Need to know more about power steering

[OilFilter]

I want to convert a truck into something of a plug in hybrid. Remove all the belt drive accessories and convert them to electric. Also need to install some sort of regenerative braking.

I've been a little confused about the power steering system. I know what kind of output the belt driven pump is capable of, but how much does the steering box actually use in terms of flow? I know there is a lot of talk about people converting to small electric hydraulic pumps for PS, but will that work on a truck? Does a truck steering box require too much power? (29" tires)

Can anybody tell me what is actually required in terms of GPM? Is there any flow through the steering box when you are not turning? How much flow is required to make a turn? I would like to have some sort of hydraulic accumulator, I'm wondering if could run the steering from this for any length of time? I'm thinking part of the regenerative braking could be to recharge the hydraulic accumulator for the power steering.

[spdfrk]

I haven't seen much on this topic but there are people out there who have put an electric clutch on their existing power steering to save energy for highway driving.
http://ecomodder.com/forum/showthrea...ing-14952.html

And there are also aftermarket columns with electric power steering too. Lookup EZ power steering.

There are also some Saturns out there people have been yarding parts from to retrofit electric power steering.

[Ecky]

I expect this thread will be of use to you:

http://ecomodder.com/forum/showthrea...ion-32895.html

You might also find this to be interesting reading, though not directly relevant to your question:

InsightCentral.net - Encyclopedia - Honda Insight Power Steering

[OilFilter]

Originally Posted by Ecky

I expect this thread will be of use to you:

That's a lot like what I was thinking. A simple 12v hydraulic pump rated at about 2GPM. Problem is the duty cycle is usually kind of low, like 1 min on, 5 min off.

I thought about an electric clutch, but I like the idea of having no belts at all. Nothing on the front engine pulley.

The other reason I was thinking about a hydraulic accumulator is to possibly install a hydraulic starter. This way I could start and stop the engine more frequently for coasting and idling.

But I have no idea if the same accumulator would have any usefulness for the power steering? It could be relatively simple to rig up a power steering pump to the drive shaft, and engage this during braking. Use that to refill the hydraulic accumulator for regenerative braking.

I may also convert to hydroboost brakes, because it is an old diesel truck (F250) and I will need a pretty large electric vacuum pump to power the brakes. It currently has a belt drive vac pump and vacuum boosted brakes.

[OilFilter]

This is the pump I was thinking about:
edit: Sorry, can't post link, I don't have enough posts yet. It's available at Surplus Center for $200. 1.4 GPM at 2500 PSI, more GPM at less PSI. 1 min on/5 min off duty cycle. 200 amps at 12v. (for 2500 PSI)

If the PS required 1000 PSI or less, it would probably be enough to power it for turns and such. Duty cycle is questionable. Probably puts out more flow than an economy car pump does.

BUT...

If I hooked that pump up to a small hydraulic accumulator, with a pressure switch to turn the pump off when full, will hydraulic fluid continue to flow through the steering box? Would I need some kind of valve to turn the box "off" when I'm not turning?

[iamnotahippee]

If you are using an electric pump that requires 200 amps, you won't be able top delete the alternator. You also don't want top be and killing a diesel. Now it doesn't need to all the time, but off and on sure is hard on them. Do you have a plan for the water pump? Do you have an idi 7.3 or a turbo?
You need to do some math here. If you spend all this money to achieve better mpg, how much improvement can you expect? How long will it take to save what you spent to get there? Unless you need the diesel, you could probably pick up a beater for less than you are looking to spend, save more fuel, and not be gambling with the safety of yourself and others with half baked modifications that may or may not keep your steering and brakes functional.

[OilFilter]

Originally Posted by iamnotahippee

and not be gambling with the safety of yourself and others with half baked modifications that may or may not keep your steering and brakes functional.

There is nothing more "gambling with safety" or "half baked" about this than most of the other posts in this section. Both brakes and steering still work at reduced power with the engine/pumps off. I'm not a little girl, I drove a one ton Chevy with a broken PS pump for years. And I'm not a complete moron, I am capable of working on my vehicle without killing people. An accumulator is a device that saves a hydraulic charge so that you still have power in the event of a pump failure.

Originally Posted by iamnotahippee

If you are using an electric pump that requires 200 amps, you won't be able top delete the alternator.

