so what is the purpose of a big tooth gear box and striate cut gears and can it been done to standard gears

 

the main purposes of straight cut gears are:
1) they are really fucking cheap to tool up for so you can whack out loads of different ratios for quickly changing round when racing to suit a circuit

2) they have less side loading which is sometimes very useful for reliability (mini drop gears or pulsar gearboxes for example)



Big tooth are just what it says, wider so they are stronger



No you cannot well extra onto your teeth to change them to be either straight cut or bigger, you make new gears in both cases.

 

as chip was saying, theres less sideloading on straight cut gears, normal gears are helical which is when the teeth are cut at an angle, like -> /////

because the teeth are at an angle, when you start chucking massive ammounts of torque through them, the two teeth in contact with each other try and slide away from each other, puts strains on bearings and shafts and if they do start to move appart, the area that theyre incontact with each other gets smaller and they can strip.