[MosquitoMoto]

Okay, I have to make up a 'shark's fin' for my race bike.

For the uninitiated, a shark's fin is a small guard plate that is mounted on the lower swingarm of a motorcycle, just ahead of the rear sprocket. The theory is that in a crash it will prevent fingers and toes from accidentally being fed into the spinning sprocket and neatly clipped off.

Now, it's an easy build - basically welding two pieces of 3mm aluminium together at a 90 degree corner joint. My question is this; having TIG'd the inside corner joint, should I also go ahead and weld the outside of the corner joint?

Is this just being thorough, or is it overkill?

Cheers,


Kym

[Coldman]

I would even if just to pretty it up.

[MosquitoMoto]

I would even if just to pretty it up.

That was kinda how I was thinking, too. So I will. But just out of curiosity, is that standard welding practice? Is an inside corner joint weld generally followed by welding the outside of the same corner joint to 'finish it off' as it were?



Kym

[Coldman]

Not necessarily. If you have done a full penetration weld from inside you can dress the outside corner to pretty it up and its all good.
If the weld has not fully penetrated you might want to weld or at least wash the outside corner.

[Poland308]

Think it would be determined by what side of the plate is going to take the most force in a crash. But I've had socket welds cut and back bent in a clover leaf pattern to see if the weld would take the abuse. That's basically a worst case scenario that a fillet weld could see.

[MosquitoMoto]

Think it would be determined by what side of the plate is going to take the most force in a crash. But I've had socket welds cut and back bent in a clover leaf pattern to see if the weld would take the abuse. That's basically a worst case scenario that a fillet weld could see.

While anything is possible in a crash, I reckon that there are very few cases apart from bike-to-bike entanglements where the shark's find would actually take a hit. But of course you always build it to take a hit regardless.

I think that in this case a neat inside corner weld followed by a wash on the outside corner will do the job. Happy to be making another useful thing in amongst all the practise.


Kym