Importing and modifying a new mini excavator from China

[dfkrug]

Speaking of wiring... The wiring on this thing as delivered is horrible. Poorly planned and horribly executed.

And to add to that, the wiring needs to be updated with the proper ignition switch that not just grounds the ignition to stop the engine, but also an AUX position for the light, the hour meter, and in your case, the hyd cutoff solenoid.

In the new wiring diagram I posted as part of this thread, the makers need to toss their starter switch, and replace it with an IGNITION switch. I just use a STENS riding mower ignition switch, and eliminate the red tee-handle cutoff switch.

Mounting the starter relay and charge regulator inside the house but not on the engine is important, too.

 

[Fredrik]

Off the truck, the hydraulics were basically uncontrollable.

Welcome to the WTF club. I too thought the language these things spoke was the same as bigger machines.

I can almost assure you more is yet to come. Please be careful.

 

[Fredrik]

Can't make this stuff up.

Translation : I't is forbidden to use machine in RANE, WATER will cause machine to melt.

 

[Aaron-BC]

Translation : I't is forbidden to use machine in RANE, WATER will cause machine to melt.

Thanks Fredrik, that's most helpful and explains my failed Hour Meter!

I can almost assure you more is yet to come. Please be careful.

I am... mostly... Thank You!

 

[Aaron-BC]

And to add to that, the wiring needs to be updated with the proper ignition switch that not just grounds the ignition to stop the engine, but also an AUX position for the light, the hour meter, and in your case, the hyd cutoff solenoid.

Thank you, yes. Adding a relay has made this part of the system usable for the time being. But- I have a list of fixes left to do and by the time I am done I don't expect much of the original wiring to remain. I will be sure to document that here but just as a teaser consider this: in nearly every case where wires are spliced or joined they have been twisted and taped. I know what I pay for crimped connectors and I assume the factory can get them much cheaper than me, so this was unexpected.

Mounting the starter relay and charge regulator inside the house but not on the engine is important, too.

This is a great point that I did not think of, Thank you.

Aaron

 

[dfkrug]

Off the truck, the hydraulics were basically uncontrollable. I have about 30 years on excavators and, even though I know what this sounds like... I'm pretty good . Running this thing made me feel and look like a rookie! I thought I just needed a bit of seat time but after a short while I realized that something was amiss. I spoke to my Finning Mechanic friend who suggested that the pilot system pressure may be set too high and was slamming open the servos.

Modern multi-pump pilot-controlled hydraulic machines are wonderful to operate. Every time I get a chance to operate one, it is a pleasure.

Don't feel too bad if you felt like a rookie. One-pump systems are a somewhat different skill, as well as 4-stick (non-joystick) direct-acting one-pump systems. The latter type was how I started, back in the 90s.

I think your guy may be correct about the servos on your machine. They operate somewhat smoother than the other direct-acting 1-tons because the 1/4" hoses add some delays and cushioning to the movement of the actuator spools. If the flow or pressure is too high, you will lose some of that. Some of these pilot controls call for only 500 psi or so of pressure. So far, I have no idea what the spec is for these tiny valves in this application. I suppose that if you adjust it too low, you would have unacceptable delays, esp without an accumulator.

 

[dfkrug]

View attachment 813794View attachment 813795
Two Outlets.

The outboard one goes directly to the pilot system.

One more thing about your 2-pump system.

It looks like each chamber is about the same size, which would deliver very large volume to the servo system. That would mean that your servo system pressure should be pretty low, maybe as low as 500psi, in order not to deliver too much power to the actuators.

I suspect that is why the Diggit's servo system uses a flow divider, which could be set up to have a much lower flow rate to the servos, vs. the main valves.

Some pumps have a label on them with the flow rate stamped on it. Single stage pumps for these machines are usually about 6.5-6.8 cc/rev.

 

[ptsg]

One more thing about your 2-pump system.

It looks like each chamber is about the same size, which would deliver very large volume to the servo system. That would mean that your servo system pressure should be pretty low, maybe as low as 500psi, in order not to deliver too much power to the actuators.

I suspect that is why the Diggit's servo system uses a flow divider, which could be set up to have a much lower flow rate to the servos, vs. the main valves.

Some pumps have a label on them with the flow rate stamped on it. Single stage pumps for these machines are usually about 6.5-6.8 cc/rev.

While the physical size of each section looks the same, the internal gears can be narrower for the pump of the pilot circuit. It's not uncommon for pump manufacturers do this, so they don't have to machine different length bodies for each pump size.

 

[dfkrug]

While the physical size of each section looks the same, the internal gears can be narrower for the pump of the pilot circuit. It's not uncommon for pump manufacturers do this, so they don't have to machine different length bodies for each pump size.

Yes, that is possible, and that is why finding and reading the label is important. Or taking it apart to see.

On the spare downsized pump we ordered from the maker (HeChuang), I took it apart to measure the volume, since there was no label.

BTW, component quality has been generally good, tho documentation, awful.

 

[Aaron-BC]

Some of these pilot controls call for only 500 psi or so of pressure. So far, I have no idea what the spec is for these tiny valves in this application. I suppose that if you adjust it too low, you would have unacceptable delays, esp without an accumulator.

It looks like each chamber is about the same size, which would deliver very large volume to the servo system. That would mean that your servo system pressure should be pretty low, maybe as low as 500psi, in order not to deliver too much power to the actuators.

Yes, in my conversation with my Finning-Friend he suggested that the required pilot pressure could be quite low. He was clearly doing a lot of guessing at the time, but he seemed to think it could go well under 500psi. He saw no serious harm coming from lowering the relief as a test as long as I didn't back the adjuster right out. I'm still trying to cobble together a method for actually getting a reading off this.

While the physical size of each section looks the same, the internal gears can be narrower for the pump of the pilot circuit. It's not uncommon for pump manufacturers do this, so they don't have to machine different length bodies for each pump size.

Yes, that is possible, and that is why finding and reading the label is important. Or taking it apart to see.

Thanks guys. I am working with my guy @ CAEL to get a manual or at least the proper component specs. The pump has a laser etched label which I'll attach here. I have yet to find product spec sheet. (admittedly, I have not yet looked very hard). If MPa = megapascal then I assume 3600 +/- PSI @ 1000RPM (?) But... flow?