Excavator boom swings and drops too fast

[r8f1k]

I have an old Case DH4B trencher/excavator combo. Finally got the excavator up and running with the controls in the two joystick SAE configuration. When I run it, the boom drops FAST. Barely move the stick and she slams down. The left and right control is not quite as bad, but it is too fast. When I swapped out the old 6 stick valve for the twin joysticks, I could see screw in orifices in a few of the ports. They had pretty small holes and they were threaded in somehow. I couldn't get them out with a big flathead, they had a slot in them. Is there anything like that I can add to the current control valve to slow the cylinders down like the orifices? They looked just like sprayer orifices.

 

[oldnslo]

Adding thread in inserts Depends on how deep the ports on your valve are threaded. You can also purchase orifice fittings and or fittings threaded to accept an orifice. Another option is in line flow control that is adjustable. These are also called needle valves. Just make sure they are pressure rated for hydraulic service.

 

[r8f1k]

Is there anything that can be placed right on the end of a JIC fitting? There isn't too much room near the control valve. If so, how do you decide what size to put in?

 

[r8f1k]

Will this work?

 

[Rich B1]

Likely the orifices you saw were orifice checks that were port options in the valve. The checks allowed free flow in one direction, restricted flow in the other.

Most circuits using orifices are typically installed to allow exhaust metering, especially on circuits that gravity can affect, like your boom down. By restricting the exhaust, there is back pressure in the cylinder to prevent it from running ahead of pump flow.

Parker did make a fitting that had an orifice check that was part of the fitting. It was available as a check and a number of sizes. I don’t know if those are available in the consumer market. Maybe contact a Parker parts store.

The adjustable flow restrictor is a good option, you can have free flow one direction, restricted flow the other. They don’t have to be at the valve, you can install them at the cylinder ports or in-line if needed.

 

[oldnslo]

Will this work?
View attachment 791399

If that is the correct size fitting it looks like it should.

 

[Unicam]

restricted orifice fitting. it will slow both ways obviously but less chance for damage. also, you can drill it out slightly if it's too slow. from my experiance adjustable flow valvces are garbage, don't hold setting, leak and prone to failing plus cost to much

https://www.tractorsupply.com/tsc/p...U4qNtb-PIgdS1vJwH07SmyUnp5wSYO_xoCz-IQAvD_BwE

 

[LD1]

What is the GPM of the machine and what was the GPM rating of the valve?

Sounds like the valve was too big. It comes up often on here but you want to try and match the rating of th valve as close as you can with the flow of the machine. If you have a machine that runs at 8gpm and put a 25gpm valve on it you loose the ability to feather the controls.

Its like trying to control a garden hose sized stream of water with a fire hose nozzle. Barley crack the nozzle and you are already at full garden hose flow....

 

[5030]

Because I'm inherently cheap, I make my own restrictors out of appropriate sized copper blanks and drill my own restrictor holes in them the copper acts as a seal too. You can use brass as well but copper is better.

 

[LD1]

Do them copper blanks cost you about $0.01 ea?

 

[5030]

Have no idea as I have a box of them on the shelf I bought years ago.

 

[LD1]

Have no idea as I have a box of them on the shelf I bought years ago.

I was inferring using a penny

 

[5030]

That works too and I've done that as well, so long as the ID of the cent will fit in the fitting. Way back when we used to put dimes in the front air lines on big trucks to disable the front brakes. That was before ABS came along. Front brakes on big trucks were an invitation for suicide on a wet or snowy road.

Nice thing about 'rolling your own' is you can start with a very small hole and work up for flow.

 

[Leejohn]

Check this out.

flow restrictor adapters

qualityfarmsupply.com

 

[r8f1k]

Check this out.

flow restrictor adapters

qualityfarmsupply.com

I love the price and set up, but I want to get JIC vs. NPT.

 

[r8f1k]

Because I'm inherently cheap, I make my own restrictors out of appropriate sized copper blanks and drill my own restrictor holes in them the copper acts as a seal too. You can use brass as well but copper is better.

Where did you get the copper blanks? What are they called?

 

[CADplans]

Is it possible that someone replaced the pump, and substituted a larger pump?

If this machine is a simple open center hydraulic system, those restrictors can shorten the life of the pump.
On open center systems, when the hydraulics encounter a restriction, the oil must open the relief valve.

When the relief valve opens, ALL of that pump horsepower is converted to heat.

Too much heat,, something fails.

Can the engine throttle be reduced to resolve the hydraulics speed problem?

 

[LD1]

 

[ericm979]

The adjustable flow restrictor is a good option, you can have free flow one direction, restricted flow the other. They don’t have to be at the valve, you can install them at the cylinder ports or in-line if needed.

This is what I did on my Branson backhoe. I put them on the boom cylinder, set to restrict flow out of each port of the cylinder. It pretty much eliminated the up and down jerkiness. They're set to restrict the outflow on the theory that restricting inflow might cause cavitation. I'm not sure it would, or if it'd make a significant difference.

Between the piston end and rod end of the cylinder moving different amounts of fluid and gravity only working in one direction, the two restrictors ended up with different settings to get things just right. That's why I went with two instead of one.

 

[r8f1k]

Is it possible that someone replaced the pump, and substituted a larger pump?

If this machine is a simple open center hydraulic system, those restrictors can shorten the life of the pump.
On open center systems, when the hydraulics encounter a restriction, the oil must open the relief valve.

When the relief valve opens, ALL of that pump horsepower is converted to heat.

Too much heat,, something fails.

Can the engine throttle be reduced to resolve the hydraulics speed problem?

The pump is original based on the parts diagram from Case. There is a HUGE oil cooler on this machine and the old hydraulic valve body had three orifices in the ports, probably to eliminate exactly what is happening.