Register free!
Search
 
     

The Green Industry's Resource Center


Click for Weather
Reply
 
Thread Tools Display Modes
  #61  
Old 11-12-2013, 10:20 PM
Digdeep Digdeep is offline
LawnSite Bronze Member
 
Join Date: Dec 2005
Location: Madison, WI
Posts: 1,760
Quote:
Originally Posted by AWJ Services View Post
What started this was I stated that on mini ex's the adv flow rating( aux circuit) would be equal to the actual hp available on that circuit. It has went downhill from there.LOL
__________________
Digdeep
Reply With Quote
  #62  
Old 11-12-2013, 10:22 PM
mxridernorth mxridernorth is offline
LawnSite Senior Member
 
Join Date: Apr 2008
Location: North Saanich
Posts: 288
I don't disagree with the results that you observed. I only wanted to correct some false assertions about pumps and the power output available. There are many configurations of pumps and the characteristics of a variable pump can configured in a variety of ways depending on what is required. If there was only one way then all the systems would behave the same and we wouldn't be having this discussion. Perhaps it's easier to think of the curve as a system curve as this more adequately describes it.
Reply With Quote
  #63  
Old 11-12-2013, 10:28 PM
mxridernorth mxridernorth is offline
LawnSite Senior Member
 
Join Date: Apr 2008
Location: North Saanich
Posts: 288
I didn't waste 4 years of my life in engineering to be wrong about the basic aspects of hydraulics. I should mention that I was also a certified fluid power specialist (though I let that slide a while ago) so I'm not talking out of my A$$. You guys can go on believing whatever works for you.
Reply With Quote
  #64  
Old 11-13-2013, 01:09 AM
AWJ Services AWJ Services is online now
LawnSite Platinum Member
 
Join Date: Jun 2004
Location: Ga
Posts: 4,208
Quote:
Originally Posted by mxridernorth View Post
I didn't waste 4 years of my life in engineering to be wrong about the basic aspects of hydraulics. I should mention that I was also a certified fluid power specialist (though I let that slide a while ago) so I'm not talking out of my A$$. You guys can go on believing whatever works for you.
It is not about believing what ever I want it is about what the machines I am referiing too and what they actually do? Not sure why the Manufacturers do not know how to make there machines do what you say they should do?
Reply With Quote
  #65  
Old 11-13-2013, 04:34 PM
YellowDogSVC's Avatar
YellowDogSVC YellowDogSVC is online now
LawnSite Gold Member
 
Join Date: Oct 2006
Location: TX
Posts: 3,508
Quote:
Originally Posted by AWJ Services View Post
It is not about believing what ever I want it is about what the machines I am referiing too and what they actually do? Not sure why the Manufacturers do not know how to make there machines do what you say they should do?
I know we were on mini ex's but in the skid steer world, I'm finding that the machines I use are within specs on high flow attachments. I run a few low flow, high rpm attachments like mowers but on mulcher, trencher, auger, and stump grinder, the machine seems to do what it says. I hooked up my low flow mower today and at full rpm, the pressure showed 1000 psi. I did not place it under load but when i shut it off and started it up, it spiked to above 3,000 psi then leveled off.
When mowing, if the blade tip speed slows, that particular gauge maxes out but I don't know how accurate it is.

I just don't see flow decreases the way everyone is describing. In my application, if the flow would decrease, I'd stall my head even with pressure supporting it. I need the rpm and that is provided by flow, correct? I'm not afraid to learn something new.. I'm not a mechanic. I'm an operator and a damn good one but I can only report on what I experience. I know that when the pressures were lower, even with .5 gpm higher flow, my older machines did not perform as well as my newer ones. Could be the system efficiency. My specs, I believe, are taken at the auxiliary couplers and not at the pump but I could be wrong.
My motor is stock but it runs at the high end of the rpm range which in turn supports the hydraulic pump. I tried matching the torque curve listed in the book for max torque and it is not as good as full throttle in supporting my pump. What that means exactly, I'm not sure other than I always want more power..
__________________

"Life is tough, but it's tougher if you're stupid."

