Its been brought up in a couple unrelated threads and I want to discuss further. Several small cars use them, mostly European models. Very small displacement but right in the psi range we would need. I think they are all basically just an electric motor coupled to a small gear pump. (Yes, I am aware of the hp requirements to turn a pump.) How would we go about doing it?
I'm thinking some sort of high-revving electric motor with gear reduction to multiply power and reduce rpm's coupled to a gear pump for its low-rpm displacement capability.
The highest displacement hydraulic power pack that I can find is 2gpm, not enough flow and I don't think they're rated for continuous duty.
I'd like to see some more on this as well. The last guy to post in the self-centering thread (from Germany I believe) seemed to have a pretty quick setup. I'd be interested in hearing what he's running.
When applying an electric motor to a mechanical pump, is there an efficiency difference between those gear driven and a factory style? I mean, is there any reason you wouldn't apply your electric motor to one of the common pumps we already use, and dial in the RPM's to create optimal working pressure and flow for what you want? I'd love to have full pressure and flow at idle :smokin:
Then you could use the old power steering spot in belt routing for a secondary/backup alternator
Full displacement at idle, no risk of cavitation at higher rpm's, and being able to steer with vehicle not running are 3 things I would practically give my left nut for. Not to mention freeing up some crankshaft horsepower.
You could always run multiple pumps. I like the idea. In a racing application you have more stress on an electrical system that is already running quite a few things though.
If I had to put together a system today this how I would start.
It would take two pumps and two motors tee'd together with checks.
Oasis air compressors use a 5 HP fan cooled 12 volt motor rated continuos, these should adapt well.
An industrial gear pump sized for your needs. Driven at a constant rpm. Tons to choose from. Wouldn't know specs until electric motors were spec'd out.
I like PSC rams and steer valves. Though I would use a Rexroth D05 control valve for the rear steer.
Relief valve right after pump going back to reservoir. I have a Sun and Hydraforce brands.
Reservoir would be custom built or off the shelf dry sump reservoir with 1 gal. min. cap. The dry sump would have the spinning return to remove air.
Fan and cooler. SPAL and Thermal- something is what I run.
I forgot the alternator that I'm using using but it is for a semi. Its in my build if I don't edit. Depending on your engine speeds and drive ratio you might need two to keep your batteries charged.
Dual batteries, Optima yellow tops is what I run.
You should pull low HP while cruising and charge the batteries and then pull high HP under loads intermittently.
Edit.
The alt is continuos 150 amp up to 9000 rpm , the drive ratio puts the engine at 4000 rpm. So it is in a good output level most of the time. If you rev too high you will need two running at lower speeds most of the time to keep up.
"The XD4000 continuous-duty DC air compressor model possesses dual fans: a 100 cfm fan built into a housing shroud, which works to cool the body and motor of the machine, while providing added protection to the unit, and an internal fan which also cools the modified 5 hp electric motor. This unique cooling combination, found exclusively on our high-quality XD4000 continuous-duty DC air compressor, provides superior operating temperature reduction resulting in an unrivaled 100 percent duty-cycle at 200 psi. "
Does 5hp continuous at 200 pnumatic psi = 5hp continuous at 1500 hydraulic psi??? I don't know, I'm asking?
1hp = 750 watts
125 amp x 12 volt = 1500 watts output = 2hp
2hp electrical output takes 4hp from engine.
Most likely you will be burning 2hp just to circulate oil so you will have to have two alternators to keep up.
10hp max hyd. load = 7500 watts or 625 amps
Why not just get rid of the whole mess and weight of the hydraulic system and just run electric geared linear actuators directly to your steering knuckles
(basically gear driven ballscrews in a sealed housing)
You would have to completely change your thinking... the steering wheel could mount anywhere... all it would need to be is a rotary encoder..
run that to a PLC to control the motors on the actuators
you could change the 'feel' of your steering with the touch of a button, want the rear to work opposite of the front... touch of a button
Build the actuators with a closed loop system and you can have self centering too..
Put separate actuators on each wheel (no tie-rod) and you can have exactly perfect ackerman steering by being able to correct the steering radius of the inside wheel.
Just thinking out loud here.....
Conventional actuators would be too slow or not enough force for high speed use. Not saying it will not work, but can you build it now within a reasonable budget?
10hp should allow most all rigs to steer with large tires in the rocks and at speed with no limitations. A lot of rigs could run on 5 HP with compromise. If you only need one pump, shut the second off when going slow.
Any reason that you would stick with a 12v motor? Why not up the voltage..You would have a better chance getting a motor thats rated for continuous duty that way
It will be under 60 lbs, should have plenty of power, will run at constant speed that is suitable for pumps, can run independently from engine so that you have steering when engine is off, and could probably be muffled to where it was barely noticeable. Takes up about a cubic foot of space. It carbureted though, does that mean its going to flood on steep hills? Or do those little carbs run at any angle like my weed eater does? (I know nothing about carbs.)
