TOY TRACTOR WITH ROTATING SOLAR PANEL AND SPUR GEAR WHEEL

The possible benefits that could be derived from solar panels in rotation movement continue to call my attention. Perhaps, it would be beneficial to integrate, for example, Solar Panels in rotation with Vertical Wind Turbines or with Hydraulic Generation Systems and possibly, in a Radar system operated by the energy of the Sun. Experimenting with Solar Panels in Rotation motion could be the initial steps to try such integrations in future projects.

Some time ago, I published: "Toy car with Solar Panel Wheel", a kind of toy car where its propulsion system consisted of a wheel (round solar panel) coupled to the “stator” of a small electric motor. Some elements I think could be improved in that project. One difficulty that I found in my experiments with this toy car was the vertical position of the Solar Panel with respect to the ground, which constitutes an impediment to the optimal use of Solar Radiation and the little torque that is obtained between the wheel and the road, making it very difficult to start running in certain areas. These electric motors generally operate at relatively high rotational speeds. If greater strength is desired, it is necessary to resort to mechanisms with mechanical gears or similar technologies.

In this Instructable I offer the steps that I followed for the construction of another toy, also with a Rotating Solar Panel, but implementing certain changes and improvements. Its design is unconventional. For example, the electric motor is arranged in a vertical position with respect to the ground and not horizontal as is generally the case. The Solar Panel is coupled to the body of the electric motor and not to its rotor shaft (in this way, the cables of the panel are not tangled during rotation). A gear is also attached to the body of the motor and this has a direct action on the wheel, which is also a gear! A slightly crazy design that like all have pros and cons.

With the interaction with this toy, the youths could approach the elementary understanding of different knowledge:

--- Use of Solar Energy in propulsion systems

--- The relativity of the states of motion of bodies

---Principle of action and reaction (if you stop the axis of a moving motor, its body could begin to rotate if it is not properly supported)

--- Gears and mechanical transmission mechanisms and how to use them depending on the design objectives

--- Axles and wheels

--- Inversion of the direction of Rotation of an electric motor of these characteristics

--- Physical quantities and physical phenomena such as Force, Torque, Mass, Inertia, Force of gravity, Center of mass, etc.

Supplies

--- Electric motor with gearbox ratio (10: 1): 12V 10W, 8mm diameter shaft

--- Solar Panel: 8W 12V

--- CNC Machine, Laser Cutter or 3D Printer

--- Plexiglass: 300mm (L) * 200mm (W) ** 10mm (H) X 4

--- 6 Screws for plastics: M4 25mm (L)

--- 4 M4 Screws: 15mm (L)

--- Various washers: 4mm

--- 8mm shaft diameter: 180mm (L)

--- 4mm shaft diameter: 50mm (L)

--- Instant Glue

--- Silicone Glue

--- Soldering iron and tin

--- Electrical insulating tape or similar

--- Cable connector

Step 1: Design Considerations

Although at the beginning I had an idea of the objective that I was pursuing, it really wasn't until I started 3D modeling that I took away a representation of what this Experimental Toy Tractor might turn out to be. My entire design was based around the electric motor that I declared in the list of materials. The one I used was an electric motor with brushes, permanent magnets and a gearbox, recycled from a large disused printer. The first thing I did was to measure it and make a 3D model of this motor, also of the solar panel that I also had. The panel would be placed in the rear part of the motor body and the shaft would be embedded vertically in the central base of the entire set of this toy. Honestly, the entire modeling would have been much easier if this electric motor had its rotational axis symmetrical with respect to the body, but unfortunately it was not like that. This meant that some pieces had to be fixed taking into account this asymmetry. If you use electric motors with a planetary gearbox you will not have this difficulty. This could be useful (affiliate link).

I would also attach a gear to the body of the electric motor. Since the part that rotates in this project is the body of the motor and not its shaft, this gear would also rotate. To convert all this movement into a linear displacement of this Toy Tractor, I would place a kind of wheel-gear that would interact with that of the motor body. The other wheel on the rear axle would be fixed and would also rotate when the wheel-gear did. The front wheel would rotate freely.

Something that worried me at the beginning was, that when the body of the motor along with the associated mechanisms rotates, the rest of the toy also did it in the opposite direction. It reminded me of a helicopter out of control. Even so, I decided to give it a try. If you designed the front part where the front wheel would be positioned away from the electric motor assembly, the lateral reaction force of the wheel on the ground would be much lower, another application of long established knowledge (levers). It guarantees the toy when on the road the movement will be forward and not as a helicopter when losing the tail propeller.

In addition to the (10:1) ratio of the electric motor gearbox I also wanted some force multiplication between the gears on the motor body and the gear on the wheel. For this, the gear of the motor body would have 10 teeth and the wheel a higher quantity, 15 or more.

