Hydro Steering Question...

[Yay!Gurrr]

Ok, I'm finally gonna spend some $ on the hydro upgrade...

so I'm planning to order a 1.5"x8" ram... but here is my quandary...

I'm currently running a J20 box. It has the larger 3.5" internal piston.

I also have my original YJ (4bolt) box with the smaller 3" piston..

I'm sure I'm over thinking things as usual but my thinking is that, by stepping back to the smaller 3" bore box would be better.. As it would free up some volume from the box 'assist' to make sure that I can supply enough to the ram to not create any 'slowness'...

So...... which one should I use ?

 

[upnover]

Mike, I have the CJ version and it does get slow at times. I will follow this to see how it goes. Why not do both boxes and see which one works best. If the J truck works best I might change mine! Which ever one you don't use you can always sell it. I have seen them go for big bucks on EBAY. Seems the issue will be volume vs pressure.

 

[drkelly]

I'd use the larger J20 box and consider stepping up to a 2" dia ram. What size tires are you running?

 

[J.C.]

This is hydro assist? Mine is 2"x8" with a stock YJ box and 42" tires. I don't have experience driving others but I think mine is OK. If anything maybe a little slow at times but I really don't notice that much.

 

[Yay!Gurrr]

Ok just doing some basic math to put some numbers to the discussion. This will compare the surface areas of the box(s) and rams.. And it will be clear why I'm hesitant to goto a 2" ram.
First the steering boxes, surface area
1) Normal CJ/YJ box w/3" piston on the assist = 7.069 in^2
2) J20 box w/ 3.5" piston on the assist = 9.621 in^2
Rams
3) 1.5" bore (w/ 1"rod) = 1.767 in^2 on the extension side and .785 in^2 on the retract side * see below
4) 2" bore (w/1.25" rod) = 3.142 in^2 on the extentson side and 1.227 in^2 on the retract side * see below
Some Math (using bore size only)
YJ box w/ 2" ram = ~10.211 in^2
J20 (no assist) = 9.621 in^2 (note this is why I can sorta wheel my jeep unassisted w/38s)

My plan was to use 2 - 1.5" rams
YJ box w/ 2 1.5" ram = ~9.621 (No reason # matchs the other one)
[ YJ box (7.069) + big end of ram 1.5" (1.767) + little end of ram (.785) = 9.621 [
YJbox w 1 - 2" ram = 10.211 in^2

I need to also look into how far each item travels to compare the total volume of fluid moved.. Box piston doesn't move that far.. vs ram throw.

This isn't to compare the 'work' being done by the 2 items(box/ram) but to depict where fluid is being used in the system.. (the assist part of the box is probably NOT the most efficient use of hydralics. )

but my using 2 rams, you can balance that out.. and using 2 smaller rams would help with my packaging.


***
I'm not an expert (or even close) this is just stuff I've learned from reading. But here is some basic explanation as to why steering can be faster one direction vs the other.
One side of the ram is 'empty' and fluid can push on the entire area of the piston. This side is usually slower but with more pressure.
The other side has the 'shaft' in the way and the surface area is reduced creating less area for fluid to push on, this make it move faster but with less pressure...

The reason it can be slow is at lower RPMs the pump isn't pushing a lot of fluid (volume)