Bean wrote:Thanks for the input been doing some homework, seems anything is safe as long as you scale down the plans?
Any rule of thumb for bore to ball clerance.
Patched balls anyone
Smaller the hole the more I hate boring it, the inerweb mentioned 3/8 - 9.5 mm wall as a safe factor
Found some 40 dia 4140 @ wk is this suitable for a 3/4 bore? also some bronze for wheels etc
Really want 50 -60 and an inch bore but can start small I suppose
This information I have given you below is a guide only .... Please make sure you complete your own research to confirm.
You may also want to consider over engineering your cannon just to be on the safe side.
Rules of Thumb for Making Cannon
Cannon external Dia = 1.5 x bore diameter
i.e. in a 40mm OD bar you could have a maximum bore dia of 26.6mm
Powder chamber needs 2x bore dia behind the powder chamber.
I.e. if your bore dia and powder chamber is 26.6mm then you'll need the bar to extend at least 53.2mm past the end of the powder chamber.
Shot to Bore clearance is usually 39/40ths
i.e. Bore Dia = one 40th bigger than Shot Dia.
You wont need to patch cannon shot but you will want to use wadding to hold the powder in place in the powder chamber.
Stale bread is good cannon wadding. It is biodegradable and wont set fire to the grass like paper wadding will
Or you can use baggies.
Check out how I make my foil baggies here.https://www.youtube.com/watch?v=u0BNxyaxIU8
Here's my Golf Ball Motar toohttps://www.youtube.com/watch?v=9X4Eu0LJQOY