The center of mass in this toy must be projected on the base to avoid falls. If necessary, additional weights would have to be placed in certain regions. After a few hours of 3D modeling with some creativity, I arrived at the results that I am proposing. I have included the assembly file in various universal formats, also STL and DXF, with these you can replicate this project if you wish. Should you have any questions or need something else, here I am!

Step 2: Obtaining the Plastic Parts

I cut the pieces from 10mm thick Plexiglass. I wanted to make it look transparent and show all the mechanical interactions and joints. If you prefer you can print the STL parts that I attached previously. Another option could be on a laser cutter using the DXF files.

In my cuts I used a 3mm diameter EndMill. Take into account when you are preparing your G-Code the thickness of the tool you use.

Step 3: Attach the Rear Wheel Supports to the Central Body of the Toy

In this operation I first used a little instant glue to initially fix the first support. Then, I made the holes of 3.7mm for the fixing with M4 screws.

To fix the other support use a square ruler so that the holes for the axes of both pieces are aligned. Repeating the same procedure, I concluded this operation as shown in the image.

Step 4: Attaching the Gear to the Motor Body

When I designed this part I made a mistake and the holes in the spur gear were not aligned with those in the motor. Don't worry I already fixed this in the DXF files and the others J! For this reason, I had to mark the new holes and repeat them with a hand drill. With the M4 screws and nuts this fixation is made. Keep in mind that in my case the motor shaft has asymmetry with respect to the body (10.5mm of displacement) and it must be taken into account. If you position this part correctly, you should not notice any unusual movement when you rotate this gear. Then insert the motor shaft through the hole made in the central base of this toy. Verify that the axle pin rests in the socket in the base created. To prevent the motor from coming off, place a fixation on the shaft on the other side.

Step 5: Placing the Front Wheel on Its Support and Fixing the Assembly to the Central Body of the Toy Tractor

First, the front wheel support must be drilled a from side to side hole, through which the 4mm axle of the mentioned wheel will pass. A vertical drill is very convenient here. In my case, I quickly made through pilot holes with my CNC Machine and then, enlarged the diameter with the hand drill. The wheel must be centered, for that use washers or other spacers. You should not go overtighten these parts as it may cause unnecessary friction. At the end of this step, put some glue on the ends of the shaft so that it does not come loose. With instant glue and screws, fix the assembly to the central body of the toy tractor, in a similar way to what was done with the rear wheels.

Step 6: Placing the Rear Wheels

Put a plastic spacer on the axle first, insert the wheel, and then another spacer. The last spacer should be flush with the end of the 10mm thick metal shaft. Put some glue on the joints, adjust the set and let it dry. At the other end of the axle insert another spacer and bring it closer to the gear-wheel, still do not glue it to the axle. Insert the whole assembly through the holes in the rear wheel supports. The gear-wheel should match and rotate unobstructed when the motor gear does. A little sandpaper in certain regions may help if mechanical obstructions appear, due to the cuts made with the CNC machine. When you have identified an optimal Wheel-Gear position, fit the spacer to the side of the wheel bracket and glue it to the axle. Insert the other wheel through the other end of the axle and repeat the previous steps. The non-gear wheel must not interact with the gear on the motor body!

Step 7: Attaching the Solar Panel to the Electric Motor Body

The electric motor I used is not flat at the rear and it made it a bit difficult to glue the Solar Panel directly. To achieve a flat surface where to stick the solar panel, I had to design a coupler. Using silicone glue, I initially attached the coupler to the motor body. Then, I placed more glue on its surface and glued the solar panel. To make it symmetrical with respect to the vertical axis of rotation, I had first determined its center and made a mark at 10.5mm offset. This mark served as my guide in the previous operation. To allow the set to dry, I left it overnight with a weight on top that temporarily fixed the whole set.

Step 8: Electrical Connections

If you prefer, you can use an on / off switch and perhaps a polarity reversal switch. In my case I omitted them to simplify the construction, but they can be useful. Also giving the little ones the possibility to use a screwdriver and exchange the polarity in the cables, can be educational and motivating. Depending on the connection, this toy will go forward or in reverse. The use of connectors may also be helpful. This connection is very simple and there are many ways to do it. When you finish, fix the loose cables with cable ties and hot silicone.

Step 9: Final Thoughts

Having carried out this project has been very interesting to me. I was always scared that it wouldn't work, but luckily it exceeded my expectations. I think I will use it a lot as a means of teaching tool with my children when certain doubts arise from the school environment. During the tests we enjoyed the fact of the possibility of load that this toy has, since it was able to move the weight of a rock and a little more!

This new project is an attractive way to stimulate the imagination and to see what is usually established from a different perspective.

I hope you found it interesting! Good luck!