The Oasis motors should be 5 HP motor, not pump output.
12 volt allows everyone to install on existing rigs without upgrading everything to make it work.
Ease of one combustion engine has a lot of value and safety over a piggyback.
Electrical systems will also have the added benefit for winching, fans, etc.
I guess I didn't ask my question clearly. That 5hp motor is rated continuous at 200 pneumatic psi but will 1500 hydraulic psi work it harder and therefore make it incapable of continuous duty? Or is continuous continuous no matter what you're doing with it? I ask because they seem to have that caveat in there, "100 percent duty-cycle at 200 psi." So if I wanted 210 psi out of that setup, would it then no longer be continuously rated?
The 200 psi and displacement is designed for the max continuous load that the motor can output or the pump can handle for heat load.
For hydro you would have to set psi and flow to only go to a max of 5 hp.
4.5 gpm at 2000 psi or 9 gpm at 1000 psi or 18 gpm at 500 psi. Just can't use more than the motor can put out. The Oasis motor may very well be rated higher than 5 hp and the pump was the limiting factor. If so you could pull as much as the motor could handle.
I'd have to go with the electric linear actuator too. Gear pumps are 75% efficient so there is a good gain there with the ball screw. And it only needs to work when you need to steer. But I don't see the need for complex electronics? Both the orbitrol and power steering boxes work in the same way, where you steer and the valve work catches-up. In the oritrol its with a leaf spring in the bottom. If that were a two way switch instead of a valve the effect would be the same, Electric steer with good feel.
When I enquired last they wern't sure it would survive mud and water imersion? (Winch Challenge) But if you're in dry-ish conditions the electric ram would work well. And that was years ago, not now, as the actuator manufacturers are always trying to bite the hydraulic guys for market share, so they get more resiliant in construction as time goes on
Can some of these people recommending linear actuators possibly list some places where one would go to buy actuators in the strokes, size, and configurations that we would need?
Is there such a thing as a hydraulic linear actuator? Maybe combining the mechanical advantage of a ball screw drive with a smaller hydraulic motor would relieve the need for such high pump output requirements?
was doing some looking on this topic and stumbled upon this...
Integrated Cylinders
not much info listed on their website, and i have no idea if it's actually feasible for the intended use being discussed here, but it's interesting if anything.
That's just taking the pump and attaching it to the cylinder. That's going to have the same issues we've already discussed.
A electric linear actuator is simply an electric motor attached to a gearset that gears it down to multiply torque and reduce speed which is then attached to a screw that turns inside of the shaft that extends. There are two stages of torque multiplication going on with it. Once at the gear drive and again at the screw based on its motion ratio. (Which incidentally can be calculated by dividing its pitch by its circumference.)
I know next to nothing about hydraulic motors but I can only imagine that they turn with much higher torque than electric motors based on their much more robust design and construction. I imagine that they turn slower, too. Thus I wonder if one could replace the electric motor in a linear actuator setup with a hydraulic motor to achieve higher force outputs? And if so, since the hydraulic motor is now being assisted by a gear drive and screw drive, would it require less pump output than our current setups require? And if so, would it be enough less output to where you could power the pump with a 1 or 2hp electric motor instead of the 5+ that would currently be required?
well obviously, but being packaged together we can assume that the motor and pump they're using are appropriate for this application, and that they could possibly fit the requirements being discussed in here.
I think you guys are underestimating the electric input power required. Yes you only need X HP but you have loss on the pump and loss on the motor driving the pump. High power 12V in a 'reasonable' size has limits.
There is only one motor I have seen in 12V that comes close. It is built differently than most, setup to run very high currents. I just went to his site and he is offering it coupled to a hydraulic gear pump so if I were going to do this I would say this is your best bet.
SS Single with 0.16cu.in (2.64cc) / rev pump - 2.6gpm @2,500psi - 250A, 3,000psi peak - 300A
Notice the specs...that is ALOT of current! If you start to get a bit more fancy with controlling it you would only have high load in use.
I would say best bet is to get a seperate 24V alternator and run 2 smaller 12V batteries from XPS/Odesys/etc in series on a separate system so if your alternator is still a little undersized for peak loads the voltage dips when drawing from the batteries doesn't effect the engine ECU.
I think I agree. I've spent hours trying to find a 5hp 12 volt motor, it doesn't exist. And when you look at the currents required for available 2hp motors you begin to see why. No stock or even high-end 12-volt system could keep up with it if it did exist. No one makes it as a result.
That's why I keep coming back to adding some other sort of torque multiplier into the system. If we did so it might reduce required pump output and allow us to run it on a more reasonable electric motor.
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