stick cylinder

[mce5802]

I am having an issue with the stick cylinder on my excavator, a 12000# Hanix without pilot controls and with a gear pump. If the stick is extended so gravity helps when you pull it in, it moves pretty fast for half the stroke, then pauses for severaI seconds once the stick is vertical. If you "stick out" during this pause it immediately moves out. Would this be a pump issue or a cylinder issue? Seems like the cylinder should only be able to fall as fast as the pump lets it but I'm no hydraulics expert. The guy I bought it from said he recently had the cylinders packed but didnt specify which ones, not sure if this would be a piston dealing problem anyway?

 

[uffex]

Good day
If you have little or no creep - drift it is unlikely that the arm cylinder has an issue it could be that a restriction valve is open all of the time or could have a pump issue. Suggest you check what speed the cylinder can make with full engine speed be sure the engine revs are up to spec.
If all the other function work good it is most probably a problem wit the cylinder circuit.
Check the arm cylinder pressures if you have a hydraulic schematic we can help some more, if you know which Hanix could be a good idea to post this on the thread.
Kind regards
Uffex

 

[mce5802]

If gravity doesn't help it it makes around 6 gpm which is the same as the bucket cylinder(which takes like 8 seconds to go from dump to curl). I've researched it and it's sposed to be a 14cc pump and I am not sure if it's the original pump because someone a Perkins 4-154 engine in it. I don't have a schematic but the parts book doesn't show any restrction valve, and lines go from pump through a block with check valves and then into the main valve body, individual circuits go from valve to cylinders. Not sure what the block does? No restrictor on cylinder parts diagram either. Model S&B 30 S. Engine rpms were about 2000, adjusted to 2550 and helped speed all the functions up but did not help with the stick issue.

 

[mce5802]

Also-it has plenty of digging force and tracking power i'd say, just really slow. Also, no creep in cylinder at all. Once it's caught up or whatever it stays where u put it. Thank you for replying by the way.

Mike

 

[uffex]

Good day Mike
Often these machines are able to increase the flow for arm in -cylinder out by connection of another pump flow. Is there a switch in the cabin for increase in cylinder speed?
KR
Uffex

 

[mce5802]

Could that be what that block is for? Both pressure lines from the pump go through it and there appears to be two spools. I haven't seen a switch but I'm still getting familiar with the machine, but I will look n get back to you.

 

[uffex]

Hi Mike
A situation occurred to me from the past, when you experience this problem is it when the arm cycles above ground. If this is the case many machines do delay not so many folk excavate fresh air dare I say (No resistance against the bucket). I will try and get some information on your model but according to what I have found this machine had a Mitsubishi engine strange if its changed to Perkins. If I can find some information I will get back to you.
KR
Uffex

 

[mce5802]

Thank you very much, I'm thinking that block is a crossover that puts flow from both sides of the pump into one circuit and it isn't working. I believe you pointed me in the right direction. I will post pics of the parts diagram n see what you think

 

[mce5802]

Also on the engine....they modified the engine mounts and hood to get it to fit so I know it's not original

 

[uffex]

Hi Mike
Im pretty sure this is your machine pumps please check and confirm.
KR
Uffex

 

[mce5802]

No it does not look like mine. Here's a pic, and the one on the machine looks real similar to what it shows in the parts manual. I apprecoats your help.

 

[uffex]

That must be of a later machine it looks as though yours has twin pumps have you a shot of the valve chest, the information I have shows that the two pumps can connect to arm in cylinder out, we checked the time you had for the arm cylinder with 6 gallons flow 7.7 out 5.2 in so I believe the speed is good for one pump.
KR
Uffex

 

[379Pete]

Common complaint, it’s just physics. A lot of the New machines do the same thing.

 

[mce5802]

It's like a 5 second pause. I've ran excavator quite a bit and know what you are saying but this is extreme. Here are pics of the parts blowup for what I think is the crossover valve and another showing the plumbing. The two spool valves on the side are for the blade and boom sideshift and are completely separate circuits run off a belt driven pump. How would the crossover be actuated , if that's what it is?

 

[mce5802]

Sorry about the blurry pictures. Can someone verify that it is a crossover valve? It looks like the two pressure lines from the pump go into this "block" as the parts book calls it and two out, one to either end of the valve body. There is a line that goes into the return pipe by the filter. It doesn't hook in to the stick out circuit that I can see. I'm curious how it is designed to work.

 

[funwithfuel]

Have you attempted to make sure that there is no air in the arm cylinder circuit at all? When you say you have a 5 second delay is that when the stick is hanging perfectly vertical?
Is this behavior the same at idle as full throttle or is there a difference in the lag time?

 

[mce5802]

Happens when stick is vertical, yes, rpms don't seem to make much difference. I guess I've put 5 or 10 hours on and assumed the air would have worked itself out but maybe not? Would you crack the line that fills from the piston end and move the lever?
Also that block has an adjustment rod with a locknut, maybe it's a pressure relief valve?

 

[funwithfuel]

Ok. Gotta be totally straight with you. I dont see a problem. When you shift the spool, you're opening a passage to tank. Gravity takes over. The arm essentially falls till it hits the center of the arc or BDC , there it sits waiting for the oil to catch up and continue pushing. Normally the anti-cavitation function would allow enough make up oil to make it less noticeable. You seem to be working with a pair of fixed displacement pumps which won't compensate.
I'd say you've got a good little machine. Uffex was trying to be polite when he said, "don't know many who excavate air."

 

[funwithfuel]

That block I will bet is described or called out as anti-cavitation valve. If it is called out as summation or conflux then it's for 2 pump flow to gain speed. Gravity is on your side, you would only have 2 pump for arm out and boom up , I would think

 

[mce5802]

Thanks for the advice, what you said makes sense. It does seem like a good machine, just slower than some. I noticed the pause moving brush. I sure appreciate everyone's feedback, I think uffex went to a lot of trouble researching it, Its good to know there are guys out there ready to help, hopefully I can return the favor.
That block has an unreadable tag, simply listed as "block" in the parts book.