switching dropouts for track conversion
I have an old lugged steel Puch that has a high bottom bracket and seems to have a good track frame geometry (although it was originally a 70s road bike). Can I take out the simi-horizontal dropouts and braze in new horizontal dropouts to make a track frame?
No. You will end up with a 70s road frame with track dropouts. If that is what you need, then it is a fine project -- but it still won't be a track frame.
Doesn't the bike frame already have horizontal road dropouts? They're not track dropouts, but you still have some adjustment available for chain tension.
if you have horizontal adjustment, I wouldn't bother. There are some frames that aren't worth preserving, and a Puch might well be one of them.
3rd Grade Dropout
There is more to it than meets the eye.
The chainstay/dropout is "higher" (vertical distance) on a horizontal dropout vs. the track dropout.
If you just chop the old bit off, slot the seatstay/chainstay ends and insert the track dropout, you will lower the BB and create a sloping (rearward) toptube, and this will effect the geometry.
You will have to do some cold bending on the chainstays (downward) to get the correct lineup (rear axle/BB/front axle). You could always make your own track dropout with a lower adjustment slot, and tailor it specifically to the old frame.
the drop outs wont do much good. If you have a chain adjastability i wouldnt even bother. Geo will still stay the same road, not track. So thertes no point really