Broken Swingarm!

[gsustaitav19822]

Ive investigated Chromoly, but its not available in SA, I would have to have it imported at a cost of 3 arms and a kidney. Funny, since we are one of the worlds leading steel producers...we sell it and then buy it back...go figure. I was wondering about Stainless steel? It has a specific gravity similar to carbon steel, but has a higher tensile strength. I am concerned about brittleness though, any ideas?

From what i have seen with stainless steel is that is a lot better on corrosion resistant but for streinght is not that good and i know that cuz i work with stailess steel and carbon steel at the place that i work building packing house machinery and that what i have notice and to me way to go would be with chromoly steel

 

[Blasturd]

There's a reason that all the big boys (Lonestar, Stellar, etc.) build swingarms out of chromoly. As far as Swingarm shop, yes they are famous for cracking out around the round tube shock mount. They're a cheap swingarm for recreational riders who don't do serious air jumps.

Is the shock mount cross tube tearing out of the 1x2? Or does the 1x2 crack like Blaners?

 

[Bluesman]

Is the shock mount cross tube tearing out of the 1x2? Or does the 1x2 crack like Blaners?

The round tube cracks out and rotates. It's only welded to the inside wall of the rectangle tube. I've never run one, but I've seen several pics of them cracked out.

 

[Blasturd]

It looks like the shock mount on them stands off of the tube far where it has a lot of leverage on that tube. Not to mention there is zero gusseting on it.

 

[Blaner]

The round tube cracks out and rotates. It's only welded to the inside wall of the rectangle tube. I've never run one, but I've seen several pics of them cracked out.

I was wondering of the possibility of running the round tube right through the rectangular tubing, so the round tube is open on the side, but to tdo that you would need a thinner round tube or a thicker rectangular tubing... it would help distribute the stress better and wouldnt crack out.

 

[Blasturd]

I was wondering of the possibility of running the round tube right through the rectangular tubing, so the round tube is open on the side, but to tdo that you would need a thinner round tube or a thicker rectangular tubing... it would help distribute the stress better and wouldnt crack out.

That will just weaken the 1x2.

I really like how the shock mount is set up on this swinger it distributes the load from the shock and would prevent the round tube from being able to roll and crack out.

 

[Blaner]

Well with the swingarm out, things are looking worse than previously realised. This thing took a beating. I have some ideas in mind, i will try to get some CAD designs going and post them up for review!

Here we go!

This is the underside...result of twisting and sharp angles. Metal fatigue...


Here you can see how the ends of the carrier wings which were acting as reinforcing created a weak point where they terminated. I have idea to avoid this next time


This is as a result of sharp angles, must be avoided...




Once it came off it totally lost its shape.










any metallurgists out there care to shed some light on the nature of these cracks??