Introduction: Protei Land Yacht
The aim of this prototype was to develop a wind train from our last model, the Windtrain Umbrella that would have both improved performance and construction. We were more interested in making a single module that functioned well on its own than a long windtrain. In essence we where developing more of a performance land yacht which could be used a basis for our next generation of windtrain.
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Step 1: Improvements From Our Last Model
Before we started drawing or planning our new design, we had to make our focus improving the weaknesses of our previous model. The main faults of our last design was that:
- The front wheel was prone to wobbling around due to the front leg of the vehicle being too long and flexible. To solve this problem, we formed the front leg of the vehicle from two 8mm aluminium poles running parallel together. This provided more overall stiffness and prevented the front wheel from rotating too much relative to the vehicle body.
- The design was very flimsy and flexible, we needed to make it more sturdy and rigid. The previous design had a very small wooden frame. This acted as more of a point for the legs to pivot around as opposed to a rigid frame that would make the model a sturdy structure. We therefore wanted to make a larger central wooden frame which would provide a firmer base for all the aluminium rods to extend from. Furthermore the shape of our new design was crucial, we therefore decided to look at alternative designs to the previous umbrella inspired setup.
- The umbrella design had very little room for electronics, therefore another reason warranting a larger wooden frame was the extra space this would allow for the electronics set up and personalisation.
- The connections between the windtrain modules were too long and flexible. This led to the trailing carriages to oscillate a lot, it appeared as if the back module was allowed to resonate as it was dragged along. This is not good for two reasons, it slows down the windtrain and weakens the structure. I therefore needed to make the connection between the modules shorter and stiffer.
- The center of mass of the sail is not aligned with the center of mass of the body of windtrain. As we can see in the picture, the center of mass of sail is about 50cm from the front wheel while the whole body is just 60cm. Although 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 opted for was to have a larger central platform which would allow a single wheel axle to run through the back of it, two 8mm aluminium rods to run down the length of it (these would form the structure for the front wheel) and a cavity that would act as the foundations of the mast.
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, thus allowing it to occupy a smaller space for collapsing and moving this vehicle around.
We made a prototype out of cardboard and left over pieces from our previous models as shown above. Furthermore we did some technical drawings to outline the dimensions and main features of the design.
The model would be made out of the following parts:
-5mm thick plywood (the laser file I used occupied a 300x500mm area, but the parts can be rearranged)
-3000mm of 8mm diameter aluminium rods
-Plastic screws and the corresponding
Step 3: Construction
The model would be made out of the following parts:
-5mm thick plywood (the laser file I used occupied a 300x600mm area, but the parts can be rearranged)
-3000mm of 8mm diameter aluminium rods
-Fabric for a sail (approxiamately 800x300mm)
I made up the laser files, using the drawings I did, and used these to cut out the wooden components for this build. I also had to cut the aluminium rods to the appropriate sizes, 4x600mm and 2x300mm pieces.
From then on I just had to put together the pieces which was done with very little difficulty and all the pieces fitted together nicely. I finally had a completed structure which I could then attach the electronics to. With thsi design I didn't include the electronic components in the planning of the vehicle, I wanted to be able to change elements of the electronics to suit the new design that I had made.
I ended up using the following electronic parts:
-2x Channel RC car controller
-4x AA batteries and battery pack
-2x High torque servos
I then arranged the electronics in the as shown by the pictures. In future models I hoped to integrate the electronics into the frame, but for now I was trialling different arrangements.
Step 4: Test
We went to test the design on a disused bit of land by the waterfront. We were hoping for this location to provide the most wind but unfortunately it was a very calm day. There wasn't sufficient wind to fully test this vehicle, however we had just enough wind to propel the vehicle downwind for short lengths. Another problem of the vehicle was due to the wheel size comp
Step 5: Amendment for a Better Land Yacht!
-How we bend the metal could be made more precise. The existing metal bending is done by bare hands, which means that will not be a good way to do for mass production. Since the means we used now will spend too much time and effort but get a product of less precision, we need to find machines to finish those work for accuracy.
-Integrating the Servos into the Wooden Frame. The position of the servos is not fixed so while the WindTrain is moving, the servos may be in misposition and fall down. We need to find a place and fix its position.
-Making a Taller Sail. The sail now can only capture relatively small wind power to propel, and that make the WindTrain quite slow even though there is homogeneous wind. The larger the sail, the larger the area of it will be and hence the larger wind power it will have.
-Height Adjustment of the Boom. The boom is quite high when we measure the distance from the plane attaching it. Most of the wind will therefore escape from the gap between the plate and the boom. We try to make a taller sail and lower the boom at the same time to increase the wind power captured.
-Let the Sail Servo Sweep in a Different Plane. The sail servo controls a wooden plate to swing in a bid to adjust the sail tension. However, the motion will hinder the swinging motion of the boom in some angles, especially in the wooden plate controlled by the servo is vertical. We will then try to make the sail servo sweep in a different plane, and we think being parallel to the ground is the best choice.
