Convert Rear PTO Snowblower to Front Hydraulic

[rswyan]

I have an Allied/Buhler Farm King 60 rear 3PH snowblower and want to convert it to a front-mount blower for use on our Kubota B2910.

The biggest issue (for me personally) is how to power it. Looks to be 3 options:

1. Build a PTO reverser box, that mounts to the rear PTO, and run a shaft forward.

2. Mechanically power it off the B2910's mid-PTO. This would require a speed reverser/reducer to reverse the rotation of the mid-PTO and gear it down to 540 from 2500.

3. Hydraulically power it off the B2910's mid-PTO. This would require an appropriate hydraulic motor and pump, and a reservoir .... and I already have a pump and a reservoir :thumbsup:

The pump is an Eaton 25500 series gear pump which came with my Kubota BH4690B backhoe. Kubota claims that the pump is rated for 2500 psi (which doesn't agree with Eaton's literature) and has a displacement of 2.05 cu. in (which does agree with Eaton's literature)

Eaton (or at least their current literature) says this pump - which is actually a model 25503 - has a 2.05 cu. in. displacement, is rated for 3600 psi (continuous), has a rated speed of 2750 rpm, and has an output of 22 GPM @ 3000 psi @ 2750 rpm:

Eaton Gear Pumps

Unfortunately to reach that output requires an input of 47 HP according to Eaton - and our B2910 only has 22 at the PTO

I'd guess that since I've already been using the pump on the rear PTO for the backhoe, I could achieve some level of performance if it were paired with an appropriate hydraulic motor - and that's where I need some guidance.

Surplus Center has three "PTO" hydraulic motors (motors with a 6 spline 1 3/8" output shaft) listed on their website in the section for low speed/high torque motors .... although I don't know that I necessarily need to use a motor with a "PTO" spline shaft (the shaft I'm mating to on the snowblower is 1 1/4" keyed)

Can anyone offer their sage advice as to what hydraulic motor would be appropriate for this pump/speed/horsepower combination ?

BTW, the reservoir I have is a 10 gallon one I bought from Surplus Center for a logsplitter project which I have gotten around to completing .... I realize this could be possibly undersized for the potential flow I might have .... but I figured winter time/cold temps/limited use ... so heat dissipation might not be a problem ......

 

[rswyan]

Guess I'll bump this .... as the original post got no replies at all ....

I've been doing some reading on some past threads regarding this issue (and had, before I even made the original post) ....

One point I wanted to clarify is that the pump I have is an "L2" series (25500 series) and the info for them is contained in the latter part of the PDF document I linked to above.

I have taken a cursory look at hydraulic motors available at Surplus Center and it seems like this one:

5.9 cu in DYNAMIC BMRS100H2KS HYD MOTOR

would work .... the continuous and intermittent pressure limits are within what my pump would be capable of delivering, as are the GPM flow requirements, and considering the horsepower requirements (or is that output/delivered HP ?) seems like it would be a good fit ...

I have some (limited) experience and understanding with hydraulics generally, and none at all really with hydraulic motors .... so I'm flying blind on this ...

Can anyone more versed in hydraulics provide some input ?

dfkrug ?

kennyd ?

AKKAMAAN ?

wdchyd ?

J_J ?

 

[kennyd]

Sorry man...I missed the original post....

I am not super great with the motors, so hopefully someone else will chime in, if not I will try to help.

 

[rswyan]

Sorry man...I missed the original post....

No worries .... there's sure alot more daily traffic here than there was 4 - 5 years ago when I was active .... hard for me to read it all, even when I have alot of time on my hands

I am not super great with the motors, so hopefully someone else will chime in, if not I will try to help.

Fair enough - and thanks for looking !

 

[KWentling]

So if you run your pump on the mid PTO @2500 RPM you get about 22 GPM. If you put 22 GPM through the 5.9 CI motor you get 861 RPM. You would need to run the tractor at about half throttle to get the proper RPM at the blower. You will not have your maximum HP available running at reduced throttle. They have a 9.5 CI that would give you 535 and that would be my choice. As far as horsepower requirements, the 43 HP rating is at 3600 PSI which I would doubt you will see anywhere near that pressure unless you jamb a rock
in it or something, and even then it would probably shear the bolts first. You'll need ｾ" hose on the pressure side and 1ｽ" suction for those flows. I would encourage you to find a bigger reservoir. Even if heating isn't a problem, aireation probably will be. Air in oil (cavitation) destroys pumps and motors.

Kim

 

[rswyan]

Kim,

Thanks for your reply !

So if you run your pump on the mid PTO @2500 RPM you get about 22 GPM.

I dunno - will I ? :laughing:

Like I said, I have pretty limited knowledge when it comes to hydraulics

It would appear that your statement above is true - based reviewing on the charts for the output flow contained in the PDF from Eaton - it is essentially the same (24 GPM) at either 1000 or 3000 psi, at the same pump speed (2750 rpm) - although that chart is a little different than what the specs actually state: 22 GPM @ a rated rpm of 2750 ..... but the spec is stated as a minimum @ 3000 psi ...

If you put 22 GPM through the 5.9 CI motor you get 861 RPM.

Right.

You would need to run the tractor at about half throttle to get the proper RPM at the blower. You will not have your maximum HP available running at reduced throttle.

A very good point

They have a 9.5 CI that would give you 535 and that would be my choice.

Ok - I'm understanding this and the reasoning for it ..... however I did look over the ratings for all the 9.5 CI motors .... and all of them are rated in the 370 to 380 rpm range for continuous and and 465 to 475 rpm for intermittent operation.

I have no idea how critical these ratings are, in terms of durability of the motor - how concerned should I be about that ?

Looking at some others that are close in displacement, that 9.59 CI "PTO shaft" motor is rated for 470 continuous rpm and 560 rpm intermittent:

9.59 CU IN PTO DRIVE MOTOR

..... running it thru the rpm calculator on Surplus Center's website yields 530 rpm @ 22 GPM ..... but at a substantially higher cost than the others (.... which is fine I suppose .... )

FWIW, I'm at the bottom end of the secondary snowbelt in Northeast Ohio - we do get snow, but it generally isn't all that bad compared to 30 miles north of here - so it would be a rare occasion where I'm having to blow seriously deep snow (greater than say 14" to 18")

Buhler website currently lists "the Tractor Engine Requirement" for this blower (Y600, 60 inch width) as 20 to 40 HP (they don't say anything about PTO HP) - I'm in the middle with 30 (22 at the PTO)

My memory is a little foggy, but I don't recall ever seriously bogging down the engine while blowing snow with it (tractor is HST) .... and I'm guessing that I probably wasn't ever running the engine at PTO speed.

As far as horsepower requirements, the 43 HP rating is at 3600 PSI which I would doubt you will see anywhere near that pressure unless you jamb a rock in it or something, and even then it would probably shear the bolts first.

Ok - that makes sense .... I'm assuming that pressure will be developed as a function of resistance against force exerted - just spinning the motor, itself alone, should develop very little if any pressure ..... free-spinning the blower, unloaded, will develop a little more .......... and blowing snow will develop significant pressure, comparatively speaking .....

You'll need ｾ" hose on the pressure side and 1ｽ" suction for those flows.

I'm reading that as 1/2" to 3/4" on the pressure and 1 1/2" to 1 1/2" on the suction side ? (something about the fonts or the way the numbers are being rendered makes it unclear my computer)

I would encourage you to find a bigger reservoir. Even if heating isn't a problem, aireation probably will be. Air in oil (cavitation) destroys pumps and motors.

I was wondering about that as I had seen some mention of air and tank sizing in another thread I read - I had never really considered it .... but yeah - with shoving 22 gallons thru a 10 gallon box in minute, I can see where things could get bubbly ...

Thanks again for your reply - and for laying it out so clearly :thumbsup:

It really helps my understanding just to be able to talk this through with someone.

 

[rswyan]

BTW, since I'm not planning on using a control valve per se (tractor motor & PTO clutch as a control valve), I'm guessing it would probably be smart to stick a relief valve in there somewhere ?

 

[KWentling]

Good catch on the RPM ratings. I just went down the line on displacements. I would stay within recommendations. If your PTO doesn't stop abruptly under load, you wouldn't need a motor spool valve to operate it. You don't want to stop a hydraulic motor instantly. The pressure spike created can blow seals or rupture the case. Pressure relief valves are always a good idea, as are filters. As far as the 22 GPM (actually calculates to 22.186) goes, that is in a perfect world. There will be losses so you might not get that, but should be close. Hydraulics are "lazy". They only develop the minimum pressure require to do the job. Not sure what happened on the fractions. You want 3/4" hose on the pressure side, and 1 1/2" on the suction. I would imagine the Buler recommendation on horsepower is PTO HP, so you are at the bottom of their guideline, and going to hydraulics will further reduce the HP. All that means is you might need to travel a little slower or take a smaller bite.

Kim

 

[rswyan]

Kim,

Good catch on the RPM ratings. I just went down the line on displacements. I would stay within recommendations.

Right - very good.

If your PTO doesn't stop abruptly under load, you wouldn't need a motor spool valve to operate it.

Got it - it shouldn't if I'm careful (get all the boulders off the driveway before they are buried with the white stuff ) .... my MMM doesn't stop abruptly when clutched, so I'm guessing I'd be ok there ....

You don't want to stop a hydraulic motor instantly. The pressure spike created can blow seals or rupture the case.

Thanks - good practical data.

Pressure relief valves are always a good idea,

The motor is rated for 2208 PSI continuous and 3091 PSI intermittent ... so I would be inclined to use something like this:

3/4" NPT 30 GPM 1500-3000 PSI RELIEF VALVE

..... plumbed in between the pump and motor .... probably leave it at the factory setting (2000 psi) and see what happens. If it is relieving too often maybe bump it up to 2200 psi ?

How high could I safely go as far as the motor is concerned ..... 3000 psi ?

as are filters.

Right - still have the unused one from the (incomplete) logsplitter project, which I can repurpose .... I'll need to recheck the size and ratings on it (flow, micron, etc.) tho' ....

As far as the 22 GPM (actually calculates to 22.186) goes, that is in a perfect world. There will be losses so you might not get that, but should be close. Hydraulics are "lazy". They only develop the minimum pressure require to do the job.

Got it.

Not sure what happened on the fractions. You want 3/4" hose on the pressure side, and 1 1/2" on the suction.

Good - will do.

I would imagine the Buler recommendation on horsepower is PTO HP, so you are at the bottom of their guideline, and going to hydraulics will further reduce the HP. All that means is you might need to travel a little slower or take a smaller bite.

Can do - it's easy enough with an HST.

Thanks again for all your input - it's helped greatly to further my understanding of this area of hydraulics :thumbsup:

 

[KWentling]

I've forgotten what your tractor PTO HP was, but it takes 25 HP to produce 22 GPM @ 2000 PSI. It is good to have the relief valve there to protect from spikes whether you can produce that pressure constantly or not. If your mower coasts to a stop you should be good with the motor circuit. Sounds like you have a plan.

Kim