How to fix this crack

[Mark @ Everlast]

Not trying to discourage you, but this is what I had mentioned at the outset.

 

[woodlandfarms]

Hey Mark. You gussett idea was run around a few times. Problem is it interferes with the hose connections below (or the ability to get to them. Trust me, it was heavily considered.

 

[SPYDERLK]

Just for crack repair. I've been told it forces the stresses into the hole. By theory the crack should not go past the drilled hole.

Then again, why crowd forces toward the end of a crack? I think it is a sound byte simplism. The actual issue being the heat build up during the weld helps to make the metal more mobile at the endpoint and the stresses naturally relieve better. ... Even better to also hit it with a needle scaler while cooling.

 

[RedNeckGeek]

Cracks propagate at sharp edges, like corners, and especially at the bottom and ends of cracks. If you drill a hole at the very end of the crack, you make a smooth rounded shape larger than the sharp end of the crack. It doesn't change the stress levels at that point, but because stresses aren't concentrated at the sharp crack tip, the crack doesn't propagate as easily.

Having said that, though, it makes absolutely no sense to drill the holes then obliterate them with weld metal.

Just as it makes no sense to weld over a crack. You may stop a leak for a while, but the stresses that led to the original crack are still there, as is the sharp tip of the crack, and you can be assured it will crack through the weld again.

 

[woodlandfarms]

So added some more welds and prepped for paint. Threw some JB Weld over the crack in the back.

 

[jack707]

Are you using fc or hard wire? For that repair? Asking because if I was doing the repair I would want penertration of the parent metal into the base that is deep. Either I would use stick and 7018 or duel shield 75/25.

 

[j.lwelding]

gouge/air arc the crack out, take it to a welder in town and he can use this process to take out bad weld, and actually make a groove into base metal to get more penetration. it wont crack again if done proper.

 

[rankrank1]

gouge/air arc the crack out, take it to a welder in town and he can use this process to take out bad weld, and actually make a groove into base metal to get more penetration. it wont crack again if done proper.

Could the OP have alternatively used his plasma to gouge in a do it yourself manner in lieu of an arc/air gouge which pretty much requires a gigantic welder? ( I do not have a plasma so I would have drilled holes at end of the cracks and ground a groove with my grinder just as the OP did myself. That said, it is always nice to explore the alternatives for future learning).

 

[Shield Arc]

I have used my plasma to scarf out welds. It works OK. For me it was hard to control the depth. With a carbon arc all you do is push the rod in deeper. Also a carbon arc will open up a crack, so it is more visible.

 

[j.lwelding]

Could the OP have alternatively used his plasma to gouge in a do it yourself manner in lieu of an arc/air gouge which pretty much requires a gigantic welder? ( I do not have a plasma so I would have drilled holes at end of the cracks and ground a groove with my grinder just as the OP did myself. That said, it is always nice to explore the alternatives for future learning).

yes plasma will work too but will require a gouging tip, not a cutting tip.

 

[woodlandfarms]

Just so no good deed goes unpunished, weld is holding after a days worth of work but found oil puddled in my engine compartment (tub). Looks like my main seal is starting to weep. whatever.

 

[Mark @ Everlast]

Is that a Deutz engine?

 

[woodlandfarms]

Yup 1011 Series.

 

[jimmysisson]

Back to flitch/fish: if you have a door header and need to use two 2x10s but only have room for 2x6s you can replace the 1/2" plywood sandwich with 1/2" steel. That steel is a flitch plate. At least in New England.
Jim

 

[dragoneggs]

I'm way late to the party and not a welder but I do know a thing or two about fatigue stress and cracking being a aerospace stress engineer for many years. That said, the first thing I would have done is understand the fatigue stress and how the crack was opening/closing before doing anything other than cleaning up any grease or grim around the crack. Maybe start by jacking up one side or the other would provide a clue if you aren't good at understanding load paths. Not knowing that info... I will say I'm with Mark@Everlast on a gusset style reinforcement plate even one that would only extend inboard some without blocking off access. A larger 'fillet' radius or gusset goes a long way in reducing stress concentrations. I also would not make the repair plate any thicker than the thickness of the adjacent structure.

