Backhoe / Hydraulics question

[Jay4200]

Questions regarding my backhoe and the health of it's hydraulic system. Woods BH9000 using tractor's hydraulics, BTW.

Power -- Out of the three main degrees of digging freedom, power from strong to weak goes: bucket curl, boom lift, dipper.

Dipper joint hold-off strength -- the dipper joint can move in response to bucket curl torque (if it is extended). For example, if I hook the bucket around a rock with the arm mostly extended, then curl the bucket to move the rock toward me (pressing against the dirt behind the rock), the dipper joint may straighten out slightly. I can imagine that the torque imposed on the dipper joint by the bucket curl pressure could exceed the blow-off pressure (I know my elbow is pretty weak at full extension), so it seems like this could easily be normal, but I figured I'd ask.

My boom leaks down such that about 1" of shaft is exposed overnight. Does this sound OK? Bucket curl doesn't appear to leak down at all. Haven't done a dipper leak-down test yet.

Thanks - Jay

 

[Jay4200]

Questions regarding my backhoe and the health of it's hydraulic system. Woods BH9000 using tractor's hydraulics, BTW.

Power -- Out of the three main degrees of digging freedom, power from strong to weak goes: bucket curl, boom lift, dipper.

Dipper joint hold-off strength -- the dipper joint can move in response to bucket curl torque (if it is extended). For example, if I hook the bucket around a rock with the arm mostly extended, then curl the bucket to move the rock toward me (pressing against the dirt behind the rock), the dipper joint may straighten out slightly. I can imagine that the torque imposed on the dipper joint by the bucket curl pressure could exceed the blow-off pressure (I know my elbow is pretty weak at full extension), so it seems like this could easily be normal, but I figured I'd ask.

My boom leaks down such that about 1" of shaft is exposed overnight. Does this sound OK? Bucket curl doesn't appear to leak down at all. Haven't done a dipper leak-down test yet.

Thanks - Jay

 

[Jay4200]

In case I'm not clear - does all of the above sound normal? Does anything sound excessive and/or indicative of blow-by?

thanks - Jay

 

[Jay4200]

In case I'm not clear - does all of the above sound normal? Does anything sound excessive and/or indicative of blow-by?

thanks - Jay

 

[JerryG]

<font color="blue"> My boom leaks down such that about 1" of shaft is exposed overnight. Does this sound OK? Bucket curl doesn't appear to leak down at all. Haven't done a dipper leak-down test yet. </font>
Very few compact loaders or backhoes don't leak down. The rate that you stated is very good for leak down. The best thing to do is either put the transport pin in or let it down to the ground when it isn't in use to relieve the pressure on the valves and cylinder packing.

 

[JerryG]

<font color="blue"> My boom leaks down such that about 1" of shaft is exposed overnight. Does this sound OK? Bucket curl doesn't appear to leak down at all. Haven't done a dipper leak-down test yet. </font>
Very few compact loaders or backhoes don't leak down. The rate that you stated is very good for leak down. The best thing to do is either put the transport pin in or let it down to the ground when it isn't in use to relieve the pressure on the valves and cylinder packing.

 

[dfkrug]

</font><font color="blue" class="small">( Dipper joint hold-off strength -- the dipper joint can move in response to bucket curl torque (if it is extended). For example, if I hook the bucket around a rock with the arm mostly extended, then curl the bucket to move the rock toward me (pressing against the dirt behind the rock), the dipper joint may straighten out slightly. I can imagine that the torque imposed on the dipper joint by the bucket curl pressure could exceed the blow-off pressure (I know my elbow is pretty weak at full extension), so it seems like this could easily be normal, but I figured I'd ask.
)</font>

How much is "slightly"? If your dipper stick moves at all
with its valve closed, then it is due to air in the cylinder or
a leaking internal cyl seal, or a leaky valve itself. If you
have only a 1" leakdown overnight under pressure, then I
would lean toward air in the cylinder. Of course, loose
pins could give you a lot of wiggle room, too.

