Table Top Bowling Game

Another tabletop bowling game. But this one's different, it uses a magnetic cannon to propel the ball.

I made this for my one of my grandsons in 2017, and as you can tell from the photo I didn't pay much attention to the details involving bowling, I used eleven pins instead of ten, I've corrected it for this design. 

Tools

Table saw (or handsaw)

dado blade (or router, plane or file)

Hacksaw

Screwdriver

1/8" brad point drill

1/4" HS drill

5/32" HS drill

41° countersink

Epoxy

PVC glue

Wood glue

sandpaper

Material

1 6" long 1/2 inch PVC threaded nipple, threaded on one side only

1 3/4" long piece of 3/4 inch PVC

   Verify the O.D. of the nipple is approximately the same dimension as the I.D. of the 3/4" PVC. 

3 1/2" ball bearings

1 1/2" rare earth magnet

12 1.75-Inch Small Unfinished Shaker Pegs Includes Tenon Length of 1/4-Inch - Amazon

1 3½" x 30" piece of 1/4" thick wood or other hard surface material, for the alley (I used some left over laminate from my office floor)

1 3/4" x 18" piece of 1/8" thick tempered particle board

1 1 3/16" x 3 3/4" piece of 1/8" thick tempered particle board

6 1/4" thick by 1" diameter felt pads

2 8-32 x 1/4" machine wood head screw (may have to modify longer screws)

1 6-32 x 3/4" flat head machine screw

2 6-32 hex nuts

On 10 of the Shaker Pegs the tenon needs to be removed, cut them off and sand the bottom of the peg level, they are the bowling pins. Save the two unmodified pegs for Step 8.

Using a hacksaw cut off 1/2 of the PVC nipple 2inches from the end that is not threaded, and drill a hole in opposite sides of the cannon as shown, for the 8-32 x 1/4" screws.

Epoxy the magnet level with the cutoff, keeping it perpendicular.

With the hacksaw cut the 3/4" PVC in half, then drill a 5/32" dia hole centered with a 0.330 diameter countersink. 

Insert the 6-32 FH screw into the hole and epoxy it in place, keep it straight, as shown. To keep the screw straight, I took a wood scrape 1/2" thick, drilled a 5/32" hole in it, then using a piece of waxed paper between the scrape and the mount, I applied the epoxy to the underside of the screw head, inserted the screw through the mount, waxed paper and scrape then tightened the assembly with one of the hex nuts.

The cannon will snap into the mount, fix it with PVC glue or epoxy.

Install the two 8-32 wood screws in the holes on the side of the cannon. The end of the screw cannot enter the muzzle more than 1/64th of an inch, file the tip down if necessary. These screws are used to fine tune the aim of the cannon to keep the bowling ball on the alley.

First a short discussion about what's going on. The cannon is loaded by placing a ball bearing, the bowling ball, into the muzzle of the cannon. Then to fire it take another ball bearing, the trigger, and place it in the trough and give it a slight nudged towards the muzzle. As the trigger gets closer to the muzzle it accelerates from the pull of the magnet and hits the magnet, the firing pin, and passes the acceleration from the trigger to the ball through the magnet.

To find out how long you're going to make the alley depends on the strength of the cannon, so it needs to be tested.

Here you have to be careful, mount the cannon on a piece of scrap 1" wide with a 5/32" hole for the screw, place it on a flat table, surround the flight path with towels to prevent the ball bearings from getting lost. Fire several rounds to see how far they go, choose a distance that assures you the ball has enough force to knock down the pins, make the length of your alley (L) about 8 inches longer. Put a 5/8 x 1/8 notch at the end of the alley to catch the ball (dado, router, plane or file) and drill all the holes as specified below.

To contain the ball we've installed a fence made from the particle board around the alley and catcher for the ball. 

To maintain the focus on the bowling pins the 2 extra Shaker Pins are installed to prevent the cannon's aim from leaving the alley.

After drilling the 3 holes, glue the two extra pegs to the alley.

Place the felt pads in each corner and on both sides in the middle on the underside of the alley, this protects the table top and offers clearance for the mounting of the cannon. 

Install the mounted cannon to the alley by putting the screw through the hole and attaching the nuts. The first nut should not be too tight to prevent the cannon from pivoting and the second nut tight enough to prevent the first nut from coming loose. Set the ten bowling pins in their tenpin layout. 

Now you're ready to load the cannon and knock over some pins!