had a chat to a mate and can get a six or seven foot length of yellow gas pipe thick wall need to know the
diameter of suggested projectile I can see a plan combining up.
Great minds ... that was the exact pipe I was thinking about (nice thick wall) but didn't have a source other than stopping at some road works with a big saw!
Would it be better to look at the design the other way round in that there must be a limited selection of pipe sizes, but many ball diameters? I'm happy to donate a couple of balls to the project.
This from the interweb. I think "proper" balls may be a pit pricy and they seem to have a range of circumfrances. Cheapo plastic balls would probably fit the bill ...
Size 3
Size 3 balls are the smallest balls and are generally used for children under the age of 8
These balls are generally 23-24 inches in circumference and weigh between 11-12 ounces
Size 4
Size 4 balls are used for players between the ages of 8-12
Size 4 balls weigh between 12-13 ounces and have a circumference of 25-26 inches
Size 5
This is the international standard match ball for all ages 12 and older, including all adult play
The size 5 ball weighs between 14-16 ounces with a circumference of 27-28 inches