 

[dfkrug]

</font><font color="blue" class="small">( Dipper joint hold-off strength -- the dipper joint can move in response to bucket curl torque (if it is extended). For example, if I hook the bucket around a rock with the arm mostly extended, then curl the bucket to move the rock toward me (pressing against the dirt behind the rock), the dipper joint may straighten out slightly. I can imagine that the torque imposed on the dipper joint by the bucket curl pressure could exceed the blow-off pressure (I know my elbow is pretty weak at full extension), so it seems like this could easily be normal, but I figured I'd ask.
)</font>

How much is "slightly"? If your dipper stick moves at all
with its valve closed, then it is due to air in the cylinder or
a leaking internal cyl seal, or a leaky valve itself. If you
have only a 1" leakdown overnight under pressure, then I
would lean toward air in the cylinder. Of course, loose
pins could give you a lot of wiggle room, too.

 

[john_bud]

It sounds all normal to me. The strength is all about the leverage from the hydraulics and the physical set up. The curl is typically physically the most advantageous. Movement speed is related to cylinder size and pump volume/rpm.

How old is your hoe? Operating hours? If it is new, you may have air. Air can be purged by extending the cylinder all the way and hold the control to force it against the stop for a count of 5, then all the way back and against the stop for a count of 5. Do that 3-5 times in a row for each cylinder. Check the fluid level in the res before and after, with the loader and hoe in the exact same position. If there was air, it should be lower. If there was a lot of air, it may even look foamy for a short while. Mine did when I put a rebuilt cylinder in.

The overnight sag sounds normal.

jb

 

[john_bud]

It sounds all normal to me. The strength is all about the leverage from the hydraulics and the physical set up. The curl is typically physically the most advantageous. Movement speed is related to cylinder size and pump volume/rpm.

How old is your hoe? Operating hours? If it is new, you may have air. Air can be purged by extending the cylinder all the way and hold the control to force it against the stop for a count of 5, then all the way back and against the stop for a count of 5. Do that 3-5 times in a row for each cylinder. Check the fluid level in the res before and after, with the loader and hoe in the exact same position. If there was air, it should be lower. If there was a lot of air, it may even look foamy for a short while. Mine did when I put a rebuilt cylinder in.

The overnight sag sounds normal.

jb

 

[dfkrug]

Oh, yeah, some b/hs have a special relief built into the
dipper stick valve for protecting it in just the situation you
describe. Curling the bucket with dipper fully extended.

 

[dfkrug]

Oh, yeah, some b/hs have a special relief built into the
dipper stick valve for protecting it in just the situation you
describe. Curling the bucket with dipper fully extended.

 

[Jay4200]

</font><font color="blue" class="small">( Oh, yeah, some b/hs have a special relief built into the
dipper stick valve for protecting it in just the situation you
describe. Curling the bucket with dipper fully extended. )</font>

My assumption was that when I'm generate full power using the bucket, the torque imposed on the dipper joint could greate pressures far in excess of pump pressure at the dipper cylinder - a blow-off valve would be prudent. Anyone know if Woods puts one of those in the BH9000?

I thought it might be indicative of blow-by, however, and the dipper is the weakest movement of the three. I guess that's why I asked. There shouldn't be air anywhere, since the BH has plenty of hours on it - although I suspect that the boom cylinder might. I noticed it making a jerky movement once - like it paused for a fraction of a second before moving. Since I haven't even had the opportunity to dig 9' straight down, the boom has never been fully extended.

Jay

 

[Jay4200]

</font><font color="blue" class="small">( Oh, yeah, some b/hs have a special relief built into the
dipper stick valve for protecting it in just the situation you
describe. Curling the bucket with dipper fully extended. )</font>

My assumption was that when I'm generate full power using the bucket, the torque imposed on the dipper joint could greate pressures far in excess of pump pressure at the dipper cylinder - a blow-off valve would be prudent. Anyone know if Woods puts one of those in the BH9000?

I thought it might be indicative of blow-by, however, and the dipper is the weakest movement of the three. I guess that's why I asked. There shouldn't be air anywhere, since the BH has plenty of hours on it - although I suspect that the boom cylinder might. I noticed it making a jerky movement once - like it paused for a fraction of a second before moving. Since I haven't even had the opportunity to dig 9' straight down, the boom has never been fully extended.

Jay

 

[CTyler]

We put in a drain tile last week and was digging as far down as it would go and in close to get the straight verticle for the drop pipe. I let off several times cause is was really pulling down on the curl and made me a tad nervous.

 

[CTyler]

We put in a drain tile last week and was digging as far down as it would go and in close to get the straight verticle for the drop pipe. I let off several times cause is was really pulling down on the curl and made me a tad nervous.