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OG13 King
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Discussion Starter #1 (Edited)
After doing a test run at TDS, my biggest compliant is that the power steering pump will not keep up with how fast I want to turn. It's not even in the ball park.

I use two motor driven Howe pumps, one for the rear, one for the front.
Both pumps were juiced up by PSC and supposedly crank out 4 gpm.
Both rams are 2.5" bore, 1.5" shaft 8" stroke.
The orbital is set up for 2-1/2 turns lock to lock.

I want to connect both pumps together (-6) into a common (-8) high pressure line and then run the line in series through the rear steer valve and orbital and then to a common reservoir tank. The reservoir tank would have one line going in (common return) and two lines coming out (individual suction).
This would double the speed without increasing pressure, which on paper would be just fine with me.
The rear steer would also be twice as fast which might be a bit fast, but I would take the trade off for a faster front.

I talked to Sean at POS and he recommended a different pump (6 gpm) which would replace the two I have now. That would make it 50% faster which might be fast enough, but it's another level of modification.

Is my plan to run two pumps together going to work? :smokin:
 

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What I would try: Not exactly what would work...

Put a check valve on both pressure lines. Set one pump to have a bit more pressure than the other. Run the rear steer off before the check valve. Run only 1 res.

Shouldn't cost too much to do and just might work...:confused:
 

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I've been discussing this for a while with a couple different guys because I'm thinking about running tandem pumps for a different reason (more pressure) but it should (theoretically) work.

My current steering system is one 6 gpm pump, running to the rear steer valve, then to the orbital, then to the cooler, then to the reservoir, and back into the pump. It's heading into its second year set up that way, and I'm very happy with how it works, so I'll definitely "bless" that portion of what you're pondering.

As for the two pumps, if you have a check valve on the outlet of each, and then T them together (ideally, IMHO, more like a Y for reduced turbulence, but you take what you can get) into one high pressure feed line, you should be able to treat that as if it were the outlet line from one big pump. The flow output will probably not be exactly pump1 + pump2 = flow; I suspect it'll be more like (pump1 + pump2) * .85ish = flow, but I think it'll work. Suction lines will need to be legitimately independent, and with one return, the suction lines will have to be sucking from a single reservoir, so that may necessitate a custom reservoir. If the suction lines are T'd together coming off the reservoir, I think you'll have at least off-and-on cavitation problems.

Couple of questions, just for giggles...
Will your rear steer control valve protest having downstream pressure? Mine doesn't care, but some valves get upset about that.
Can you cram 7-8gpm through the rear steer valve?
I forsee that being the (flow) limiting factor, potentially, but with two pumps tied together, you should be able to get more fluid flow than even the big 6gpm pumps can make.

Edit: If you decide to try it (I would, but I only have one pump on my engine, and the mounting of the second pump is what's tough for me to come up with, so I haven't bothered yet) and find that the rear steer is too fast, you can always add a flow restrictor into one of the lines from the valve to the cylinder, to slow the rear steer down a little.
 

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OG13 King
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Discussion Starter #5
The rear valve would definitely take it as was made for -8 lines going in instead of the -6 that I use. I wonder about the Charlin orbital valve.
I could put the rear valve first or second. Does it make a difference?

I was thinking of cobbling it together at first with tees at first to see if it works.

Scott, do you feel that you can turn as fast as you need to without exceeding the flow rate?
Do you have the roughly the same ram dimensions and is your orbital as fast as mine?
 

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Hvy_Chevy said:
I'd say just buy a larger pump.
Does 6gpm from one manufacturer equal 6gpm from another? How much back pressure do they test it at, and at what RPM?

Who makes the best pump?

JR, when are you not able to steer fast enough? in prerunner mode? in trying to save a roll mode?


I'm really surprized that it isn't even in the ballpark, I mean the piston area is only 3.14in^2 if the stroke is 8 inches lock to lock that is about 25in^3 or .11gallons of volume. So at 6 gal/min it should take you 1.1 seconds to go lock to lock. That's about as fast as you could spin the steering wheel around 2.5 times even if it's not connected to any hydraulics. It's just a little slower than the trophy trucks running the best Howe racks can go lock to lock.
 

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sorry I lost part of my reply somehow.

The other thing is if the problem is at low RPM, using one of the TC based pumps will work better than the P based pump, because the TC pump will put out full flow at a lower RPM, especially when the pump is modded for really high flow.
 

