GOAL-H 1c
At least 65 km/h
Achieved by sizing the output sprocket for the chosen electric motor. The gearing decides whether the bike delivers torque on a climb or top speed on the flat – we size it for this target.
Technology
What is inside TESMOS
This page is deliberately detailed: supervisors, the examination board and technically minded partners should be able to follow exactly what we keep, what we replace and what we develop ourselves.
Concept
Kept, replaced, newly built
The starting point is a used 450 cc motocross bike, fully functional except for its combustion engine. That is exactly what makes it ideal: a proven chassis at the price of a broken vehicle. The bike is already in the workshop.
We remove the entire combustion engine including tank, exhaust and all related components.
We integrate an electric motor, a self-built battery pack with a battery management system and a powerful motor controller.
We keep frame, swingarm, suspension, brakes and the entire periphery. Where production engineering is already mature, developing our own would be busywork.
Targets
What we hold ourselves to
Two numbers drive the entire design. Everything else follows from them.
GOAL-H 3a
At least 45 km of range
This determines cell type, system voltage, capacity and the physical layout of the pack. At 2,500 euros the battery pack is the most expensive and by far the most demanding assembly in the project.
Assemblies
The four core systems
Frame and mounting components
Motorcycle chassis, motor mount, CAD model of the frame, small parts and brackets plus all manufacturing and assembly elements. The choice of manufacturing methods – 3D printing or CNC – is in progress.
Drive unit
Electric motor, battery cells, the pack as a CAD model, the welded cell assembly, the finished pack plus wiring and safety components. Motor, cell type and BMS are currently being selected.
Control electronics
Microcontroller, motor control software, sensors, control logic and the fine-tuning parameters. The controller is the interface between rider input and motor controller.
Display and sensor system
Interface concept, the user interface software, a display in a self-designed handlebar housing, riding modes selectable via buttons, GPS module and wheelie module.
Why 3D scan the frame?
Motor mounts, the battery enclosure and every bracket have to fit a frame to the millimetre – a frame for which no CAD data exists. Either we model it by hand or we scan it. A precise digital model decides how often we have to remake parts, and with it our cost and our schedule.
Mechanical design
From the frame to a part that fits
The frame is rebuilt in CAD or captured with a 3D scanner. On that basis we design the mounting elements and every bracket.
- Frame rebuilt in CAD (goal H 1a)
- Mounting elements for the electric motor
- Mounting elements for the motor controller
- Battery pack modelled in CAD
- Housing for the handlebar display
- Small parts and brackets
Optional goals
Once the essentials are done
Two extensions we will build if the schedule allows. They are declared optional on purpose – they are not a promise.
GOAL-O 1
GPS system
Software that sends live GPS data to the display and evaluates it – the basis for track logging and for analysing test rides.
GOAL-O 2
Wheelie control
Electric motors deliver full torque from the first revolution. Wheelie control limits acceleration so the bike does not flip backwards.
Safety
Safety concept
A self-built battery pack holding several kilowatt hours is the point where both the examination board and every material partner look closely. That is why the safety chain is in place before the first ride, not after.
Emergency stop
An easily reachable emergency stop disconnects the main circuit independently of the software. It acts directly on the main contactor so that a crashed microcontroller cannot prevent shutdown.
Ready button
Switching the bike on does not make it ready to ride. Only a deliberate second step on the ready button enables the drive, and only with the throttle closed. Pulling away at power-up is impossible.
Thermal throttling
Temperature sensors on motor, controller and battery report to the control unit. Once limits are exceeded, power is reduced in stages before shutdown – the bike gets slow instead of stopping without warning.
Tilt cut-off
An attitude sensor detects a crash. If the lean angle exceeds the limit or persists for too long, torque is cut to zero immediately. A bike that keeps spinning its wheel after a crash is more dangerous than one that stops.
Side stand switch
With the side stand down the drive stays locked out. The switch is wired so that a broken cable fails towards the safe side: when in doubt, no release.
BMS and fusing
The battery management system monitors cell voltages, current and temperature and disconnects when limits are crossed. On top of that: a main fuse, a service disconnect and wiring sized for maximum continuous current.
For test rides we add: step-by-step commissioning with the
rear wheel on a stand before the first ride, full protective gear, never
alone, and no ride without clearance from our supervisors. The risk analysis
in the proposal lists “damage during the test ride” as the risk with the
highest impact – we treat it accordingly.
Data sheet
Technical data
Target values and, once measured, the values actually achieved. That comparison is the core of the thesis. We only enter figures we can prove.
| Parameter | Target | Measured |
|---|---|---|
| Top speed | at least 65 km/h | pending |
| Range | at least 45 km | pending |
| Donor vehicle | motocross, 450 cc, engine defective | acquired |
| System voltage | being sized | pending |
| Battery capacity | being sized | pending |
| Continuous and peak power | being sized | pending |
| Total weight, ready to ride | being sized | pending |
| Charging time | being sized | pending |
Questions about the technology?
We are happy to explain in detail how we arrive at our design choices.