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I also had wondered about running pumps off MDT cummins on my 12v, but also that also can give me the engine driven air compressor. :evil:

I like how people think out of the box sometime.
 

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Yeah, necropost I know, but I have been following this thread for awhile and slowly planning my build out. Recently I have been getting parts together and I ran across these 2-stage "log splitter" pumps:



First, some specs:

Price: ~$120-250
RPMS: 3600
PSI: 3,000*
Inlet: 1"
Outlet:1/2"
Gear type pump
Overhung load up to 90 lbs!!!
Additionally, they are a bit smaller and slimmer than normal gear pumps. The port sizes are also more optimized for the size rams we use.


As we all know, we don't need a lot of force to turn our wheels. We need more than conventional vehicles, but not massive tonnage levels of force. We only need that when we get into the rocks and such. Most of the time a little boost is all we need, especially when we are moving forward at any small amount of speed. Conversely, we usually aren't cranking on the wheel super fast when we are going slow(at least I'm not). Unless you are a comp driver, there usually isn't a need.

That's exactly where a pump like this would shine (I think). They put out high flow and low pressure until a preset resistance is felt which seems like it can be around 400psi to 900 psi. Once that preset is reached, the flow drops and pressure goes up to 3,000(or whatever you have your relief set at. So you are really only using high pressure if and when you need it, making for an overall safer system with less heat and wear. When the pressure goes up like that, the flow drops off significantly(like 1.5-7gpm depending on pump). I think that means if you were driving fast and hit something, causing a pressure spike, this would help mitigate the steering kicking back on your hand.

Additionally, the 90 lb. overhung load rating on the Dynamic brand of pumps hopefully puts to bed some concerns about running pulleys off of these.

Another bonus is that the pump body itself is only 2 5/8" wide. The mounting face is 2 7/8". Packaging could be a lot easier with this pump than some others.
 

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Pressure is resistance to flow. If there is little pressure required, like driving on the highway, then there is only minimal pressure being developed. It is also very unnerving when you are steering your rig and suddenly the flow considerably drops off. When this happens the steering will slow down considerably, and you won't know when this is going to happen. This pump seems like the worst type of pump to use for steering. That said, I think you should try it and report back.
 

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those 2 stage pumps are used when you dont have enough power to drive big single pump for cylinder speed.

i have been using gear pumps in my rigs and they are super simple, cheap run cooller and dont have any moving valves inside.
they dont burn up like normal steering pump.


they do wear but its more slow wear
usually low rmp power fades away first.

current buggy has 1:1 driven 19cc/rev gear pump and now after couple years of hard wheeling pump has dropped some low rpm power.
 

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Pressure is resistance to flow. If there is little pressure required, like driving on the highway, then there is only minimal pressure being developed. It is also very unnerving when you are steering your rig and suddenly the flow considerably drops off. When this happens the steering will slow down considerably, and you won't know when this is going to happen. This pump seems like the worst type of pump to use for steering. That said, I think you should try it and report back.
This^, unpredictability in your steering speed and/or pressure are generally considered to be a bad thing.

Aaron Z
 

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I get where you guys are coming from, but I don't think it quite as unpredictable as it's being made out to be. I know when I am binding or am going to be putting some strain on the steering. I'm pretty sure under normal driving conditions, this thing would never kick into Hi pressure mode. Even if it does, I ran the calcs and it drops steering rate to around 1 full rotation/second, far from unacceptable.
 

