Getting rid of the green

[Ironman]

Originally Posted by Whitetrash

Is the directional valve for the motor open center? I'm wondering if bringing the mast down creates a flow bottleneck on your return side of the system. especially since you say the mast comes down fine once the engine stalls. Which kills the extra flow from the pump. If the valve for the motor is open center you have another return path for pump output. If not I'm thinking you need more capacity flow wise on your return side

First off, the original hydraulic system is untouched. I have tapped my pressure system into the old pump output and even used the original hose. So I can't see any thing wrong with that part of it.
What I don't know much about, no matter how many times I have used them, are flow control valves.

Trash, I think you are onto something. The motor direction control valve is open center. If there is a floating shuttle spool in that flow control, then maybe back pressure would force it into a position that closes flow from the pump. I have had, and used, power beyond type of flow controls before and I guess this one may not like back pressure.
I spect the filter will have a certain amount of resistance to flow as well.

I guess the solution at this point is to spud another fitting into the hydraulic tank...nice, now its full of oil. Then put in a flow divider and feed one divider output to the mast and one output to the flow control valve. The FC valve will dump straight back to the tank with out filtration through the new tank port. And the motor return to tank can still be hooked as it is through the filter.
Soooo, I have to go to town next.

ORF, the muffler is there so it's easy for someone to pump smoke up my ass about global warming. And this year has been a miserable cold one.

[terry lingle]

Originally Posted by Ironman

.
It's impossible to load the motor and pump when lowering.
(

That is not true.
The spool int the valve body blocks the pump port while lowering to ensure that the return fluid flows in the correct direction.
There was probably a switch somewhere that stopped the pump while lowering the mast.

Is there a relief valve in that pump circuit?

I put a non standard tilt cylinder on my forklift as well as new valves because all the original equiptment was missing when I got it.

This lead to a scary situation because the tilt needed more pressure than the mast for a given load. If you activated both controls the mast moved ( fast) to full forward tilt while the displaced fluid bumped the mast about 3 inches.

This lift will pick 26,000 lbs at 2250 psi so the effect can be very violent as well as expensive

The solution was a pressure control on the mast circuit that requires positive pressure to move the cylinder in both directions. this pressure bump is set to just more differential than the difference between tilt and mast pressures at max load.

[Ironman]

Originally Posted by terry lingle

That is not true.
The spool int the valve body blocks the pump port while lowering to ensure that the return fluid flows in the correct direction.
There was probably a switch somewhere that stopped the pump while lowering the mast.

Is there a relief valve in that pump circuit?

I put a non standard tilt cylinder on my forklift as well as new valves because all the original equiptment was missing when I got it.

This lead to a scary situation because the tilt needed more pressure than the mast for a given load. If you activated both controls the mast moved ( fast) to full forward tilt while the displaced fluid bumped the mast about 3 inches.

This lift will pick 26,000 lbs at 2250 psi so the effect can be very violent as well as expensive

The solution was a pressure control on the mast circuit that requires positive pressure to move the cylinder in both directions. this pressure bump is set to just more differential than the difference between tilt and mast pressures at max load.

Thanks Terry.
OK, there is a relief, currently set at 1500psi.
The valves all have switches on the bottoms.
There is a spare double acting valve in this block. All mast/tilt cylinders are original with original plumbing.
If you open the valve lowering, the engine loads up, the mast does not operate smoothly, and it lowers slowly til the engine stalls then lowers normally. It's as if there is back pressure on the return to tank.
Tilt cylinders operate properly and smoothly.
Are you sure about the battery forklifts mast valve having a closed port during descent?
If so, I may be temporarily skunked. I may have to have an electric dump valve(that switch may be good for something.)
Today I managed to raise a sales person at Brand Hydraulics, who said what Whitetrash said. He said there can be no back pressure on the return line.

[terry lingle]

Not sure they all have that system but one I had worked that way. It drove every new operator crazy until they understood what was happening.

The fact you are stalling the motor when you lower the mast suggests that the valve is blocking the flow from the pump through the valve to the return circuit.

Are there any unused ports on that valve block in the,mast control section? If so you may be able to plumb it differently so the pump does not load when lowering the mast.
Not sure how that pump flow will affect the lowering function especially when there is no load on the mast.

