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“NILMINI” the Electric Mini

“NILMINI” the Electric Mini

Vimukthi Randeni is a motoring enthusiast. He is also a final year Mechanical Engineering student at the Moratuwa University. We at Motor would say that Vimukthi is “our kind” of budding Mechanical Engineer.

 

There was a disused Mini sitting inside the “Motor Lab” of the Engineering Department of the University. Any other fellow motoring enthusiast would like to have restored the old Mini to its original condition. But Vimukthi is no ordinary motoring enthusiast. He also has a bent towards creativity.  He saw the old disused Mini and a question came up in his head. “What would it take to convert this old Mini to run on electricity?” He discussed this idea with his collegues and ideas and support kept coming… but first, they needed to find out how this car ended up in the University.

 

The story goes that the car had been donated to the University by its first Vice Chancellor Dr L H Sumanadasa. In 1966 Sumanadasa became the founder director of the Ceylon College of Technology (CCT) which in 1972 became the University of Sri Lanka, Katubedde Campus with Sumanadasa as its first president. Sumanadasa was appointed Vice Chancellor of the University of Sri Lanka and retired in 1975. The Katubedda campus was awarded independent university status as the University of Moratuwa in 1978. The University awarded him an honorary doctorate in 1980. So presumably when Dr Sumanadasa retired in 1975, he donated his Mini to the Engineering Department. It stayed there, largely unattended for 40 years, however thankfully under cover - until a few months ago when Vimukthi and his team decided to embark on his project.

 

Although showing its age, the Mini still has its original blue (hence the name Nil-mini) paint and upholstery. The body is still solid, with no rust to talk of. Several people have asked Vimukthi if he is going to spruce up the Mini; but he says that he prefers the car to be in its original “as found” state.

 

Being a University project, Vimukthi had very little funding for it. However, plenty of resources were available by way of expertise, machinery and tools. Both as a cost saving, and to keep the Mini as “original” as possible, Vimukthi decided to retain the original gearbox/differential and drive-train. Our first question was “why retain the gearbox at all? Could you not couple the electric motor direct via the differential, or indeed mount two motors on two wheel-hubs?” The answer was that all that would have been possible if they had the funding. If they were not to use a gearbox, the electric motor would have had to be more powerful; or as suggested if they were to use two hub motors, that too would have been much more expensive.

 

As the gearbox and differential are housed in the sump of a Mini, this involved some innovation in order to get the drive from the electric motor to the gearbox. The coupling of the motor to the gearbox involved manufacturing three gear-wheels and a final drive shaft, which were all designed and manufactured within the University. The 14 HP electric motor purchased from China, is mounted on a cover-plate on top of the sump (where the petrol engine previously sat). A programmable controller delivers power from the battery bank and controls the regenerative braking function. The accelerator pedal is connected to a potentiometer which regulates the amount of electric current supplied to the motor.

 

Driving the car could not be simpler. Just get in, switch the toggle switch to the “on” position. Move the gear lever to the required gear (no clutch necessary) and simply accelerate! Vimukthi gave the Motor team a fast drive through the narrow avenues inside the University compound, and the car seemed to accelerate better than a standard 1000 cc Mini. It also seemed to handle better than a standard Mini. This is probably because of the fact that the center of gravity of the car would have moved to somewhere in the middle of the car as the weight of the engine has been removed, and a bank of batteries have been added to the boot!

 

The focus of the Minlmini project has been to convert a petrol powered car to run on electricity. That has certainly been achieved. Vimukthi estimates that the car would run for some 36 kms on one full charge of the batteries. For this project, they used six 90 ampere lead-acid car batteries which are not ideal for this application. But then a Nickel/Cadmium or any such battery would have cost easily ten times the cost of these six batteries! This then was the cheapest option available.

 

The car is not road-legal in that the brakes need attention, and things like signals etc don’t work. At any rate the car does not even have its registration papers – so it will necessarily be confined to the premises of the University! A worthy and enthusiastic project nevertheless.

 

Vimukthi wants to acknowledge the people and the sponsors who supported this project. They are: Mr Rohan Pallewatte of Lanka Harness Co. Pvt. Ltd.; the rest of the Project Team consisting of Anuradha Herath, Chathura Ganemulla; and supervisors Sasiranga De Silva and Dr Nirosh Jayaweera.