Need to know more about power steering
 

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.

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.

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

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.

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?

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.

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. :rolleyes: An accumulator is a device that saves a hydraulic charge so that you still have power in the event of a pump failure.

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...

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

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.

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.

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.

Alright, what about some solenoid valves around the box to bypass fluid when it isn't needed? Or a solenoid to turn the accumulator off when no power is wanted.

From my googling I get a rough number of 2-4gpm of flow requirement for PS boxes. No idea what mine actually uses. But let's say you have a one gallon accumulator at 3000 PSI and your steering box needs 3GPM at 1000PSI. You should be able to have full power steering for 1 full minute with that reservoir and a regulator and no other power input. That would be much more than one turn or stop. And I really only need power steering when the vehicle isn't moving, any other time the solenoid valves could be off.

They have been doing a system like this for the hydroboost brakes in bigger trucks recently. They have an electric hydraulic pump and a small accumulator in the event of power loss. I'd like to do my brakes like that with a totally separate pump for it.

I'm just curious, how do you plan on turning your pump on and off? Manual switch? Or?

Another thought, maybe the steering box could be deleted, and instead use hydraulic steering rams?
2x8x1.25 DA DOUBLE ROD HYD CYL

They shouldn't flow when not being used, right? I think the control valve may be very expensive though.

This is the hydraulic pump I was looking at:
12 VDC 1.4 GPM 2500 PSI HYD PUMP UNIT
I might go with 24v instead of 12v. Could also probably add some sort of cooling fins to the motor to help the duty cycle. At only 1000 PSI it probably uses quite a bit less than 200 amps and has a slightly longer duty cycle.

If I had a big enough accumulator, I could use a hydraulic motor to assist the engine for acceleration as well as being a starter. This is what they are experimenting with for hybrid systems in big trucks.
Something like this would be really sweet:
25 GALLON VICTOR PISTON ACCUMULATOR 13069-J :D

Hydroboost is from the late 70s at the latest, it is not new.
The steering box by passes up to 15gpm when its in full by pass and develops minimum pressure.
If you try to give the power steering box fluid from an accumulator the fluid will dump through the open passes of the steering box in a few seconds.
When you are not using power assist the steering box goes to full by pass and the pump only develops no more than 200psi.

Do not power the brakes with anything but the master cylinder. I have worked on equipment that uses hydraulic power to actuate the brakes. Just don't do it.
For one the hydraulic brake proportioning valves cost around $800.
Why alter the brake system when you can power the brake booster with a $60 vacuum pump with tank and its a fail safe?
If you lose hydraulic pressure on direct acting hydraulic pressure fed brakes you have no way to stop.
Same thing with the ram steering, if you lose pressure you have no way to change direction.
Brakes that are tied in to the main hydraulic system and ram steering are fine for equipment that moves at very low speed. They are not for a motor vehicle.
This is why all on road vehicles have mechanical linkage to steer the wheels. Its required by law.

How are you going to get a hydraulic motor to move the vehicle?
These are fairly large, very expensive and heavy.
Accumulators are expensive and very big and you have to have some where to put all that fluid when not in the accumulator.

The most efficient brake system is a vacuum boosted master cylinder. You can power them for free with engine vacuum from a gas engine or power it with a vacuum pump.
How can you do better than free?
Then if you EOC you can use a small vacuum pump as a backup.

I'm talking about hydroboost brakes as I have said over and over. They run off the power steering system and require very little flow. An accumulator, even a small one, would work fantastically as part of this system. It is what they are using from the factory on at least some medium duty trucks now.

And hydroboost brakes work better than vacuum brakes.

I was mostly joking, but all the assumptions you are making are wrong. Just browse what Surplus Center has to offer. Hydraulic motors are stupid cheap and relatively small. A hydraulic motor is a pump and a pump is a motor, depending on whether power is being input or hydraulic pressure applied. A hydraulic motor could be tied to the engine like a belt assist hybrid, or some other place in the driveshaft. It allows for easy regenerative braking into an accumulator, which entirely removes the need for batteries in a hybrid. They are already doing this in big trucks, google hydraulic hybrid.

