K-Boom with fixed rotating grapple?

oceans

Well-Known Member
I’ve seen a few videos from one company that is running a fixed rotating grapple setup on a Palfinger. This seems like an ideal setup if the weight doesn’t steal too much from the chart.

I’ve done a lot of searching but can’t seem to go any further down this worm hole with what time I have available. Anyone know anything about this?
 

deevo

Well-Known Member
I’ve seen a few videos from one company that is running a fixed rotating grapple setup on a Palfinger. This seems like an ideal setup if the weight doesn’t steal too much from the chart.

I’ve done a lot of searching but can’t seem to go any further down this worm hole with what time I have available. Anyone know anything about this?
You can ask Brad at grapple pros they aren’t far from you in Quebec he sells all sorts of grapples, grapple saws etc. He’s a meçanil dealer also. Don’t know why you’d want something that big and heavy at the end of your boom though, takes away a ton on capacity I’d imagine.
 

Gus_B

Member
I’ve seen a few videos from one company that is running a fixed rotating grapple setup on a Palfinger. This seems like an ideal setup if the weight doesn’t steal too much from the chart.

I’ve done a lot of searching but can’t seem to go any further down this worm hole with what time I have available. Anyone know anything about this?
It looks almost like a Vosch grapple that's been modified to fit on a knuckleboom.
Typically these are used for excavators.

 

Lumberjack

Well-Known Member
It looks like a custom mount from the boom the excavator tilt rotator to a normally excavator mounted rigid grapple and saw.
 

Gus_B

Member
It looks like a custom mount from the boom the excavator tilt rotator to a normally excavator mounted rigid grapple and saw.
Yes I agree and I would suggest you do not consider it if this is the case. The dynamic stresses on such narrow diameter final extensions on a knuckleboom with a flyjib would eventually be structural failure with a fixed rotating grapple device.. The twist forces if you do something even slightly improper will create an unexpected bending moment and result in a catastrophic failure. There is just not enough steel and strength in my experience on a knuckle boom to handle a fixed attachment like this which is why they are used on short reach excavator arms which are massively stronger compared to a knuckleboom. It would void any warranty your crane may have.
I probably would not even consider it on a drywall style crane which have much larger diameter, stronger and much greater twist resistant final extensions.
K cranes are meant to go up and down not side to side under load. A device like this can create unexpected side to side stresses which knucklebooms were not designed for.
Just my 2 cents from someone who's been both a crane operator and in the knuckleboom industry for 25 years.
 
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oceans

Well-Known Member
Yes I agree and I would suggest you do not consider it if this is the case. The dynamic stresses on such narrow diameter final extensions on a knuckleboom with a flyjib would eventually be structural failure with a fixed rotating grapple device.. The twist forces if you do something even slightly improper will create an unexpected bending moment and result in a catastrophic failure. There is just not enough steel and strength in my experience on a knuckle boom to handle a fixed attachment like this which is why they are used on short reach excavator arms which are massively stronger compared to a knuckleboom. It would void any warranty your crane may have.
I probably would not even consider it on a drywall style crane which have much larger diameter, stronger and much greater twist resistant final extensions.
K cranes are meant to go up and down not side to side under load. A device like this can create unexpected side to side stresses which knucklebooms were not designed for.
Just my 2 cents from someone who's been both a crane operator and in the knuckleboom industry for 25 years.
If that’s the case, what happens when a dangle saw makes a cut and the load of the grapple/beach becomes a dynamic force? From what I understand, if a grapple saw is good for x and a particular area in the chart, the operator must go lower to allow for the force.
 

oceans

Well-Known Member
You can ask Brad at grapple pros they aren’t far from you in Quebec he sells all sorts of grapples, grapple saws etc. He’s a meçanil dealer also. Don’t know why you’d want something that big and heavy at the end of your boom though, takes away a ton on capacity I’d imagine.
Thanks Devon. I know him and his outfit...bought a nice rotating grapple from him last year. How’s your truck?
 

Gus_B

Member
Oh that’s good! 90% done going down to FRF today to see and play with it, just waiting for the place that’s doing the Dump box to take it next. I’ll bet some pics
FRF is a quality firm and they do great work. Congrats on your new truck I'm certain you will be very happy.

Oceans I'm not an engineer so I'll explain it the way I see it in my simplistic way.
Let's say you are a 12ft tall human being and have a 6ft branch in front of you that weighs 60lbs equally on both sides from the center point that you want off your lawn.
Common sense dictates that when you go to pick it up you grab it with your hand at the middle point which is 3ft in the center so it's balanced as you walk off with it in one hand/arm and throw it out. If you were to grab the same branch lets say 2ft in from either side it would cause your wrist and arm to twist as you're lifting it and be rather uncomfortable. If you were to wrap a strap around it at the 2ft mark (either side) then lift it with your arm/hand you would not feel the twist on your wrist as the strap would be adjusting for the difference in the stresses/weights on either side so your wrist or arm would not notice the difference as the weight would be the same in the up/down direction. Linkages at the tip of cranes act similar to this strap scenario I gave when it comes to grapples. If one side is heavier than the other the linkage helps compensate for the twist. There is still twist (more so if the linkage dead ends) but not as severe. It's still not great and tough on the boom but much better than something that is completely fixed and has no give at all. Please forgive my Homer Simpson analogy.
 
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allmark

Well-Known Member
That looked very inefficient the way it was used. The problem I see is potential stress on boom if not properly designed and no saw guard which leads me to believe it is adapted.If you look at 2:15the jib extension cylinders were overloaded (causing the boom section to pull out) by retracting the Inner boom and dragging the piece because it would not lift it.
 

oceans

Well-Known Member
It is only 26000. My thinking was more along the lines of holding a piece nearly center and cutting manually just to prevent things from moving in tight areas. Thanks for chiming in, Mark. And thanks for your article in TCI.
 
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