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I get where you guys are coming from, but I don't think it quite as unpredictable as it's being made out to be. I know when I am binding or am going to be putting some strain on the steering. I'm pretty sure under normal driving conditions, this thing would never kick into Hi pressure mode. Even if it does, I ran the calcs and it drops steering rate to around 1 full rotation/second, far from unacceptable.
depends how many rotations you have from lock to lock.
and like i said its ment for low hp engines/e-motors witch dont have enough power to run big pumps for pressure. it gives no advantage over single pump when you have power to turn single big one. it will just make more heat/take more hp to turn and ad unwanted extra flow to system
 

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depends how many rotations you have from lock to lock.
Absolutely true. I am shooting for around 4.5, so the numbers work out well for me. For someone trying for less turns lock to lock, it wouldn't really make sense, although they do have models throwing out 28 GPM, so that's more about sizing your system properly.

and like i said its ment for low hp engines/e-motors witch dont have enough power to run big pumps for pressure. it gives no advantage over single pump when you have power to turn single big one.
I get where they designed the pump for low HP motors, and to me, if it can perform the task we need, so much the better. The pump I am looking at only consumes ~5-6 HP-ever. As the draw rises on the low pressure side, it kicks down and only runs the high side and the power required drops off. Compared to a similarly specced regular gear pump which can pull down as much as 20-25 HP, that's less loading, system wear, and issues. Here's a chart showing (representative) power demand curves. Also, I have put in number overlays over the image because the originals are so hard to see.



So to summarize, the advantages as I see them are:

-Rated for overhung load(pulley)

-Smaller packaging

-Appropriately sized ports-large inlet; outlet sized closely with Orbitrol inputs

-Lower HP, less power to run, less wear/tear



it will just make more heat/take more hp to turn and ad unwanted extra flow to system
I'm not following your logic on this. Comparing apples to apples:

Normal gear pump rated @ 11gpm
3,000 RPM
3,000 PSI

According to HERE

You are consuming 19.253 HP


2-stage gear pump rated @ 11gpm
3,000RPM
3,000PSI
According to chart above, it is consuming ~6 HP

The rest of the time, the same logic that applies to an "idling gear pump" says that the pump only consumes 5% of max horsepower (see same link above for that reference). The 2 stage cannot add any extra flow to the system any more than the "normal" gear pump which is also always putting out 11gpm. It actually flows less because it disengages it's low pressure portion while the "normal" gear pump is always spinning full blast.

So what this 2 stage pump is doing is costing us less horsepower across the board no matter what, especially when we are using it to create the most pressure.
 

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I'm not following your logic on this. Comparing apples to apples:
Normal gear pump rated @ 11gpm
3,000 RPM
3,000 PSI

According to HERE
You are consuming 19.253 HP
2-stage gear pump rated @ 11gpm
3,000RPM
3,000PSI
According to chart above, it is consuming ~6 HP
The rest of the time, the same logic that applies to an "idling gear pump" says that the pump only consumes 5% of max horsepower (see same link above for that reference). The 2 stage cannot add any extra flow to the system any more than the "normal" gear pump which is also always putting out 11gpm. It actually flows less because it disengages it's low pressure portion while the "normal" gear pump is always spinning full blast.
So what this 2 stage pump is doing is costing us less horsepower across the board no matter what, especially when we are using it to create the most pressure.
We are talking about an open center system right?
We have a tractor that has 8.3GPM available in an open center hydraulic system for the implements (separate from the 4.9GPM that the steering has dedicated to it), when the hydraulics are not in use and the hydraulic fluid is warmed up the system sits at about 250PSI (per the gauge that I have teed into the line feeding the loader valve). Using the Surplus Center calculator (Surplus Center) it is using 1.4 HP to circulate the fluid when I am not actually using a valve.
If you had a 11GPM pump on a system with a similar "idle pressure", it would use 1.8HP to circulate the fluid when you aren't using any of the valves.

Aaron Z
 

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4.5 lock to lock and 1 rotation in 1 second will be slow and even for small tire turning you have to spin your wheel a lot.


2 stage will take more power at same psi/flow and only because you are spinnig extra pump too
like your link says
Formula: HP = PSI * GPM / 1714

and in the open center orbitrol you are only using amount of flow you need and rest is returned to tank
 

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We are talking about an open center system right?
Correct

We have a tractor that has 8.3GPM available in an open center hydraulic system for the implements (separate from the 4.9GPM that the steering has dedicated to it), when the hydraulics are not in use and the hydraulic fluid is warmed up the system sits at about 250PSI (per the gauge that I have teed into the line feeding the loader valve). Using the Surplus Center calculator (Surplus Center) it is using 1.4 HP to circulate the fluid when I am not actually using a valve.
If you had a 11GPM pump on a system with a similar "idle pressure", it would use 1.8HP to circulate the fluid when you aren't using any of the valves.
The Metaris calculator I linked is coming back with 1.21HP for the 8.3GPM and 1.925HP for the 13.2(8.3 and 4.9). Seems like they match up close enough to the Surpluscenter number and the chart I posted.

