4 WD HEAVY DUTY ROVER

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

1. 4x Motor 130 rpm 15nm 24v
2. 1x ESC
3. 4x Tires
4. 4x Felgen
5. 4x Snap in vents
6. 2x 12v car battery
7. 2x 12v car battery charger
8. 1x cut off switch
9. lots of relays
10. 1,8 m² Aluminium 5mm

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...

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.

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.

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.

Explanation for the relay circuit:

needed:

1. over 100A Safety and on off switch
2. 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.

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.

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

Designed to protect the motors and wheels from front impact, also pushing objects gets easier. Also more storage is added.

Steel plate, laser cut and welded together.

To mount the motor at the right place an adaptor was needed.

For measuring I milled it out of wood first.

The finished adaptor is made out of 200x70x20mm Aluminium piece

First I cleaned up the welds and put a 2k filler (Mipa) on the holes.

The frame was painted with a 1k adhesion paint, 2k primer and 2k paint in Ral 6031.

Afterwards I used a 2k clear coat for protection

I got this decent forest colours from

www.militaerlacke.de

I had steering stuttering moves, because of that one geared motor broke.

Need to use more reinforced motors

Need to build a better solution for the lights and camera.

All in all, even with the broken motor, it was a great sucess because of the skill improvement while building.