Need to know more about power steering

[OilFilter]

Originally Posted by oil pan 4

A hydraulic accumulator will not work since the steering box bypasses fluid when there is no power assist needed to turn the wheel.

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.

Originally Posted by oil pan 4

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

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?

[OilFilter]

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

[oil pan 4]

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.

[OilFilter]

Originally Posted by oil pan 4

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?

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.

Originally Posted by oil pan 4

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.

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.

[JRMichler]

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.

[oil pan 4]

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?

[OilFilter]

Originally Posted by JRMichler

Keep in mind that a power steering system needs a manual backup mode that works with any possible power assist failure.

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.

Originally Posted by oil pan 4

Put together a parts list we a curious to see what you are using and how much it will cost.

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.

Originally Posted by oil pan 4

Do you know anything about hydraulic controls and instrumentation?

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

[oil pan 4]

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.

[OilFilter]

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.

[oil pan 4]

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.