Possible Air In Backhoe Dipper Stick Cylinder - Cycling Doesn't Eliminate - Help

[LD1]

Okay. So after watching some YouTube stuff on Floppy Bucket Syndrome, you might be right. I've been doing all my backhoe work with the tractor at idle (~1400rpm) to keep the motions a little less jerky until I get a better feel for the thing. After I get home tonight I'm going to try it at a higher RPM to see if that makes a difference. If so, then I think you hit the proverbial nail on the head with the pump not keeping up and it drawing a vacuum in the cylinder. I'm also going to try smaller (not fully extended) movements of the dipper from around the 7 to 5 o'clock positions to see if that still has the issue or if it's just when "gravity wins out" and forces the dipper down from a higher position.

Yea, at idle it makes things worse if that is indeed what is going on.

At Idle....say ~700-800rpm.....you have about 1/3 the flow you have at PTO RPM....give or take.

So hypothetical.....say at PTO RPM your machine can pump 6 gallons a minute into the cylinder.....you are only giving it ~2 gpm.

Gravity is constant. It dont know and dont care what RPM the tractor is at. Its force on the dipper is the same. Again, hypothetical lets say gravity is causing a void of 4 gallons per minute that need replenished......do you see the issue?

 

[snymat68]

Yea, at idle it makes things worse if that is indeed what is going on.

At Idle....say ~700-800rpm.....you have about 1/3 the flow you have at PTO RPM....give or take.

So hypothetical.....say at PTO RPM your machine can pump 6 gallons a minute into the cylinder.....you are only giving it ~2 gpm.

Gravity is constant. It dont know and dont care what RPM the tractor is at. Its force on the dipper is the same. Again, hypothetical lets say gravity is causing a void of 4 gallons per minute that need replenished......do you see the issue?

I'm with ya. I'll post back tonight after I try things at higher rpms.

 

[snymat68]

LD1, you were spot on. Worked perfectly at 3000rpm (540pto). 1400 (idle) has the severe lag at bottom dead center. And 2000rpm was laggy but not as bad.

Also, I talked to a guy at the dealer and he checked one on the lot and it behaved the same way. I learned something today. Thanks for the help and insight! I'm happy it was something this simple.

 

[Tractor Seabee]

i think LD called it. On my BX I do not get full flow till about 2K RPM. That seems to be my sweet spot for smooth full power BH ops. Like you say the higher the RPM the faster and jerkier it works. I increased my hyd pressure to 2K PSI which lowered my sweet spot to the 20K. A full RPM I find my self banging into things with the dipper. Find that sweet spot and practice there, the learning curve was pretty short for me. I was soon operating w/o looking at the controls.

Ron

 

[LD1]

LD1, you were spot on. Worked perfectly at 3000rpm (540pto). 1400 (idle) has the severe lag at bottom dead center. And 2000rpm was laggy but not as bad.

Also, I talked to a guy at the dealer and he checked one on the lot and it behaved the same way. I learned something today. Thanks for the help and insight! I'm happy it was something this simple.

I am glad it was nothing actually wrong on a new machine. I had a feeling......but glad it panned out to be right.