Below-bowl rampsThe marbles that swirl around the bowl eventually fall out one of three holes at the bottom. Two of these holes lead to ramps that move the marbles over to where they are dropped onto percussion elements. The third hole just drops them straight down.
Clamped and waiting for the glue to dry. I pressed the part down on the table in the orientation shown while applying the clamps to ensure proper alignment. Be careful when you apply the clamps - they often cause parts to slip out of alignment.
Once the glue was dry, I'm drilling the exit holes for the ramps. I'm using a 5/8" (16 mm) drill. A drill that is a tiny bit larger would be ideal, but such drill sizes are very hard to find. A 3/4" or 18 mm hole would be too large. For a hole that large, marbles might go through a hole at an angle and then miss their target below.
The problem with 5/8" or 16 mm is that some of the marbles are slightly larger than that and will get stuck in the holes.
My solution was to sand out the inside of the hole. I don't have a sanding spindle that small, so I used a piece of 1/2" dowel (about 12 mm) and cut a slot in it. I then put a piece of very coarse sandpaper in that slot. No need to glue the sandpaper into the slot, but the important thing is that the lower edge of the sandpaer is at an angle. This helps the sandpaper wrap itself around the dowel as the spinning dowel is pushed into the hole
With the drill lowered into the hole, the drill is moved up and down while the work piece is pushed in various directions. Ideally, the hole will get enlarged by about half a millimeter. Some larger marbles may still get stuck in the holes, just put those marbles aside.
Marking the location for the pilot holes of the longer of the two ramps. Make sure the ramp lines up with the hole in the bowl and that it points towards the corner of the machine. The back edge of the ramp should not extend past the edge of the hole, as space will be very tight.
Also make a pencil line for the outline of the ramp on the bottom of the bowl.
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