Another option :

Could you add a separate closed center valve (no flow unless the valve is actuated) for the mast that dumps directly to the tank? That option would eliminate the possible back pressure issue as well?

[bunkclimber]

I'd plumb the hyd drive motor circuit valve return directly back to the tank,without going thru the filter.The lift/tilt circuit can go thru the filter on it's way back to the tank,acting as a 'kidney' loop,it'l filter the system oil effectively enough without hurting flow.Two returns,(direct) tank ports are needed.A bit more work to drain the tank again,but sure makes it simpler in operation. A bit more expensive solution would be to go with a two-section pump,one section for drive and one for implement(lift/tilt)...no limitations there except your wallet.Whatever you do work out,you'll wonder how you EVER got along without a fork..I've had one 10yrs now and can't function without it.

[Ironman]

Ok. Back at it. I've been sick as a dog for a while. Come to think...I've never seen a sick dog. But the fever and hacking is about over.
I put in the flow divider to split of the motor circuit from the mast circuit.
That didn't help. And I completely blew the seals out of my hose press. That didn't help either.
I removed the hyd motor thinking that the gearbox was at fault. I was grasping at straws.
Nothing wrong there. So I removed the directional valve, and there it was. This is a BLB modular valve, with parts interchangability within series. So you can have multi spool, motor, single acting, double acting, detent, spring return, etc, all at the swapping out of one part.
And they sold me a valve with a single acting spool in it. Turns out a customer bought it with a single acting spool installed, never used it, and returned it. Some goober re-stocked it with the wrong spool in it.
I probably never needed that damn flow divider.
So today I felt well enough to put it all back together and make a victory lap around the yard and park back at the shop.
Next efforts are to complete the accelerator pedal linkage, and figure out what to do about the mast.
Terry, do you think, if I pull the spool out on the mast valve, could I machine another groove on the spool to allow for pump recirc while dumping the mast?
I can't see the casting being altered especially for this use. I suspect the Mfg. altered the spool instead.

[terry lingle]

Gerry we can do anything
I take it that even after you modified the circuit the mast control plugs the pump.

Just be sure that what you do will work before you cut there is no going back.
Can you get a spare valve from the place you got the machine from? ( a go back plan)


If you do try to machine it I think you will need to mask off the spool surfaces you do not want to damage and grind that spool to create open center. just chuck it in the drill press jury rig a support for the angle grinder and gently cut it down but do not overheat or warp it .

[Ironman]

Yeah, the mast control still plugs off the pump.
If I can't get a spare valve to murder, I will try to set up linkage to the spare valve in the block and use it to dump pressure when descending.

Umm, why would you grind the spool? I'm sure I could cut it in the lathe, and if it destroys carbide I'll be forced to start up the tool post grinder.

[terry lingle]

I would grind it because I would not risk damaging the surfaces or introducing a bend in a precision ground part.
I have never tried cutting a spool but i suspect it will be very hard so I err on the side of caution.

By all means use the tool post grinder.

[Ironman]

except for some wiring.

I would not risk damaging the surfaces or introducing a bend in a precision ground part.

Well, seeing as you put it that way, I took the cowards way out.
I plumbed a hose from a port in the spare valve spool back to the tank. Then I lit up the gas axe and heated and bent the lever over to contact the mast lever, and cut off the excess.
There were two unused returns on the tank that were 1/2 and 3/8" so I did not have to add another. They seemed a bit too small to me, but worked well in this application. The mast works perfectly with or without a load, and the motor is happy. Running 4 ft of return hose was less work then tearing down a valve and machining.
Without added counterweights, the f/l will lift up the back of my pickup. However, when my fast ass is off the seat, the back wheels come off the ground an inch.
So I will have to add the iron to the counterweight after all.
I am very pleased with the delicate control I have with the hydraulic drive. It is very easy to sneak under a pallet or a piece of equipment, and as I did not use a motoring spool, it also effectively brakes the machine. The speed is exactly where your foot tells it to be in acceleration or deceleration.
Here's some pics of the end result.
1 is how I modified the third valve handle so it is active on the down stroke of the mast
2 shows the return line second from right that diverts pump flow to the tank. It works flawlessly.
3 It was suggested I cut some ventilation holes....I couldn't help it, a winged skull on a forklift
4 shows the operators compartment, and the accelerator pedal attached to the flow control
5 here's the whole package.