How To Make Your Own Rube Goldberg

The Ultimate Addition to Your Track

Tired of boring featureless tracks? Add some real character to your home track, build your own Automated Chequered Flagman. Y.M.R's "Rube Goldberg" used to be a dull, stationary track figure (ex Scalextric track photographer from the 1960's) until we rejuvenated him into an action figure for the 90's.


Note Rube's Flag Arm, His Lever (or Third) Arm and Pushrod Thru Table

Rube's flag arm is activated by two pushrods which are driven by a small HO scale slot car underneath the table. The HO car is attached to a pivoting board with a small balance weight (for just the right amount of traction) and remains stationary. The HO car is wired up to the accessory power source (12V) so it doesn't steal power from the 1/32nd cars, and it's speed is made variable using one of our old controllers. The HO car drives a "Rolling Roadbed" which acts as a cam and drives the pushrod in a circular motion much like the drive wheel of an old steam locomotive. This motion is redirected upward, thru the table, to Rube's levered (third) arm and thus to his flag arm, a tube in his shoulder being the pivot point. If you are skilled enough to build your own track (and that doesn't take a whole lot of skill), you can certainly build your own Rube.

Things You Will Need

Scrounge around in your parts boxes for an old HO slot car, an old 12V controller, some bits of wood and wire and a scale model track figure (2-2.25 inches tall for proper scale). From your local hobby store, you will need to buy a length of "piano wire" and a piece of brass tubing that will allow the piano wire to move freely inside it. (The tubing minimizes any friction in the moving parts). I also splurged and bought a small plastic arm (referred to as a "90 Degree Bellcrank Assembly" which is used in model airplanes for pushrod linkages). While you could make this unit yourself, for $1.29 CDN, it will save you a lot of time diddling with the pushrod connections under the track table.

Construction

Start with Rube. Take the figure and cut off one of his arms (no anesthetic needed). Drill a hole thru his shoulder so you can insert a small length of brass tubing which you can epoxy in position later. Take a four inch length of piano wire and insert it halfway into the tube. Bend one side of the wire one way and the other side, the other way, so the wire ends up looking like a "Z". The front piece will become Rube's new "flag arm" (and flag pole). The back piece of wire will become his "lever arm" (or "third arm"). Build up the new flag arm with masking tape and epoxy so it resembles his original arm. I made the chequered flag on my computer, cut and glued it to the flag pole at the end of his new flag arm. Take the "lever arm" wire and put a very small loop near the end. The pushrod will eventually connect to this loop. Paint up Rube and screw-nail him securely to the track at the finish line. Drill a hole thru the table top, straight down from the lever arm loop and insert a piece of brass tubing in the hole to act as a bushing for the pushrod where it comes thru the table. That's all you need above the table.


The "Drive Unit" on the left and the "Bellcrank Unit" on the right

Now you need to make two units for under the table, the "Drive Unit" and the "Bellcrank Unit". The Drive Unit houses the "Rolling Roadbed" which can be made any number of ways. It has to be circular so it will spin. I cut two wooden plugs with a "plug cutter" and glued them together. I used wide elastic bands on the roadbed surface to give the HO car traction. Bang a small nail in the side of the rolling roadbed off the centre line and this will be the cam. The throw of the pushrod is determined by the distance of the cam from the centerline of the roadbed. Attach the HO car to a small block of wood and wire it to an old controller. The wiring is similar to that described in our manuscript for building the track itself, but this is a completely separate circuit. The block of wood is attached so it pivots freely and a small weight can be positioned (thru trial and error) to give it enough downforce to drive the rolling roadbed. A large nail thru the centre of the rolling roadbed (with a large enough pilot hole) serves as an axle and should allow it to spin freely.

The "Bellcrank Unit" houses the "Bellcrank" (duh) and needs to be installed directly under Rube's lever arm loop hole. Next, you need to connect the drive unit to the bellcrank unit with a piece of piano wire looped around the cam. Next, connect Rube's lever arm to the Bellcrank Unit. The Bellcrank is perfect for this as it is easy to connect and adjust with a small screw driver. You'll be glad you forked out the $1.29 CDN ($.75 US?).

An now for the fine tuning. Friction is your worst enemy and you will have to play around a bit to reduce it. Friction on the Rolling Roadbed was my biggest problem but it was solved by making two "bearings" out of small brass strips (or, if the budget allows, you could use two penny coins). Drill a hole in the centre of the penny coins to receive the nail that serves as the axle for the Rolling Roadbed. This makes a near perfect bearing surface (what do you expect for two cents!) and the roadbed should spin very freely. Attach the pennies to the roadbed with a couple of small nails. As long as the pushrods are lined up fairly well, the brass tubing should let the wire slide freely. A couple of drops of oil always helps. Finally, Rube's flag arm will wave according to the leverage that is applied by the cam. You may find you have too much or too little play. The "Bellcrank" solves that problem as it has three positions on each side, allowing any number of combinations (actually nine for those of you still awake).

Final Tips

1. Build the whole thing at your hobby desk and get it working "above the table" before you install it "below the table" (unless you really like working above your head while lying on the floor).

2. Line up all the pushrods, connections and bushings in as straight a line as possible to reduce friction.

3. Keep the Drive Unit and the Bellcrank Unit about 12-24 inches apart (ie make the first pushrod that long) in order to give the pushrod plenty of room to swing.

4. For added movement of the flag, I used a length of brass tubing around the wire of the flag arm and attached the paper flag to it. This way, the flag swings freely around the flag pole and, with a little practice on the controller, you can get some truly outstanding waving action out of old Rube. Even the 1:1 scalers would be proud!

You are done!!! Let me know how it goes or how I might improve these instructions. Have fun, I did! ...and you'll be amazed at how everyone (under the age of 50) dives under the table and says "How did you do that?"

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