Got a leaky shimmy damper (Navajo). Rebuilt it with fresh orings, all good, no leaks. But can someone help me understand best way to refill it?
If I extend it fully and fill from backside of the piston, I have to leave an air bubble in it so that it can function, because as the rod enters the chamber the displaced volume from the rod compresses the fluid and if no air bubble it just hydraulically locks. But with the bubble it has a portion of its stroke that is free to move and so sort of useless and not dampening at all.
If I fully compress it fully and fill it from the rod side end gland, then what happens when it extends is a vacuum is drawn behind the piston as that volume increases and it tends to want to pull that vacuum closed and close the damper when released, back to fully compressed position.
Steering dampers I’ve played with before on motorcycles have a rod sticking out both end glands so combined volume in the chamber on both sides of the pass thru piston is constant. Or, dirtbike shocks that have a separate reservoir and the changing volume due to rod displacement is taken up by a diaphragm and a pressurized chamber.
Not the case with this shimmy damper. It’s just a rod with a piston and a .020 hole in it with no diaphragm and no rod sticking out both sides.
What am I not understanding?
If I extend it fully and fill from backside of the piston, I have to leave an air bubble in it so that it can function, because as the rod enters the chamber the displaced volume from the rod compresses the fluid and if no air bubble it just hydraulically locks. But with the bubble it has a portion of its stroke that is free to move and so sort of useless and not dampening at all.
If I fully compress it fully and fill it from the rod side end gland, then what happens when it extends is a vacuum is drawn behind the piston as that volume increases and it tends to want to pull that vacuum closed and close the damper when released, back to fully compressed position.
Steering dampers I’ve played with before on motorcycles have a rod sticking out both end glands so combined volume in the chamber on both sides of the pass thru piston is constant. Or, dirtbike shocks that have a separate reservoir and the changing volume due to rod displacement is taken up by a diaphragm and a pressurized chamber.
Not the case with this shimmy damper. It’s just a rod with a piston and a .020 hole in it with no diaphragm and no rod sticking out both sides.
What am I not understanding?
