Grim Reaper

like, even if we choose the universal motor...theres a prob as u noe, torque = current x area x magnetic field x no of turns...

increasin either wud cause a prob except for increasin magnetic field n for that again we need high electricity supply n thats possible is we use mini batteries same as aircrafts as they are light weight, n high output providers...but expensive

still for the thing, using nano or micro-tech building universal motor wud be best idea as they r 1 of the most effecient output providers

Yo! U'll require high output motors like a miniature universal motor kind as it can provide high efficiency giving good enough speed

again, the electricity providing problem is there...^^

and as for the air powered engine, u require a comressed air cylinder which is pretty heavy n also cumbersome if u attach...lol