On fish plates and stress risers, their shape is meant to to gradually change the stress along a structural member. Abrupt changes in cross section means abrupt stress level changes. Another thing that is a good idea to understand... is how you are changing the cross section by adding the repair plate. This is important in bending situations because the added plate can change the neutral axis of the cross section and potentially cause much higher operating stresses on the opposite side of the cross section and causing new problems. This is why it is generally a good idea to make repairs/reinforcements symmetrical if possible. For instance if you were adding a doubler to an 'I' beam you should beef up both top and bottom even if you are only fixing one side. Anyways my :2cents:

 

[Shield Arc]

I'm way late to the party and not a welder but I do know a thing or two about fatigue stress and cracking being a aerospace stress engineer for many years. That said, the first thing I would have done is understand the fatigue stress and how the crack was opening/closing before doing anything other than cleaning up any grease or grim around the crack. Maybe start by jacking up one side or the other would provide a clue if you aren't good at understanding load paths. Not knowing that info... I will say I'm with Mark@Everlast on a gusset style reinforcement plate even one that would only extend inboard some without blocking off access. A larger 'fillet' radius or gusset goes a long way in reducing stress concentrations. I also would not make the repair plate any thicker than the thickness of the adjacent structure.

On fish plates and stress risers, their shape is meant to to gradually change the stress along a structural member. Abrupt changes in cross section means abrupt stress level changes. Another thing that is a good idea to understand... is how you are changing the cross section by adding the repair plate. This is important in bending situations because the added plate can change the neutral axis of the cross section and potentially cause much higher operating stresses on the opposite side of the cross section and causing new problems. This is why it is generally a good idea to make repairs/reinforcements symmetrical if possible. For instance if you were adding a doubler to an 'I' beam you should beef up both top and bottom even if you are only fixing one side. Anyways my :2cents:

It would be nice, if you would have put that in English. So we could understand what you said!

 

[ArlyA]

I wish I could have written my fish plate description as well. Nonetheless, without seeing the actual crack and the stress the frame member is cycling through, its very hard to give advice on the repair plates design via internet forum. This is why I tried to give examples of a few fish plate repairs.

I'm way late to the party and not a welder but I do know a thing or two about fatigue stress and cracking being a aerospace stress engineer for many years. That said, the first thing I would have done is understand the fatigue stress and how the crack was opening/closing before doing anything other than cleaning up any grease or grim around the crack. Maybe start by jacking up one side or the other would provide a clue if you aren't good at understanding load paths. Not knowing that info... I will say I'm with Mark@Everlast on a gusset style reinforcement plate even one that would only extend inboard some without blocking off access. A larger 'fillet' radius or gusset goes a long way in reducing stress concentrations. I also would not make the repair plate any thicker than the thickness of the adjacent structure.

On fish plates and stress risers, their shape is meant to to gradually change the stress along a structural member. Abrupt changes in cross section means abrupt stress level changes. Another thing that is a good idea to understand... is how you are changing the cross section by adding the repair plate. This is important in bending situations because the added plate can change the neutral axis of the cross section and potentially cause much higher operating stresses on the opposite side of the cross section and causing new problems. This is why it is generally a good idea to make repairs/reinforcements symmetrical if possible. For instance if you were adding a doubler to an 'I' beam you should beef up both top and bottom even if you are only fixing one side. Anyways my :2cents:

 

[GLyford]

It would be nice, if you would have put that in English. So we could understand what you said!

What, doesn't every tractor come with a mechanical engineering degree?

 

[Shield Arc]

What, doesn't every tractor come with a mechanical engineering degree?

I was very spoiled. 99% of the time we were required to have an engineer on the job site with us. So if we didn't understand something, all it took was a radio call to the job site office, or just stop by and ask the engineer to explain it to us.