Cracked Exhaust Manifold Repair

[Roger B]

I was experimenting with my fuel injected 12cc twin

https://www.modelenginemaker.com/index.php/topic,7883.0.html

when I noticed the exhaust was getting noisier. A quick inspection showed that the exhaust manifold had cracked again. The last time I was able the silver solder the crack but this time needed more thought as the pipe was now completely broken and would fall apart as the silver solder melted.

I made a splint from a piece of 6mm bore brass pipe and managed to support it so the manifold would not fall apart. I tried just using silver solder paste but had to add some more solder from a stick.
I reassembled the engine and all seemed ok but then I noticed some nasty resonance vibrations that were very likely the cause.

<a href="https://www.youtube.com/watch?v=rhonJ6N0KV0" target="_blank">http://www.youtube.com/watch?v=rhonJ6N0KV0</a>

I then made up a support bracket from 0.5mm steel sheet soft soldered together and a U bolt from a piece of 1.6mm stainless TIG welding rod. This was fitted with a dab of Loctite on the threads and hopefully problem solved.

[Roger B]

And the finished job.

[PaulR]

That'll stop the wobbles!

[Sanjay F]

Very nicely made......didn't realise how small the U bolt was until it was against the ruler!   

[RReid]

Nice repair job, Roger. But I have to wonder if there isn't a chance constraining the end of the exhaust won't lead to further cracking later?

[Roger B]

Thank you all 

Ron, the pipe is not under any load/deflection from the clamp so I hope that there are no further problems. I think next time will need a new manifold, certainly a new main pipe.

The main problem is the higher vibrations from the engine in it's 360° form. When I was using the 180° crank it was much smoother but wouldn't work with my fuel injection.