4.5 lock to lock and 1 rotation in 1 second will be slow and even for small tire turning you have to spin your wheel a lot.
To clarify, my system is based on a 2 turns per second rate, but when the flow drops off(Hi press side engages), the GPMs available are enough to support 1 turn per minute at 1500 rpm. As it climbs to 3,000rpm I have full flow at the 2 turns/sec. rate.
I set my steering up with a good amount of turns lock to lock because my rig is going to see speed as well. I don't need twitchy rock crawler steering when I'm going fast. The greater turns lock to lock helps keep the steering tame under those conditions. I based the choice on the Hydro steering bible:

"Depending on vehicle usage - street driven, trail only, rocks, mud, etc. and personal preference / driving style this number will vary - usually from about 2 to 6, with 4 being a reasonable value for street/high speed driven rigs and 2-3 for dedicated trail/rock rigs."
 

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ZF PS pumps?

I stumbled across those ‘ZF’ aluminum PS pumps. They looks interchangeable with TC pumps, same mounting bolt patterns (but spacing & bolt hole ID unconfirmed), same shaft diameter. Application: 2003-up Dodge Rams with Cummins. They’re supposedly better than the older cast iron pumps as mopar superseded them with those ZF pumps. They’re commonly identified by their bolt-on plate on back side. They can be bought complete with reservoir (looks big, for OEM anyway) for under $200 on rockauto.

Anyone looked into them yet?



 

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Discussion Starter #514
First thoughts are diesel rpms being half that of gas engines, but it's possible they're spinning it faster with a pulley. I have a 2016 Cummins so I'll look under the hood when I get a chance. The bolt-on back plate would imply possibly higher operating pressures.
 

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First thoughts are diesel rpms being half that of gas engines, but it's possible they're spinning it faster with a pulley. I have a 2016 Cummins so I'll look under the hood when I get a chance. The bolt-on back plate would imply possibly higher operating pressures.
They either use a smaller pulley or its twice the size to flow twice as much as a "gasser" pump to compensate for lower engine rpm.

It'll bet on option 1.
 

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I did read through the other thread and what @patooyee & @jpf_412 said don’t make sense. Gassers & Diesels have similar idle speed so why they’ll be any significant difference beside likely more pressure required to steer with ease under the heavier Cummins engine.

If I read correctly automotive pumps simply bypasses roughly 1,500 rpm and above.
 

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Discussion Starter #517
I did read through the other thread and what @patooyee & @jpf_412 said don’t make sense. Gassers & Diesels have similar idle speed so why they’ll be any significant difference beside likely more pressure required to steer with ease under the heavier Cummins engine.

If I read correctly automotive pumps simply bypasses roughly 1,500 rpm and above.
You're right. It's been so long since I've dealt with this stuff I'm forgetting my facts. Thanks.
 

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Discussion Starter #519
It begs the question of why though? Presumably that pump may operate at a slightly higher pressure, but I doubt flows much more, which is what most are wanting. I wish there was a way to find specs.
 

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It begs the question of why though? Presumably that pump may operate at a slightly higher pressure, but I doubt flows much more, which is what most are wanting. I wish there was a way to find specs.
It seem like anything with steering you need to sacrifice a newborn for specs. :shaking:

To answer your question; are ZF PS pumps an option to use? More modifiable/hot-rodding ability? Viable alternative?

On a google search, the ZF pumps are commonly used in VW, Audi, BMW, Porsche, Mercedes and some Volvos since ~80’s. Few sources (unverified) claims the ZF pumps are regulated at ~1,600 psi
 
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