Props and thrust No2.

[peterboshoff]

Got it figured out at last.
In short - to double the thrust on a specific motor you need to double the prop size and use a gearbox with a 4 : 1 gear ratio.
So you will have twice the prop size running 4 times slower but with twice the thrust.
Some allowance has to be made for efficiency loss due to friction etc. in the range of 10 - 20%( the slower and bigger the prop size the less friction.) This is specifically for coreless motors, but will apply to other motors as well.
The Didel website has plenty aricles on their website and it makes interesting reading.

[BridlingtonFlyer]

Increased thrust yes Peter but at the cost of speed