Wild boom and swing on BH

[familyman]

My BushHog 650 has a very sensitive boom/swing lever. I have to move the lever extremely carefully and feather it at the end of the actions to keep the boom from quickly whipping around and up and down, causing the tractor to lurch and jump. The crowd and curl functions are slower and much smoother. Does anyone know if this is normal, or could there be something wrong with the valves or some other aspect of how it's assembled or installed?

Charley

 

[Henro]

On my Kubota Backhoe, I think the boom and boom swing are more sensitive than the crowd and curl. So it may be like you are experiencing.

With use things settle down as you get more practice. At least they did with me...

I know there are flow restrictors installed for some or all of the functions on my backhoe. Read that in the manual somewhere I think.

Now if for some reason the flow restrictors were supposed to be in your backhoe and were not, then you could have some really quick movements, approaching unsafe I would suspect but don't really know.

Is your backhoe a used one you got from someone else, rather than one you purchased new? If so, it might be worth checking into what flow restrictors are supposed to be in place and whether they are there or not.

 

[v8dave]

Just like Henro's BH, mine is fairly sensitive in the Boom and swing. Believe it or not if you can operate two controls at once, such as lifting/dropping the boom while swinging back and forth, the sensitivity reduces as you spread the power across the two cylinders.

I have gotten used to the sensitivity on the swing. But, I still have problems on occasion with the boom.

Henro is correct, there are restrictors on the Kubota backhoe. The manual shows the smallest restrictor on the swing (.055") and with a larger (.094") on the boom and dipper. I plan on asking the dealer to put a smaller restrictor in the boom circuit when I go in for the 50 hour service. If possible, I'll ask to see the change so I can undo it if necessary.

I also rented a backhoe and an excavator and they also seemed to have the same sensitivity I find in my Kubota. I suppose altogether I now have about 70 hours on a backhoe of some type.

Total time on the Kubota B7610 is now 38 hours. About 20 on the backhoe. It continues to get easier to coordinate all the time. It may be that I have the boom "feel" by the time I take it in and I may not have to ask for the smaller restrictor.

Keep on digging, it definitely gets easier with more practice.

Dave

 

[familyman]

Yes, the digging gets easier all the time. After 13 hrs I no longer have to think much about the controls, until I start getting tired. I've learned to use the power of the curl and I make good progress now. The boom and swing fuctions get dramatically slower when I simultaneously employ the crowd/curl lever, often nearly stopping. God forbid that I should stop using the RH stick without feathering the left -- then the boom leaps! I will definitely look into the flow restrictor issue, but, as always, I'm curious; will changing a flow restrictor effect only the speed or does the power get reduced as well? Thanks again, guys.

Charley

 

[SteveH_CT]

I haven't seen anyone mention RPM's ... On my tractor the RPM I'm operating at makes a huge difference when I use the BH. What speed do you have the engine running at? I rarely exceed 1500 RPM's when I use the BH. Makes me look a lot smoother /forums/images/graemlins/wink.gif.

 

[v8dave]

Regarding engine speed.

When I'm digging in a lot of rocks, which is about half the time, I use full speed (2,600 rpm). And, the backhoe is more twitchy to operate.

I followed the advice offered here a while ago to cut down the engine speed when I'm not in the hard stuff. I now use about 1800 or 2000 rpm as a starting point. 1500 rpm is just too slooooooooow to be useful. I ran the'hoe 3 hours today and never went over 2000 rpm.

Regarding restrictors:
I'm not an expert, but I believe that ultimately the same force will be reached with a restrictor in the line.

If its any consolation, I hired a backhoe and operator to do some digging last year. I had a stream bed rerouted--major boulders and rocks in the stream. This guy on a Case 580-Super, with several thousands of hours, jerked the boom on occasion. He didn't jerk on the swing though.

Dave

 

[SteveH_CT]

Wow - I've never run my engine that fast yet - ever. I don't have any 3pt attachments so no need for me to hit that speed. The advice I've gotten here and from my dealer is that the unit won't produce more lifting/pulling/digging power at higher RPM's - it's just faster responding.

Well good luck with it - just keep away from houses... make sure dogs and small children are at a safe distance... and make sure you don't have too much coffee before you run it /forums/images/graemlins/grin.gif.

 

[familyman]

Regarding engine speed, I definitely get more digging power at 2000 than at 1500 rpm, but I do look smoother at lower rpm's! I'm glad rated speed was mentioned -- I guess it's not really needed for BH work. No, the left stick problem for me is that the movements are just way faster than for the right stick. I guess more training time will get me used to this but I wonder if it is the same on all backhoes?

 

[JerryG]

At one time or another I have tried about every RPM. I almost always use it at about 1500 or lower if in close quarters or a very tight place. As far as power with more RPM, hook up a pressure gage. It will produce the same pressure at 1500 as at 2500, but the speed (flow) is faster.

 

[TORQUIN]

Higher RPM does give you a little more digging power. I have noticed this on mine. An easy example to replicate it is with the FEL. When lifting something heavy and the FEL stops lifting, rev the engine up a little and the FEL will pick up some more. I have to do this sometimes when placing the larger stumps on top of the burn pile.

I cannot explain why this happens. Perhaps it is because the higher RPM gives higher flow, and further cylinder travel, before hitting the pressure limiter?

Chris