See also: Kingston University builds 102mph electric bike
Kingston University has revealed its 102mph electric bike, destined for the all-electric TTXGP race on the Isle of Man this year.
Designed by six final-year engineering students, the bike is expected to average 70mph around the 38 mile course.
Power comes from a 72V lithium ion phosphate battery through a motor originally designed by UK inventor Cedric Lynch, and made by Indian firm Agni.
"It's a slightly up-rated Agni, one of the 95 series which is reinforced around the armature," the University's director for motorsport and motorcycle engineering Paul Brandon told EW. "We run it at 72V. The motor will take a continuous 200-250A depending how we cool it, and we can peak at 400."
At 400A the motor delivers 26kW (37bhp) at the spindle.
Although a brushed design, Lynch-type motors are legendarily efficient.
Did Brandon consider anything else?
"You need a relatively small motor. Some are brushless, but three to four times the weight and not four times the power," he said. "Most people are using the Agni motor, some teams are running two. One team is running an M1 from Green Motorsport."
The M1 is a 3 phase 48V AC water-cooled motor that can deliver 18kW continuously and be over-run to 27.5kW for five minutes.
The battery is lithium-ion phosphate - based on lithium iron phosphate (LiFePO4) - from Lifebatt.
Higher capacity cobalt-based Li-ion cells were considered, but there were sponsorship issues, said Brandon, and iron phosphate Li-ion cells are more robust when used hard. "If they are shorted out, the final state of the battery is open circuit," he said.
Without electronic protection, cobalt types can catch fire when overloaded.
The bike's electronics have been made or modified at the University.
"Kingston has sorted out the power management side: the way we are monitoring what is going on and the power controller," said Brandon. "The controller is an existing product we have done modifications to. It runs at about 95% efficiency which is better than the original."
The controller feeds a PWM signal to the motor. "The battery seems to cope quite well," said Brandon. "It is a large pack and so has a large amp-hour capacity. We are only discharging at around 2C but it is rated as a continuous 8C."
Cooling air for the battery passes though gaps in the pack to take heat away. Hundreds of miles from the Isle of Man, the Kingston team has to model the course to calculate the best way to use its limited energy over the course. "We use spreadsheets quite a lot to analyse the race course requirements," said Brandon. "The first half is twisty-turney stop-start and the second half is a 400m climb and back down again."
To simplify calculation, rather than model each corner individually, the power consumption through a generic corner has been applied to all the corners.
Spreadsheet figures are being compared with a third of the final battery pack loaded as though travelling over part of the course.
Kingston's entry is based on a Honda NSR250 chassis. "It is carrying an extra 30kg if compared with the weight of original without fuel," said Brandon.
Alongside the Kingston entry, there are 23 other bikes in the TTXGP in June, from countries including America, Austria, Germany, India, Italy and the UK.
Among these is one from motor-maker Agni which is using two of its 95 motors and Kokam lithium-polymer battery of 63 cells of 70AH each - about 16kWh. "This will give 40 to 50 horsepower averaged over the length of the race, which should be good for about 120mph top speed," said Agni, which has converted a 2007 Suzuki GSXR600.
A last minute hitch for Kingston is loosing its rider on a technicality.
"We did have Maria Costello - female Isle of Man lap record holder - but a rule change means she cannot ride," said Brandon.
Now anyone riding the electric TTXGP race cannot realistically participate in the petrol-powered Manx Grand Prix - run on a different week to the famous Isle of man TT race.
"We are looking for a rider that is correctly registered for the TT course but not a Manx GP rider," said Brandon.