Still been working through this system. I’ve had ample seat time on both dirt and the hwy with a combined 2-3k miles. The steering works well enough but it has had a darting problem at the initial turn in. I would say, “I want to drive this nice sweeping curve at 65 mph.” And the Jeep would reply, “Really? Because I want to change lanes”.
I formulated a model that the rod seals were the cause of this. They created a large amount of sticktion. My theory was that the force required to overcome the static friction of the seals was much higher than the dynamic friction once rod was sliding. My brother has a similar steering setup with a surplus center cylinder that doesn’t drive like mine. It is smooth and predictable.
Naturally the next step was to spend money in unneeded rebuild kits to learn some things. And learn things I did. The surplus center rod seals have a much more favorable U cup seal profile that doesn’t grab onto the rod as tightly. It’s a subtle difference. But there nonetheless.
Unfortunately the required groove dimensions for each seal are different. Darn. Can’t just install the surplus center seal. I called up a local shop that manufactures seals and spoke with them about a lower friction option that the polyurethane seal that came stock. We came up with a seal machined out of graphite impregnated ptfe and energized by 3 o-rings. A couple weeks later I had a few prototypes in my hands.
As I disassembled the cylinder and removed hydraulic lines and the seal heads, I used a fish scale to measure the force it took to slide the rod back and forth in the cylinder. Amazingly it took 89 lbs of force to start moving which immediately dropped off to about 25 lbs of force to keep it moving. That is a huge difference between static and dynamic friction and is starting to fit the model of what the problem was.
With the new seals installed, I forgot to measure the force with my fish scale. Oh well. Wasn’t about to disconnect hydro lines again. As I started to bleed the system, it became very apparent that it was different. I had the front end off the ground and was steering back and forth with the engine off to purge the air out. The force required at the steering wheel was significantly lower than before and much more consistent to get the cylinder to move and maintain the movement.
Once fully bled I fired it up and the feeling in the steering wheel was a much lighter feel. On the ground the tires steered smoothly. But the real magic was driving it the first time. Around sweeping curves, it doesn’t dart anymore and the steering is predictable. It feels much better than it used to when I had convention hydro assist as well. Now it’s time to start figuring out rod seals for lots of cylinders and start selling kits. I’m planning on offering kits with a full rebuild option or just the rod seals for a quick seal head removal and seal swap. I’m pretty sure it will be possible to come in at or lower cost than the psc rebuild kit cost.