Yes, accumulators are expensive, but so are batteries, and they last much longer. Accumulators can be built with nothing more than heavy pressure vessels and some plumbing.

Keep in mind that a power steering system needs a manual backup mode that works with any possible power assist failure. That includes loss of hydraulic oil, loss of the pump, failure of any hose, and failure of any single part in the system.

Rather than reinvent power steering, you would be far better off to convert it to manual steering.

I have hydroboosted brakes in my old diesel suburban.
When I put the diesel engine in a newer nearly rust free one I will not be moving the hydroboost. I will use the existing vacuum boosted brakes in the new suburban.
Hydroboost is nice but I am over it.

Put together a parts list we a curious to see what you are using and how much it will cost.
Do you know anything about hydraulic controls and instrumentation?

You're right, the ram steering wouldn't work for that reason, but no, I'm not ever going to drive a truck without power steering again.

I might post some updates along the way but I do not plan on doing a detailed write up. I'm far from the first person to ever convert to electric PS. It does seem like maybe you and I are the first ones to ask how much flow is really needed.

There are really very few parts involved, and most can come from Surplus Center at surplus prices. It's just standard hydraulics more or less...it's just that a steering box is different than most other hydraulic "stuff".

I do think that a hydraulic accumulator is a good replacement for at least some of the battery bank in a hybrid, due to the extreme cost of batteries and limited life. Think of it kind of like an ultracapacitor, but cheaper. It's a really good way to reabsorb the braking power. But putting it back into the steering doesn't help a lot either, since the steering really doesn't use a lot of power with an electric pump.

Much of my interest in hydraulics for the truck has to do with the fact I want a hydraulic starter. It would crank the engine at darn near idle speed for instant starts, and have a much higher duty cycle than electric starters. I'm also looking into electric oil pumps for the engine and trans to keep the oil flowing while the engine is off for only a short time. During my normal commute, I can coast for up to 6 miles in different places with the engine off at the speed limit. I want to get rid of idling almost entirely.

Yes, quite a bit. Not quite as much about automotive PS systems though.

Have you calculated how much power you can get out of an accumulator?

What do you think the size, weight and cost of an appropriate hydraulic motor to move a vehicle is going to be?
You say they are small and cheap, I want to know how small and cheap.

Basically anything you can do with an electric motor, you can do with a hydraulic motor. HP for HP, a hydraulic motor will be smaller than an electric motor. It can be a less efficient way to transfer power, but, that depends on how the system is setup.

Do some looking around here:
Surplus Center

This motor is just one example:
5.3 cu in PARKER MZG3AB876S1 HYD MOTOR
Relatively small but moves 37 horsepower at 1800 RPM! That is of course if you have the flow rate to back it up. You'd have to have a BIG accumulator for something like that, but say you only need it for 30 seconds to accelerate, that's not a ton of of flow. I've heard that UPS is trying this in new delivery trucks.

Many different motors are available in different price ranges, efficiency, size, pressure, etc.

That's how I'm going to do my hydraulic starter. A motor belted to the engine through an electric clutch. It could also assist with movement with a large enough motor. The electric starter will remain as a backup.

They also make hydraulic wheel motors, which would be FANTASTIC if they could be built into the front wheels of a RWD vehicle, but would create a ton of logistical problems.

Main problem I see with that hydraulic motor is its only going to make like 80 foot pounds of torque.

I will tell you the same thing I told "stillsearching". If you want to make a truck a hybrid with some kind of funky fwd, start with a 4x4 truck, convert the transmission to rwd and attach a motor to your front axle via a drive shaft.

But if you gear swap the front axle to something like a 5.xx gear set then you can get about 400 foot pounds of torque at the wheel up to about 35mph. Which would be pretty lethargic.

