| home > | Ajax < Libby > Teal | 24 September 2026 |
| Libby - Shadow Liberator reborn - by David Buckley | March 2023 |
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In March 2023 I dragged the dilapidated Liberator remains out from under the Laser-Cutter and decided to refurbish it.
Base size 20" x 15" x 10" to top of Skirt
Rear Track 13 1/2" => 3mm wheel travel per degree when turning on the spot
Front track (nominal) 10"
Wheelbase 9 1/4" forwards, 13" in reverse
Castor radius 1 7/8"
Rear wheels 6 1/4" dia. => 499mm circumference ~> 500mm
Drive
10 tooth XL on gearbox
60 tooth XL on drive wheel
72 tooth belt 1/4" wide
free running 120 rpm => max speed 1m/sec
free running ~3/4 amp, heavy load 3 amp, moderate load 1 - 2 amp
Wheel encoder
80 tooth MXL on wheel
32 tooth MXL on encoder
50 count encoder
=> 125 counts per wheel revolution => 500 / 125 =4 mm per count
with Quadrature decode => 1mm per count
=> 1/3deg / count for rotate and 1 /6deg for curve with one wheel stopped
Motor/gearbox from Maplin 12v Auto Polisher,
output shaft held in chassis mounted ball race
Gearing 13:76 14:54 ~22.55:1
free running max wheel speed 120rpm =>2rps => 1 m/s (motor speed 120 *6 *22.55 =16,236 rpm)
Front castors from abandoned Supermarket trolley
Chassis and Skirt plates - wood
Libby with witness LEDs lit
- I stripped it all down, cleaned it and resprayed everything;
- replaced the missing wiring in the Skirt plates;
- added witness LEDs activated by the Skirt microswitches, they are also under computer control;
- replaced the missing foam padding round the edges of the Skirt plates;
- remade the two side IIC boards with an added PCF8591 4 channel A/D convertor to read the IR whiskers (not yet made);
- made a similar IIC board for the rear Skirt plate;
- remade the power distribution for the base;
- remade the electronics shelf and fitted two motor driver modules which were spare from when I originally made Liberator.
- made a housing for the Base Ultrasonic Array.
- refitted the upper and lower body complete with their Ultrasonic Arrays.
- more - Libby refurb. Log