Grapple jaws not holding

[Flowj]

I have a MX4800 with a 72 inch grapple controlled by a Land Pride 3rd function valve. When I clamp on a log I have to keep hitting the clamp button while moving the logs or the clamping force will bleed off. Is this normal?

 

[DeepWoods]

All of my equipment is different than yours, but my grapple will lose its grip over time. If I carry anything for a distance I have to touch the close button every so often to get a better bite. I’ve never dropped a load because of it, it’s just something I have learned to watch for.

 

[trueg50]

Yup, I've have the same experience (on a smaller machine).

 

[TheOldHokie]

I have a MX4800 with a 72 inch grapple controlled by a Land Pride 3rd function valve. When I clamp on a log I have to keep hitting the clamp button while moving the logs or the clamping force will bleed off. Is this normal?

Welcome to the reality of spool valves - they leak. The typical fix is a dual pilot operated check valve. Cost you about $150 to add one to your grapple:

• Valve : $80
• Two nrw hoses: $40
• Fittings: $20

Dan

 

[GreensvilleJay]

NOT 'normal', at least in the World of Hydraulics where I come from. Either the 3rd function valve is of poor design,quality and worn out or the cylinder's ram seals are leaking

 

[TheOldHokie]

NOT 'normal', at least in the World of Hydraulics where I come from. Either the 3rd function valve is of poor design,quality and worn out or the cylinder's ram seals are leaking

ALL spool valves leak and the
third functuon valve is a spool tyoe valve. Its not only normal it is ubiquitous behavior.

Dan

 

[GreensvilleJay]

OK, I'll rephrase,... QUALITY,PRECISION , properly designed and machined spool valves will have very MINIMAL loss of oil.
I've got 66 year old valves on one tractor that do not leak as the poster describes. Rockshaft system keeps 800# blade up for better part of 2 weeks.

 

[TheOldHokie]

OK, I'll rephrase,... QUALITY,PRECISION , properly designed and machined spool valves will have very MINIMAL loss of oil.
I've got 66 year old valves on one tractor that do not leak as the poster describes. Rockshaft system keeps 800# blade up for better part of 2 weeks.

Spool leakage is a published specification. A good quality spool valve from Bucher leaks 5-6 cc per minute @1500 PSI. Cross specs 10-12. Prince is in the middle of that range.

Kubota valves have a reputation for even more.

Dan

 

[Flowj]

I guess I'll just continue to do the Nintendo button press procedure while moving with the load. Thanks.

 

[TheOldHokie]

I guess I'll just continue to do the Nintendo button press procedure while moving with the load. Thanks.

Check valve is easy and cheap.

Dan

 

[North Idaho Wolfman]

Might be the design of the grapple.
You see that happen with dual lid or dual cylinder grapples more then you will single lid/ cylinder.

 

[Smokeydog]

Raking or pulling with the grapple can easily double the line pressures in the grapple circuit causing increased wear on valves and cylinders. Tractor hydraulics are protected on the pump side of the control valve with relief valves. Dynamic loads from loader bucket, grapple are not. Pushing, pulling, long lever arms like logs and shock loads can double the pressure your tractor supplies. Technique and awareness goes a long ways on how you can protect your system from wear. I have 10,000psi gauge plumbed in M59 that I can monitor loader lift pressures while working. Higher capacity loader equipment have cushion valves that help protect circuits downstream of loader valves. KSR, Kubota Soft Ride, helps cushion carrying loads.

Operated grapples from remotes and solenoid valves. All leak a little and get worse with wear. Knowing how they work helps prevent needless wear.

Seeing trees down from last night’s storms. Going to get a workout today.

 

[TheOldHokie]

Raking or pulling with the grapple can easily double the line pressures in the grapple circuit causing increased wear on valves and cylinders. Tractor hydraulics are protected on the pump side of the control valve with relief valves. Dynamic loads from loader bucket, grapple are not. Pushing, pulling, long lever arms like logs and shock loads can double the pressure your tractor supplies. Technique and awareness goes a long ways on how you can protect your system from wear. I have 10,000psi gauge plumbed in M59 that I can monitor loader lift pressures while working. Higher capacity loader equipment have cushion valves that help protect circuits downstream of loader valves. KSR, Kubota Soft Ride, helps cushion carrying loads.

Operated grapples from remotes and solenoid valves. All leak a little and get worse with wear. Knowing how they work helps prevent needless wear.

Seeing trees down from last night’s storms. Going to get a workout today.

Thats all very true but even low end equipment like a BH70 has port reliefs in the valve to protect against high line pressures on the work circuit side of the valve

Dan

 

[The Evil Twin]

I guess I'll just continue to do the Nintendo button press procedure while moving with the load. Thanks.

Lol

 

[Flowj]

It is a dual jaw dual cylinder grapple.

 

[TheOldHokie]

It is a dual jaw dual cylinder grapple.

I have similar and I find it difficult to get a solid grip with both lids let alone maintain that while moving irregular objects.

Dan

 

[FTG-05]

I've never had that trouble with my Skid Steer Attachments 48" grapple and Construction Attachments electric valve.

I move some heavy logs with my tractor:

This is the heaviest log I've moved with my tractor. It was the trunk of a Shagbark Hickory that came down in a microburst and missed hitting my house by about 4"!

What you see here is as high I could get it, that's it.

Front tires did NOT like it!

The trunk left where it broke off:

 

[Jasonized]

Ahh yes…. We ended up taking down a couple of large trees last weekend.. I had a piece or two where the only height off the ground I could get was by rolling back the grapple.

I plan on cutting them in half before moving them to my work spot!