Marble Run System

I really loved the idea of being able to free-form sculpt the track of a marble run through the air. This design tries to provide that. The track is connected to support rods by means of ball-jointed connectors that allow the angle of the track to be adjusted to support the marble around corners etc. The aim of this is freedom of play and simplicity.

The rails that the marble runs on are Ø4mm OD nylon air hose. The ball joint connectors use spherical beads as the ball. The Ø4mm air hose conveniently snugly sockets into these beads and forms the support stand-off.

Non 3D Printed Materials:

• Spherical Beads Ø8mm variety from the following link (The internal diameter of beads isn't usually listed but I got lucky with these and they snugly fit the 4mm air line): https://www.aliexpress.com/item/1005006281267833.html?spm=a2g0o.order_list.order_list_main.10.32db1802Bk0it5

• Nylon Air Line Ø4 x Ø2mm. I got mine from here: https://www.aliexpress.com/item/1005008597042539.html?spm=a2g0o.order_list.order_list_main.96.32db1802Bk0it5

• 2m x 8mm Fibreglass rod (ideally plastic covered to avoid the fibreglass splinters)

• Wooden bases to support the fibreglass rod. The bigger they are the more stable the marble run will be.

• 1/2" Bearing Balls

3D Printed Materials

I printed all of mine from PLA. Ideally you should use something better but it does work.

Assembly

The Rod connectors need to be assembled like this from a small length (70-80mm) of the Ø4mm Air Line listed above as shown below. To avoid cracking the spherical beads put them in some hot water first. 

For the Fibreglass rod hoops drill two holes in the wooden base (without going all the way through) and then bend the pole around and plug it in to each hole. Just make sure that the holes are snug so that there is no possibility of the poles flicking out! Consider creating a tripod structure out of 8mm rods if you want better stability or if you have other 8mm rods that do not bend like fiberglass. 

Track construction

You have a lot of freedom here but a few things to note:

• It will be useful to cut up the Air Line into 1-2m lengths so that you have options and can stop and start them. There are joiner pieces in the 3d components list that join track segments together but you can't use these very well on really tight curves.

• Between each rod connector assembly the method of track installation is to connect one rail to both rod connectors.

• Then add the second rail by adding in splitter components every 150mm (6in) or as needed.

• To support high-G moves on the track (loop de loops) you usually need to add in rigidity by using more rod connectors.