Step 6: Improved Prototype
We decided to act on the issues brought up with the previous model. We therefore redesigned some elements of our previous vehicle to produce a slightly modified update.
The changes made where:
-The laser cutting files were redesigned so that the electronics could be integrated with the frame of the vehicle. Furthermore we changed the plane of sweep for the rear servo by including a cavity for it to sit in.
-The previous model had small wheels that got caught up in cracks and deviations in the test surface. We therefore decided to make the new version with bigger wheels. The radius of the new wheels used was 70mm which was almost double the height of the previous wheels. The back axel could remain the same, but the front wheel fork had to be elongated to allow extra space for the bigger wheel. This was accomplished by a simple change in the laser cut files.
-The sail was made longer, we did this by using two 600mm lengths of aluminium rod instead of the previously used 600mm aluminium rod. We had to remake a sail out of the fabric that could suit these dimensions better.
-The metal was bent using a vice. We secured two identical aluminium rods running parallel in a vice, we then applied a force to adjacent parts of the rods creating a more accurate bend and reducing the difference in the form of the two rods.
-As well as integrating the servos into the base plates, we built a box that would sink into the base plate that would house some of the electronics. This would keep the electronics neatly in one place, as well as providing some protection from the elements.
-To provide more strength in the mast, we added pieces of string between the top of the mast and the extremities of the wheel axels.
-We wanted to make the design more collapsible and easier to transport. We therefore replaced the 8mm wheel axel at the back with a 10mm diameter aluminium rod which was fixed in place. This would then have two 8mm aluminium rods with fixed wheels that could slide in and out of this central rod. This would allow you to pull the wheels out when you want to travel with the landyacht in a way that we though would preserve the strength of the vehicle.
-To allow people to film from an fpv angle, an extra slit was added to the front piece. This would allow you to slot a mobile phone in, secured by rubber bands, to record or stream an fpv video of your ride.
Step 7: Test 2
Due to a lack of wind we set up a fan in the workshop to test this prototype.
-The new wheel axels did not compromise any strength or rigidity of the main frame, but they added extra width and fulfilled the desire for a collapsible system.
-The string attached to the top of the mast added a lot more strength in the mast. It reduced the amount of flex in the mast and removed some of the force acting on the connection at the base of the mast.
-The box housed the electronics very well although the parts rattled around within the box, and the corners of the box caught the main sheet.
-The extra slot for the phone allowed for a very smooth and clear video, however it was too low relative to the front wheel. This meant that the front wheel was the main focus of the video and occupied most of the screen.
Step 8: Improvements
Although our previous design ran well, we wanted to improve the following features.
-The box will be designed so that the baseplate of the main frame will form the base of the box. This will save weight and the need to manufacture extra pieces. Furthermore we are making the top of the box hinged as to make it more secure and rigid when the vehicle is moving around.
-The peg that the main sheet runs through is going to be elongated so that the hole is above the top of the box. This will reduce the chance of the mainsheet getting caught on the corners of the box. Also the peg will be made wider as to add strength to it and allow for wearing down of the wood over time.
-The string that was used to add lateral support to the mast will be replaced by steel cables. These will add more strength and will be secured in a different manner. The string was secure to the wheel axels by masking tape, which over time weakens and tears. Therefore we are looking at drilling holes in the axels and using screws and loops to secure the new cables.
-The electronics had a tendency to rattle around in the box, we are therefore adding a sheet of velcro to the base of the box. The electrical components can then be secured to the base of the box with small pieces of velcro. The velcro will be cheap and accessible, whilst allowing for customisation of the product.
-Although the phone mount worked to some degree for my model of phone, we want to make a more versatile platform that can be adapted for other filming devices. We are therefore researching the possibility of securing a tripod mount or ball and joint to the front rods or the the front of the base plate. This would allow for people to add their own mounts as well as providing a platform that can work with a greater range of devices.
Step 9: Summary
We have decided to stick with this final prototype. We are therefore looking into the availability and accessibility of the following parts required:
8mm Diameter Aluminium rods (total=2825mm): -3x600mm -2x400mm -125mm -100mm
10mm Diameter Aluminium rods (total=1040mm): -140mm -2x150mm -2x300mm
3x120mm Diameter Scooter Wheels + 6xBearings
250x160mm 4mm Thick Acrylic
280x610mm 5mm thick plywood
2200mm String Or 2200mm Steel Cable/Wire + 2xEnd Clamps/Fasteners
1100x650mm Sail Fabric
2xFusonic MG-A-15KG Servos + Servo Heads
1x4AA Battery Pack
TX + RX
Furthermore we would like some feedback from people regarding our design and its potential uses. We have already handed a deconstructed model to a group of under 10 kids, and with no instructions left them to figure it out as shown. We now want to see how easy it is for others to understand, and the ways people modify and use it themselves.