Backhoe L48 sub frame broke

[rbargeron]

messtrap, is the crack along the top of the tube? Any chance of posting a picture?

Drawing of the subframe attached.

 

[LD1]

Certainly would like to see a picture of the damage.

How old is the machine? Did you buy it new?

 

[Jay4200]

The ROPS has never been off the machine. Even if it was, it has nothing to do with the water in the subframe. The part that blew out is the long piece that goes from the FEL brace to the backhoe brace. It is a sealed piece, welded at both ends. Kubota rep advised me to drill drain holes in bottom of both sides of frame for drainage. Putting new frame on, kubota would only cover 850.00 of the 2,444.00. If I knew how to weld I would have fixed the old one.

Condensation? No way. Take it to a weld shop and have it welded professionally - it shouldn't cost more than a hundred bucks, 150 tops.

 

[messtrap]

Yup, crack is at the edge on top of the tube. I will take a pic tomorrow and hopefully I can figure out how to post it. I bought the tractor new in 2009. I'm sure the picture is worth a thousand words.

 

[messtrap]

Did take it to a professional weld shop. Not as simple as welding the crack, the entire leg is hydro-formed and pulled the frame slightly making it hard to get the backhoe on and off. Take a look at the pic tomorrow night when I post it.

 

[messtrap]

I have no idea what I'm doing, these pics are when the frame was still on the tractor. It should be rectangular steel, not circular!

 

[skyhook]

That is strange, just curious, has the tractor ever been driven in water.

 

[rbargeron]

View attachment 391294View attachment 391295View attachment 391296
........these pics are when the frame was still on the tractor. It should be rectangular steel, not circular!

Good pictures. Along the cracked corner, the material looks like it was weak, maybe from the start. The tube also looks curved - like maybe a jack was used there to lift the tractor. If the tube was already weak that might explain the bellying.

Back in my teaching days (metallurgy for engineers) we looked at cases in lamellar failure in rolled material, where the internal layers have impurities with different hardness, severely weakening it.

I'm having a hard time imagining how enough water got in and froze to cause this. But the edges of the crack look like old rust. If the tubing was weak, and a crack got started, it might eventually let in enough rain unnoticed. I dunno.

Is the back end bent where the backhoe attaches? How does the frame tube on the other side look?

 

[messtrap]

Hello rbargeron, the tractor has never been driven in water deep enough to even touch the frame. To answer your questions rbargeron, I'll take some pics of the frame tomorrow, it's sitting in the yard and you'll be able to see all the answers to your questions. The frame was fine late fall when I pressure washed it and got it ready for winter. The spring is when I noticed the damage. (No way the pressure washer filled it either, I can't find a crack anywhere. The existing crack I believe rusted after it burst open. Take a look at the pics tomorrow night, Really stands out off the tractor.

 

[Pepsiboy]

Hello rbargeron, the tractor has never been driven in water deep enough to even touch the frame. To answer your questions rbargeron, I'll take some pics of the frame tomorrow, it's sitting in the yard and you'll be able to see all the answers to your questions. The frame was fine late fall when I pressure washed it and got it ready for winter. The spring is when I noticed the damage. (No way the pressure washer filled it either, I can't find a crack anywhere. The existing crack I believe rusted after it burst open. Take a look at the pics tomorrow night, Really stands out off the tractor.

messtrap,

From what I can tell on the pics, is looks to me like metal was defective from the factory. I have seen this before when I worked in the sheet metal shop. It is called 'lamination'. That is where slag or dirt got onto or into the metal when it was being rolled in the mill. MOST of the time it can be seen on the flat steel as a shadow or blister. HOWEVER, there are time when it can not be seen until the metal is formed. During the process of bending the steel, is USUALLY shows up as a split or crack. :2cents:

BTW, I have over 20 years experience in precision sheet metal working with mild steel, stainless steel, aluminum, and titanium. Also, 10 years in machine shop and 5 years welding.

Please post pics of unit off tractor. Thanks.

Dave