Twitter @Cedar_Clearing
Reply With Quote
  #66  
Old 11-13-2013, 04:56 PM
mxridernorth mxridernorth is offline
LawnSite Senior Member
 
Join Date: Apr 2008
Location: North Saanich
Posts: 288
I believe you YellowDog. Your machine being a skid, has the power to run the high flow at high pressures. You can pretty much ignore the pressure drop across the couplers because I doubt they are more than 7-10 psi each.
Reply With Quote
  #67  
Old 11-13-2013, 08:25 PM
Nelson M Martin's Avatar
Nelson M Martin Nelson M Martin is offline
LawnSite Member
 
Join Date: Sep 2007
Location: Ontario
Posts: 175
Quote:
Originally Posted by mxridernorth View Post
Hydraulic output horsepower can't be greater than engine horsepower. My T153 has max 38 HP available so theoretically this is the maximum that you can utilize.
gpm = 1714 x HP/psi. So at 3000 psi, my machine's theoretically max flow is 22 gpm. My TL140 has 81 HP and at 3000 psi the theoretical max flow would be 46 gpm.
with this formula my T770 magicaly has 157 gpm max flow at 1000 psi
out to lunch these numbers
Flow meters/pressure gauges will only show me what the specs say in the book
max 36.6 gpm and max 3500 psi
But mind you these machines can be tweeked for better performance
Reply With Quote
  #68  
Old 11-13-2013, 09:44 PM
mxridernorth mxridernorth is offline
LawnSite Senior Member
 
Join Date: Apr 2008
Location: North Saanich
Posts: 288
Quote:
Originally Posted by Nelson M Martin View Post
with this formula my T770 magicaly has 157 gpm max flow at 1000 psi
out to lunch these numbers
Flow meters/pressure gauges will only show me what the specs say in the book
max 36.6 gpm and max 3500 psi
But mind you these machines can be tweeked for better performance
That is the max theoretical flow at that pressure. Do you think I'm making this stuff up?
Reply With Quote
  #69  
Old 11-14-2013, 06:18 AM
Nelson M Martin's Avatar
Nelson M Martin Nelson M Martin is offline
LawnSite Member
 
Join Date: Sep 2007
Location: Ontario
Posts: 175
Quote:
Originally Posted by mxridernorth View Post
That is the max theoretical flow at that pressure. Do you think I'm making this stuff up?
This theory of flow might work on a piece of paper for sure...........
But not in the real world of machines
Reply With Quote
  #70  
Old 11-14-2013, 07:52 AM
Digdeep Digdeep is offline
LawnSite Bronze Member
 
Join Date: Dec 2005
Location: Madison, WI
Posts: 1,760
Quote:
Originally Posted by mxridernorth View Post
I believe you YellowDog. Your machine being a skid, has the power to run the high flow at high pressures. You can pretty much ignore the pressure drop across the couplers because I doubt they are more than 7-10 psi each.
I asked my buddy who is a service manager at a nearby Bobcat dealer to grab a machine for me and run it through its paces with a flow meter. He grabbed a T770 and here are the results he sent me. no shock that the actual flow through the meter decreases as the pressure increases. Notice that the maximum actual hydraulic hp is well below 3000psi.

40.4 GPM @ 382 PSI
38.9 @ 1000 (22.6 hp)
36.55 @ 2000 (42.6 hp)
35 @ 2500 (51 HP)
31.2 @ 2750 (50 hp)
28.6 @ 2800 (46.7 hp)
26.1 @ 2900 (44 hp)
21.1 @ 3000 (36.9 hp)
13 @ 3100 (23.5 hp)
12.5 @ 3200 (23.3 hp)
11.5 @ 3300 (22.1 hp)
11.3 @ 3400 (22.4 hp)
4.2 @ 3500 (8.6 hp)
0 @ 3550
__________________
Digdeep
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump





Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ©1998 - 2012, LawnSite.comô - Moose River Media
All times are GMT -4. The time now is 08:19 PM.

Page generated in 0.07715 seconds with 8 queries