Huh??? :confused: You can get a hydraulic motor in almost any RPM and torque rating you could ever want. If you find a good deal on a motor that isn't perfect, gear ratios, or pulley ratios, are extremely easy to change. Hydraulic motors are available in high speed, low speed, high torque, and low torque. Just like a gas motor. Your post doesn't make any sense.

But for that matter I am not talking about a complete engine replacement, 80 ft lbs of torque is a LOT if it's just a booster.

Charles Gray, the EPA head of the hydraulic hybrid work (2006) with Parker Hannefin and the University of Michigan as well as Ford, stated that he could hold a 500 horsepower hydraulic motor in his hand.

Check US 7677208, my patent for a hydraulic in wheel drive as well as 10,000 other applications, including the ability to store electricity.

Here's a link
http://www.google.com/patents/US7677208

regards
mech

Y'all are overcomplicating it again.
 

Reusing the original power steering pump and just adding an electric motor via belt drive or shaft coupling is SOP in the EV conversion world. I have one friend who did this on an electric Dodge Dakota, but he only turns the pump on for low speed parking maneuvers. If he's moving at any speed, no power required. Another friend used the Toyota MR2 electric power steering pump in his electric F250 pickup. It stays on more of the time, but also does the job fine.
Only caveat is that if you turn the pump on in the middle of turning the steering wheel, it can move suddenly with a violent jerk.

I was talking about that one small motor you linked.
I asked what motors you think would be good for doing a hydraulic hybrid, you linked that little motor. I don't think its big enough.

Did you miss the part where I said "this is just one example"? I'm not going to write you a complete hydraulic conversion manual.

But more on topic, yes, a 37hp motor would do WONDERS in a hybrid. That is likely enough power to move a pickup truck down the highway at 55mph. It could also probably accelerate to at least 25mph without any additional power. An equivalent sized electric motor would cost more, weigh more, be physically larger, and need hundreds of amps to power it.

I'll remind you that the diesel engine in my F250 was rated at only 155 horsepower in 1983. Yet that was enough power to tow 15,000lbs.

That's really cool, I've always wondered why MFRs don't put more effort into wheel motors of some type, seems like it could be not only more efficient, but cheaper to manufacture.

I would love to see the day I could buy such a thing as a conversion part for other vehicles. Much like all the electric motors that are available these days. I think trucks really need a way to reuse their braking energy, and batteries are not a complete solution.

It probably would be relatively easy to directly couple an electric motor to the stock PS pump and spin it at idle speed. No question that would be enough power. And it would sure make the plumbing easy! Might be able to find a motor with a longer duty cycle than that other pump I was looking at.

The largest motor that I could find and would fit is 3/4hp that weighs about 33lb. and cost $400 for a decent one or you can buy a cheap $150 motor every few weeks as they burn up.
It might have a very long duty cycle if it were not in a 200'F environment.
I already know it takes about 200 watts to spin the power steering pump over at close to idle speed at no load (not trying to turn the steering wheel) just letting all the fluid bypass.
Note pump speed may be slightly higher than crank speed, in at least some vehicles the power steering pumps appears to be slightly over driven. So pump speed may be closer to 1000rpm.
If it takes 1000psi to drive 2.5gpm through a steering box that is about 1.5hp when turning the wheel.
Not a problem for a 12v DC motor at room temperature or start up, in those conditions you could run a motor like that at 200% load for a minute or 2 with no ill effect. But start with the motor at 200'F warmed from heat coming off the engine, I would expect that motor to be scorching hot after maybe 30 seconds of use and if it has a thermal over load it will trip.
This is why I am going to use a hydraulic power unit slung down low and forward, maybe even just behind the bumper (not next to the scorching hot engine) and only weighs about 20lb.

This mod is fairly common to do in electric vehicles, but the motor driving the power steering pump isn't sitting near 900'F exhaust manifolds.