power angle dozer blade problem

[ecphsca]

I have a Cub 5234 with a front quick connect that I attach a dozer blade or snowblower to. The angle cylinders locate the bottom of the attachment. Control is by FEL joystick. The angle cylinders each have the rear pressure hose attachment and then another port that connects the other end of the cylinder to the opposing cylinder with a hose. Problem is that each cylinder will extend when activated but the opposing cylinder will not retract. This pushes the bottom of the attachment very far forward. (cutting edge of the snowblower will be elevated) There doesn't seem to be any fluid in the hose connecting the cylinders (it does have a "T" with a plug) Not sure how it would get hydraulic fluid anyway. Cylinders can be retracted with engine off by operating valve and applying mechanical pressure. Cub dealer just centered the cylinders and disconnected the quick attachment connectors and said "here ya go!". Never going back there. How does this system work and any idea what might be wrong with it?

thanks

 

[mrmikey]

Not quite clear on your explanation.
Are the cylinders double acting, i.e. do they have a port on each end of the cylinder (sounds like they do)?
If so, there should be two 'T's, each supply from your joystick would go to one of the 'T's' .The two ports on the same T should go to the retract port of one cylinder and the extend port of the other cylinder. The same with the other supply line from you joystick only the opposite ports of each cylinder.
One cylinder retracts as the other extends.

There's another way to do it if you have a double acting cylinder that doesn't require any T's at all. Only thing is, it requires that the retract end of the cylinder be open to atmosphere allowing a lot of moist air inside which will eventually corrode the barrell. All you do is connect one of the two pressure lines to the extend end of each separate cylinder. As you extend one, it pushes the opposing one back thru the linkage.
I think Fisher uses that method but their cylinders are single acting ....Mike

 

[oldnslo]

I have a Cub 5234 with a front quick connect that I attach a dozer blade or snowblower to. The angle cylinders locate the bottom of the attachment. Control is by FEL joystick. The angle cylinders each have the rear pressure hose attachment and then another port that connects the other end of the cylinder to the opposing cylinder with a hose. Problem is that each cylinder will extend when activated but the opposing cylinder will not retract. This pushes the bottom of the attachment very far forward. (cutting edge of the snowblower will be elevated) There doesn't seem to be any fluid in the hose connecting the cylinders (it does have a "T" with a plug) Not sure how it would get hydraulic fluid anyway. Cylinders can be retracted with engine off by operating valve and applying mechanical pressure. Cub dealer just centered the cylinders and disconnected the quick attachment connectors and said "here ya go!". Never going back there. How does this system work and any idea what might be wrong with it?

thanks

Cylinder plumbing question:

On the "Rear" pressure hoses. Are they each run seperately to a quick disconnect on the FEL valve?

On the rod end or top port. Is there any valves in the hose or does the hose just go from one cylinder to the other? Is there oil in this line? Does this look like a high pressure hydraulic line or lower pressure line?

Are the cylinders the same size?

Any mechanical binding which would prevent the swing under load?



From what you are describing it sounds like the cylinders should operate together in a "Master - Slave" operation. Where extending one cylinder will cause the other to retract via mechanical linkage and or possibly hydraulic assist.

If double acting cylinders and the rod end is full of oil extending one cylinder will force oil to the rod end of the other cylinder and retract it.


Can you watch the hoses and see when you angle the blade do BOTH bottom hoses stiffen like they are under pressure?

Does the rod end hose stiffen like it is under pressure? If



My Meyer plow operates this way and it works fine.

 

[J_J]

You said that the dealer disconnected the QD's, did you connect the QD supply back up.

If no flow, check the QD for correct operation.

If still no flow, remove the QD from the hose from the valve, and place in a bucket and operate the valve. You should have flow. If not, check your valve. Is it lever or solenoid.

Is your valve going into relief?

 

[ecphsca]

Not quite clear on your explanation.
Are the cylinders double acting, i.e. do they have a port on each end of the cylinder (sounds like they do)?
If so, there should be two 'T's, each supply from your joystick would go to one of the 'T's' .The two ports on the same T should go to the retract port of one cylinder and the extend port of the other cylinder. The same with the other supply line from you joystick only the opposite ports of each cylinder.
One cylinder retracts as the other extends.

There's another way to do it if you have a double acting cylinder that doesn't require any T's at all. Only thing is, it requires that the retract end of the cylinder be open to atmosphere allowing a lot of moist air inside which will eventually corrode the barrell. All you do is connect one of the two pressure lines to the extend end of each separate cylinder. As you extend one, it pushes the opposing one back thru the linkage.
I think Fisher uses that method but their cylinders are single acting ....

Thanks guys, FYI The machine only has 140 hours on it and all equipment is original. QD's are not restricted and no other valves present near the cylinders Control valve seems to be working fine and lines stiffen when activated. Worked fine until it didn't. Not sure if they are single or double acting cylinders but they each have two ports. The port to extend is supplied by the control valve, the retract ports are linked together by two short hydraulic hoses with at "T" fitting in the middle. I'm thinking that maybe oil or air in the unpressurized portion of the cylinder passes from one to the other retracting the opposing cylinder.(closed system) However no oil is discharged when I disconnected this equalization(?) hose and worked the cylinders. (also thinking it would have to be oil since the cylinders locate the bottom of the attachment and air would compress too easily making it "floppy" - and prior to the problem it was rock solid. Perhaps a fitting is cracked or maybe even the hose has a leak. I will check for that this weekend. If a volume of oil is supposed to be in the closed system how would you re-fill if it had leaked out?

 

[mrmikey]

....the retract ports are linked together by two short hydraulic hoses with at "T" fitting in the middle

What does the third port of the T connect to?.

......air would compress too easily making it "floppy

Not going to be working against air, the hydraulic fluid will take the strain regardless of which side of the plow is being pushed on. You could fill them with oil, it'd be a bit tedious but it could be done. Saying that, I'd put a bit of oil in the hoses just to keep it lubed.
To me, it sounds as if it's two double acting cylinders each used as single acting. The rod end is connected on both with the short hoses to keep crap out of the cylinder, since it's the rod end of both, there's no size differential so there's no pressure genetated.
One thing that does make me wonder, why is it T'd instead of just joined ..Mike

 

[Bugsyinc]

If the cross over with the tee in it is not sealed, there is nothing to force the other side to oppose.

Make sure that tee is plugged.

 

[ecphsca]

The T is capped.

 

[J_J]

If those are DA cyl, shouldn't the hose connect the base on one cyl, and the rod end on the other cyl. I know the volume is not equal.

One cyl should be extending, and the other retracting.

 

[mrmikey]

If those are DA cyl, shouldn't the hose connect the base on one cyl, and the rod end on the other cyl

Anyone I've seen that's the way it is like I said in my first post.
The way the op described is would work as well, a bit less plumbing is all you'd be saving as well as you're losing some hydraulic force as you're only using the barrell end of one cylinder rather than the rod end as well as the barrell end....Mike