40 gpm Hi-Flow machines

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JustAwrench

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Joined
May 9, 2005
Messages
34
Just a thought-I'm reading a lot posts with concerns of the new 40 gpm Hi-flow's potential for damage to older hi-flow attachments. I'm sure you guys are aware that by backing off the throttle, your flow rate goes down. If you have a deluxe panel, you can display engine rpm and with flowmeter, match flow to a specific rpm, and run your attachment without fear of damage. Of course, you may need all the rpms you can get for maneuvering, but that depends on what you're doing. Also, if you have multiple operators and you fear that one may overflow the attachment, you can block his use of hi-flow by password(with deluxe panel, that is) until he is trained to your confidence.
 

500K_773

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Joined
Mar 5, 2004
Messages
342
Can you limit RPM's through the deluxe panel? I'm guessing probably not because it's a mechanical linkage from the hand throttle to the fuel pump.
I don't even want to think about the price of a flow meter. Somewhere between $300-$500???
 

JustAwrench

Active member
Joined
May 9, 2005
Messages
34
Can you limit RPM's through the deluxe panel? I'm guessing probably not because it's a mechanical linkage from the hand throttle to the fuel pump.
I don't even want to think about the price of a flow meter. Somewhere between $300-$500???
No-you can't limit rpm's with the panel. You should'nt need to buy a flow meter, either-your dealer should have one. If our customer wanted to know how many rpms his new hi-flow was turning to push, say, 32 gpm, we would fall all over ourselves to let him know, and it would take all of five minutes. Limiting auxilliary gpm, thoough is a good idea, and I'll bet it would be doable through a software mod since the solenoids are pwm and variable-think I'll bring that idea up to my DSR-thanks 500K.
 

wingspar

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Apr 30, 2005
Messages
29
No-you can't limit rpm's with the panel. You should'nt need to buy a flow meter, either-your dealer should have one. If our customer wanted to know how many rpms his new hi-flow was turning to push, say, 32 gpm, we would fall all over ourselves to let him know, and it would take all of five minutes. Limiting auxilliary gpm, thoough is a good idea, and I'll bet it would be doable through a software mod since the solenoids are pwm and variable-think I'll bring that idea up to my DSR-thanks 500K.
Shane, does Bobcat still use gearpumps for the aux hyd? I didn't think slowing the RPM's down would work very good for limiting GPM, but I guess I haven't tried it in a work situation. Can it still reach max working pressure? One thing about higher GPM, it's not as hard on the attachment hyd motors as higher pressure can be. So if you can live with the faster RPMs at the attachment, I don't think it's a real big deal. At higher pressures, geroler and gerotor type hyd motors become more inefficient too. I'm starting to like CAT's aux system more and more. They use a pressure compensated, variable displacement piston pump I think. It maintains max pressure but backs off on the GPM when the going gets tough. This allows the attachment to maintain max torque when you need it most. Handy for trenching and blowing snow etc. P.S. We share a cool first name! -wingspar (Shane)
 

JustAwrench

Active member
Joined
May 9, 2005
Messages
34
Shane, does Bobcat still use gearpumps for the aux hyd? I didn't think slowing the RPM's down would work very good for limiting GPM, but I guess I haven't tried it in a work situation. Can it still reach max working pressure? One thing about higher GPM, it's not as hard on the attachment hyd motors as higher pressure can be. So if you can live with the faster RPMs at the attachment, I don't think it's a real big deal. At higher pressures, geroler and gerotor type hyd motors become more inefficient too. I'm starting to like CAT's aux system more and more. They use a pressure compensated, variable displacement piston pump I think. It maintains max pressure but backs off on the GPM when the going gets tough. This allows the attachment to maintain max torque when you need it most. Handy for trenching and blowing snow etc. P.S. We share a cool first name! -wingspar (Shane)
Yeah-bobcat uses fixed displacement gear pumps for loader auxillliaries. Flow is directly related to engine rpm. Max pressure is limited by main and port reliefs so if the engine horsepower is available, even at reduced rpm, it will still build whatever pressure is needed to do the job. I'm not so sure that overpressure is harder on equipment than overflow, but pressure is always limited by system relief, and like amps in an electrical circuit, it's only going to build what the task requires. Flow is usually limited by max governed engine rpm but with the new hi-flows there is the possibility of overflowing the attachment. Overflowing is damaging for a number of reasons-heat buildup, cavitation, exceeding design limits of the rotation/reciprocation speeds of components, etc. So, in short and after much hot air, if you back off on the throttle, pressures are still available(as long as engine hp stays up), but things will slow down.
 
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