It all started by the wish to build a little rover, which is capable of doing more...

When a friend showed me his selfmade electric skateboard and told me about his "big offroad wheels" I had to react and somehow this is the result.

Specs:

Autonomous Rover controlled by Pixhawk

Splashproof

Supplies

4x Motor 130 rpm 15nm 24v
1x ESC
4x Tires
4x Felgen
4x Snap in vents
2x 12v car battery
2x 12v car battery charger
1x cut off switch
lots of relays
1,8 m² Aluminium 5mm

Step 1:

With this documentation I want to walk you around the process of the whole making starting from the first sketches.

I started by choosing the wheels to calculate the needed rpm. I knew that my robot should be fast enough to run nearby, so it should habe at least 8 km/h. In the beginning I was searching for motors capable of providing 15 km/h but I wasn't able to find any with the needed rpm an nm.

For 8 km/h and a wheel with 41cm a rpm around 120 is needed so I started to search through every webshop and all motors alibaba could provide in this torque range.

In the end I found this one and ordered it:

24v worm gear wheel chair motor 25nm 120 rpm

Because of the dimensions the mounting I chose was the best solution, so the shape of the robot was already done. For checking dimensions and to get a first idea of the size I build a model out of cardboard and wood.

I planned the widh of the rover to fit through doors and to be capable to store 4 batteries in it for a capacy of 24v and 120 Ampere.

Next I started sketching...

Step 2: Frame

I decided to do a puzzle design.

This design uses a puzzle shape to support the building and welding process. So when everything is put together just point welding would do the job.

Step 3: Chassis

A friend of mine was able to do the plasma cnc job for me.

Big thanks to you at this part ;)

So here are the pictures of some nicely cut 5mm Aluminium and a first assembly test.

Step 4: Wheel Adaptor

To connect the wheels to the motor I had to design a adaptor. It is turned out of steel. For dimension checking the part was 3D printed first. The wheel adaptor also puts the wheels away from the frame so it doesn't collide.

Radnabe MK3 Drawing v2.pdf
Download

Step 5: Wiring Relays AC Loading and Safety Switch

Explanation for the relay circuit:

needed:

over 100A Safety and on off switch
cut off loading relay: so when the AC is plugged in the voltage to the controller is cut down and the charger charges the batteries. The relays also prevent a backflow into the charger when the AC is turned off.

K1 K2 12V 100A Relay closed

K3 K4 12V 10A Relay closed

K5 230 V/AC 5 A switching relay

F1 fuse next to the battery

F2 and F3 Fuse between motor controller and motors left and right side

Switch 1 connects K1 and K2 to 12v and closes the 24V circuit between the two 12V batteries. On this way the power for the motor controller is provided. Next to switch 1 is also a safety switch, which will open the S1 circuit so K1 and K2 closes.

Step 6: Motor Wiring

The motors are controlled by a Sabertooth controller.
At this point I have to advertise this controller because of his great safety features, which saved the pcb in the testing process more than one time. For controlling the sabertooth I use a flysky telemtry transmitter to get also the voltage and amperage drawn from the batteries.

Step 7: Lights

There are multiple lights build in this rover.

The face of the rover has 10W white red blue and infrared Leds. The blue and red one are capable of flashing.

Also there are two 10W Leds build in the side of the vehicle.

Every led got a little aluminium heat block and no lens, because only the nearfield is important. The lights are controlled by RC PWM 10A Relays. On this way everything can be controlled by the flysky transmitter. For the flashing I use this module:

Big and loud fail:

sufficient cooling too difficult in small housing with 10W

DC DC module exploded

RC PWM not working correctly (in combination with flash module)

New choice:

4 Relays controlled by the output of pixhawk