This^, unpredictability in your steering speed and/or pressure are generally considered to be a bad thing.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.
depends how many rotations you have from lock to lock.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.
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.depends how many rotations you have from lock to lock.
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.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'm not following your logic on this. Comparing apples to apples:it will just make more heat/take more hp to turn and ad unwanted extra flow to system
We are talking about an open center system right?I'm not following your logic on this. Comparing apples to apples:
Normal gear pump rated @ 11gpm
According to HERE
You are consuming 19.253 HP
2-stage gear pump rated @ 11gpm
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.
CorrectWe are talking about an open center system right?
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.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.
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.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.
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.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.
You're right. It's been so long since I've dealt with this stuff I'm forgetting my facts. Thanks.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.
It seem like anything with steering you need to sacrifice a newborn for specs. :shaking: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.