Mk3 A Big Carbide Cannon

I was inspired by Rob Howard's big gun and since he raised the bar with those tractor tires I needed to raise it again if I could.
My design is based loosely on the US 57mm anti-tank gun of WWII. Here are photos of my Egg Gun.
It uses a 6" Sch.40 Tee and a 3" x 36" barrel. With a foam sabot it sends a tennis ball into the next county.
Due to failures of the plastic plugs, we do not fire projectiles from this gun anymore.

The Mk3

The drags spread out and get pegged to the ground.

What the enemy sees.

The elevation mechanisim.

The drags close in and the pegs rotate to make the tow ring.

The breech handles facilitate opening the gun for ventilation between shots. The piezo ignitor is actuated through a lanyard operated bellcrank.

The charger measures the precise charge of Bangsite, one teaspoon, per shot.

The charger uses for a plunger a 1" diameter cylinder. Bored through this cylinder is the measuring cavity.
The cavity is .531" in diameter and is bored through at 45 degrees.
On the left the plunger is in the up position and carbide fills the cavity.
On the right the plunger is in the down position and carbide falls into the cannon sump.

Now I have had a 6" PVC plug fail! This was while firing a tennis ball with a tight- fitting styrofoam wad. This makes the third failure while firing tennis balls. Cannon of this size should be made from metal or used for noise only.

These projectiles are yet to be tested:
Discarding Sabot Dart Projectile
Discarding Sabot 1" Ball Projectile
The tennis ball has been fired in front of 2" white foam wad and goes like crazy!
Foam Wads

Firing Test 26 November 2001
General notes:
  • Fired with long lanyard
  • Fired from behind a sheet of particle board
  • Fired with a quilt over the cannon

    First Test
    • No projectile
    • One teaspoon Bangsite (from charger)
    • Recoil: Not measurable
    • Remarks: Nice Loud Bang!

    Second Test
    • Tennis Ball in front of 2" white styrofoam wad
    • One teaspoon Bangsite (from charger)
    • Recoil: 2"
    • Remarks: On charging, the gas generation pushed the wad down the barrel half way fast enough to expel the tennis ball! Nice Loud Bang! Ball flew like a rocket. Later it was discovered that the charger plunger broke during firing. The charger was removed and the gun was charged with a 1-1/2" plug for the remainder of the tests.

    Third Test
    • Dart with discarding sabot. Dart weighs 91g and sabot 12.5g.
    • One teaspoon Bangsite
    • Recoil: 1"
    • Remarks: Nice Loud Bang! Dart hit the ground about 25 yards out and the fins were all bent up. I think the sabot disintegrated during firing and the dart was never accelerated to full velocity. No damage to the cannon.

    Fourth Test
    • 20oz Coke bottle filled with water (1-1/2 lbs) in front of two 2" white styrofoam wads.
    • One teaspoon Bangsite
    • Recoil: 5"
    • Remarks: Nice Loud Bang! Bottle hit ground 20 yards out and put a big scrape in the turf. Then it bounced over the 7' berm and could not be found in the overgroth beyond. No damage to the cannon.

    In conclusion, I believe Rob's cannon failed because of a faulty breech plug. However, firing should be done with a long lanyard, standing off to the side and wear eye protection!