Frame Keeps Cracking =(

[xxSLiMxx]

Alright so the problem i am having is my frame keeps cracking on every 5-600kms. So after having a peace welded on for me to mount the motor to, it cracked the frame (indicated by the RED line) So i took it back to my welding guy and got him to add the brace (outlined in YELLOW) and he welded the frame where it cracked. He had told me that if the frame cracks again its going to happen near the brace (the BLUE line) and it did!!

So here is my question! What should i do to fix this problem. I'm going to have him weld the crack and maybe "insert good idea here" Any ideas would be much help.

Thanks in advance, Slim

 

[DuctTapedGoat]

Weld, sleeve, then weld, sleeve, then weld, sleeve again.

First - what kind of frame is that and what kind of metal is it?

I would really say weld a sleeve over the entire bottom tube from the downtube forwards, then reinforce that joint in the front.

 

[xxSLiMxx]

Weld, sleeve, then weld, sleeve, then weld, sleeve again.

First - what kind of frame is that and what kind of metal is it?

I would really say weld a sleeve over the entire bottom tube from the downtube forwards, then reinforce that joint in the front.

Micargi Puma GTS frame.

 

[DuctTapedGoat]

Good times - it's steel, so it wouldn't be tough at all to sleeve it.

http://i52.tinypic.com/2z5ojg4.jpg

You definitely don't want to just keep pushing it forward until it snaps at the crank housing, so I'd go above that.

 

[xxSLiMxx]

What do you mean "sleeve" it? Can you explane a little bit more? I think i know what your talking about, but i just wanna make sure!

 

[DuctTapedGoat]

Get steel pipe with the inside diameter of the outside diameter of the tube you want to reinforce and weld it to the tube.

Basically it's like when you laminate multiple pieces of wood together to make it stronger - you're laminating tubed steel to make it stronger.

When you just replace a stressed/broken part of that tube, the welding makes it stronger - like broken knuckles - and then the weakest point moves further down the line, and eventually it's going to come up into your bottom bracket, so those current welds would need to be reinforced.

 

[rustycase]

Would I be wrong to say the frame quality is not the best, and certainly not up to the task at hand?

The welding may be affecting the steel, causing it to become brittle.
You will be chasing your tail.

Pinned sleeves could help, and gussets on everything with minimal welding???

Perhaps a strongback welded along the length of that lower tube???

Good luck,
rc

I'm thinking Crmoly welding benefits from both pre-heat, and post heat...

 

[Oddzball]

well, look at the mounting he has going on. I assume you welded that post there so you could mount the motor?

You are putting a lot of weight and trogue at the weakest part of the frame.

The motor on these things pushes forward and down when engaged. Right against that bar you welded on there.

The right way would to run that bar all the way up to the top.

 

[xxSLiMxx]

Would I be wrong to say the frame quality is not the best, and certainly not up to the task at hand?

The welding may be affecting the steel, causing it to become brittle.
You will be chasing your tail.

Pinned sleeves could help, and gussets on everything with minimal welding???

Perhaps a strongback welded along the length of that lower tube???

Good luck,
rc

I'm thinking Crmoly welding benefits from both pre-heat, and post heat...

Yes the frams isnt made of the best steel sadly.

well, look at the mounting he has going on. I assume you welded that post there so you could mount the motor?

You are putting a lot of weight and trogue at the weakest part of the frame.

The motor on these things pushes forward and down when engaged. Right against that bar you welded on there.

The right way would to run that bar all the way up to the top.

I like your idea sofar. I dont know why i didnt just do it like that the 1st time! I think thats how im going to get my welding guy to do it!

 

[DuctTapedGoat]

Ahh, good call Oddzball. That would be a great way to do it!