Hydraulic snowblower 4

[Skidderr226b]

I m trying to find out the type and size of hydraulic motor to run a snowblower with a pump that put's out 15.6 GPM @ 3300 rpm....Also if anyone would know at what rpm and torque does the motor would have to run at on hydraulic snowblowers...Thank you

 

[tbuelna]

The auger speed for your example is probably around 500-600 rpm. If you know the hydraulic circuit pressure, you can work out the motor shaft torque.

 

[Skidderr226b]

Once I know the circuit pressure how do I fimd out the torque....is there a formula...saying for example 2500psi.

 

[tbuelna]

If you know the fluid flow rate (15.6 GPM) & fluid pressure (2500 psig), and estimate the efficiency of the motor (say 85%), you can calculate the motor's horsepower. Given the horsepower and rpm at the motor output shaft, you can also calculate the shaft torque. You can easily find the equations for HP,torque,rpm and hydraulic pressure,flow,hp,efficiency with a quick internet search.

 

[hydtools]

Hydraulic motor torque = psi x cu. in. displacement / 2π. Torque units are lb. in.

Ted

 

[Skidderr226b]

Pump puts out 15.6 GPM @ 3300 psi...I know that the snowblower is 5ft wide and the rule of thumb is 5hp/ft of snowblower... In my case 25hp..I also know that PTO snowblowers turn at 540 rpm . the hydraulic shop are asking me what rpm and torque that I want....can anyone calculate this for me...thank you

 

[hydtools]

In order for a motor to turn 540rpm with 15.6gpm input it needs to have a displacement of 15.6*231/540 = 6.67 cu.in./rev
That torque that size motor will deliver at 3300psi is 6.67*33000/(2*pi) = 35,032 lb.-in. or 2,919 lb.-ft.

Can you find a motor that size or close to that?
Will the torque be enough, too much, too little? Snow load on the blower will determine torque demand, and directly pressure demand. As the snow load varies so will the hydraulic pressure.
Will your prime mover, gas or diesel engine, deliver what the pump will demand? Will the engine speed be controlled by a governor or fixed throttle opening? Where on the torque curve will your engine be operating at the speed required to have the pump produce 15.6gpm? If too low on the torque curve the engine will slow and stall.

Ted

 

[Skidderr226b]

Thanks for helping me out Ted...only thing is that the pressure is 3300 psi.,just changes the answer a little... I have seen some 6.2 cu.in. motors with 177 ft.lbs. of torque..... Gonna have to look some more for higher torque values motors...any suggestions on types or perhaps model numbers that you might be familiar with. I know they have to be equipped with a bypass valve so when it stops it doesn't lock up...Tx

 

[hydtools]

Oops, one too many zeroes in the pressure number. Torque should be 292 lb.-ft.

You should have a relief valve in the circuit to safeguard components if the snowblower stalls.

Ted

 

[hydtools]

You might look at CharLynn motors.

Ted

 

[Skidderr226b]

To answer the rest of your questions Ted... I will be running this blower off a Caterpillar skidsteer 226B . it has a 2.2 l turbo diesel engine.. I m not sure but I think the pump ratings are at max throttle... I wouldn't see myself doing snow less than max throttle...they are made to run high....unless there is little fluffy snow where you wouldn't need to. Tx

 

[Skidderr226b]

I found this one.,.Char-Lynn 2000 series: 1 1/4 Shaft, 6.2 CID, SAE 10, 742 RPM, 2630 Tq, 254083 torque is 2630 in.lbs.

 

[HPost]

Hi Skidder...

The pumps on the 226B will have a max working pressure that is independent of engine speed and the machine is capable of achieving the max pressure at low idle and high idle. All engine speeds in fact.

Cheers

Adrian

Adrian Wright CEng MIMechE
Engineering Specialist
Hydraulic Systems
Caterpillar (UK) Ltd

 

[Skidderr226b]

Thanks for the great info Adrian...i wasn t aware of that....what would you think about the motor that I just listed. Tx

 

[hydtools]

I understand now this will be run on a Cat skidsteer. Are there accessory ports that you will be connecting to? The Cat hydraulic system will have circuit protection already in it, so you will not have to worry about additional pressure relief to protect your snowblower motor.

For 16gpm flow rate, I would opt for the -12, 1-1/6 thread port and 3/4 inch pressure hose and 1 inch return hose. Keep your pressure losses down.

I expect for a snowblower you would want speed so that the blower can throw the snow. Torque available will determine how heavily you can load snow into the blower and still keep the blower speed up.



Ted

 

[Skidderr226b]

Hi Ted...what do you mean by "opt for the -12"... And yes the skidsteer has accessory lines that you can connect to...comes built in by Cat....I will still need a check valve on the motor that allows oil to bypass whitin the motor when the valve is turned off right....so the flywheel on the blower keeps turning when the valve is turned off...???

 

[Skidderr226b]

Accessory ports

 

[hydtools]

Yes, you would need the bypass check valve. Char Lynn may have a bypass check valve as an option. Check the directional valve on the skid steer auxiliary circuit. If it has a motor spool, you would not need the check valve.

You indicate that the motor has SAE 10 ports. I'm suggesting you select SAE 12 ports.

Ted

 

[Skidderr226b]

What would be the difference between a 10 and a 12 ports...please explain to me..thanks!Ted

 

[tbuelna]

The difference is the cross section area of the flow passage.

Even a -12 fitting at 15.6gpm would have a flow velocity well over 15 ft/sec, which is what I would use for a hydraulic motor inlet port.