Still working on a boom lift to get it dialed. Have 2 issues I would like to resolve. 1. Boom lowering is slow. Not raise, just lower, which is odd... That means this is not a pump or pressure thing. I will note that someone dinged the welded steel rod end oil supply tube on the cylinder. I was trying to reason that it could be causing this but it raises just fine. However, could it be messing with my load checks? This issue occurs with both the basket control and base control. The base does not use a proportional handle, just a toggle switch. 2. Turret swing is not consistent. Basically it acts like it needs a counterbalance. I will apply full handle to either L or R, it will start swinging fine, then it seems to outrun it self a bit, then stop or slow way down, then try to catch up again. This could get dangerous swinging close things. It's like the return oil needs better control. The lift does run a variable piston pump so I guess it is possible the pump is changing up but I don't hear any real engine load change. I have provided a schematic because it is not marked well and I don't do hydraulics enough to remember all the symbols and such. Hopefully you guys can pitch me some things to check.
Schematic did not upload. There will be a lock valve and a restriction for boom lowering, it's a safety issue. If you think it's too slow, then pressures, lock valve, and if by chance it's adjustable, the metering orifice need to be checked. I would think the swing function would have a counterbalance valve, when we can see the schematic maybe we can find it.
Uploaded. My bad! Regarding lowering speed, I have been on several lifts and I think anyone will agree that something is wrong. Bad enough that on the ground, you might question if it is even going down!
Okay, I'm not a manlift guy, so I'm probably not going to be much help. I assume "Topping" is boom lift, because there's no valve or circuit other than that shown? In that circuit the restriction is shown at the control valve, it's an X across one of the work port lines which would be a fixed orifice, so it's probably built into the manifold valve itself? It does show a holding valve assembly, don't know if it's on or near the cylinder. On the swing, your talking about the main rotation, not the platform swing? They don't show a counterbalance, only crossport reliefs, and a note that the reduction is 500:1.
yes, they call the boom cylinder the "topping" cyl...lol I just looked at it and took pics. There is certainly a holding valve mounted to the cylinder at the piston end. There are valves screwed into both sides of it, and one appears to be adjustable. However, I will have to comb a bit to see if I can learn if that is just adjustable relief or if that indeed is down speed adjustment. I mean, I know for certain something is not right, but now a matter of finding it. What I would like to do is manually push the little pin in the prop valve for 'boom down' and first ensure it is moving all the way. If not, that will prove just an electrical problem and I much prefer electrical over hydro issues...lol On the swing issue, it should be well noted that during initial testing (weather has not permitted further tests), the hydro tank was low on fluid and pulled air. This was obvious as the pump started talking while crawling and travel slowed when pump started talking. Oil was added and that corrected the travel and noise issues, but further testing was not performed.
I don't see any indication of an adjustable flow control, I would guess that the adjustment would be for the cracking pressure of the lowering lock valve. Might try turning it IN a quarter turn and see what happens. SUN valves at least you turn them in to reduce cracking pressure. Yeah, if the pump was pulling air that would certainly make for intermittent action.
Well we have some progress. And rather stupid results. So the prop valves operate a pilot spool so that was my first question....is the spool moving correctly. Each prop valve has a manual little brass plunger on it you can push with a screwdriver. I have no idea if these have spring returns but they certain don't return. I pushed one on the boom and realized I lost all boom up. Started playing with it and even removing one of the prop valves and realized the mag plungers work fine, pilot spool seems to be smooth as butter, but the stupid buttons on the ends are sticky! I worked the boom spool side to side a lot and about every 10th stroke she tries to hang up about half stroke. I worked with it a bit and feel this area will have to be addressed before I go any further. All other valves feel good except this one. I cannot completely write off the pilot spool but what little testing I did not it, it was mint.