View source for Ford KAsket

{{Racer
|ProfilePic=Placeholder.jpg
|BuiltBy=Ian Beaver
|Theme=Ford KAsket - a coffin
|FirstRace=Scrumpy Cup 2022
|CurrentStatus=Resting
|Motor=Various
|ESC=Generic 1500W eBike controller X1 or X2 plus Arduino controller
|Battery=48V Li-Ion (2x 6S)
|Transmission=Chain with various gearings - sometimes unequal to each wheel.
}}

==Construction==
Chassis, steering, axles are all scratch-built from mild steel. Similar to MecCarNo but with heavier-gauge parts - particularly M16 for front stub axles and kingpins rather than the M12 used on MecCarNo.
Braking is rear-wheel only by a standard cycle disk(s) with cable caliper.
Bumpers are 12mm HDPE.
The chassis is extremely low to the ground - perhaps 50mm clearance - allowing the kart to be narrow but remain stable in corners.
The theme bodywork is constructed from 10mm builder's ply, with genuine coffin parts for decoration.
==Powertrain==
Drive was initially by two converted alternators using two 1500W eBike controllers. A single throttle thumblever was input to an Arduino, which monitored the current used by each controller. The Arduino allocated throttle settings out to the two controllers and also turned on or off the field currents of the motors, to attain best performance.
The two motors each drove one rear wheel. Each wheel was braked by a standard cycle disk, with cable-operated caliper. A single brake lever operated both. Wheels are standard 4" split-rim mobility-scooter items with standard mobility tyres (front) and 4.10-4 Minimoto knobblies (rear). Rear wheel dia approx 10".
The kart was intended to experiment with the following benefits potentially afforded by two motors:
*No diff required, and no scrubbing losses. This wasn't successful: the extra motor weighs as much as a diff, and its losses appeared to outweigh the modest losses from a typical diff. The complexity of an extra brake was required - whereas a solid axle requires only one. If a brake is fitted to its input then a diff also requires only one disk.
*If the motors are geared differently, then the low-geared motor can be prioritised to give maximum acceleration but it can also be disabled (with zero field current) at high speed, leaving the high-geared motor to take the kart to a higher top speed.  This feature was automated by the Arduino, with the only user control being the single throttle. This was even less successful: these eBike controllers throw an error when the field current is turned off and require power-cycling at standstill for them to restart, stymieing the feature.
*If full power is demanded, but at a speed where a single motor would be unable to draw enough current to make full use of the fuse-limit, then current can be allocated to both motors. This was somewhat successful, but the same could be achieved simply by fitting a bigger single motor (and a current-limiting controller) instead.
For subsequent races the axle was made solid, and driven by a single Vevor 2000W brushless motor with 2000W eBike controller. Gearing was 11T to 64T giving about 11700 motor revs per mile. Motor's no-load speed is 4300rpm, giving a theoretical speed of 22mph.
==Theme==
Transportation space constraints required low-profile bodywork, so a low surrounding wall of plywood was fitted, in the shape of a truncated coffin. Coloured mahogany and with some genuine coffin fittings. Some genuine 'Ford' blue-oval and 'KA' boot-badges, with 'sket' CNC'd from mirrored plastic sheet appended, provided the name.
==Other Lessons==
At constant cruise the eBike controller of the non-prioritised motor tended to overheat. The Arduino was throttling it to prevent excessive fuse current, but FETs produce more heat when constantly switching (PWM'ing at part-throttle) rather than when turned on (at full throttle). So any design which drives a controller for a long duration at part-power should over-spec the controller.
==Race Results==
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[[Category:Racers]]