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.