Snowblower Snowblower powered by tractor's onboard hydraulics

[Pks]

Snowblower powered by tractor\'s onboard hydraulics

Have any of you seen or read about a snowblower that was powered by the tractor's on-board hydraulics?

My neighbor and I are doing a conversion on a JD 770, where the snowblower attaches to the FEL in place of the bucket. We already have an old motor and drive system on the blower.

The motor hasn't been tested yet (it's from an old combine). If it requires too much GPM to drive it for the 1100 RPM we need, then we'll get a different motor; one that matches the input torque and RPM of the blower and GPM delivered by the tractor.

Right now, I'd like to see what other folks may have done etc.

Overall, I want to check if I need to add additional fluid storage capacity and an additional oil cooler to keep the oil from foaming and overheating. I'm guessing the JD 770 is good for about 11 GPM.

 

[RobS]

Re: Snowblower powered by tractor\'s onboard hydraulics

<font color="blue">I'm guessing the JD 770 is good for about 11 GPM </font>

That might be a tad high. My 790 (next version of your tractor) has 5.6 gpm on the implement pump and 4.3 gpm on the steering pump. They list total as 9.9 but I don't think you can get that out of one hose since the pumps are hydraulically seperate /forums/images/graemlins/smile.gif

 

[Pks]

Re: Snowblower powered by tractor\'s onboard hydraulics

Thanks RobS. I'll change my data to use 5.6 GPM.

 

[DUMBDOG]

Re: Snowblower powered by tractor\'s onboard hydraulics

The ones that I have seen require 13 gpm to operate. Here is a link to a site that lists them with bobcat type quick plate attachments.

FRONT MOUNT SNOWBLOWER

 

[RickB]

Re: Snowblower powered by tractor\'s onboard hydraulics

It is HIGHLY unlikely that you will get the required flow from your tractor. Any orbit motor you find to twist at that speed will require something on the order of three to four times the flow you have to develop sufficient torque to blow snow. A PTO pump is available to do the job, but the tractor is marginal on HP for even that.

 

[DocHeb]

Re: Snowblower powered by tractor\'s onboard hydraulics

At 5.6 gpm and 2000 psi, a 1100 rpm motor will be generating 6.5 horsepower (not counting for system inefficiencies.) I suspect this will not be enough for a snowblower of any size greater than a walk-behind.

 

[rambler]

Re: Snowblower powered by tractor\'s onboard hydraulics

We see this idea pop up here a couple times a year. While it's a good idea & heck I would like one just like it - we can't change the laws of physics.

You just won't get close to enough hp through the hoses to make it work.

I don't know the hp of your tractor, but you need 13-21 gpm flow, to create the 20 hp or so you will need. Since hydraulics are an inefficient way to transfer power, you probably need close to 30 hp just running the pump if you want a pto pump to run it all - does your tractor have that to spare? It would take a big resiovor, and probably a cooler, to get it all working. Bobcat attachments will run a big hyd motor like you want, but it takes a pretty stout Bobcat, not the lowest model, and they are in effect a giant hyd motor with a huge resiovor & cooler.

Sorry.

--->Paul

 

[keeney]

Re: Snowblower powered by tractor\'s onboard hydraulics

I seem to remember that 1 GPM at 2000 PSI is on the order of 1 HP for estimating purposes.

This is in agreement to what another poster has pointed out. To get he over 20 HP you want to run a 60" or wider snowblower, you will need closer to 20 GPM.

Also, as another has pointed out, you will need to account for the loses of the hydraulic system. I would estimate an even lower efficiency - more like 60% net between the pump, hoses, and the moter. So you need to put over 35 HP in to get the 20 HP out the other end. And you need a cooler that can dump the other 15 HP out as heat.

Hydraulics are good for flexible power connections, but kind of suck for efficiency. Drive-trains and roller chains, on the other hand are very efficient. Typically in the mid to upper 90's percentage range for a well-balanced, well-lubricated system.

The best way to get 20Hp from your tractor to the snowblower is with a driveshaft or a chain.

- Rick

 

[Pks]

Re: Snowblower powered by tractor\'s onboard hydraulics

DocHeb,

Just curious, do you have calculations that can support the numbers you state?

 

[RonL]

Re: Snowblower powered by tractor\'s onboard hydraulics

Peter

The formula for hydraulic horsepower is: GPMxPSI/ 1714

Hydraulic pumps are generally 85 to 95% efficient as are hydraulic motors. Most positive displacement gear pumps and motors are in the 90% efficiency range. 20 HP input will yield 18 HP hydraulic power. At the other end this will yied 16.2 HP at the hydraulic motor, minus the losses in the lines. Resistance to flow can be calculated for different size lines. I don't think the resistance to flow is as great as others have suggested.

Gear pumps and motors will have their displacement given, usually in cubic inch displacement per RPM. There are 231 cubic inches per gallon, so the formula for determining GPM is: RPM x displacement in cubic inch/ 231. At the other end, the inverse of this formula can be used to determine the RPM of a motor.

You want to have the snowblower at least as wide as your tractor and you will want at least 4 HP per foot of width. 20 HP for a 5 foot wide snowblower. 20 GPM at 2000 PSI will give you 21 HP out of a 90% efficient motor. Most tractors will not give you anywhere near this output. You can get a PTO pump that will give you this kind of output. The pumps slip over your PTO shaft and lock on. Usually a bracket is fabricated that bolts to the pump and slips over the drawbar. This keeps the pump from spinning. A reservoir is connected to the 3 point hitch. Usually a reservoir the size of the GPM rating of the pump is used but a larger reservoir helps to dissipate heat.

The huge snowblowers that they use at airports are hydraulically powered. The snowblowers are mounted to all wheel drive trucks with super heavy duty front ends. There is a seperate engine on the back of the truck that powers the hydraulic pump.

RonL