Convert/Redo hydraulic snow pump

[fitterski]

You still need a res.... CJ

Looks like maybe a 10 cu-in pump will be my upper limit & maybe 150 gpm max. That 'small' reservoir would then still need around 30 gallons i.e. almost a full size drum! Do you mean radial piston units or axial? I would run them only a fraction of the time so those durability specs would be more than adequate.

The more I get into it the more problematic it becomes. 300 lbs each pump & motor & reservoir is 900 lbs. An Allison 6-speed automatic can do all of that and more at 350 lbs. The mechanical solution does open other issues of course

 

[CJONE]

Looks like maybe a 10 cu-in pump will be my upper limit & maybe 150 gpm max. That 'small' reservoir would then still need around 30 gallons i.e. almost a full size drum! Do you mean radial piston units or axial? I would run them only a fraction of the time so those durability specs would be more than adequate.

The more I get into it the more problematic it becomes. 300 lbs each pump & motor & reservoir is 900 lbs. An Allison 6-speed automatic can do all of that and more at 350 lbs. The mechanical solution does open other issues of course

All piston units, just like a bent axis. If they are closed or open loop is what matters. A open system returns the full pump output back to tank. A closed system just returns the charge pump volume to tank. Piston units are more efficient so less cooling needed but it comes at greater expense. You are always better to mechanically drive something if possible so if you can do that, I would go that direction. Hydrostats work great for forward and reverse applications and speed control, you need neither so direct drive or a open loop system would fit you better. 50gpm at 5000psi is almost 170hp and that is electric brake so that would be in the 225+ range for diesel.CJ

 

[fitterski]

CJONE;

I spent my life thinking that 6000 psi was a lethal weapon. Just talked with a mechanic friend who 'updated' me i.e. that today it is commonplace. I will recalc to maybe a nominal 5000 psi and that should save weight all around. I would just instinctively prefer a closed system as it may become the speed control as well, it would keep the fan at x/y of the engine speed.

 

[fitterski]

There, i added up the beans for a nominal 5000 psi setup and the pump volumes (weights) look much better now. I hope I didn't screw up the calc anywhere

 

[CJONE]

CJONE;

I spent my life thinking that 6000 psi was a lethal weapon. Just talked with a mechanic friend who 'updated' me i.e. that today it is commonplace. I will recalc to maybe a nominal 5000 psi and that should save weight all around. I would just instinctively prefer a closed system as it may become the speed control as well, it would keep the fan at x/y of the engine speed.

Ya, it is! 3500 will pierce you without feeling it. But to get the HP and force modern equipment needs, the higher pressures are common now. Higher pressures = more done with less weight. With hydrostats 6k is actually common now. A lot of the snow cats are running close to this for their drive systems. I have pumps rated to just under 7k. If you build a hydrostat system you CANNOT have a overrunning situation with your blower. You must install a bypass line at the motor with a checkvalve facing the pressure side, we will say this is line A. Line A is pressurized for forward motion, If when you shutdown fast either from running out of fuel or by accident, the motor will pressurize line B from a overrun and the check will open allowing oil to enter line A and still feed the motor so it does not destroy itself. Most of the time this is not a issue but with large fans in a single direction application it does happen. I don't know if this would happen with a snow blower but it is food for thought. CJ

 

[CJONE]

oh and remember that large displacement piston motors are not common and are expensive. Normally you would run lower CC or CI motors through a planetary reduction system for the rpms you are looking for. When you are talking 20+ cuin motors gerollers are used but 3000-3500 is max on them and they usually don't like higher rpms like 600 and up. Just another fly in the soup for you! CJ

 

[fitterski]

those motor torques are in error, i made 2 separate goofs, should approximate 1500 & 1000 ft-lbs

 

[fitterski]

Thanks 4 the pointers CJONE, all those 'system design' issues will have to be addressed in time. For now I'm shooting for ballpark figures that let me have some basic ideas. Many manufacturers do use a reduction gear on higher powered fans but those also add weight and cost. I suspect they have other reasons for doing so since they reduce to 540 which happens to be the standard PTO speed. IF all else is equal I'd go for the simpler method with motor only. This is also something to explore, I'm also tending to downsice as my formulas get more precise so hopefully the final motor volume might be only around 15 cuin.

 

[CJONE]

Alright, did a little looking and a 26 series Sundstrand motor is efficient into the 400 rpm range. It is 13.87 Cuin and is a E pad mount, sooo this is a large motor FYI. I can get these rebuilt fairly reasonable. It would fit what you want to do. 55 gpm would get you 900rpm and over 900 ft lb of torque at 5000psi and 157 hp at the shaft. Soooo I hope the blower is stout!! Most don't want to spend the $$$ to do this right so I usually don't get in this deep on the net. A 23 series Hydrostat will supply enough oil to power this unit. You will need to somehow control your RPMs on that engine from load to no load, these pumps like constant smooth rpms. CJ

 

[fitterski]

I cooked up some more #'s, they are definitive of nothing but do give me a much needed "sense" of the thing. The fan is strong enough but it sits on the original JD throughshaft auger gearbox, not sure but it's only about 1-1/4" shaft. That gearbox comes off if i go hydraulics and using the existing platform. In all cases a smaller motor will turn just the auger as is mostly done on skid-steer blowers for example. The original JD blower had been designed for about 50hp ))

I can make a fan but this one might be based on drawings made by experts or bought as-is, they put a lot more into the design than i could and it does make a difference. The target spot is still in the left top box but "A" it's much too soon & "B" i will stray from it if i have to.