1 : Basic axle with U-join, reliable but the U-join can be broken with torque, be carefull and use with a portal axle (8/24 reduction after the U-join)
2 : Bevel gear axle, without U-join (save U-join) ,not very reliable because with lot of weight, there are lot of friction (steering axel is driven), but this axle is smaller than the U-join axle, adapted with maximun 1kg
3 : Variant of bevel gear axle, more reliable than the precedent, without U-join so this is very strong. Be carefull about the 12th with lot of torque. Adapted with >1kg, If the truck
is very heavy, prefer the knob gear (for high torque).
4 : My prefered version, without U-join (no risk to break them), without Bevel gear so without friction of steering axle because there isn't steering axle and driven. This type of axle can support
lot of weight without friction and are reliable. Credit goes to zblj because he has been developed them on his third TT.