I made this RC car for my class project. The main reason I wrote this intructable is to teach people not only how to build a RC car like this one of mine, but also how are RC car designed, and how do they works, so they could be able to design their very own RC car. I will talk about steps to make this RC car, but also more important the "why" behind the steps. So let begin!
*More pictures needed*
Step 1: Gathering Materials
You will need the following material to build this RC car. I also attached the amazon link if you need:
1. two 3v-12v DC motors, one for steering and the other one as the engine. I used this one: https://www.amazon.com/Flormoon-Electric-0-5-3V-1... and this one: https://www.amazon.com/Flormoon-Electric-0-5-3V-1...
2. Set of Gears with bore diameter 1.5mm, including regular gears, gear racks, and pulleys. They will be used in the steering system and in the gearbox of the engine. I used this one: https://www.amazon.com/Lucksender-Plastic-Single-...
3. 1.5mm metal axis, for gears and wheels. I used this one: https://www.amazon.com/uxcell-Steel-Round-Stock-L...
4. two momentary DPDT switches for remote control, I used this one: https://www.amazon.com/gp/product/B0012ZE8IC/ref=...
5. 9V batteries. They power up the RC car.
6. Battery boxes for 9V batteries, these allow you to change batteries, and has integrated switches that can be used to switch off the car/remoter. I used this one: https://www.amazon.com/Battery-Holder-Switch-Wire...
9. jump wires
10. Wheels. I used these: https://www.amazon.com/RC-Plane-Wheel-Plastic-Air...
You will also need to 3-D print the frame of the car. The .obj file used for 3-D print is attached below.
Besides these materials, you also need some tools to make the RC car. Here is a list of them:
2. Hacksaw (for cutting the axis and possibly the pop stick)
3. Hot-glue and hot-glue gun
4. wireless-drill with drill-bits
5. hammers (for fitting axis and gears together)
Step 2: An Overview at the RC Car
Before start building, let's first step back and take a look at the big picture. The whole RC car is consisted of two parts: the remote-control car, and the remoter. Furthermore, the remote-control car is composed of the frame, the steering system, and the engine, while the remoter is composed of the frame, the DPDT switches (double pole double throw), and the batteries. We are going to build the RC car part by part.
Step 3: Building the Engine
The first part we are going to make is the engine, without it your RC car won't be able to move an inch. It is consisted of two parts: the motor, and the gearbox. For this step you need a DC motor, card boards, gears, pulley (as shown in the picture, don't have to be exactly the same size), 1.5mm axle, vise, hot-glue, and hacksaw.
You might think that you can just connect the motor to the wheel, and you are done with the engine, but the problem is that the torque (torque measures the force of rotation, in this case, it measures how strong a motor is) of a DC motor is too small, which means it is to weak to move the car.
This is why we need the gearbox. A gearbox is a set of gears connected to each other that slows down the rotation of the motor. Because the slower the rotation, the greater the torque, the gearbox could increase the torque of your engine. How does it work? Well, when one gear is driving another, if they are attached to the same axle, then bigger gear driving smaller gear will increase the torque (gear 2 to 3, gear 4 to the pulley in picture 1), if they are attached to different axles, then smaller gear driving bigger gear will increase the torque (gear 1 to 2, gear 3 to 4). Gearbox is basically many gear driving one another, which increases the torque.
To build this engine, first attach a very small gear to the motor, as the one in picture 1. You might need the help of hammer to do this. Make sure this small gear is very close to the flat top of the motor, otherwise you will find difficulty meshing other gears with it.
Once you are done, you need to cut 4 pieces of card board - 2 longer pieces, 2 shorter pieces. Their width should be longer than the diameter of your motor. Then, as shown in picture 2, you need to cut holes in the longer pieces of card boards for motor to go through. After that, you are going to hot-glue the pieces of card board to the motor to form a box-like structure, as shown in picture 1. The longer card board at the top, as shown in picture 1, should be aligned with the flat top of the motor. This box-like structure will hold the gears in the gearbox and prevent them from tilting.
Once you finished the box-like structure, you can start to position the gears and make holes on the card board box around the motor for the axles of the gears as shown in picture 1. Then, you should cut the axles to desired length, attach gears to them, and fit them into the holes on the box. Use washers if you need to keep them in place.
When you are done with the gears, hot-glue a triangular piece of cardboard to the back of the engine, it will help support the engine later when it is attached to the frame.
Step 4: Install the Rear Axis
The rear axle is going to be connect to the engine and drove by it. A pulley should be attached to it at the breach of the frame. You should insert the axle into one of the holder, then insert it into the pulley, twine the rubber band around the pulley, then insert the axle into the other axle holder, because once the rear axis is inserted into both of the holders, you won't be able to twine the rubber band around the pulley unless you cut it up.
