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Author Topic: Power Steering Issues - update 5/20  (Read 3826 times)
rv_safetyman
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« on: May 17, 2010, 11:49:59 AM »

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
« Last Edit: May 20, 2010, 07:59:44 PM by rv_safetyman » Logged

Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
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bobofthenorth
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« Reply #1 on: May 17, 2010, 12:12:32 PM »

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. 
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« Reply #2 on: May 17, 2010, 12:35:41 PM »

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
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rv_safetyman
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« Reply #3 on: May 17, 2010, 03:35:59 PM »

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
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Jim Shepherd
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85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
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« Reply #4 on: May 17, 2010, 03:56:53 PM »

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
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« Reply #5 on: May 17, 2010, 04:16:34 PM »

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
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« Reply #6 on: May 17, 2010, 05:42:48 PM »



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.
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« Reply #7 on: May 17, 2010, 07:18:55 PM »

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
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« Reply #8 on: May 17, 2010, 07:26:13 PM »

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
« Last Edit: May 17, 2010, 07:30:12 PM by luvrbus » Logged

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« Reply #9 on: May 18, 2010, 07:19:19 AM »

 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!!!! Grin  Seriously though, maybe go to an equipment dealer and talk to them?
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« Reply #10 on: May 18, 2010, 08:23:35 AM »

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! Grin

Modified from following post. Embarrassed
« Last Edit: May 18, 2010, 08:31:36 AM by Dreamscape » Logged

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« Reply #11 on: May 18, 2010, 08:26:27 AM »

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.
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« Reply #12 on: May 18, 2010, 08:29:00 AM »

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! Cheesy
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Ed Hackenbruch
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« Reply #13 on: May 18, 2010, 08:39:45 AM »

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. Grin  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.
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« Reply #14 on: May 18, 2010, 08:52:00 AM »

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"  Grin
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rv_safetyman
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« Reply #15 on: May 18, 2010, 01:49:44 PM »

Thanks guys.  Yes, Ed, you have seen me talking to myself.  Indeed, I sometimes answer myself Grin.

Just so we are straight, my PS is always in the system.  The other port/circuit is EITHER the jacks or the fan.  I switch to one or the other via a quick connect.

Bob of the North called the other night and we went over some of the possible issues.  He came up with an interesting thought.  If the motor is switched to the high speed, there could be more restriction.  I will finish that wiring when I am in Iowa and do some playing.  I could easily switch to high speed when I am on tight roads at slower speeds.

Kent Widdison also called and we went over the complete system (I got it from him).  He had it on his bus and it ran fine.

My guess is that I have plumbed too big of lines to the fan and am losing flow in that circuit.

BTW, I have been chastised a time or two about telling folks not to go to a small steering wheel.  Well, if I had had a small steering wheel a couple of corners would have been interesting Shocked.  I won't chime in again on those threads, as you all know my opinion. 

Jim
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Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
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« Reply #16 on: May 18, 2010, 02:54:39 PM »

I always talk to myself because I'm the only one who knows what the hell I'm talking about.
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« Reply #17 on: May 18, 2010, 03:02:07 PM »

Jim, Can you provide the complete part number of the pump you are using? Can you provide a schematic of the system including line sizes? Part number of the hydraulic fan motor?
Having a hydraulic background, my initial confusion is you mention it being a 2 stage pump. According to the manufacture this is a fixed displacement gear driven pump which will deliver X number of cubic / inches of hydraulic fluid per revolution regardless of pressure. The faster it spins, the more volume it delivers. The slower it spins, the less volume it delivers. Pump pressure is a product of downstream flow resistance. In other words if a pressure gauge was installed at the pump outlet and the pump outlet was piped directly back to tank, the only flow restriction would be the piping back to tank. Therefore the pressure gauge would indicate very low pressure to no pressure depending on the line size back to the tank. In this case the smaller the return piping, the higher the resistance thus higher pressure.
Now as in any hydraulic system using a fixed displacement pump, there must be a safety relief or regulator to limit the maximum system pressure or there will be a disaster.
Depending on the circuit design you have, my initial thought to your comment on hard power steering at slow speeds is, low engine rpm means low pump volume and the hydraulic fan being the path of least resistance is passing what little volume the pump is outputting which in turn will cause the pressure to drop.
My suggestion would be to add a restricting orifice to the inlet to the hydraulic fan motor. An orifice size could be calculated based on system components, piping sizes and lengths or you can simply experiment by installing an orifice to the inlet of the fan motor and installing a gauge visible from the drivers area but connected to the inlet of the PS box underneath you. As you drive with the fan running and making a turn, you will want to size the orifice so the gauge pressure does not fall below the PS box min pressure needed. The smaller the orifice the more pressure you will have to the PS box. Now there may be more to you system that meets the eye like volume and pressure requirements needed for the hydraulic fan motor but without a complete schematic and part numbers of the components in your system this is my only my initial thoughts.
Kenny
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rv_safetyman
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« Reply #18 on: May 19, 2010, 06:01:04 AM »

Kenny, thanks for offering to help.  I wrote to Haldex with part numbers that appeared on the pump and motor.  Here is their reply:

These are special W900 Series products we make for Daimler Trucks North America.  

