's hydraulic fluid tank or would you need to add or should you add a dedicated tank to run the pump on its own? There are a couple of projects for which I would like to use hydraulic motors for but the CUTs simply don't have the necessary flow.

You would most likely need another tank. Most small tractors don't have big enough tanks

 

[flingwing1969]

You would most likely need another tank. Most small tractors don't have big enough tanks

That is my thought. 22gpm, for example would empty the CUT's tank pretty quickly.

 

[CincyFlyer]

That is my thought. 22gpm, for example would empty the CUT's tank pretty quickly.

Well, it would be returning, but the biggest issue would be overheating a small fluid volume. I'd get a cheap carry-all, and a PTO pump/tank/valve from Surplus Center.

 

[NCMau]

If you get 7 GPM, and, say, 2200 PSI, you have about nine horsepower to play with. Anything above about half of that will likely run your 21" blade, but you'd need a 7 GPM motor "just in case". I wouldn't go with more than that (certainly no more than your 10 GPM), and you'll need a belt or gearing to get your blade speed. Probably something with 2.5 to 3.0 CID would work. Surplus Center has a bunch in that range for $150 more or less.

For further clarification, the 7 GPM PTO pump coupled with a 10 gl. tank is dedicated to the loader . I don’t want to invest in another pump and I was hoping to use one of the motors I have. The project is a small 21” deck vertically mounted to the side of the bucket.
In my way of thinking using motor #2 with 7 GPM pump, would cut the 18 GPM and the torque to approx. 40%, but the blade with a 5x speed increase would run about 1500 RPM (theoretically). I can easily increase the speed to 6x which would give a speed of 1800 RPM. The question is the 400 lb-in be enough for a 21” blade?

 

[farm boy00]

For further clarification, the 7 GPM PTO pump coupled with a 10 gl. tank is dedicated to the loader . I don’t want to invest in another pump and I was hoping to use one of the motors I have. The project is a small 21” deck vertically mounted to the side of the bucket.
In my way of thinking using motor #2 with 7 GPM pump, would cut the 18 GPM and the torque to approx. 40%, but the blade with a 5x speed increase would run about 1500 RPM (theoretically). I can easily increase the speed to 6x which would give a speed of 1800 RPM. The question is the 400 lb-in be enough for a 21” blade?

A good comparison but not perfect would be a gas push mower. Go off of those numbers for reference