Bike seat tube is messed up

Question

I was testing my seat and as I was sitting on the bike on the highest level of the seat post.
My seat post came off and bent my seat post, so I ordered another, but now my seat tube doesn't allow my new seat post to fit in even though I bought the same size.
I got a wrench and made my seat tube bigger and finally it fit but now my seat clamp doesn't fit.
Now I ordered a 34-point-something seat clamp which finally worked but now my  problem is my seat clamp isn't tight enough.
My seat goes left and right and when riding for a long time my seat goes down. Is there anything I can do?

My seat tube used to be 28.6 after this incident my old clamp didn't go back in, so I got a 30mm seat clamp but that still didn't work.
So I bought a 34.9mm seat clamp as I thought maybe if I get a bigger size and then really tighten it down it might work as I don't know my bike seat tube size, Then the seat tube in the frame was out of shape.
Could you give me advice on what clamp size to get?
I just bought 2 clamps 28.6 and 31.8 hope one fits.

Argenti Apparatus · Answer

What’s happened here is that you have expanded the diameter of the top of the seat tube, in the process it looks like you have made some small cracks on the top edge, and created a number of burrs. That’s why the original seat post clamp will not fit anymore.
The larger clamp obviously does not work as its diameter is too large to clamp down on the tube with enough force.
Given that there is a reasonable length of seat tube above the top tube, I’d say that this is rescuable by carefully cutting the deformed area away. Removing 5mm from the top of the tube and smoothing the area below to remove burrs may be enough. The slot in the back of the tube may also need to be extended to allow the seat clamp to compress the tube.
No offense meant, but given that you’ve made a big mess of the seat tube with your own efforts, I’d enlist the help of experienced bike mechanic, who will also be able to assess whether the seat tube can be cut back safely.

Bike seat tube is messed up

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