With a top speed of 2mm per hour we believe we have produced the worlds slowest electric powered racing car.
The little guy sitting on top of this was added later and is understandably hanging on for the ride of his life!
Why might you ask would we do this?
Well we were trying to see if we could use a left over battery powered wall clock mechanism to do something a little different and then it turned into this.
This device is driven by the "minute" hand mechanism of an electric clock and will take an impressive 25 days to travel one metre which means it is an interesting item to have on your desk and if left undisturbed will likely take about a month before it falls off the edge!
If you have a few hours and the parts you too could have this on your workshop bench, or you could give this as a gift to friends or family who are overly cautious drivers to provide them with some inspiration?
Whatever the reason it is simple and fun to build.
PS. as suggested by feedback you can tell the time by how far the car has traveled :)
Step 1: Materials
1. Electric clock mechanism that you can get from a low cost wall clock.
2. Tamiya gear and wheel set that you can purchase from a model shop. In particular you need the following
- Worm gear
- Metal wheel axle (just a steel rod)
- Axel gear suitable to be driven by worm gear
- Three wheels
- Another steel rod for third wheel
- wheel bush x 3 used to ensure wheels turn freely
3. Styrene 3mm thick 6cmx2cm for axle mounts
4. Glue - 2 part epoxy suitable for plastics
5. Mounting screws x 2 for holding axle mounts in place
Step 2: Construction
1. Worm drive gear
Take the clock hands off the clock mechanism and carefully identify the "minute" hand drive. All the hands are generally driven by series of concentric plastic cylinders. The minute clock hand will have the right sized hole in it so you can use as a reference for how big the hole in the Worm Drive Gear.
Drill out the worm drive gear so it fits tightly onto the minute hand drive cylinder on the clock mechanism then using 2 part epoxy glue set this in place.
2. Back wheels
Build two wheel mounting brackets from the styrene plastic and drill holes to position the axle in the correct place. Add a bush to each side so that the wheels can turn freely.
Press on the plastic gear to the center of the axle. We will glue this later once other parts are in place.
Attach the back wheels to the clock mechanism using one very short screw in each side and tighten up.
NOTE: Take care to ensure that the mechanism case is not cracked or the inner workings are damaged.
Position the axle so that the worm gear and the axle gear are appropriately meshed. Then glue the gear onto the axle in place and also the two wheel mounting brackets.
Once dry put AA battery into mechanism and use a marker to determine which way you wheels will turn so you can add the front wheel onto the correct end of the clock mechanism.
NOTE: Do not try to turn the wheels manually as worm gears do not allow this and you will break teeth off the gears.
3. Front Wheel
This is constructed using a single metal rod and wheel with a bush mounted in the front of the clock mechanism with glue. (See photo)
NOTE: It is important to consider the weight of the battery so when constructing the third wheel make sure the unit does not over balance in one direction or the other. Ideally you want it balanced around the back wheels with the front wheel lightly touching down to minimise friction.
Step 3: Testing the Unit
Put an AA battering into the clock mechanism and check that the worm drive is engaged with the axle gear and that the clock mechanism is turning internally ( you can hear this easily)
The best way we found to test was to place the unit on graph paper and mark out the position of the wheels and then stand back and let it rip! Well actually go away for a few hours and then check to see if there was any movement.
We initially got the third wheel on the wrong end of the clock mechanism despite our best efforts to predict its direction so you may need to change this like we had to.
Happy drag racing :)