Any idea why the ram would have a shoulder on the tube and this shoulder would ride on a beefy trunnion - but why the clearance tween the trunnion and the cylinder? ~ This topic is directed at a three ram Upright 24', battery over hydraulic, indoor scissor lift. Sometimes when almost at the lowered position it would hang up and not go all the way down and then there would be a bang when it settled. Snooping around could not find much to puzzle over and the occurrence was once in a blue moon. But then it was observedi: the ram sometimes swings (actually slides) inside the trunnion and the result of this change occasionally allows it to hit a conflict and stop the completion of the movement. The corner of the elbow of the middle ram has been rubbing and there is a sign of some wear....yes missed this on prior looksees but the use of a pocket super LED flashlight (makes me feel like the DOT! LOL) helps focus the visuals. To maintain the improved relationship, temp tested by shoving a wood shim in the gap between the trunnion and the ram cylinder and will observe that for a time then maybe a more permanent locator such as a rubber collar or a plastic sleeve. Yes the gap tween the trunnion skirt is a bit less than 1/4". Would have expected like 1/64 or so. This condition seen on all three rams and not the idea this has worn elliptically. Never contemplated the ram would have a shoulder and that it rested on the trunnion - figured the trunnion was part and parcel of the ram. But some viewing on browser indeed shows some pics of shoulders on ram tubes. This machine gets greased and cleaned/checked out regularly and have not seen any zerks not take lube or other oddities. Is this a normal fitment issue for a trunnion to shoulder style ram or is is an Upright unique fitment issue? Seems odd they allowed this much room for fitup. Should be 4 pics in this post. The machine, the trunnion, the worn corner on the elbow, and the shim in the gap (pic is looking up at the bottom of the trunnion skirt).
Always remember "Polish law says it can't fall up". Not unusual to see that much clearance. Check the pin on the rod ens of the cylinder also. That could be worn quite a bit and not guide the cylinder properly.
I don't think I'd worry about the clearance either. Its obviously made that way, I don't think you've worn a 1/4" groove in it. You can see where its been hanging up on the elbow fitting and the end of the cylinder, but I don't think that has anything to do with the clearance on that cylinder. More likely its bent or tweaked the whole "scissor" rack from driving around with it up in the air and hitting a I- beam or driving across a small drop and bouncing it all. It doesn't look like a brand new machine, and most of those see hard rental use before they hit second market.
Seems as though the ram shoulder would bear onto the trunnion and that would be it, but apparently placing the wood wedge has kicked the ram the other direction a wee bit but plenty enough perhaps to not allow it to collide. The rod end of the ram is connected to the scissor by way of a link...such a feature allows these rams to float about it seems.
Could also be the trunnion or the sleeve on the cylinder worn just a bit. Probably wouldn't take much.
As to the shoulder mount allowing for some movement: It occurs to me that when the machine is at rest and all the hydraulic pressure is removed, the ram is likely to slide in the trunnion aided by gravity. Upon raising, the sudden application of hydraulic pressure will likely result in a motion between the ram and the trunnion in addition to the intended expansion of the scissor linkage(s). That small amount of movement [mentioned by Theweldor] may make for a small amount of wear, and after a time the ram no longer aligns perfectly .... the clearances for the ram to the scissor members are reasonable but not exceptional and the one ram happened to be the one that catches on the cross member - leading to the condition being observed. This doesn't actually point to the why of the clearance but when looking at the machine and thinking 'what if' the ram needed to be rebuilt....would the loose assembly of the ram to the trunnion aid in removal of the ram from the scissor without having to remove the trunnion from the scissor assembly? The small piece of wood shim appears to be all that was needed, the shim is no worse for the installation ergo not splintering or crushing .... and hooray there has been no "binding of the ram". Lot of up and downs these last couple days. Thinking of swapping the wood shim for a rubber wedge (decent door stop) and a hose clamp to hold it in place.