Power Steering Issues - update 5/20

[rv_safetyman]

Note, I have updated the status of this problem in a post down the thread quite a ways.


I have installed my hydraulic fan to cool the charge air cooler.  It does a pretty good job.

As a part of that design, I had to change hydraulic pumps.  My replacement pump is a Haldex W900 model code 190.  It is rated for 4000 PSI max.  It is a 2 stage pump with priority supposedly given to the PS outlet.  I am using Dextron for the fluid.  The pump is gear driven on the front of the engine in the typical Series 60 location.

We checked the pump (disassembly and dyno) and it checked out good.

My PS problems come at low engine speed for the most part.  Although it was hard to make fairly sharp turns in the last mile even at 1500 engine RPM.  This same pump also powers my jacks.  I noted that I had to put the engine on fast idle to raise the front.

Each circuit (fan, jack, and PS) are on separate circuits with their own spin-on filter.  I change from fan to jacks with a quick disconnect.

So, here comes the questions:

1)  Should I be using a different fluid?

2)  How hot should the fluid be?  The tank seemed to be at about 130* after about an hour of running.

3)  What else should I think about doing?

I will change the filter today to see if that helps, but I think it is a bypass type filter.

Thanks, Jim

[bobofthenorth]

I'm no engineer Jim so bear that in mind but I think its flow not pressure that matters in this situation.  I believe that pump flows 19 cc/rev or .00502 gallons per rev.  Somebody smarter than me will know what the drive ratio is so that we can convert that to available GPM at 1500 RPM.  That appears to be a standard gear pump so when you say "2-stage" do you mean that it is a 2 section pump?  If that is the case I believe that would double the flow. 

[luvrbus]

Jim, the power steering on your Eagle requires 7.2 gpm and 2000 lbs of pressure do you have that from the pump the temp is good 

good luck

[rv_safetyman]

The literature does not give a flow rate directly. 

My pump displaces 1.159 cubic inches per revolution.  I can do the conversion, but I have no idea what the ratio is for the crank to pump. 

I got a call and the person suggested choking down the fan drive.  I currently have 3/4 inch hoses going to and from the pump.  Would not be too hard to put some fittings in the line to choke it down a bit.  Thoughts?  Part of the question involves what priority really means.

Jim

[JackConrad]

I don't know about 2 stage hydraulic pumps, but on our fire engine the 2 stage (water) pump could be set for parallel (more volume) or series (more pressure).  Jack

[luvrbus]

Jim, that pump is made by Barnes have you checked their site you may have a Hi/lo for example 13 gpm on lo pressure and 6 gpm on high pressure.I'll do some checking for you later choking the flow is going to make more heat

good luck

[Paso One]

So, here comes the questions:



2)  How hot should the fluid be?  The tank seemed to be at about 130* after about an hour of running.

Normal for hydraulic oil operating temperature is.... in my experience is 100 *  above outside ambient temp.

[Dreamscape]

Jim,

Do you have any solenoids in the system to allow flow to one and not the other? I'm assuming you would not want the pressure to go to both power steering and jacks at the same time. I'm only trying to pull from my past experience, when adding/tying systems together it can be tricky. I would run both into a manifold, solenoids on each, and plumb from there. I'm just searching here, as I'm not an engineer like youself.

Paul

[luvrbus]

Paul, Jim use a quick disconnect to go from steering to jacks he will get around to a manifold some day.
Do you have any info on that pump he is using I cannot find much on it even on the Barnes site

good luck

[Ed Hackenbruch]

 Jim, on any piece of equipment that i have ever run you have very little power to the hydraulics at idle or low speed. On backhoes/trackhoes for example you set the throttle to wide open when working. Smaller lines would probably help increase your pressure at low rpms but you would probably decrease your flow rate somewhat too which might not be good.  Maybe talk to an engineer?  Oh wait, you are an engineer and i have seen you talking to yourself!!!!   Seriously though, maybe go to an equipment dealer and talk to them?

[Dreamscape]

I'm thinking maybe Jim should disable/block the flow to the jacks to isolate the problem. It seems that the pump is only capable of delivering enough power for it's intended purpose. I"m just shooting from the hip here!

Modified from following post.

[bobofthenorth]

He's already done that Paul.  The only things in the current system are the charge air fan and the power steering.  He needs both of those to run at the same time.

[Dreamscape]

He's already done that Paul.  The only things in the current system are the charge air fan and the power steering.  He needs both of those to run at the same time.

Whoops, I forgot that the from the original post. CRS at it again!

[Ed Hackenbruch]

Flow to the jacks shouldn't make any difference as long as he is not activating the jacks, which i don't think he would be doing when he is making a turn with the bus.  On a piece of equipment you basically have a feed line that goes to a valve body, (think junction box here). This feeds the various controls. If you have enough flow and pressure you can do several functions at the same time,  ie. you can lift a boom, curl a bucket and swing all at the same time.  If flow and or pressure is reduced for any reason you may not be able to do more than one function at a time or even at all.

[Ed Hackenbruch]

Jim,  putting fittings in the line or lines may or may not help depending on where in the line you put them. Instead you may have to change to a smaller line to get the change you want.  ( Disclaimer,... I am an Operating Engineer, not a "real" Engineer so take this all with a grain or 2 of salt"