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

 

[NCMau]

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

Good suggestion. A 6.5 HP gas engine torque is approx. 8 ft-lb @ 2500 RPM which should be broadly within the framework of my project.

 

[CincyFlyer]

For further clarification, the 7 GPM PTO pump coupled with a 10 gl. tank is dedicated to the loader . I don稚 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?

Actually, lower flow (GPM) will give you lower speed, but the torque is a function of pressure.

 

[NCMau]

Actually, lower flow (GPM) will give you lower speed, but the torque is a function of pressure.

So what does it mean in my situation, the torque with lower GPM will not change?

 

[Coyote machine]

Your tractor is not suited to your desire to run the 21" mower. It doesn't have enough GPM to spare to run your mower blades at adequate RPMs, while allowing for adequate flow and hyd fluid cooling for your tractor You wanting to not spend adequate $ to set it up so it 'might' work adequately, and not to scorch your tractor's hydraulic fluid are incongruent.
IMHO, unless you buy or find parts necessary to guarantee enough flow for both tractor and mower, you should abandon the project.
For what uses exactly do you want to hang a 21" mower on your bucket? There may be other ways to accomplish your task(s).

 

[NCMau]

Your tractor is not suited to your desire to run the 21" mower. It doesn't have enough GPM to spare to run your mower blades at adequate RPMs, while allowing for adequate flow and hyd fluid cooling for your tractor You wanting to not spend adequate $ to set it up so it 'might' work adequately, and not to scorch your tractor's hydraulic fluid are incongruent.
IMHO, unless you buy or find parts necessary to guarantee enough flow for both tractor and mower, you should abandon the project.
For what uses exactly do you want to hang a 21" mower on your bucket? There may be other ways to accomplish your task(s).

The reason why I don’t want to change my loader PTO pump and tank is because this project is not exactly high priority. If it would work with what I got, fine, otherwise I can skip it. I do have other ways of accomplishing the task, like a modified walk-behind sickle bar mounted on the bucket. This bar, however is not suitable for any growth bigger than 1/2” at best. Also it is a PITA to mount. I was looking for something simpler.
I remember few years back reading one of your posting when you purchase your Samurai, and you were pretty happy with it. It’s amazing that it does a good job running just with 3 GPM (if I remember correctly). Anyway it’s a sweet machine, but man, it’s not cheap.
Another alternative I could have without using hydraulics is to mount the deck with a horizontal electric-start gas engine... possibility.

 

[CincyFlyer]

So what does it mean in my situation, the torque with lower GPM will not change?

No. But since horsepower is a function of torque and speed, you'll have less power.

 

[NCMau]

No. But since horsepower is a function of torque and speed, you'll have less power.

It makes sense. But I will try a quick down'n'dirty prototype just to satisfy myself.

 

[Leejohn]

The next best thing would be a 2 cycle lawn mower. There still around, but parts are mostly NLA.

 

[CincyFlyer]

The next best thing would be a 2 cycle lawn mower. There still around, but parts are mostly NLA.

Yeah, I'll sell him my LawnBoy.

 

[LD1]

Why are you looking at such low speed high gpm motors for?

They make about every possible rpm and flow motor there is.

Your tractor makes 7gpm.....say you want to dedicate 4 gpm to that. And you want 1500rpm....

Just select a pump that will produce 1500rpm at 4 gpm.

No point in buying a slow pump....and slowing it down even more by not delivering the flow.....just to step it back up via a 5:1 pulley. Which by the way....is an EXTREME step to do with a single belt. If your mower pullet is a mere 4" diameter.....that means you need a big honking 20" pulley on the motor.