Hydraulic motor sizing/performance question

[Jay4200]

I have no idea what the sizing spec of a hydraulic motor means, so please bear with me.

I want to use a hydraulic motor to rotate the chute on my snowblower. The cheapest high-torque / low-speed hydraulic motor I can find ($80) is a 2.5cu-in motor rated at 1115 RPM at 12GPM (2250psi). My tractor's hydraulics (BX2200) are somewhere in the 5.5-6 GPM range, and probably in the ballpark of 2000psi. If I hook up this motor to a 5.5 GPM source, will it turn at ~500RPM? What is the cu-in rating used for?

If anybody can point me to a site that explains the calculations for specifying a hydraulic motor, please do. I'm an electrical engineer, so the more technical the better. Thanks!

 

[LD1]

Flow = Speed.

Size of the motor and pressure determine the rotating torque.

The 2.5 cu in rating is how many cu in of fluid it takes to make 1 revolution.

So... 5.5gpm in. There are 231CI in each gallon of fluid. So you would be passing 1270 CI of fluid per minute through it. 1270/2.5 = 508RPM theoretical. That is not counting for efficency loss and assuming you actually will be getting 5.5GPM to the motor.

The way it is rated now, 1115rpm and 2.5 ci @12gpm....

12gpm is 2772 CI.
2772/2.5 = 1108RPM. So their rating is right on (+/- a little).

 

[dfkrug]

So, JAY, if you want low speed, then you need a large displacement motor, which can be several
times the cost of a low disp motor.

Or, you can use a cheaper motor and use sprockets & chains, or gears to slow things down.

Or, you can use a cylinder and leverage to rotate your shute, since you do not need full rotation.
At least one TBN member has done this, I can not remember who. In this case, a larger
diameter cyl will be slower, but you can slow it down with small hoses and even a restriction
orifice.

 

[J_J]

I have no idea what the sizing spec of a hydraulic motor means, so please bear with me.

I want to use a hydraulic motor to rotate the chute on my snowblower. The cheapest high-torque / low-speed hydraulic motor I can find ($80) is a 2.5cu-in motor rated at 1115 RPM at 12GPM (2250psi). My tractor's hydraulics (BX2200) are somewhere in the 5.5-6 GPM range, and probably in the ballpark of 2000psi. If I hook up this motor to a 5.5 GPM source, will it turn at ~500RPM? What is the cu-in rating used for?

If anybody can point me to a site that explains the calculations for specifying a hydraulic motor, please do. I'm an electrical engineer, so the more technical the better. Thanks!

Surplus Center

Go left side, under hyd calculators, select motor speed and torque.

Your 2.5 motor using 5.5 GPM will turn at 508 rpm, 796 inlbs

 

[BukitCase]

Sooo, to reverse the math, that motor would turn your chute one complete revolution in just over a tenth of a second.

Might wanna find a slower way, or just use the CHUTE to throw the snow :=)

 

[rswyan]

Why in the world would you want to use a hydraulic motor ... as opposed to a hydraulic cylinder ... to do chute rotation ?

 

[boggen]

Why in the world would you want to use a hydraulic motor ... as opposed to a hydraulic cylinder ... to do chute rotation ?

with a hydrualic cylinder, you get in rather ugly spot to even be able to do a 180 degrees rotation.

 

[boggen]

small hyd motor you can get, with a adjustable hyd valve. seems a little costly....

why not a 12v electrical motor and a cheap 12v dip switch to adjust direction?

 

[rswyan]

with a hydrualic cylinder, you get in rather ugly spot to even be able to do a 180 degrees rotation.

I'm using a hydraulic cylinder on my Buhler Farm King 60" blower and I have in excess of 180 degrees of rotation.

It's all in the mechanism (that the cylinder is acting on) that actually rotates the chute ...

 

[SPYDERLK]

Sooo, to reverse the math, that motor would turn your chute one complete revolution in just over a tenth of a second.

Might wanna find a slower way, or just use the CHUTE to throw the snow :=)

Yeah. And at about 60ftlb of torque. Gear it down to reasonable speed and EVEN MORE torque. Probably not a good plan to use a hyd motor.

 

[wpabx2230]

I bought a Danfoss DH36 on eBay cheap. I had no idea how it would work. It works very well. It is plenty fast enough. I used the stock rotation
setup but ground the notches the entire way around the chute. See attached photos of motor mounting.

 

[Jay4200]

Wpabx2230 has pretty much exactly the setup I want do build. He even has the same snowblower, although his tractor is a couple of years newer . Whats the spin rate on that thing?

Thanks for the explanation of cu-in rating - makes perfect sense. 500 RPM might be a little fast, but probably not outrageously so. I could always put in a flow restriction if need be.

Why hydraulics instead of electric, you ask? With a loader setup installed, the BX22xx quick hitch uses the loader valve to lift and lower the blower. Since the controls are already there for an extra degree of freedom, why not use them? A joy stick up and down for lift n' lower, then back n' forth for rotation is about the most intuitive control I could imagine, and I've always wanted to set up a joystick chute control - the BX has me 1/2 way there already. Hooking a hydraulic motor to the existing chute rotation mechanism is trivial, as shown above. Setting up a cylinder is a seriously complex and expensive proposition. I have a hydraulic cylinder rotation (and flapper) on my big blower - the cable/hoop mechanism would be complex to build, and must be precisely engineered, as evidenced below (and yes, I know the chute cable is routed backwards - left over from the PO - its fixed now):

 

[J_J]

You can either gear the motor down or use a priority valve to send a few GPM's to the motor. The Excess flow will go to tank or to another function.

For example, with a 10 GPM flow, the flow control valve would supply 2 GPM to the chute motor, and the other 8 GPM would go downstream for the 3pt.

You can go large cuin, but might be more expensive, larger fittings, etc.

A divider valve will send a dedicated flow to the chute motor and the rest to the 3pt.

11.9 cu in GRESEN 1016 HYD MOTOR

 

[BukitCase]

Seeing the pix makes a bit more sense of this - in effect, those notches and the "rotary spring" are acting as a worm gear, so your 500 rpm would probably translate to maybe 3-4 seconds for a full rotation of the chute.

Prior to the pix, it sounded like you were going to direct drive the chute - hence my smart-azz comment :laughing:

Gotta forgive us "non-snow blower people", we got about 8 inches this year, typically around 0-3", and prior to this year the late 60's was the first and last time we ever saw more than a foot... Steve

 

[Jay4200]

Gotta forgive us "non-snow blower people", we got about 8 inches this year, typically around 0-3", and prior to this year the late 60's was the first and last time we ever saw more than a foot... Steve

You don't know what you're missing - nasty machines. My big blower could easily eat a car. As for the smart-azz comment, I thought it was pretty funny.

 

[BukitCase]

Jay, glad you took it as it was intended - plus, I learned something about a piece of equipment I DO NOT lust after

(If you knew me better, you'd appreciate just how RARE that is )...Steve

Oh, BTW I was stationed in Mass. for about 2-1/2 years in the late '60's, so I DO know what I'm missing - and I'll KEEP ON MISSING it, thanks very much :laughing: