Have one gushing on a large 40ft scissor lift. Book refers to the cylinder as a 5x4 so i think that is 4" stage one, 5" stage two. Total stroke is probably 3ft. I just don't know if these would in all cases have some sort of piston? The heads on each stage are just the screw cap type that use a spanner wrench. Heads will come right off the end. I just cannot see how you can have much of a piston on the 2nd stage which is just a 1/4" thick barrel? But surely there is something to prevent over travel?
The Piston is the Outer most end of the Inner most section, the subsequent seal ring ends of the barrels in the stages form additional 'Piston' surface but the actual working piston is at the outermost end.
I guess my ultimate question or thought is if I should just unscrew the caps and just rebuild the heads and not worry about the piston ends right now? I know that seems half baked but this scissor hasn't seen seen 10hrs action in the 8yrs I have owned it. The cylinder is single acting and worked just fine other than the head seals have just completely fallen apart. I guess we could reason the piston seals are probably like this as well and could pose contamination concerns, just not sure how I want to proceed.
Head or retainer nut seals are more for dirt/comtaminants than pressure seals If leaking at those the barrel seals are done and the internal barrel surfaces likely need dressing up/honing
Honestly don't think the surfaces will be of issue. These types of cylinders just don't get the cycles like other equipment. I believe these cylinders are 30+ yrs old on original seals and the head wipers are coming out in chunks.
That is my point Head nut wiper seals falling apart means contaminates and moisture had access to upper barrel area with the barrel seals all the way in, gushing means seals on the barrel sections are bad.
These cylinders run inverted. At least seems like someone got smart on that design....
Well...... The cylinder is torn down. Stupid simple and just glad that I did because the piston bearings are COMPLETELY toast. Actually, the pistons have been riding on the bores and hurt them pretty bad. However, I realize the pistons have absolutely no seals, and there are even slots in the pistons to allow oil movement. The only seals are on the heads, which ride the OD of each rod, which are in near perfect shape. The seals are so bad and broken, I cannot even tell what they were and shocked oil didn't just spray out. each head has a bearing, seal, and wiper. Looks simple. I will have to clean up the bores so the new bearings don't get shredded instantly but it does look like this one will go back together pretty quick and easy. Nothing like a CAT cylinder.