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Power assist idler arm

TRINDU

TRINDU

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Instead of a conventional idler arm, I'm using a RHD power steering box on my IFS 4runner. Would drilling and tapping the boxes for standard hydro assist, and connecting them as such, utilize the RHD box as a power assist instead of dead weight?

behold the artists rendering:

new van go.png


(pay no attention to the brand of parts, visual representation only)
 
Last edited:
This is something I’ve wanted to do (and cane up lightly in one of the steering threads, I’ll have to look), I think it has tons of merit.

I don’t think you want to criss cross the lines, you want both boxes to swing in unison versus fighting each other.

But yeah, cap off the feed and return lines for the second box and give it a go. I don’t think the second servo valve will internally recirculate with the in/out capped off so it should be good to go.
 
Oops, I glossed over the fact that you show mirrored boxes. I was thinking of two identical boxes, in which case you want the same assist connections. But for your mirrored setup, hmm I believe you have it drawn correct
 
Yeah, what you're doing should work. You've just reinvented the slave steering gear that's sometimes used in medium and heavy trucks.

I'm not sure that the valve setup on the stock RH steering gear is correct for that so you might wind up having to fuck with it to tune out some dumb interaction.

I've long wished Ford had made a mirror of the 80+ van/truck box because then doing what you're trying to do would be the easy button for swingset steering.
 
AgitatedPancake said:
Oops, I glossed over the fact that you show mirrored boxes. I was thinking of two identical boxes, in which case you want the same assist connections. But for your mirrored setup, hmm I believe you have it drawn correct
Click to expand...

my thought process on how fluid is moving between the boxes. Pistons would be moving in the same direction (in this instance to the right).

box fluid.png
 
TRINDU said:
my thought process on how fluid is moving between the boxes. Pistons would be moving in the same direction (in this instance to the right).

box fluid.png
Click to expand...

It's dictated by which side of the piston the sector shaft on. With the piston moving down as drawn, having the sector shaft on the left side of the piston will spin it clockwise, if the sector shaft is on the right side of the piston it will spin counter clockwise.

I'm conflicted though, as you have it drawn there is almost trying to be a closed loop system (unless the boxes are mirrored). Where the unpressurized side of one box is filling the side of the second box that you actually want to pressurize. You want to pressurize the active side of both at the same time. Hmm
 
AgitatedPancake said:
It's dictated by which side of the piston the sector shaft on. With the piston moving down as drawn, having the sector shaft on the left side of the piston will spin it clockwise, if the sector shaft is on the right side of the piston it will spin counter clockwise.

I'm conflicted though, as you have it drawn there is almost trying to be a closed loop system (unless the boxes are mirrored). Where the unpressurized side of one box is filling the side of the second box that you actually want to pressurize. You want to pressurize the active side of both at the same time. Hmm
Click to expand...

I'm guessing, but id like to do it right the first shot.

Boxes are mirrored, so the pistons will be traveling in opposite directions? making my drawing all wrong.

The conception I'm working on is treating the RHD/idler box piston as a ram.
 
TRINDU said:
I'm guessing, but id like to do it right the first shot.

Boxes are mirrored, so the pistons will be traveling in opposite directions? making my drawing all wrong.

The conception I'm working on is treating the RHD/idler box piston as a ram.
Click to expand...

Yeah with the mirrored boxes, if the pitman arms are facing the same direction (makes sense, because idler) the pistons will need to be moving opposite directions.

But that is actually how you have it drawn in both this latest drawing and the OP, besides the arrow on the second piston direction. With the lines criss crossed as drawn, opposite sides of the pistons are getting pressurized at the same time.

Something like this is how I see it. Yellow circles are sector shaft location, red side of the box is under pressure while steering right, blue side is free returning.

box fluid.png
 
AgitatedPancake said:
Yeah with the mirrored boxes, if the pitman arms are facing the same direction (makes sense, because idler) the pistons will need to be moving opposite directions.

But that is actually how you have it drawn in both this latest drawing and the OP, besides the arrow on the second piston direction. With the lines criss crossed as drawn, opposite sides of the pistons are getting pressurized at the same time.

Something like this is how I see it. Yellow circles are sector shaft location, red side of the box is under pressure while steering right, blue side is free returning.

box fluid.png
Click to expand...

Got it, I was thinking about the flow of fluid, rather than pressure applied.

Would it be wrong to say I'm effectively doubling the pressure/volume demand of the P/S pump? Is drilling out the orifice enough? GM p pump (think a 2005ish 6.0L has the highest ratings)? something more advanced?
 
TRINDU said:
Got it, I was thinking about the flow of fluid, rather than pressure applied.

Would it be wrong to say I'm effectively doubling the pressure/volume demand of the P/S pump? Is drilling out the orifice enough? GM p pump (think a 2005ish 6.0L has the highest ratings)? something more advanced?
Click to expand...

Doubling the volume yeah. The same pressure from the pump will be able to do twice as much work though, it's essentially just acting as your hydro assist cylinder. I don't recall the volume of fluid the box needs compared to a 1.5" or 1.75" hydraulic cylinder off the top of my head, but my hunch is it's less. Meaning it's less taxing on the pump than a standard assist cylinder is.

You can drill out the fitting slightly, but that doesn't effect flow at idle, Just gives you more flow from like 1,500 to 3,000 rpm. It can lead to the steering being hyper sensitive on the freeway at ~2,000-2,500. So all I can say is make very small drill size adjustments. Smaller pulley is the real answer, physically spins the pump faster and produces equally more volume, by whatever percentage overdrive.
 
Aussie. Although I’ve never had any luck figuring out how to purchase them via the internet. Finding pictures of this stuff is scarce as hens teeth as it is.

Having mirror castings would’ve helped me in the past when I made a dual steering gear system on a friends derby car. Rules were something about steering gears and no full hydro rams. Rules didn’t say how many steering gears or orbitals….

I could use a RHD casting in my KOH racer right about now.
 
TRINDU said:
my thought process on how fluid is moving between the boxes. Pistons would be moving in the same direction (in this instance to the right).

box fluid.png
Click to expand...
Doing that you'd get no more force doing that because the amount of area under pump pressure is the same (the piston in the first box). And you'd have to muck with the valve system on both boxes to get it to work like that because the same process that directs pressure into one side of the cylinder in the box also connects the back side to tank.

What you want to do is tap both boxes and connect them in parallel. Basically plumb the second box like it's a ram. And maybe do some shit to delete the valve from the top of the other box so that doesn't cause you problems (though it should just work as is because there's nothing connected to it and the force on the input just idling there should never be more than the torsion spring).

You should be able to figure out which hose goes to which side of the slave box pretty easily just by thinking about the location of the teeth on the shaft and which way the mating teeth on the piston would have to move to turn the shaft a given direction.
 
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