Electric Power Steering

[TrailTamer]

Am I wrong in thinking that a power steering pump will use more hp than the extra load on the alternator with electric?

Id say that depend on what situation.

the PS pump, via drive belt, will use more HP when under load at the instant than with the EPS as the HP loss via the alternator should be considerably less than a PS pump because you have a battery in reserve to handle large current draws. And I don’t think there is an alternator capable to consume more than a PS pump anyway.

PS pump will always win on maximum power consumption. EPS theoretically will consume more power over the time due to losses in converting mechanical power via alternator to electric and back to mechanical power via motor in the EPS. This is with assumption both systems’ output or “work” is equal.

unless you race with battery removed. Lol.

 

[AgitatedPancake]

Hmm this is an interesting conversation. Slightly different application, but it seems like a few of these options may work well. I've got a 75 CJ5 on 31"s I want to convert to power steering. This conversation could really break the normal convention of doing such a swap. I could leave the manual box and add one of these electric column assists (and upgrade the alt as needed), and be done with it. High ratio box should help take some load off the assist versus the quick steering you guys are getting in your UTVs, which hopefully helps with the extra weight it's working against.

Or I could do one of those JL pumps with a power box and not have to add accessories to the engine, but I am still adding a hydraulic system which would be sweet to avoid for the sake of simplicity. Just for grins thinking of other applications as well, does anyone know the duty cycle on those JL pumps?

 

[TrailTamer]

or use the JL pump as a lift pump feeding into the main ps pump

 

[HYDRODYNAMIC]

Just because it has a 125A fuse I would not assume it will consume that much power continuously. I would venture a 80-90A @ 13.5V would be a better estimate. Likely not more than 1.2 kW

And I would guess the pump drive is going to rely on the fluid to cool it at those power levels. That may cause de-rating if you try to use it in an off-road application.

Regular hydraulic systems don't consume max power continuously either. I think his comparison was just meant to compare peaks.

I agree, I don't see how the small EPS motor housings are going to be pulling anywhere near the fuse rating on a continuous basis. I was trying to keep the math simple for full hydraulic, full electrical, or hydroelectric to show if they were in the same ballpark. Its a mess of efficiencies. Also depends on where you want to call out the HP. Then you can choose intermittent vs peak. Brushed vs brushless. Vane vs gear. restrictive vs free flowing.

Full hydraulic is going to be less than 85% efficient to achieve the pump flow and pressure vs mechanical input after the belt that is 95% efficient. In some systems it might be 50% using a fast spinning big vane pump and restrictive plumbing. That means the pump is pulling double the HP off the engine compared to the rated pump output. Then factor in 85% or less after the pump for directional flow control restrictions.
5 HP at the crank x .95 = 4.75 HP at the pump x .5 = 2.4 HP in the oil x .85 valve = 2HP at the wheels

In a hydroelectric the pump should be near a constant 85% efficiency after the 75%-80% brushed motor efficiency after the belt and alternator. Then another 85% for directional flow control.
5 HP at the crank x .95 = 4.75 HP at the alternator x .60 = 2.85 HP in the battery x .75 for the motor = 2.13HP at the pump x .85 = 1.81 in the oil x .85 for the valve = 1.54 at the wheels

Full electric is going to be around 75%-80% efficient for a brushed motor. No account for the mechanical gear efficiency.
5 HP at the crank x .95 = 4.75 HP at the alternator x .60 = 2.85 HP in the battery x .75 for the motor = 2.13HP at the wheels

 

[ManKrawler]

Have you considered just using a bigger unit? The Vue unit is 500 watts. The f150 is over 3x that at 1750. I bet there's units out there between those as well.

Don't want to bleed to far into sxs.. but already have a steering rack solution that is working, and besides, if you fab in a new rack may as swap the knuckles and steer from the front with a Howe rack and a TC pump. At that point I realized it should have been another buggy build.

Amperage draw is an issue and I wanted to know what this supposedly 850W unit pulled so I swapped the 60 amp mega fuse for a 40 amp breaker and have not popped it yet. Worth mentioning an alternator could be driven off the stator side of the crank, powering any larger steering unit.

But, the motors/controllers get warm and shut off and it is not a charging system issue at this point I am certain. We used to essentially have front spools, and it was just awful; we are now running prototype units much like a TruTrac, and they run much longer before steering failure. Allow them to cool and they come back, the longer they cool the further they run, it's a linear relation. This is an 850W in line (vue like) unit steering flat 35's on a SXS. I think this experience should be considered when considering for a full sized rig. If I started over, no way I would run electric, I am pretty tired of it.

My theory is the constant feedback on both ends, tires constantly working and driver constantly steering, simply overworks the motor and controller. These units see no where near that type of force in a road application, and while I am sure there are exceptions I am not convinced if you took my 850W unit and doubled it's capacity, draw, and output the issue would be solved.

Always interested in feedback, my experience is limited.