The aim of this prototype was to develop a wind train from our last model - the Windtrain Protei Land Yacht. And that would have both improved performance and construction compare to the last model we had. We were more interested in making a single module that functioned well on its own than a long windtrain first. This model is essential to our next WindTrain development as much of the problems in the last model has been solved.
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Step 1: Improvements From Our Last Model
in order to improve the weaknesses of our previous model, we focus on the weak point of the last model - Protei Land Yacht.
The main faults of our last design was that:
- The size of the last model is not very convenient for any person to bring it out, especially here in Hong Kong. Therefore we try to scale down the whole model at the same time strike a proper balance between the joy of seeing such big toy and the convenience.
- The production of the front wheel part in the last model has been considered as a waste of human resources, time and material. And the front wheel part is too long so that the last model cannot easily turn its direction. The weight of the extended front wheel part has also been a burden for the WindTrain which is only propelled by wind.
- The design was a bit flimsy and flexible, though we have a great improvement from the first model Umbrella. We needed to make it more sturdy and rigid since kids would probably be the owner of it. The previous design had a very small wooden frame. We discovered some weak points too during the testing for our last model. We therefore make a larger central wooden frame which would provide a stronger base for all the parts. We have also cut the extended front wheel part in order to make it more "kids-proof".
- The previous design had too much room for electronics, therefore another reason warranting a scaled-down but stronger wooden frame was the best choice allowing for the electronics set up.
- The distance between the center of mass of the sail and the center of mass of the body of windtrain can be further minimized. The unalignment of them will exert a turning effect to the WindTrain itself. Despite the fact that we may not be able to align them in the same line, we should always try to narrow down the distance between them by moving forward the center of mass forward, so that the windtrain can go straight without much effort to control.
Step 2: Design
The design we choose for was to have a smaller central platform. There will be a cavity that would act as the foundations of the mast, as well as the platform for electronics.
The collapsable element was the mast, it would be made up of a telescopic section that could slot on top of a section that was attached to the base frame. The lower section would be mounted to a pivot, but this time we will add the platform for universal camera mount which fix the position of mast.
The model would be made out of the following parts:
- 5mm thick plywood (the laser file I used occupied a 240x530mm area, but the parts can be rearranged)
- 1580 mm of 8mm diameter aluminium rods
- 280 mm of 10mm diameter aluminium rods
- Plastic screws and the corresponding
- 3 wheels
- 1 Servo
- 1 Remote Control
- Kite Fabric
Step 3: Construction
After collecting those materials used in the improved model, we then focus on the fabrication process. The process is much much easier than the first time we make WindTrain since most of the problem has been solved. The most time-consuming process is to put all the parts together. But this is our aim as we want kids to enjoy the process of making something out of pieces of wood. I have also uploaded a manual of how to put all parts together.
Step 4: New Feature: Elastic System
As the whole design is collapsible, the elastic system is designed to prevent the parts from missing. The system is applied to the mast and the back wheel axle. The system is designed which is easy for a kid to assemble. We just need to let the bungee cord to go through the aluminium tube, and put the washers on both ends. After that, we should tie a knot to prevent the cord from slipping off. The system is easy for any kids to understand the design idea behind, and the parts are so simple to find it around in the shop near by.
The main parts of this system are:
- bungee cord
Step 5: New Feature: Camera Mount Platform
The kids can enjoy the ride on WindTrain by simply setting his phone on it. We add a new piece of wood part in the bottom of the mast. By attaching the camera mount yourself on the platform, the kid can have much more fun with the WindTrain, since they can ride the WindTrain in a totally different angle.
Furthermore, the platform piece has been designed for fixing the position of the mast. The moving mast is one of the problem in our previous model, especially when the wind is blown from behind. The turning effect that the wind exerts will let the mast fall down. The piece is effective to fix the problem while kids can add some gadgets onto it.
Step 6: Problem Remain
The problem of the WindTrain is that we do not have a adjustable outhaul system. In the previous version, we used a servo to control the sail tension but it turns out that this way is not effective enough to control and too sensitive for any small change in wind direction and speed. Meanwhile, it does put more weight onto the WindTrain.
This time we use the elastic string to solve the problem. The more the wind blowing to the sail, the larger the angle of boom deviated from the central line. The larger the angle, the stronger the tension the elastic string to pull the sail back to central line. Theoretically, it works. However, in reality, the tension the string exerted depends very much on the setting up, which means the length between 2 knots. If the kids tie it too tight, the WindTrain would have problem travelling downwind while it would not be able to travel upwind if the string is too loose to produce pressure difference on its two sides. It would be very nice if we can have a adjustable outhaul system and at the same time have less weight carried on it.