Construction report Phantom Mini-T by Tim Corbett from Australia
Driveline
The Mini-T is a tadpole recumbent trike based of an earlier human powered vehicle known as the Phantom TT. Both vehicles were designed solely by Tim Corbett, and were built predominately by Tim Corbett, with fabrication assistance from time to time, noted below.
Phantom TT.
Phantom Mini-T, prior to its first race in 2015.
Jarrod Lambourne (wheel disc mould machining, chassis moulds), Wade Edwards (mould fabrication, bodywork fabrication), Braden McKay (mould fabrication, bodywork fabrication), Tom Bastian (mould fabrication, bodywork fabrication, custom mid-drive spool fabrication), BriAnne Addison (general assistance). Windscreens were vacuum formed by Plasmould (Moolap) on tooling fabricated by Tim Corbett. Wheels were laced by Chris Fry of VeloTechnics (West Geelong). Sundry items lasercut by JR-Laser. Both vehicles are rear wheel drive and front wheel steer with central ‘car style’ steering.
The chainline shown above is of an earlier chassis variant based on a rear wheel drive Rohloff hub and required the use of a 106t chainring. These were abandoned after the first version of the vehicle due to the heavy driveline power loss was noted. This has since been replaced with a second chassis based on an intermediate mid-drive/transfer spool, driving a standard rear MTB hub with single speed gear attached. Due to space limitations, only 7 gears can be used. The gear range features two broadly spaced launch sprockets and 4 narrowly spaced running sprockets (28, 22, 17, 15, 14, 13, 12). Cranks can be exchanged to suit the rider, with available lengths between 145 mm–175 mm in 5 mm increments. Drive/cruise speed for various length record attempts is modified by changing the front chainring between 39-42 teeth (12 or 24 hour attempts) up to 55 teeth for 1 hour through 6 hour hour attempts. Drive exits the mid-drive transfer spool on the right hand side of the bike from a 32 tooth SRAM narrow/wide chainring, and drives a 13t rear sprocket on the rear wheel. The chain is guided to the rear under two Terracycle 14 tooth idle rollers, and returns via Polyethelyne chain tubing. The rear chain
Critical dimensions
Basic 2D CAD sections of the Mini-T.
34
2019-2
Overall length 2580 mm Width at maximum cross section 530 mm Depth of maximum cross section 610 mm Ground clearance 90–115 mm (tyre dependent) Overall height 700–725 mm Track width at front wheels 450 mm Track Length 1120 mm The section profiles are based on NACA6600/6700 series airfoils that have been hand blended and iterated over time. Note that the ~106t chainring shown is no longer used.
Mid-drive spool. Right: pedal boom with middrive spool fitted, prior to installation on the chassis.