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OG13 King
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Discussion Starter #8
I can hit the limit just backing it out of the driveway, I mean it's really annoying.
On the old car I used a 2"x 8" with a 1-1/8" shaft. The pump had not been tweaked and it still kept up with my turning speed.

I just checked it; at 900 rpms it's about 3-1/2 seconds L to L.
 

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I don't see how it would steer any different than it did with the old rig. I know the old rear ram was really small in diameter compared to your new one but I was thinking that the area inside your new front ram would be close to the same as your old one, thus acting the same as before.
Were younot happy with the steering on the old rig??
 

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That is pretty slow. I think you must have a serrious restriction somewhere, like a line that was put together wrong or got kinked. Your old piston area was 2.73in^2 or about 13% smaller than your current ram. if they use the same amount of travel to go lock to lock then it should be 13% slower with the same pump. I would be curious to see the result if you did the same test at 2500 rpm.
 

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OG13 King
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Discussion Starter #11
The old one was acceptable.
The new ram does displace more volume, in fact when ordering the new orbital valve we had to get the fastest (biggest?) one to make 2-1/2 turns work with the new, bigger ram.
I don't know, maybe it's me but I could use something faster.

What would be a *normal fast* time L to L ?

Since the front and rear are the same, I checked the speed using the rear ram, just hold the valve open and time it.
 

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OG13 King
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Discussion Starter #12
OK.
This time, I went out with a timer instead of counting one thousand one... :flipoff2: .

2.5 seconds at 900 rpm.
1.5 seconds at 2500 rpm
I tried to account for my reaction time.

It doesn't look that bad. I don't know why it's bugging me, I guess I'm just in a hurry to steer this fawker.
 

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You say connect them in series.

I would say you want to connect then in parallel for more GPM.
A pump is a pump for the most part. Most Fire engines have two stage pumps, and can be switched for either pressure of volume. Series for pressure and parallel for volume.
 

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Bigger pump ~ K.I.S.S. man. Life is to short for custom mounts and pumbing nightmares and any 'what ifs' (i.e. time, fab, room, failure possibilities) that go along with it.

I'm thinking that a 6gpm will give you significantly more than a 4, and I'm not talking about the obvious 50% more volume. I've programmed industrial plating facility's were a 1 HP pump made a bath infinently more productive than a 3/4 HP (both pumps NEW). Meaning, yes its more powerful, but the slight up in power made HUGE jumps in productivity usefulness.

Admitadly, I'm not savy on the steering side of the equation, but from what I've seen in other applications, little differences in pump size gives huge results.

The flow output will probably not be exactly pump1 + pump2 = flow; I suspect it'll be more like (pump1 + pump2) * .85ish = flow, but I think it'll work. Suction lines will need to be legitimately independent, and with one return, the suction lines will have to be sucking from a single reservoir, so that may necessitate a custom reservoir.
I'll also agree with Scott, chances of getting 100% of two small pumps is unlikely ~ and if it fails to perform, where will you be then? Even more pissed and saying 'hine-sight is 20/20 ~ btw, anyone want to buy this totally 1-off custom res?'

You have a super bling machine. You stuck with what works. You've been waiting to get this on the trail and finished up. I say K.I.S.S. ~ and get to the trail that much faster.

Sorry for the spelling. In a hurry.
 

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OG13 King
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Discussion Starter #18
heep86 said:
can you buy/make smaller pulleys? for the existing setup. is the turning speed acceptable if you rev the motor a little bit?
Yeah, I think at 2,500 rpm the turning speed is fine.
I haven't got a lot of positive response for gearing up the pumps, though.
 

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JR - I am running a similar setup. I have station's 6 gpm pump going to a flow control valve and running both F & R circuits. I am also using a 2.5x1.5 cylinder (mine is a 10" stroke but wth). With the fcv biased all the way to the front it will turn every bit as fast as I can turn the wheel. Mine is set for closer to 3 turns lock-lock, using an 11.2 ci orbital. If I were you, I would purchase one of station's pumps to replace your front pump, and leave your rear circuit alone. This will be the easiest solution, and give you great results!
 

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I'd run the 6gpm pump. I loved it in my rig, was plenty fast for bombing down fire roads, and wheeling in deep snow.
 
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