It's intermittent, and only 200 amps at 2500 PSI. (PS system is less than half that pressure) And 200 amps is still easily doable with batteries; however, you might notice this post is mainly about regenerative braking. Regardless of what the pump motor is rated at, it will only use roughly the same amount of power as those Toyota and other OEM electric power steering pumps people like to use, plus a little more, because it's a truck and not a car.

I may build a bearingless/brushless alternator around the unused crankshaft pulley, much like a lawnmower uses, but it would have a switch to turn it off most of the time. Brakes will also recharge the batteries.

I'm not going to get into the "why" discussion, it's not relevant here. It's just what I want to do. Let's talk about technical facts here. I could ask why you would ever buy a Prius, but...

[Ecky]

Food for thought, but the electric power steering fuse in my car is only 40amp.

[oil pan 4]

Originally Posted by OilFilter

I've been a little confused about the power steering system. I know what kind of output the belt driven pump is capable of, but how much does the steering box actually use in terms of flow? I know there is a lot of talk about people converting to small electric hydraulic pumps for PS, but will that work on a truck? Does a truck steering box require too much power? (29" tires)

http://ecomodder.com/forum/showthrea...ing-29002.html

How much power does it take? I don't know but I am going to find out here pretty soon.

Originally Posted by OilFilter

Can anybody tell me what is actually required in terms of GPM? Is there any flow through the steering box when you are not turning? How much flow is required to make a turn? I would like to have some sort of hydraulic accumulator, I'm wondering if could run the steering from this for any length of time? I'm thinking part of the regenerative braking could be to recharge the hydraulic accumulator for the power steering.

A power steering pump found in Saginaw P1 and P2 pumps can make about 3gpm at idle and pump 15gpm in a P2 at 5,000rpm and 20gpm at 5,000rpm with a P1. Recirculating ball steering boxes work from 800psi to up to 1,500psi. From what I can find most OE setups are limited to less than 1,200psi.

A hydraulic accumulator will not work since the steering box bypasses fluid when there is no power assist needed to turn the wheel.
Don't believe me? Just pull the return hose off the power steering pump and start the vehicle and see what happens.

[oil pan 4]

Originally Posted by OilFilter

This is the pump I was thinking about:
edit: Sorry, can't post link, I don't have enough posts yet. It's available at Surplus Center for $200. 1.4 GPM at 2500 PSI, more GPM at less PSI. 1 min on/5 min off duty cycle. 200 amps at 12v. (for 2500 PSI)

If the PS required 1000 PSI or less, it would probably be enough to power it for turns and such. Duty cycle is questionable. Probably puts out more flow than an economy car pump does.

BUT...

If I hooked that pump up to a small hydraulic accumulator, with a pressure switch to turn the pump off when full, will hydraulic fluid continue to flow through the steering box? Would I need some kind of valve to turn the box "off" when I'm not turning?

Just forget about the accumulator. The power steering system works completely opposite of what you would need to make an accumulator work.

The pump curve for these pumps looks something like 2.5gpm at 0psi, 2gpm at 1500psi and 1.5gpm at 2500psi.

Should draw around 100 amps at 2gpm and 1500psi.
I have a fluke325 amp clamp so I will know precisely how much power its using.
Bailey pumps has the perfect pump 2.1gpm with a relief set at 1,400psi.

You do not want to turn the box off. The steering box is just like every other kind of actuator, when its full of fluid and it gets moved by out side force, it starts to pump fluid. You actually want to open the hydraulic connection between the pressure and return lines when your electric pump is "off".
When you turn the wheel the box is still trying to move fluid around. That is why I am getting a "single acting pump". I am going to try to convert the "dump" valve to normally open. "On" will turn the motor on and close the valve so that all the fluid is forced through the box. "Off" will kill power to the pump and open the valve allow all fluid to bypass.

I found this out when I pulled the power steering pump off my Camaro years ago. I removed the P/S pump and drove down to the parts store because I was 17 (which means I was broke) and had just enough $ to get the pump but not cover the core charge.
I noticed after removing the pump the wheel was easier to turn, I figured fluid was going everywhere, then sure enough when I got to the parts store the disconnected lines had spewed fluid all over the drives side under the hood.