These are posted in the Archive, but the pictures don't work.
I've just come across a stash of old cannon pictures, and decided I'd post my third and fourth spudguns (the first and second ones I lost the pictures to long ago, but I will say that they were a DWV pneumatic and small over/under combustion).
This goes to prove that we were all n00bs at one point in time.
Cannon #1 - The PPC 600
Chamber: 3x12" SCH-40 (~89in<sup>3</sup>)
Barrels: 1.5x48" and 1.5x29" (interchangeable, muzzle-loaded)
Fuel: metered propane injected by syringe. Mixture fan (PC case fan).
Ignition: dual spark on simple piezoelectronic igniter
This was my first large combustion, made from a piece of DWV 3" that I had used on my very first cannon (a pneumatic). The female adapter on the back of the cannon was an ABS adapter I found in the woods, and the rest of the parts came fresh from the hardware store. I had painted the pipe black, but I scraped it away with a screwdriver before gluing the fittings on it, then later sharpied the spots that were white.
This thing was powerful, though, and could send apple cores through 1/2" plywood easily.
Cannon #2 - The PPC 1000
Chamber: ? - probably 4x14"
Barrel: originally 2x54", swapped out for a breech-loaded 1.5x96" one
Ignition: handle-mounted BBQ sparker going to two spark gaps
Fuel: metered propane through super-simple propane meter. Mixture fan (PC case fan).
Built this to fire racquet balls, only to find out that I couldn't squeeze them into 2" SCH-40 like I thought I could. I swapped barrels out when I wanted more distance and the old barrel smelled like eggs (I tried to challenge myself to launch a raw one without breaking it).
Also, my first use of metered propane with a bona-fide propane meter (although performance-wise there's no difference between a syringe and meter).
This thing sent taters out of sight with the 96" barrel.
Like all good old things, these launchers were scrapped and thrown away. Pictures are below.
EDIT: CONFOUND YOU UPLOADER. I uploaded these in perfect reverse order like always, but the uploader mixed them all up. I leave it to you to figure out.
EDIT: ^-- new website, inline uploads, carry on...