Results 21 to 32 of 32
06-07-2010, 09:09 PM #21
06-08-2010, 04:55 AM #22
You say it is lifting to the left. Check the left cylinder for fluid leaking/bypassing internally making it weaker putting more pressure on the right cylinder/side.
06-08-2010, 05:51 AM #23
I'd also agree with Sami's statement regarding the likelihood of additional cracks showing up with Magnaflux or similar testing. I've seen lots of machinery with similar fatigue failures where all sorts of welds and straps and other reinforcements have been applied, and in most every instance the only real result was chasing the crack to some nearby location where it reappeared in a short time.
That said, if the cracks are a result of some previous use like a hammer, a repair less extensive than complete removal of the affected area would likely have a good chance of surviving for the remaining life of the machine, since the fatigue source is no longer present.
In looking further at the pics, I wonder if there could have been an initial failure of a cold weld at the sleeve thru the arm, and that the crack could actually be a low cycle failure due to deformation rather than a high cycle one such as the hammer would produce.
06-08-2010, 06:16 AM #24
Every trip with a skid steer is impact loading. No suspension and a very short wheelbase jars the snot out of everything. Now you put a load on the lift arms that is just short of tipping the machine forward and drive across frozen ruts. Even worse when you put a young person in the seat that can take the beating and they push it even harder. Give that skid steer to an old guy with a bad back and it will never break.
If you fix it as good as new, it will break just like new.
I would cut out the old bosses in the lift arm assembly. I would remove about 6" of the inner plate. The inner plate looks like 3/16, I would replace with 5/16. Only go about 50% heavier on the new plate. Then make new pin bosses and weld them in place. I would weld up the spacer plate where it is cracked and add a reinforcing strap about equal to the original thickness.
I would price new yellow support arms from a dealer before attempting to repair the existing arms. Also replace all the pins and bushings everywhere.
06-08-2010, 07:40 AM #25
Wow, thanks for all the replies and suggestions.
So far it's not working out so well. Did a simple three point hook on the boom and got the cylinder undone pretty easily. Lifted the boom to unload one set of arms and the pins must be pressed into the boom and the bolt hol is the same size on the pin as the boom. Pressing against the arm just bends the arm. Sprayed the pins woth Kroil, hope it loosens the rust so I'm only fighting the press fit.
Called the dealer up and the arms are available but very expensive, $400-500 each. They said the pins are a real pain to get apart if it isn't brand new.
Interestingly enough when using the cylinders to lift the boom it shifts to the left a lot and is tilted that way when the booms up. Without the cylinder theres a good bit of slop in the arms. I left the boom in the air last night and it didn't drift down so I think both cylinders are in decent shape
On the boom, the inside plate measures .250" and the outer .200".
06-08-2010, 08:06 AM #26
The canted load on the pin is a pretty common one, as in the wheels, spindles and axles of say one of the heavy classes of off-road truck racing or hard landing jumbo-jet, that don't enjoy the New Holland's balancing symmetry provided by the rugged assembly, including the opposite arm in combination, creating a sort of balanced "clevis" or forked assembly as a whole, mitigated of course by minor assembly flexure. This shifts the stresses to far more shear than bending moment in those 2 very close pivot assemblies. As far as I know, there has not been an epidemic of that failure in the thousands of NH skid-steers of that design. None of the beaters in my use anyway, many of them with wallowed bushings.
Repeated over loaded lifts would simply raise the back wheels, something that happens innumerable times on all skid-steers with enough lifting capacity, as in the "reverse wheely", (full hit on the material pile, big load/hard reverse then hard opposite skid) 2 wheel quick turning technique of slick operators, (fun) to no ill-effect. Well, the hydraulic fluid does get a little warmer in 8 hours.....
Perhaps a badly out of balance hydraulic load, either hydraulic pressure between the cylinders being out of balance, or that job or just operator habit that required repeated smashing and lifting into say slab demo on one bucket corner, combined with shot bushings slaping hard.
Not nearly enough damage showing on that arm to have torn the socket like that, I'm on the fatigue side. The demo hammer idea has merit, if the unlikely senario was an off-center positioning of the hammer, and the work was overhead.
Wild guess, flawed factory fabrication, lotta' weld heat, forbidden cold splash?
06-08-2010, 08:10 AM #27
the pin, why does it have a nut on the end of it ? is it factory, or did
someone replace it with a bolt ? It doesn't look factory to me, I thought they
had a different retaining method.
The symptons lead me to think the pin is bent, causing it to flop to the left.
The "hard to remove unless new" leads me to believe they get bent
in use, or they get a groove worn in them and they "self captivate"
Jamie, I can't seem to post the link here, but the newholland website, parts diagram
list's 4 "service bulletins" for that area, along with some "weld plates".
06-08-2010, 09:50 AM #28
Rider;- I know I'm bing a PITA but I've BT DT often enough to know the pitfalls,...... only you will know whether it's worth actually doing.
One ram lifting more than the other?............ look for twisted frames etc etc.
If it was me doing the job I'd get the lifting arm off and do a full dimensional, angle and ''straightness checks - this takes time.
Then do the same with the mounts on the machine, for which I used to jack up and pack the machine level in both directuions and arrange independent datums from which to work.
Omitting to do that could (will) result in repeating the situation that's caused the cracks in the first place.
Only then will you know where and how to start going about sorting the job out,....... which for me often involved making jigs to work to......... just laying the bits on the average concrete shop ain't going to cut it.
06-08-2010, 10:20 AM #29
I am on my 8th NH loader and have never seen one crack like that. I have had one that was around here for over 5000 hrs. It had been used and abused tipped over sideways and run into by a truck. Mine were always at least one size bigger but that just lets you use them harder yet. My guess is that the bushings wore through and got into the frame of the loader causing the stress cracks which led to the arm cracking out like that. They make bushing replacements that we have done on several of our machines ususally around 3000 hrs. Lately I just make sure someone else owns them by that time. Mine are usually only 2 or 3 yrs. old when we trade so that tells you the story of what a 15 yr old loader has been through
06-08-2010, 10:41 AM #30
A fatigue failure? A fatique failure that happened
on both the black arm, and the yellow arm, *simultaneously*?
This was a massive shock overload. Granted the
corrosion around the eye on the black arm didn't help,
but the failure began at the edge and worked its
06-08-2010, 10:46 AM #31
06-08-2010, 11:22 AM #32
digger doug, the pin recesses into the boom about 2" to handle the load and the bolt just keeps it there. Thanks for the heads up on the NH site.
My buddy has had this one for about five years now, used it on his farmette / scrap yard. It has been run by yard monkeys on occasion... He has a spear, a bucket, and a set of forks for it. It came up last month because it wouldn't run in the 'run' mode, only 'service' and it won't let you raise the boom in service. I had to redo a bunch of buggered wiring and replace the fuse block by the engine (it had been cobbled by others) and finally realized that the problem was the battery being about shot so in run the glowplug circuit was pulling the battery low enough that the fuel relay would drop out giving an 'error 2' (fuel ckt. failure). He noticed the cracks when we was unloading it at the farm and brought it back up.
I'm sure it's been abused, when he originally got it the shock absorbers for the steering arms were shot and it would jerk and shake bad.
The yellow bar cracks are recent. I think they are from the boom failing causing the pin angle to change and overstress that bushing which has about 1/8" of play like most of them do.
I still haven't played with it anymore, been running errands over lunch.