I figured it would be best if I revised the design. I had thought of a few improvements since I built my marble machine blocks.
I started by making the ramp block pieces. Here I'm cutting the ramp shape on my table saw. After I cut most of the blocks, I had the idea of starting with a rectangular piece just large enough to yield two ramp pieces when cut through at an angle.
The best way I have for guiding a router through an arbitrary 3D shape is my 3D router pantograph. So I made a 2x scale template for the path that the router is to follow.
I use a 5 mm metal shaft as a stylus to run in the grooves.
I first set up the pantograph on my table saw, but then I still needed to use the table saw, so then I set it up on top of my horizontal boring machine, which I haven't really used in a long time. Mostly, I have been using it as a stand for my slot mortiser (see picture here).
I used my slot mortiser to pre-cut a 1/2" slot in the blocks, just to reduce how much material I'd have to remove with the ball nose bit. The straight bits always seem to cut better, and with the bigger router on the slot mortiser, I can also remove material faster with it.
I used a wedge to clamp the workpiece on the pantograph base. The wedge pushes a piece of plywood against the workpiece. The piece of plywood is held down by guides on either side.
Cutting out the pieces. Too bad my hands obstruct the view to the stylus in the grooves in this photo.
A problem with marble tracks like this is that the impact of the marbles gradually causes the track to "un-build" itself. Wherever the marbles need to go around a corner, each marble knocks the blocks a little further apart until there is enough of a gap for marbles to get stuck or fall out.
So as with my modular marble machine I added holes to the bottom for interlocking, though only 1/2" holes this time.
I cut all these holes with a 1/2" endmill using my pantorouter. The nice thing about using an endmill instead of a drill is that the holes have flat bottoms.
I made a 2x sized template with four notches that were the same size as the follower bearing. That way, I just have to clamp the piece in on the machine once, then place the follower bearing once in each slot and plunge.
After making the pieces, I round all the edges. With each piece having 12 edges, that's a lot of edges, but I can do these quite rapidly on the belt sander.
If I leave the piece touching the belt as I flip from one edge to the next on the end, the corners also get rounded off.
Lots of track segments made!
Now, to make some stepped "riser blocks" to connect the track pieces together.
The riser blocks need to have a step, because the next ramp that the marble rolls onto is always one height increment lower.
I cut a whole lot of pieces to length on my table saw sled.
Then two more cuts with the sled to cut out a notch.
This all went quite fast.
An aside, I have been monitoring dust levels with my Dylos air quality monitor, and it's really surprising how little airborne dust results from making crosscuts with the sled. The sled deflects most of the sawdust straight into the saw. The router, on the other hand, produces incredible amounts of airborne dust. I'm glad I built an air cleaner
My horizontal boring machine turned out not to be a great place to set up the pantograph, because, with so many identical pieces to drill, it was worth setting things up on that machine. The horizontal boring machine is really good for repeated precise drilling operations, and with so many blocks with holes in them, that was the perfect machine.
The reason I used the horizontal boring machine and not the pantorouter or slot mortiser for those holes is that I made all the holes 29/64", and I don't have a 29/64" endmill or router bit. The holes are 3/64" (about 1.2 mm) smaller than the holes in the ramps so that the buttons on the blocks will have some slack in the larger holes in the ramps.
I had to make some
custom sized dowels for the buttons.
You might say, "why not just make the holes bigger, so you can use 1/2"
dowels", but that would have required a 35/64" drill or endmill, which I don't have.
A neat trick for cutting lots of short dowel pieces is to make a piece of wood with a notch the same width. This serves as a guide, and helps to hold the dowel as I cut it on the bandsaw.
Trying the stepped riser blocks with track segments. They fit nicely and prevented the ramps from sliding around.
Testing by running lots of marbles down the tracks. So far, so good.
Now, to get the marbles from the bottom back up to the top, it helps to have some sort of elevating device. I came up with a marble pump, but with a simplified design, using just a lever. Making the simple marble pump is a bit tricky, so I will leave that for a future article.
I took the blocks I had built so far, the marble pump, and some parts from my modular marble machine to a local hacker space gathering to let some really big kids play with it. I was keen to see how others would use the blocks.
From watching others play with the blocks, I realized there was a problem. The horizontal increment for all my blocks is 32 mm, but the vertical increment was 12 mm (A and B vs C on its side). People often placed blocks on their side to get height, but 32mm is not an even multiple of 12 mm, so that caused the height increment to no longer work out evenly.
So I changed the design to use a height increment of one third of 32 mm, or 10.66 mm. Three height increments in D and E work out to the same hight as C.
With a new vertical increment, I had to make all new ramps and blocks. With my jigs already set up, this went quicker than the first time around, though it still took a whole day.
Next: Marble lifter
Next: Marble lifter