Reconditioning the Armstrong Shock Absorber or Hydraulic Damper

The shocks I reconditioned, due to the absence of written technical material, were done by trial and error. I had taken some others apart earlier so I had a bit of an idea what was involved.

The whole thing, as I see it with the shocks, is that they wear the shafts, where they rotate in the bushes, and/or they wear the bushes in which the shaft rotates. Either way the wear allows excessive movement of the shaft in the seals causing the seals to wear out and allows the oil to escape, thereby starving the hydraulic operation of its most important component, the hydraulic oil. It then no longer is a hydraulic operation, but merely a wishbone operating in a fairly dry, elaborate housing!

When I dismantled the front shocks, which are in quite good quality, in that they have cast iron bodies, the only real wear I found, was on the shafts, and that the seals were shot. I subsequently found that the bushes were in good condition with no wear on them.

I dismantled the shocks in the following manner:-

So there you have it. If you get stuck with the resizing of the shaft, I can probably get them remade. I cannot remember how much it cost to have them done, it depends a lot too, on the amount of chrome build they have to put on the shaft.

The rear ones Shock absorbers are a little bit different, but similar principles apply. Instead of having 2 arms there is only one arm, and the opposite side of the body is sealed with a welsh plug, and its only the fit of the shaft in the 'rocker' that holds the shaft and arm in place. It is most important that when taking the welsh plug out, no damage is caused to the body. Also these shocks are an alloy body and I found that I had to go through about 5 shocks before I found two that were not fractured/cracked in the body, round the bottom of the cylinders.

To check for fractures/cracks clean the shocks, but DO NOT buff them or scratch them in any way. Get a magnifying glass and minutely inspect the end of the shock, round the ends of the cylinders. If there's a line there or it looks like a crack, then the probability is about 99.9% that it is racked. Once they crack they are RS, and all you can do is check the next one! If you want to confirm that its cracked, fill the shock with any thin oil, even kerosene would do, mount it in a vice and pump the arm through the full extent of its travel, as fast and as hard as you can. If it's cracked then the oil will squirt out of the crack.

Also you will find that the shaft runs in the actual body, there being no bronze bushes in the shock (like the front), unless it has been repaired before. If there is wear in the body then it will have to be machined out and bushes made for it. Also if the shaft is worn its a similar matter to the front shocks to have it built up.

Best of British.