Boom Lift salvage yard

[TVA]

So if I understand correctly, each counterbalance Dynamic brake valve uses the travel wheel hydraulic motors as a braking mechanism, kind of like an engine brake in a truck? And the heavy duty springs adjustment determines the stopping distance from 1 to several feet? And after it stops then the parking brake kicks in?

And it looks like the mechanical brake drum in the wheel hub is really a parking brake since there is just one small hydraulic line going to one small adjustment needle on the drive brake valve cylinder block?

Something like that, the only thing that on manlifts ( at least on newer ones ) everything is on counterbalance valves - safety thing! Dealing with humans!

 

[Ronray]

Thank you everyone. Looks like I've got some more testing to do. I'm going to cap off all of the beefy exit lines from the valve block and check the exit pressure on each one individually. And if I am still getting the reduced pressure at 1200 lb instead of the inlet pressure of 2500 lb, then I am thinking I will just start removing the internal components from the inside of the drive brake valve block and see if that affects the exit pressure on each exit port?

 

[TVA]

What way of thinking made you come up with that idea?!

OK, let’s start with publishing that diagram AGAIN, because I’m not gonna be looking for it in archives!
Stop jumping all over the place, randomly checking stuff , and come up with method and the plan!
2500 psi, is it what you see on your main control valve test port, or you see at your drive block inlet?

 

[Ronray]

Thanks for your patience TVA!

2500 psi is what I get on the Drive block Inlet both forward and reverse lines and also what I get at the proportional valve manifold, and 2500 PSI is also the maximum PSI rating on the identification plate for the machine. 1200 PSI is what I get on one of the large beefy Outlet lines from the drive brake block. I have not yet tested the other three block outlet ports.

I am attaching the hydraulic schematic entire page and the zoomed up drive brake block section, and a hose diagram page.

 

[TVA]

What happens if you plug the shift/break port? Still loosing pressure?

 

[Ronray]

I can also upload pictures of the Dynamic brake counterbalance valves and the flow divider valve within the drive brake block if you would like to see those.

 

[Ronray]

What happens if you plug the shift/break port? Still loosing pressure?

Yes I was still losing pressure when I did that test previously. And I also blocked off the inlet and Outlet lines to the little two Speed Shift cylinder as well, which was something that you had suggested I try previously.

 

[TVA]

Funny like they show on diagram that shift cylinder and break release on the same branch outside the block, but in reality it is different ports in the block.

 

[Ronray]

Funny like they show on diagram that shift cylinder and break release on the same branch outside the block, but in reality it is different ports in the block.

I know what you mean. These PDF service manuals leave a lot to be desired. PDF Pages out of order, and different part numbers showing on that valve block for example on the hydraulic schematic than what it shows on the parts page. And this marklift Model 62 PDF manual had absolutely no description about the dynamic break counterbalance valve adjustments, but I found the description in a PDF manual for a marklift scissor lift. And I was also recently advised that marklift used the same exact drive brake block part number 21214 on all of it's boom lift and scissor lift models, thousands of which were produced. Which surprises me that I cannot find even a used one.

 

[TVA]

Did you measure the pressure on both inlets of drive block, or only on one?
Your MCV show pressure reducer but only on one side. Can it be what reduced your pressure but you have gauge on different side on inlet and outlet?

 

[TVA]

Did you measure the pressure on both inlets of drive block, or only on one?
Your MCV show pressure reducer but only on one side. Can it be what reduced your pressure but you have gauge on different side on inlet and outlet?

Actually - scratch that! I was wrong!

 

[TVA]

Does it have low pressure both directions? Forward and backwards?

 

[Ronray]

I measured high pressure at 2500 PSI for both of the inlet lines to the drive brake block, but I have only tested one of the four beefy outlet lines. That's on my to-do list.

 

[TVA]

I measured high pressure at 2500 PSI for both of the inlet lines to the drive brake block, but I have only tested one of the four beefy outlet lines. That's on my to-do list.

Let me clarify: you had 2500 on one inlet going one way and 0 going the other way, and totally opposite on the other inlet? Or it’s 2500psi regardless?

 

[TVA]

Another very important question: does your inlet pressure drops when you trying to drive or it’s stays the same?! Trying to find out weather block is bypassing or restricting.

 

[Ronray]

Let me clarify: you had 2500 on one inlet going one way and 0 going the other way, and totally opposite on the other inlet? Or it’s 2500psi regardless?

I have one pressure gauge. I wanted to eliminate the turret rotation manifold as a possible leak source , so I connected the Gage to one of the two beefy lines that goes into the drive brake manifold. I did not t the gauge into the line, but instead just made the gauge a dead-end connection for that hose, and the other incoming hose to the drive brake manifold I just capped it off. When I engaged Drive function, I left it fully engaged for about 5 Seconds and the pressure held at 2500 lb, which tells me that there were no leaks between the proportional valve manifold and the drive brake valve block. Then I did the same test with the other incoming line to the drive brake valve block and it also held pressure at 2500 lb.

If I remember correctly, I capped off three of the four out going beefy hoses from the drive brake manifold to the hydraulic motors and also capped off the parking brake line from the drive brake manifold and another line from the drive brake manifold to the two speed shift cylinder, and put the gauge on the one remaining beefy hose from the drive brake manifold as an end connection. Both of the inlet hoses from the proportional valve Bank to the drive brake manifold were connected. When I engauged the drive function, the pressure gauge only went up to 1200 lb and held it at that until I disengaged the drive function.

So either the drive brake valve block was leaking fluid back through the other incoming hose, or it was just blocking off the higher pressure?

One more notation that may be of help, when I have the valve block off of the machine and all four exit ports capped off, if I blow into one of the large two Inlet ports, a lot of air comes out of the other inlet port.

 

[TVA]

Shuttle valve for shift cylinder and park break release would be the first suspect for cross port leakage.

On the picture red arrow either shuttle valve or check valve for counterbalance marked with yellow arrow.

 

[Ronray]

View attachment 201885 Shuttle valve for shift cylinder and park break release would be the first suspect for cross port leakage.

On the picture red arrow either shuttle valve or check valve for counterbalance marked with yellow arrow.

Yes TVA, the local hydraulic shop I took the block to said the same thing and I watched the technician remove both of the shuttle valves and look at the little spring and steel balls and the seat inside the block ( picture posted earlier in this thread) and he could see no visible damage, and he also took some measurements with a micrometer inside the shuttle area of the block, and said he could see no damage, but would recommend replacement of those shuttles, and he looked for some part numbers on the shuttle cap head and sides, but could find no numbers.

So I am curious, if I remove the shuttle cap and springs, and physically hold the balls on their seat with my fingers or a stiffer spring or something, should that keep the air from passing between the two large beefy Inlet ports to the hydraulic brake block? Maybe I could spend the balls around and see if that provides a better seal? Or install stiffer Springs to hold the balls more tightly to the seat?

 

[Ronray]

okay I'm just now editing this. So I'm guessing the ball and spring in the picture is the check valve, not the shuttle valve? And also FYI there are two sets of these balls Springs and caps, one on top of the block and one on the bottom of the block, and each one connects to a separate Dynamic brake block counterbalance valve with the big heavy duty spring that you have the yellow arrow drawn to.

 

[TVA]

There’s a difference in shuttle valve and check valve. You show two checks and one shuttle! Although sometimes one shuttle can be comprised by two checks.
Your shuttle valve should look like longer two step cartridge valve, and should have no springs in it, if it’s ball or spool a I can’t tell you. But it should have passage to both inlets and shift cylinder and park break hoses.