GPM Question

[J_J]

Even with those figures, there doesn't seem to be enough Hp to run everything.

However if he only runs the 20 GPM pump, it would take about 51 HP.

If he only runs the the other 20 GPM @ 3000 psi, that would take about 41 HP.

Total is about 92 HP if both pumps are running at max.

If the machine is only using low GPM's from each pump, then the engine could run without stalling.

The Komatsu pump running at max and at max pressure would require about 116 HP.

You think they are fudging on the ratings?

 

[glastron23]

JJ, your thinking in fixed displacement pump requirements. With the a1 pumps, pressure/flow compensated/torque compensated pumps, you can have high flow/low pressure, as the stain on the hydraulics increases the pump will start to shift the swash plate from high flow/low psi to a lower flow/higher psi. this requires less horse power to run. as far as having the extra pump for the blade/swing its highly unlikely to run both at the boom and blade at the same time. check this from Rexroth The compact variable pump A1VO - YouTube

 

[J_J]

I understand that, but at some time, the load will call for max GPM and pressure.

I have a variable speed pump on my Power-Trac, and when I jump on it, it will load up the engine, and if I am doing anything with one of the other pumps such as the gear type PTO pump, I have to back off the pedal to recover.

 

[mjcountrybumpkin]

The 75 will bury the bobcat that simple. Flow , hp , pressure. They do not matter comparing these 2 machines. No matter home much lift capacity you have if you don't have enough counter weight your going no place quick. If you need or want the bigger machine then that's the way to go.
Happy digging

 

[npalen]

Probably should distinguish between the terms force and power.

 

[glastron23]

Probably should distinguish between the terms force and power.

YUP ..
JJ with a compensated pump you will not get full GPM and MAX psi at the same time, as soon as the swash plate piston starts to see high PSI it has all ready starts to destroke .. it has to

 

[Arc weld]

Can almost guarantee the Komatsu is a much more refined and sophisticated machine than the Bobcat. Komatsu makes some of the most advanced excavators in the world...Bobcat, not so much. There are variable displacement pumps and then there's load sensing, pressure compensating and a host of other advances in hydraulics.

 

[NWOutlawMX]

Great info, more in depth research leads me to the Komatsu being a grey market machine - nothing to do with hydraulics - but in the final decision. Here's a picture of the rock I tried to pick up and the stump I need to tackle. I like the mobility in tight quarters with the mini's but on the other side (as you can see) I need something in the 20-30K lb range. There's a lot more of these stumps and rocks. There was another rock slightly smaller that I moved (slowly) but don't know if i could pick it up and put in a truck.

 

[xtn]

I guess you mean force. Otherwise it would be just as true to say the reverse.
larry

Yes, thank-you.