Sometimes it is good not to look professional, but instead to show exactly how low tech something really is. A good professional show can hide many defects, while amateurism shows everything.
The truth is that I am a biologist with limited means who has used the scientific approach to solve gearing problems, rather than the customary engineering approach. This scientific approach revealed a whole lot of new insights that I then used to create the invention. Biology and gearing might seem worlds apart, but that is probably why there was so much left to discover.
The gearing calculations used in the prototype are very good, while the rest of the prototype makes painfully clear just how limited my means are and also how little a biologist knows about engineering. The prototype is very impressive because it proves the new technology as well as showing off its huge potential.
So it is a bit like the first plane. That plane could only fly a few hundred meters, but its potential was clear. Engineers then got to work on it and created the planes we all fly in today. This video shows you the first flight as it were, and if you are an engineer then you can now create something great.
Considering my very limited resources it is astonishing that the prototype works at all (it costs around a $100), let alone that it works so well. More that anything this proves that the technology is extremely cheap, forgiving and efficient.
|gear ratios from 1:1 to 1:9|
|59 unique gear ratios|
|gear shift in 0.08 sec|
|max output 595 rpm|
|372 rpm at full speed|
|consists of 9 conical involute gears|
|8, 10, 12, 14, 16, 18, 20, 22, 24 teeth|
|3D print 0.4 mm nozzle, Lego motors, Arduino|
|Costs around a $100|
In the prototype the main Lego motor drives two identical white Lego gears. Each white Lego gear has a slip coupling inside it. In theory this is to compensate for when a multi-ratio gear instantly changes gear ratio. The second white Lego gear then drives a square black shaft. This square black shaft then drives the input gear on the little sliding contraption. As you can see the square black shaft allows the sliding contraption to slide over it while still being able to drive the input gear unhindered.
In the sliding contraption the square black shaft is connected to a helical bevel gear (15 teeth) with a quarter shift per tooth. This then intermeshes with a second gear (12 teeth) that is connected to the conical involute gear (12 teeth) that drives the main gear. We call this the input gear.
The input gear can drive any of the gears in the main gear by simply sliding to the correct position. It has 9 gears to choose from. The top gear on the main gear has 8 teeth, while the bottom one has 24 teeth. So the main gear will rotate 3 times faster when the input gear drives the main gear at the top (8 teeth), then when it drives the main gear at the bottom (24 teeth). We have placed the input gear right at the top so that it will drive the main gear at full speed (= 372 RPM).
At the other side of the main gear we have an identical setup. Here the main gear drives the output gear.
The two strings connected to the sliding contraption on either side pull it to the correct position. A Lego motor pulls one string, while the other string is pulled by a spring powered pulley system.
Note that even this very bad quality 3D printed prototype does not make a lot of noise. If these were spur gears that would be very different. This is because of to how the tips of the gears are cut.
At full speed and with the output gear intermeshing with the single-ratio gear that has 24 teeth (position at the end of the video), the output speed is 3 times the input speed that comes from the motor. At this speed a truck with a 1 meter diameter wheel would be going a 112 km/h on the highway. So this very cheap prototype is outputting a real world speed.
If the position of the input and output gears on the main gear were reversed, then the output speed would be a third of the speed of the motor. So this prototype has gear ratios ranging from 1 to a third, to 1 to 3. Or stated more conventionally: from 1 to 1, to 1 to 9. In all, this prototype has 59 unique gear ratios. This is why it is called a New-CVT. But as it is fully gear based with only very few components it is also superior to all current transmissions.