One Wheeled Lunar Rover Build Photos

Battery pack: 24V pack made from 16 "Headway" LiFePO4 cells assembled in pairs with square copper plates between them. Bought from Germany as harder to source from China/Hong Kong these days

Battery management system is from an e-bike shop. Wire runs to junction between each pair of cells and it evens out the voltage between each pair during both charging and discharge. Also I discovered that cheap Chinese BMS modules tend to cut out with a current draw of around 30 Amps, to protect the batteries. I know this from riding my machine with an ammeter designed for big drones temporarily in circuit. However since the cells in my pack are made up in pairs I am now using a BMS that cuts out at 60 Amps, slightly more is OK in short bursts.

Pack and BMS wired up. Master cut out is a simple T handle switch designed for trucks. It can handle well over 100 Amps continuously. Also wired to the battery pack is wiring for a monitoring unit (not shown), the white wires with multi pin plug on the end, which will alarm if any of the cell pairs are below about 2.7 volts which stops damage to the cells, it also displays the voltage of each cell pair individually in a sequence.

Welded frame. Looks simple but took ages to make. Battery pack slides in underneath from the rear, in alloy box. Mounting at front for the hinges of the retractable skid mechanism. Also angled mountings at back for where the drive mechanism and lower wheel frame will bolt on. Edges bevelled so they do not dig into thighs when riding the machine (i.e. a load more cutting and welding). Also mounting slots to bolt on various alloy panels, seat etc.

Battery box bolted up from underneath. Battery protected with plastic foam etc and then taped up as it has to endure large shocks if you crash the machine, do not want battery to break free. Front handlebar mechanism from a mountain bike has been welded in. Circuit boards for electronics will fit into rectangular areas under the seat.

Electronics going in. Arduino Mega to the right. OSMC power controller to the left (now replaced with a Sabertooth controller).

No matter how hard you try you always seem to end up with the "spaghetti" look, just too many wires in a small space. PID control knobs for setting the balance controller constants are to right. In the end these were no use under the seat and were moved to the outside of the machine in a relatively protected space.

Underside of seat. Seat is for a cafe racer style motorbike. Underside is never quite flat so modifications using marine ply and metal strips created to form a lightweight mount that attaches to all the bolt holes on underside of the seat and also locates with mounts on my custom frame.

Cafe racer seat bolted on. Some panelling on around BMS at the front. Linear actuator to retract/deploy the front skid also bolted onto front of frame. Master kill switch in place - the big red T shaped handle.

Strange grey panel in front of seat is there for a reason. If you crash you tend to tilt forwards onto skid. The idea is that you tend to slide forward on seat, now sloping downwards and forwards until you hit this stop point, with legs out each side and hopefully roll to a halt rather then flying over the front. Also you can see a stainless tubular steering link with a ball joint at each end between the handlebars and rear of the lower frame that carries the motor and wheel.

Sorting out the 1960's MACH meter. The original mechanism was entirely mechanical dependent on difference in air pressure across 2 holes each end of a tube sticking out of the side of and aircraft. Needle pointer is now moved using a servo motor from car dashboard, driven by an Arduino Nano. There are pages on www.instructables.com if you search, on how to make something like this.

The MACH meter displays the amount of power the main computer is commanding the power controller deliver to the motor, from -100% (full reverse) through the mid-point (zero power) to +100% (full power forwards).

New handlebars in place, a little higher. Mach meter in place on its own panel. The handbrake lever is an electric switch from a children's electric scooter. It is used as a deadman switch, let go and the Arduino stops all power to the motor. The twistgrip on one handlebar is used to make machine lean forward or back, and is used to control acceleration forwards and braking (when you want to lean back to make it slow down).

White thing is 3D printed and is a mount and ducting for a 24V cooling fan I have also salvaged from some 1960's avionics.

This fan system is totally over engineered and is the shiny object in the right hand photograph. It cools the motor power controller.

USB socket visible below MACH meter on side, for changing the control program on the main Arduino Mega, without need to remove the seat.

Also here are the decals ready to be fitted.

Decals fitted.

People may wonder why I do this hobby. I started back in 2009 with skateboard style devices but these unicycle machines are just brilliant fun to ride, more like riding an animal than a machine, as while the computer constantly makes adjustments to keep it balanced in the front/rear direction, you still need human input to control the speed and to steer it. Was in a bit of a sandstorm when this photo was taken hence the goggles.