Fun with manual racks!!!

[R/T]

No, I used a manual rack from a K-Car in my Daytona. Not a Pinto rack...

This rack was from an unfinished Shadow drag car that was parted, I had it laying around and figured the Son's Shadow was the best use for it.

Two owners back the guy building it worked at Autozone, the rack is painted blue and it is marked "remanufactured" in yellow paint, it was never used as the car was not finished - Zero miles on it.

I *suspect* it's a K car unit, it bolted up to the K member.

Maybe he used different tie rod ends, who really knows what the history trail is.....

[rbryant]

I am messing around with an electric power steering pump from an MR2.

That way you can drive it normally around town and turn it off if drag racing. It also has an adjustable pressure valve so you can add exactly the amount of boost that you want in your steering.

Ok well I actually just like how it fits better in my charger with the SRT4 engine than the stratus PS pump did but it has some extra benefits and flexibility...

-Rich

[zin]

I am messing around with an electric power steering pump from an MR2.

-Rich

I really like this idea, especially if we could figure out a way to vary the "assist" by speed, as well as setting the min/max "assist"...

Does the adjustment come from PWM a solenoid, or???

Mike

[rbryant]

I really like this idea, especially if we could figure out a way to vary the "assist" by speed, as well as setting the min/max "assist"...

Does the adjustment come from PWM a solenoid, or???

Mike

It has a valve for setting the max assist.

It also has a high/low motor speed that can be switched via a simple relay. So it isn't as advanced as PWM assist but it is still pretty good.

I am just going to run it max speed below 20mph and then low speed above 20mph. With a frequency switch I can control the speed and build in a hysteresis.

-Rich

[zin]

With a frequency switch I can control the speed and build in a hysteresis.

-Rich

Your going to confuse the rest of the class talking like that! Though I would imagine trying to say it another way would just confuse the issue...

I imagine a simple circuit that worked off the SDS would be able to auto-switch the hi-low assist, giving us a speed sensitive PS! Next thing you know we'll have traction control and variable valve timing... (something I'm casually investigating).

Mike

[Juggy]

i have a manual rack here from a neon.
i plan to get it installed sometime...not sure when

for now i have the lines looped, and have been driving like this with no PS pump for 3K miles or so....

[rbryant]

Your going to confuse the rest of the class talking like that! Though I would imagine trying to say it another way would just confuse the issue...

I imagine a simple circuit that worked off the SDS would be able to auto-switch the hi-low assist, giving us a speed sensitive PS! Next thing you know we'll have traction control and variable valve timing... (something I'm casually investigating).

Mike

Hysteresis is basically an overlap.

If I decide that I want the pump to switch from high->low at say 40mph but I wouldn't want it to immediately turn back from low->high at 39mph or it will be constantly cycling.

The hysteresis makes it so that it doesn't turn the pump back to high until you drop much lower to something like 25mph.

-Rich

[zin]

Hysteresis is basically an overlap.

If I decide that I want the pump to switch from high->low at say 40mph but I wouldn't want it to immediately turn back from low->high at 39mph or it will be constantly cycling.

The hysteresis makes it so that it doesn't turn the pump back to high until you drop much lower to something like 25mph.

-Rich

And now class... You know the REST of the story...



I normally associate hysteresis with sensors, as such I refer to it as a "dead band" of resolution, the amount of actual change required before a sensor registers a change.

In this case, I guess it is more of a band of transition... Though it seems like without PWM or something other than a switch, the transition would be abrupt regardless of the MPH it occurs at... I imagine though that how disruptive it would be would depend on the MPH it happens and what kind of driving you might be doing at the time of transition... As such, I would think you would want to pick a speed at which you'll not likely be doing any "spirited" driving, thus reducing the possibility of a "surprise" boost of assist.

I wonder if you could achieve a transition from high to low assist by switching back and forth between the two modes, basically PWM the high and low assist switches? Doing so in a slope up or down based on an increasing or decreasing MPH signal from the SDS... If so, you could create a very smooth transition from high to no assist based on MPH... If the hardware will tolerate the cycling, I think the circuit would be fairly simple, especially for some of our resident electronics gurus...

What'cha think?

Mike

[rbryant]

In this case, I guess it is more of a band of transition... Though it seems like without PWM or something other than a switch, the transition would be abrupt regardless of the MPH it occurs at... I imagine though that how disruptive it would be would depend on the MPH it happens and what kind of driving you might be doing at the time of transition... As such, I would think you would want to pick a speed at which you'll not likely be doing any "spirited" driving, thus reducing the possibility of a "surprise" boost of assist.

