Originally Posted by TC1

Thanks. So, to OP, repairing this frame presents at least the following issues:

* Barring sentimental value, it isn't sufficiently valuable to make a repair worthwhile. Would literally cost more than replacement.
* Not all welders who are equipped to weld aluminum will be equipped to weld a bicycle frame, which tends to be very thin material. Contrary to what most expect, welding thin material is harder than welding thick material, and requires even more specialized equipment, and skill.
* Even if you could find a welder with the tools, skills, and willingness, that's only half the job. In order to restore the frame to its previous strength, it will need to be heat-treated ( baked in a large oven, effectively ) after welding. Even fewer welders are equipped for that.
* If you want it to look professional after repair, it will need to be repainted, too. Again, not many welders are equipped for that.
* Even if you could manage all that, there's the question of whether or not your repair will be stronger than the frame originally was -- which is very unlikely. And if you broke it once, and it is not stronger post-repair, you're probably going to break it again.

All of which is say, I don't think you want to try repairing that frame, unfortunately. Strip the parts off, hang it on your wall, and remember all the good times with your dog, each time you gaze on it.