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Repairing Cracks In Fender Pan

welding cracks sheet metal

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#1 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 12:39 PM

I tried searching the forums for the last hour for an answer to this question, but came up blank.

 

I need to repair cracks in the sheet metal on several tractors.  I have a Lincoln flux core wire feed, with infinite adjustment on both amps and wire speed, so I can fine tune the weld I get.

 

I know to drill a small hole at the end of each crack to prevent further cracking. 

 

On hinge points, I would probably clean up the welds, make a shallow V along the crack, weld, then carefully grind smooth. Then back up the weld with a non-galvanized washer, etc. welded at the pivot point.

 

Other cracks that cover a small area can be done the same way.

 

My problem is cracking around the seat holes on my JD 420.  The cracks radiate out from each hole, and some of them are 3 to 4 inches long.

 

IMG_20130705_112633_076.jpg IMG_20130705_112640_448.jpg IMG_20130705_112608_754.jpg

 

I'm thinking of welding up the cracks, then making a sheet metal stiffener that covers the whole area, drill the holes for the seat mounts, and put other holes in the stiffener to plug weld in several places, then stitch weld around the outside edge. I'll mount the stiffener on the underside, and round the corners a lot to avoid creating stress points.  The metal I have looks to be a piece of 16 ga bare steel.

 

If anyone has experience doing this, or a better idea, please let me know.

 

Regards,

 

Smitty


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#2 John@Reliable OFFLINE  

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Posted July 05, 2013 - 12:48 PM

I would do like you said but only weld fender washers on the back side for seat, which should be enough.


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#3 Nato77 OFFLINE  

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Posted July 05, 2013 - 12:54 PM

I would just weld both sides and grind the welds back smooth if you want it to look good. I'm not familiar with what the seat pans look like on them though.

Putting a plate on the back side should work too. Just don't weld to much around the plate, its needs to have some flex.


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#4 Texas Deere and Horse OFFLINE  

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Posted July 05, 2013 - 01:08 PM

To avoid warping, do several spot welds allowing cooling time between the spot welds.


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#5 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 02:07 PM

Well, I got the pan off and it looks like some one has already repaired many of the welds... unfortunately some of the cracks run right down the middle of the welds. A lot of the bolt holes have large chunks missing out of them as well. I suspect the metal has work hardened over the years from all the flexing, and just a weld won't solve the problem. l  I think I'm going to have to make a plate and do multiple spot welds. 

 

Thanks for your input...

 

Smitty



#6 olcowhand OFFLINE  

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Posted July 05, 2013 - 02:11 PM

If your plate will need to cover a wide area, as I suspect, then on the reinforcement plate, drill holes towards it's center so you can add some spot welds there also.


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#7 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 02:42 PM

So, here's what it looks like... pretty bad cracks all over... 

 

IMG_20130705_121901_514.jpg IMG_20130705_121906_067.jpg IMG_20130705_121909_648.jpg

 

Smitty



#8 LilysDad OFFLINE  

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Posted July 05, 2013 - 04:16 PM

I would do like you said but only weld fender washers on the back side for seat, which should be enough.

 

 

 l  I think I'm going to have to make a plate and do multiple spot welds. 

 

Thanks for your input...

 

Smitty

Why do you need to weld the washers/plate in place? It's not going anywhere with the bolts inn it.? A few welds to hold it in place would be it.



#9 Sawdust OFFLINE  

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Posted July 05, 2013 - 05:44 PM

I would weld a plate covering as many hole & crack areas underneath as I could. This would bring back the area structurally as a whole.


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#10 JDBrian OFFLINE  

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Posted July 05, 2013 - 07:52 PM

I have a 317 fender deck that is ripe but not as cracked as that. Mine is more rusted. I was planning to put a plate under the seat area as well. I'll be watching how this goes. I was thinking of going heavier than 16G - maybe 1/8" but I can see where some flex would be a good thing. Thanks for posting. 



#11 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 07:57 PM

Here it is with holes drilled--broke one drill bit, and had to sharpen another one 5 times... the metal where the welds are is pretty hard...

 

Smitty

 

IMG_20130705_142814_937.jpg IMG_20130705_143636_393.jpg



#12 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 08:05 PM

Why do you need to weld the washers/plate in place? It's not going anywhere with the bolts inn it.? A few welds to hold it in place would be it.

Well, the areas around the holes are cracked out and missing pieces, plus there is a long crack from one bolt hole to another.  I've seen this happen where the whole pan breaks out and falls down...

 

The tractor was built in 1983--over the past 30 years, the constant flexing from riders getting on and off, plus just moving around has caused the metal to flex and work, and get harder... much like when you bend a piece of wire back and forth until it breaks.  Even though it gets hot, it isn't the heat that breaks it, it's the change in the metal structure that gets hard and brittle, and instead of flexing, it finally ruptures and breaks.

 

I think washers will only forestall more cracks... if you look in the last picture,you'll see where it had been previously welded... most of those welds have new cracks running right through the middle of them... the metal has reached the end of its service life and needs some major support. 

 

I doubt if new fender pans are available, and shipping a used one would be very expensive, and no guarantee as to condition when your get it.

 

Regards,

 

Smitty



#13 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 08:11 PM

I would weld a plate covering as many hole & crack areas underneath as I could. This would bring back the area structurally as a whole.

I agree.  I'm weighing whether to use a similar thickness of metal that covers the whole area--using spot welds as Daniel and others suggested, AND reinforce the holes with washers, or use slightly thicker metal that would actually support it without much flexing.  The thinner metal may not give enough support, and the thicker metal may result in new cracks around its edges.

 

 

Smitty



#14 Utah Smitty OFFLINE  

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Posted July 05, 2013 - 08:12 PM

I have a 317 fender deck that is ripe but not as cracked as that. Mine is more rusted. I was planning to put a plate under the seat area as well. I'll be watching how this goes. I was thinking of going heavier than 16G - maybe 1/8" but I can see where some flex would be a good thing. Thanks for posting. 

Well, if we weren't an entire continent away, I'd sell you a 317 pan to save you the trouble...  I have two machines, and don't want to try and get them both running... 

 

Smitty



#15 ol' stonebreaker OFFLINE  

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Posted July 05, 2013 - 09:02 PM

 Smitty, once you get all the welding done, buy a needle scaler from HF and peen the heck out of all welds to stress relieve them. And I mean peen them until the ripples are all gone. As the weld cools it shrinks putting stress on the weld and the parent metal alongside it which makes it crack again. The peening stretches the welded area relieving the stress.

                                                    Mike


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