The easy way to do it is to only allow it to turn off when the steering wheel is pointed straight ahead. Whenever the wheel is turned off center you have max assist. This is what Toyota did but it requires a sensor in the steering column and I haven't looked at how to adapt it or how to create one that works for our cars.

The other option is that for spirited driving you just throw a toggle switch and turn it to full power and override the highway mode. A three way toggle switch would be the best. It would have OFF (drag mode), Always High (autocross mode), and Speed sensative HIGH/LOW (highway mode).

The other thing to consider is that if you pushed the switch point up to 55mph or so you don't need much assist at that speed so the transition wouldn't be as bad.

I wonder if you could achieve a transition from high to low assist by switching back and forth between the two modes, basically PWM the high and low assist switches? Doing so in a slope up or down based on an increasing or decreasing MPH signal from the SDS... If so, you could create a very smooth transition from high to no assist based on MPH... If the hardware will tolerate the cycling, I think the circuit would be fairly simple, especially for some of our resident electronics gurus...

What'cha think?

I will have to see how much power the high/low mode switch in the motor takes. It is normally connected to a relay and you can't do PWM through a relay. The PWM driver would have to be able to drive the full current of the switch so it might take a big transistor or a pair.

I think the PWM COULD basically allow the motor to run at a different RPM by cycling the motor high/low/high/low but I am not sure if that would damage it. I think it is too complex of a solution compared to the steering wheel sensor that Toyota used or a simple autocross mode switch.


Honestly I might just leave it at full power all of the time. The pump pulls under 10amps of current when not under load (when not turning) anyway.

The brushes are also replaceable without disassembling the motor if they wear out.

The other thing to consider is that conventional power steering assist is actually engine RPM dependent (pump turns faster at higher RPMs) and we hardly notice the change...

-Rich

[zin]

It is normally connected to a relay and you can't do PWM through a relay. The PWM driver would have to be able to drive the full current of the switch so it might take a big transistor or a pair.

I think the PWM COULD basically allow the motor to run at a different RPM by cycling the motor high/low/high/low but I am not sure if that would damage it. I think it is too complex of a solution compared to the steering wheel sensor that Toyota used or a simple autocross mode switch.

The other thing to consider is that conventional power steering assist is actually engine RPM dependent (pump turns faster at higher RPMs) and we hardly notice the change...

-Rich

Our hydraulic system is such that it never operates at a point of insufficient pressure, it just by-passes more and more as the RPM goes up, so it's not quite the same thing.

However, I can say that I have done PWM through a relay with no problem, though it is typically at a fairly low frequency (25-35HZ). I would think this would be adequate for the purpose at hand.... If we were to PWM the motor, I can imagine it would prefer a higher frequency. I should note that the relays I'm typically dealing with are the "Bosch" or "ice cube" type, not the solenoid style you are considering, though I suspect they would live at the lower frequencies...

Food for thought anyway!

Mike

[rbryant]

Our hydraulic system is such that it never operates at a point of insufficient pressure, it just by-passes more and more as the RPM goes up, so it's not quite the same thing.

Ok that makes sense.

I think the best idea is to just run the thing at full speed and adjust the pressure via the adjustment valve. Then it is always running basically the same assist all the time way that the stock pump does. For long trips kicking it down to always run at low speed would save some minimal gas mileage and would still provide some assist.

Lots of people run the stock power steering rack with no assist so even on low it would be better than that.

I will let you know what works and what doesn't once I try it.

If someone follow my lead and buy the 94-99 MR2 power steering pump I already have a design for a 1/4" 6061 bracket for it that bolts to the 2.4 block and could be adapted for the 8V block. I did it in 3 pieces and had them welded together and then drilled mounting holes afterward to attach it to the block.

-Rich

[shackwrrr]

http://www.bakatronics.com/shop/item.aspx?itemid=581


pwm motor controller. It can be controlled with a 0-5v signal. You could easily make a dash switch with multiple selections for different conditions along with a speed control ramp for everyday diriving.

they sell different amp units

[zin]

http://www.bakatronics.com/shop/item.aspx?itemid=581


pwm motor controller. It can be controlled with a 0-5v signal. You could easily make a dash switch with multiple selections for different conditions along with a speed control ramp for everyday diriving.

they sell different amp units

And pretty cheap too!! Very interesting! Thanks!

Mike