4130 is much stronger than the carbon steel (which im assuming is just a form of mild steel). 4130 tubes are also extruded from a die (cold drawn) when they're made where as the mild steel ones are most probably rolled hot from sheet to save a fair chunk of money. But, mild steel is much stronger than the 6061 or 7005 grades of aluminium most commonly used in trials frames. So, personally, i dont really see the need in spending the extra money for 4130 when chances are that if it did crack, it would crack on the weld anyway.
The frame is almost done, just have to cut the top chainstays in and sort out the dropouts but I'm now thinking about strengthening plates. So where is the most common places for frames to crack so I can make sure I make those areas as strong as possible
t-poo's are great to learn on just because they're so terrible. If you got a new 'modern' geo in like a years time its like gods greatest gift. Also, they're built like brick s**t houses and so you'll never break it.
im almost certain that frames arent made of 7075 because 7075 is virtually impossible to weld without it cracking due to it cooling so quickly in relation to the rest of the material. i did look into making it from this but it just wouldnt work. it wouldnt be that hard to heat treat the welds would it?
the proiblem is that i dont have access to a lathe big enough or a cnc machine to do that haha
either way im still trying to find someone to tap the threads for me. ive messaged a few companies but they all said that they either dont have the taps or wont do it because they only use them for chasing the threads