LW-7 Backhoe Controls

[dogfarm]

My Kama 554 has a LW-7 backhoe with a "Tractor Digger" manual that has no information on the hydraulic specs. The controls for the boom arm are extremely sensitive so that unless I'm really careful, the boom jumps all of a sudden. The control seems to be all off or all on and needs only a light amount of movement to get to the "all on" state.

Does anyone know if there are any adjustments that would make the control less sensitive? Alternatively, does it make sense to replace the control unit with something from Northern Tools?

 

[Willl]

Boom control on a BH has always been the touchiest stick and requires a certain amount of finesse compared to the others.
Next in the touchy line up would be swing control. Most BH have an adjustable restricting valve on the swing circuit to help you control this. You could install the same for your boom.

How much seat time you got on the hoe ?

 

[dogfarm]

Thanks for the reply Willl!!

I've got about 15-20 hours on the hoe when I dug a trench between the house and garage. I had a CASE W8 with a hoe about 20 years ago that I used to dig up stumps while clearing land for my house. That one had nice controls that were no trouble.

The side-to-side is somehwhat hard to control - not as bad as the boom. The lift is ok and the bucket control, is ok. I'll look for a restricting valve on the side-to-side. If the boom is typically harder to control, are restricting valves on that line common? I see Northern Tools has a flow control valve that restricts flow in one direction with no restriction in the opposite direction. Do you think this would work? I suppose I could use two to cover both extend and retract.

 

[JoelD]

On my prior backhoe, which was scratch built, it was very touchy on the boom. I installed a fitting which is a blunt fitting and drill a small hole in the blunt end and then install in line with the hydraulic hose, I installed one for left and one for right.

Made a big difference.

Joel

 

[dogfarm]

Good idea, Joel! A flow restricting orifice! How big a hole did you drill?

 

[RonMar]

Yep, the chinese hoes are not as refined. My HW-03 exibits the same issues. One reason for the swing sensitivity is the small size of the boom swing cylinders. Given the same ammount of fluid flow, the smaller swing cylinders will stroke considerably faster than the other cylinders on the hoe. A flow restrictor would help a lot here, but the rub is easilly interfacing one with the choice of Metric "O" ring face seal fittings used by the chinese on these hoes. I have an idea for one that looks like a shoulder bushing and that would fit into the existing metric ORFS fittings used on the hoe. I just havn't got around to machining any yet I find however that if I combine movements(anything but boom up) while swinging the boom, that it is much smoother as the fluid flow is divided amongst other cylinders.

Another issue, which you may have seen is that if you try some other movement at the same time you try and lift the boom, the boom actually falls as the fluid escapes from its heavilly loaded cylinder, to feed the other cylinder that is under a lighter load. Mine does this because there are no individual spool load check valves on the chinese valve. This is real annoying as real speed comes from being able to combine functions. I pretty much have myself re-trained to not attempt to combine any other function when I am lifting the boom up. A selective restrictor like you mentioned might help a little here, but again, interfacing one with the existing plumbing will be very difficult...

Even with these faults, I like mine. It has been a pretty big bang for the small bucks I have invested in it.