Radio-Controlled Wagon

Hello, my name is Eduardo and I'm currently a student in college studying mechanical engineering. This project is a Radio Controlled Wagon used to carry things around. The vehicle is controlled by a RC controller similar to an RC car. The frame is made from steel square tubing and the panels are from wood. I made this project to make carrying things around easier. This is a perfect thing to have around when going on a picnic or camping outdoors since it allows you to move things from your car to your campsite without having to go through the trouble of doing it yourself.

This Instructible will serve more as guide/inspiration rather than a step by step tutorial since a lot of the components I already had or were scrapped from other things.. Here are all the materials I used to build my version but this will vary depending on the specific components you source. These are the main important components but I left out a lot of the smaller ones such as hardware, wiring, basic tools, etc. since most of these things you can find in your home workshop.

Frame

1. 3/4" Steel Sqaure Tubing
2. 5/8" Steel Square Tubing
3. Various Size Flat Bar Steel
4. 3/8" Plywood

Mechanical Components

1. 0.75" Steel Round Stock
2. Tie Rod
3. 5/8" Harbor Freight Wheels
4. Door Hinges
5. Chest Lock
6. 5/8" Hex Bolt
7. Bearings

Electrical Components

1. Cytron Motor Driver
2. Electric Motor with Axle [Scrapped from a wheelchair]
3. Linear Actuator
4. Battery
5. RC Transmitter

Tools Required

1. Drill Press
2. Welding Machine
3. Bandsaw
4. Lathe
5. Grinder
6. Soldering Iron

First step is to build the frame of the vehicle. I used a combination of 3/4" and 5/8" steel square tubing. I based the frame off of the rear axle so I recommend to design your frame based on that. I designed my frame through Fusion 360 and will leave the file attached to this so you can go check it out. I also attached a 2D CAD drawing to give you an idea on the dimensions of this vehicle. This step will require you to use some kind of saw and cut all the parts to length. Then, you would weld all the pieces together based on the design.

Second step is to build the rear axle mounting bracket. This will vary depending on the transaxle you source. The transaxle I used is from a wheel chair and did not have any mounting holes on it. I used a few pieces of flat bar steel to create a bracket that would go around the square part of the axle. Using a milling machine for this part would be ideal but I instead had to weld some flat bar to get the desired shape. A pdf of the 2D CAD drawing is available below. Also, include two mounting holes on each side of the bracket so you can mount it to the frame. I had to use a lathe to create spacers for the bracket to not move since the bracket is not bolted or welded to the actual transaxle itself.

The third step is to fabricate the steering joints. This step requires a lathe but can be skipped if you don't want any bearings in the spindle. I used 3/4" steel round stock to create a 5/16" bore to allow a bolt to go through and mount it to the frame. I also made a slightly bigger bore on each of the stock to press fit a bearing for smoother steering. Next is to weld a 5/8" hex bolt perpendicular to the round stock. This is where the wheel will be put on. Then, you will weld some flat bars to the round stock with a hole. This is where the tie rod will mount on both sides to rotate each wheel at the same time. One of the spindles will require another flat bar with hole to be welded on since that's where the linear actuator will be pushing.

The fourth step is to make the spindle mount. For this, it is important to have flat bar steel that is fairly thick like 0.2" since the front wheels will be resting on this. Three pieces of flat bar need to be cut similar to the drawing attached. The two shorter ones will need a hole so you can mount the spindles to. Then, weld each mount so all pieces are perpendicular to each other. After, you can weld it to the frame. The location of where to weld it exactly will depend on the rear axle and front wheels you plan on using since you don't want it to be too high or too low.

The fourth step is to adjust the end stops on the linear actuator. This will depend on the model of the linear actuator but in my case, I had to disassemble the actuator and physically move the end stops to the desired position. I had to 3D print a new base for the enstops and figure out where to place them. This step can also be done later once you have the steering set up as then you will know where exactly is the minimum and maximum travel distance for the linear actuator to move so it doesn't brake any compoenents.

The fifth step is to install the steering mechanism. One spindle on each side and the tie rod put connecting both spindles. Next, install the linear actuator by drilling a hole into the frame. You want the linear actuator to be close to being parallel with the tie rod. During steering, the linear actuator will slightly rotate so you want to have a hole to mount to on either end. You can also install the front wheels and secure them with a stop nut.

The sixth step is to install the wood panels. Originally was planning on using sheet metal but wood was cheaper. You want to cut the wood to create panels all around the open areas of the frame so stuff doesn't fall out. Drill holes to mount the horizontal pieces of wood and attach the vertical pieces using metal brackets. You also want to build a chest preferably near the back to store all the electronic components. Use hinges to create a door that you can open and close to access electronics.

The final step is to assemble the electronics. I used the Cytron Motor Driver to control the two motors. You will want to run the wire of the both motors to the inside of the chest and connect it to the motor driver. For the battery, I used an 18V Makita battery. Next, you will want to connect the RC receiver to the motor driver. Once all that is done then you have a working vehicle. There might need some tuning for the RC transmitter but should be straightforward.