For a long time I wanted to make automata with some kind of self driven mechanism. This car is the first step in this direction. It has a working engine, driven by 2 rubber bands and comes in a kit that is only 105 x 210 x 1 cm in size. This is the standard size of a postcard. I sell these and ship them in an envelope and they make awesome Birthday cards (who would not want a rubber band driven, wind up, laser cut plywood car kit as a gift). If you are interested in one get it here:
Buy It Here!
All the bits and pieces.
As with many of the things that I have been making recently, it is a laser cut model. Most of the parts are pressed out from 3 mm plywood sheets. The axles are 4 mm dowels and everything assembles quite easily. Download the instructions* here:
*Note the hard part of developing a kit is, for me, the instruction manual. Again writing the manual took more time than developing rest of the whole kit.
A video with some instructions to make assembly easier is available HERE:
1 of 2 postcard sized part sheets.
All the parts removed and sorted.
A small bit of CA-glue (supper glue) is needed to ensure there is no slippage of the gears on the axles. This is in different to many models that can be assembled without glue – but to tame the 2 band power of the engine it is necessary in this model. A bit of wax on the gear teeth allows for smooth running of the mechanism.
CA-glue needed mostly on the drive gear.
The best part of the car is the gear system. In contrast to the gears in the Strandbeest model, there is an increase in the number of rotations from the drive gear to the final gear, rather than a reduction. The reason for this is two fold:
- First it is to allow the car to run farther than just 2 turns of the wheels. Two turns is close to the maximum that the rubber bands can be wound. With the gear ratio of 1:3 and 2 sets of gears the large wheels turn approximately 18 times making the car go 3 – 4 meters on only 2 turns of the key.
- The second reason is to slow down the mechanism. The gear train ends with a flywheel and total gear ratio of 1:27. The moment of inertia of this small flywheel is enough to slow down the mechanism sufficiently (although the car still moves reasonably fast).
Mechanism in action. Drive to fly wheel ratio = 1:27
I am very happy with how this model has turned out. Let me know what you think about it, or feel free to get your own (here) if you think it is awesome.
I am already busy designing a new model and are currently very exited about it. Follow me on any of the social media channels to see what it is.