Daimler P/N 61280126 is our model number W9A126L3G24C03AXS  - W900 Series pump
Daimler P/N 61280121 is our model number WM9A125R3R64VNBJS - W900 Series motor



They are a system (pump/motor) designed for a Thomas bus from what we can tell.

The PS plumbing is unchanged from before the hydraulic pump/motor change. I did route the return hose from the old reservoir to the new reservoir.  Per the BK thread, I am dumping the return into the top of the reservoir.  Kind of wonder if that adds air to the fluid somehow.

My fan circuit is very simple.  3/4 hose to a quick connect, 3/4 hose to the motor, and then 3/4 hose to the reservoir (with spin on filter in the line).  I just guessed at the hose side.  The ports are pretty large, so I figured that the motor need a lot of flow.  I ran a fairly straight 1 inch supply line from the tank to the pump.

Here is a photo of the pump:

Jim


« Last Edit: May 19, 2010, 06:03:45 AM by rv_safetyman » Logged

Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
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« Reply #19 on: May 19, 2010, 06:18:52 AM »

Jim, isn't the power steering a open center hydraulic system and the fan a closed hydraulic system or the other way around not for sure 

good luck
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« Reply #20 on: May 19, 2010, 07:02:29 AM »

Clifford, I am pretty sure that both are open center systems (fluid flows at all times through both circuit).

In the case of the fan, the fluid is always doing work.  In the case of the PS, I think the fluid flows to the return until the PS calls for assist.


Jim
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Jim Shepherd
Evergreen, CO
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Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
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« Reply #21 on: May 20, 2010, 08:10:25 PM »

OK guys, we left on our trip today.  I felt as nervous as a whore in church!!  First is the whole engine/transmission situation given my track record.  The next was the issues with the new hydraulic system.

Bottom line, all went well.  My blood pressure dropped to its normal boarder-line level after about an hour.  The engine and transmission ran very well.

I was really nervous about the power steering.  However, there was not problem one.   I even went a round about way to get to the highway so that I did not have to drive on our tight twisty canyon road.  Turned out that I did not need to take that route.

I did change the spin on filter for the PS circuit.  Can't believe that would make that big of a difference.

I shot the temperature of the reservoir and it was always in the 120-130* range.  And it is not full.  The charge air cooler fan did a good job as well.  I can tell that I will need to wire up the high speed for the really big hills, but I won't see those till I get back home.

We have about 350 miles to go tomorrow, so we will see if we have a repeat of today's good results.

Maybe it is about time that something goes right Grin Grin

I do plan to put dip tubes in the return lines so that fluid is returned into the fluid.

To show you how well things went today, we found a truck stop that had $2.96 diesel (no charge for CC)  *AND* red diesel for my auxiliary tank (for Aqua-Hot and generator) at $.44 off the normal diesel.  I needed 30 gallons so that worked out well.  Our local station has a price differential of 20 cents - what a ripoff!!!

Fun reporting a good day for a change!!!!

Jim
« Last Edit: May 20, 2010, 08:15:38 PM by rv_safetyman » Logged

Jim Shepherd
Evergreen, CO
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Somewhere between a tin tent and a finished product
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« Reply #22 on: May 21, 2010, 05:29:41 AM »

have been following along and learning...you deserve to have the problems worked out....more fun to drive and enjoy than to worry and work on..... Grin Grin Grin
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« Reply #23 on: May 21, 2010, 05:46:09 AM »

Jim, I'm so glad you were able to actually get down the road and have no engine/transmission problems!  Way to go!


I don't think I saw where you mentioned exactly what it was that caused your original transmission ECU to fail.  What was the root cause analysis on that?
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« Reply #24 on: May 22, 2010, 07:03:01 AM »

Quote
 By Brian Diehl:  Jim, I'm so glad you were able to actually get down the road and have no engine/transmission problems!  Way to go!


I don't think I saw where you mentioned exactly what it was that caused your original transmission ECU to fail.  What was the root cause analysis on that?

Brian, I am not exactly sure how the ECU got screwed up.  As I approached Raton Pass on the way home from Albuquerque, I made a quick decision to pull over and turn on the misters (charge air cooler issues).  For some reason, I kicked the transmission into neutral (a normal process for me at very slow speeds).  When I kicked it into neutral, the transmission seem to react strangely.  When I went to take off, the transmission did not want to shift.  I tried it a couple of more times and after about 4 times, it shifted and we went on down the road.  About 100 miles later, the transmission would not shift out of 10th.  I nursed it to a rest stop and did a bunch of trouble shooting with my Pro-Link.  The results were that the ECU had "failed".  That is when I put the replacement ECU on and ran into the gear ratio incompatibility and got to go home behind the hook.

I am not sure if the ECU has gone belly up or if there is a software issue.  I have taken it along with the wrong gear ratio ECU to the Eaton rep to have them reprogrammed.  My hopes are that the original ECU is not toast.

I still have a hard time understanding how my kicking the transmission out of gear would cause the ECU to "fail"

I will also post this on the thread about the AutoShift problems to keep everything together.

BTW, we just traveled 700 miles and did not have any problems - what is wrong with this picture Grin

Jim
« Last Edit: May 22, 2010, 07:20:34 AM by rv_safetyman » Logged

Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
Blog:  http://rvsafetyman.blogspot.com/
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