Step 5: Installing the Engine
Hot glue the engine to the right of the breach of the frame with the gears pointing left, and make sure that the pulley of it is lined with the breach. Then, use the rubber band to connect the two pulleys attached to the engine and to the rear axle. Also hot glue a battery holder with battery behind the engine and connect it to the engine
Step 6: Build the Steering System
To build the steering system, you need the frame, the 3D printed steering piece, axle, pop stick, card board, and a DC motor.
first flip your frame around, you need to insert two pieces of axles into the two holes in the front part of the frame from its bottom, they will be the steering axle that two front wheels rotate around when steering.
Insert the two 3-D printed steering pieces into the steering axle, and use hot glue to fix them. Be careful to keep the end with hole of the steering pieces pointing to the front of the frame. When those are inserted, use some kind of bushing to make sure that they don't fall off - I used a long piece of pop stick, but you can also use bushings or even hot glue.
Flip your frame around so the steering axle pointing downward. Now insert 2 pieces of axle into the holes in the steering pieces pointing upward, and use hot-glue to fix them. Make sure that they are long enough for the next step. Check out the pictures if you are not sure about how long they should be. They will be the connecting axles for their function
After that, use pop stick to connect the two connecting axles as shown in the picture, but don't fix it to the axles with hot glue. Use bushing to prevent it from getting off, and hot glue a gear rack onto the pop stick. Make sure that the pop-stick and the gear rack is parallel to the frame. The two steering pieces will rotate together because of the connecting pop stick.
Attach a small gear to the DC motor, and hot glue several layers of card board to support it so the gear could drive the gear rack. This motor is the steering motor of the car.
Last of all, insert two pieces of axles into the side holes of the steering pieces, and use hot glue to fix them. These axles will later on be the front axles where the wheels will be attached to, so make sure they are long enough.
Step 7: Overview at the Remote Control Circuit
There are several ways to remote control a RC car. You could wirelessly control the RC car by using transmitter and receiver, and maybe Arduino board, but you could also control the RC car with wire by using DPDT switches. I chose to use the DPDT switch for I burned my transmitter and receiver.
Step 8: Build the Remoter
To build a remoter that controls the RC car by wire, you need: a DPDT switch, battery holder and battery, and wires. First of all you should wire the circuit part of the remoter referring to the picture: connect terminal A and F, connect terminal C and D, then connect B and E to the battery holder with battery, and A and D to the steering motor. Make sure that the wire connecting A and D and the motor is long enough so you can remote control the car. I learned this circuit from https://www.instructables.com/id/How-to-control-a...
When you are done with the circuit, you can start to assemble the parts of the remoter together. I simply hot-glued the switch to the battery holder, and some loose wire to the battery holder as well. You could make a case for the remoter with card board if you want.
For people who want to know how does DPDT remoter works:
The direction of rotation of a motor is switched when the direction of current flowing through it is switched, which means, the two wires connected to it - positive terminal and negative terminal are switched. DPDT switch works by switch the negative and positive terminal. A DPDT switch has 3 states: ON(1) - OFF - ON(2). When it is on ON(1), terminal A of it is connected to terminal B, and D to E. When it is on ON(2), terminal C is connected to terminal B, and F to E. the positive and negative terminal of the motor is switched when the state of switch is switched between ON(1) and ON(2)
Step 9: Attach the Wheels to the Axis
Hot glue 2 wheels to the rear axle of the car, and insert the other 2 wheels onto the front axle of the car, then hot-glue 2 bushings to the front axle to prevent the wheels from falling off. Don't hot glue the wheels to the front axle since it cannot rotate
Step 10: Congratulation
Congratulation! You have made yourself a remote control RC car!
But wait! There are a lot of ways to modify or improve it.
You could replace the DPDT switch remoter with a wireless remoter. This set of transmitter and receiver: https://www.amazon.com/Channel-RC-Transmitter-Rec... is recommended.
You could also add another DPDT switch to control the engine of the car. I didn't because the DPDT switch I am using is to hard to turn that I need two hands to control one switch. You might want to use this kind of DPDT switch if you want to use two switches: https://www.amazon.com/uxcell-Position-Rocker-Swi....
You could make a case for the remoter - I didn't because turning my switch requires making effort, and I am worried that card board case will easily be broken. However, if you are using transmitter and receivers, or some other electronics, you could definitely make a case for the remoter.
You could also make a case for the RC car using the card board, and decorate the case.
The frame of the car can be made using other materials - 2-3 layers of card board would be strong enough, pop-stick structure would also work. The axle holders can be made of straws.