Cracked lift arms

[Filthy58]

Hi, first time poster, (waves from Aussie), Just wondering if anyone has had any experience with the lift arms cracking on a 753G with radial lift? Some time ago, I ripped the top mount of the tilt ram clean out of its mount. I had that professionally repaired and reinforced along with some cracks where the lateral brace that carries the tilt ram, is connected to the lift arms. I now notice that I have some other cracks starting to appear on the upper side of the tilt ram mount, where it is welded into the lateral brace, rather than across the pin hole as it did the first time. There is also a small crack in the actual frame of the machine, around the pin hole for the rearmost end of the lift arm on the RHS only. It is starting to look like I might be dealing with some serious metal fatigue, which surprises me at 4,000 hours. My old C series did 8,000 hours with none of these problem. It occurs to me that perhaps the larger locally made Daiken bucket that it came with, and which is quite a bit bit bigger than the one fitted to the C series, might be the culprit? Anyone had similar experiences?

 

[skidsteer.ca]

I think you hit the nail on the head. Thes machines are rated at 50% tipping capacity. They will lift almost double that. But there is no douubt the boom flexes some under the load and anything that flexs will eventualy crack. If the crackes are showing up early, then the machine has likely been overworked.

Bobcat has a guide as to what volume of bucket should be used with each machine for the material you choose to handle. There is a reson for it.
Of course most skids get used as swiss army knife, often the only machine the operator has available, they get asked to do more then they should.
Ken

 

[waggles]

That's why they made the newer S130 lift arms bigger and wider. A friends has a 753H thats been repaired at the top pivot points and down on the center tilt ram as you describe, these machines have lots of power so it flexes quite a bit then metal fatigue sets in. When you weld it back up you will need to add plating around the pivot points to spread the load and add gussets to the centre brace to increase torsional rigidity. It can be done just takes time and money.

 

[Tazza]

That's why they made the newer S130 lift arms bigger and wider. A friends has a 753H thats been repaired at the top pivot points and down on the center tilt ram as you describe, these machines have lots of power so it flexes quite a bit then metal fatigue sets in. When you weld it back up you will need to add plating around the pivot points to spread the load and add gussets to the centre brace to increase torsional rigidity. It can be done just takes time and money.

Did you buy it new?
My 743 when i got it was in a sad sate. Cracks in the lift arms and bobtach. I welded them up and put internal plates to strengthen the welded points. They have not re-cracked.

 

[Filthy58]

Did you buy it new?
My 743 when i got it was in a sad sate. Cracks in the lift arms and bobtach. I welded them up and put internal plates to strengthen the welded points. They have not re-cracked.

Yeah, it was new. Reckon its fairly poor for 4,000 hours but it's not had a luxurious life. Maybe I did it when it fell over.....oops. Handy to know it fixes okay. Had visions of chasing cracks all over the machine like a bad scene from Earthquake. Thanks Tazza.

 

[Tazza]

Yeah, it was new. Reckon its fairly poor for 4,000 hours but it's not had a luxurious life. Maybe I did it when it fell over.....oops. Handy to know it fixes okay. Had visions of chasing cracks all over the machine like a bad scene from Earthquake. Thanks Tazza.

That's pretty poor from a new machine that you know exactly what it has done. I can't really see a flip over causing the cracks.
With the cracks, as long as you drill the ends they shouldn't keep moving. When i did mine, i sued a plasma to gouge them out. As long as you extend slightly past the crack it won't move. If there is any crack left, it can keep on going even if you weld over it.
If you ran a rock breaker, you may have cracks all over the machine They can be pretty tough on a machine.

 

[Filthy58]

That's pretty poor from a new machine that you know exactly what it has done. I can't really see a flip over causing the cracks.
With the cracks, as long as you drill the ends they shouldn't keep moving. When i did mine, i sued a plasma to gouge them out. As long as you extend slightly past the crack it won't move. If there is any crack left, it can keep on going even if you weld over it.
If you ran a rock breaker, you may have cracks all over the machine They can be pretty tough on a machine.

I'm thinking the most likely culprit is using the auger attachment over to one side instead of in the middle. Especially since most of the augering I do requires getting the machine up on one or no wheels, the tie down point at the rear, and with the rest of the weight on the auger. Kind of obvious when you think about it. Not quite how Melroe envisaged it being used I'll warrant.

 

[Tazza]

I'm thinking the most likely culprit is using the auger attachment over to one side instead of in the middle. Especially since most of the augering I do requires getting the machine up on one or no wheels, the tie down point at the rear, and with the rest of the weight on the auger. Kind of obvious when you think about it. Not quite how Melroe envisaged it being used I'll warrant.

I can see that adding more stress, but i would have thought it would have handled it.
I know when i was drilling holes for my shed, i had mine up like that. I had a bottle jack under the back so i could get as much weight on the auger as possible to get through the rock. Took a long time, but i got there.