To paraphrase Louis Renault: 的'm shocked, shocked to find that my $500 grapple is going to break!?/P>
Come on guys, the reason that the grapple that I bought weighs so little and the cost was low was minimal engineering and materials. This is a design laid out by a couple of guys in a welding shop, not with a PE going over the calculations for all contingencies. I agree the stress loads at the cylinder mount were not considered and will be modifying mine when I have the time.
Plus pushing over a tree with the front of the grapple is the worst bending load you could put on it. I知 sure the thought process was only for grabbing things with the grapple upper jaw.
I agree with one of your points, that pushing over a tree with the upper grapple arm as the contact point was a mistake. However we all make mistakes and suffer the consequences. I could bust a $3000 grapple just as easily by applying force where it was not designed to resist.
The light duty grapple design is fairly standard, well worked out over years by many different manufacturers. Was it designed by a team of nerds at NASA or Toyota, no, it is an evolutionary design born of practical experience. I rather doubt the original Bush Hog design was worked out on a Cray computer either. As I'm sure we all know by now, the upper pivoting arm of any grapple is designed only to clamp not push so even if the grapple had been designed by a team of German mechanical engineers something would have bent or broken. Maybe what we need is some equivalent of replaceable shear bolts worked into the design.
Regarding materials, this manufacturer skimped on the 1/8' wall tubing. Mistake. However, my $500 very similar grapple from Millonzi has 1/4" top tubing so I'd say that Wildkat's error was either not dropping one or two of the bottom tines or adding $50 to the price tag and instead using heavier duty top tubing. There is nothing cheap or untested about 3/8" bottom tines or the way that the upper grapple arm is made or attached. Upper grapple tips can bend on rocks or with extreme twisting force if ungussetted. Easy fix.
Before anyone goes running off to buy a "quality" engineered grapple like a $3000 800lb Anbo, do a little research on what CUT owners with cheap 48" light duty grapples think about these implements. I think you will find the great majority quite happy and more than a few that feel it is the single best implement investment they have made. You'll also find a few folks who did spend a lot on Anbos and then twisted them too.
I'd write this episode up as providing two "live and learn" lessons. 1) Manufacturers shouldn't use 1/8" tubing unless they do invest in more engineering design work and 2) operators need to understand the risk of allowing the upper grapple arm to be the primary contact point between a powerful tractor and a solid object. The manufacturer's error was one of commission and they really should correct it. The operator's error was obviously one of attention ommision and the type of thing that we all are capable of doing. If the top tube hadn't busted and force continued to be applied, I would guess that the next thing to fail would have been to twist the upper grapple side arms themselves. Not as easy a fix.
