cracked swingarm

[PUD]

I just noticed the swingarm on my 95 cr500 has a crack along one of the welds is it ok to just have rewelded?

pud

 

[Buzz Bomb]

If it's small it will most likely be alright to weld it, but if it's big, I'd just buy a new swingmarm. A big crack will probably crack again after it was welded.

 

[TRAIL]

if its weded right it should not crack at the weld.

 

[PUD]

Originally posted by TRAIL
if its weded right it should not crack at the weld.

It cracked just along the outside edge of the weld.

pud

 

[jmics19067]

I usually start more fights than it is worth with this statement but, If it was a stress crack,just welding it will crack again. If the virgin piece was stressed to failure and you just run a bead , no matter how good, over the crack when that peice sees the same stress it will either crack right in the middle of the weld or right next to it.

If the crack formed because of the original weld wasn't up to snuff rewelding it may cure it

Either way I would look at welding the crack and plating /gussetting over the repair<space permitting> to try and transfer some of that stress away from the problem area.Unless the cost of repair exceeds the cost of a new part.

 

[Ol'89r]

Originally posted by jmics19067


If the crack formed because of the original weld wasn't up to snuff rewelding it may cure it

PUD.

If the crack is right next to a weld it is possible the original weld didn't have enough penetration. Take it to someone that does TIG welding. Have them grind the crack out at least 3/4's of the way through the thickness of the swingarm. Also, grind it past both ends of the crack to insure that the crack is completly gone. Then weld it up using a tig welder.

Like jmics said, a gusset would be a good idea if it is a large crack. This spreads the stress over a bigger area.

Good luck. :thumb:

 

[MikeT]

Not sure how it is with a Aluminum, but with steel, the weld is usually 70KSI (or 70,000 pounds per inch) while the material you are welding is either 36KSI or 50KSI. So the weld is stronger than the welded material. If the crack formed outside the welded area, then I speculate that something might have happended during the welding process that made the surrounding metal brittle. Either that or you just overstressed it by landing very hard.

 

[jmics19067]

So the weld is stronger than the welded material.

You are correct but I am not talking about the properties of the base material and filler rod. What I mean to say is concerning welded assemblies and stress concentration. If you can overstress a weldment to find its weakest point and then repair it without gussetting you will still have same problem at the same stress levels. "Weakest link in the chain" situation.

A crack repair is basicly a butt weld and there a few instances where you would see a "perfect " weld ,IE, same filler rod and base material,ground down smooth so that the weld area is the same as the base material ,but not one we would see in most every day life. So usually you would have a lump of excess weld < thicker walled material> of a different alloy <usually stronger> . so your stress point is in the same spot but since the weld is better than the base metal,our crack forms right next to it.

Which is why I suggest gusseting, to try and move the stress concentration point to either an area that has less leverage or to stronger section. I also believe that when I make a gusset I try to avoid using sharp ,square corners. I try to make my plates rounded or ovaled to try minimize me forming a concentration point with my gusset.