Yesterday in London, Sir
Clive Sinclair launched what he describes as a
substantially improved version of his
battery-powered bicycle propulsion system, Zeta -
zero emission transport accessory. At £100
(including VAT, postage and packing), Zeta II is
two-thirds the price of its predecessor; it comes
in two parts, a driving unit and a battery pack;
it drives the front wheel rather than the rear;
and it has a more efficient motor, writes John
Stansell.
Zeta
II can power a typical cycle on a flat road at
12mph for five miles, or up to 15 miles if the
cyclist pedals as well as using the power
assistance. The system can be used on public
roads legally by anyone over 14 without needing
tax, insurance or a driving licence. But the
noise could be a drawback - it sounds like an
angry hair dryer.
The
original Zeta - whose battery was mounted in the
same box as the motor and control electronics -
was attached by a clip to the rear forks, just
above the back wheel. This caused problems on
some cycles, when the clips slipped, twisting the
unit and sometimes derailing the drive belt.
Sinclair claims the new system - which fits to
the bolt through the front forks holding the
brake callipers - cannot twist and the belt
cannot be derailed.
The
drive unit - which, like Zeta I, uses a flexible
rubber belt that moulds itself to the shape of
the wheel has been modified so that the greater
the power required, the higher the downforce on
the tyre, which he claims prevents slip.
Sinclair
also says that the separation of the battery unit
and motor has cut the overall weight, because it
allowed the design team - led by Alex Kalogroulis
- to use plastic mouldings rather than aluminium
alloy. The 12V battery is a standard lead acid
type which can be discharged and recharged 500
times at a typical recharging cost of 1p and a
battery life of about five years.
Sinclair
investigated other types of cell - notably nickel
cadmium - but the added cost and recharging
problems of Ni-Cad cells convinced him that lead
acid was still the best solution.
People
wanting longer range can buy a spare battery for
£30 or install a larger one, but Sinclair says
that a survey of 100 of the 10,000 Zeta I users
in the UK found that only 5 per cent wanted
longer range.
Sinclair
has long held the view that electric propulsion
would meet the transport needs of the millions of
people who only make short journeys, and would
have a major effect on pollution. He says he
would like to develop a lightweight four-wheeled
car, but is inhibited by the cost, the lack of a
suitable battery design, and perhaps by the
legacy of the unfortunate C5 three-wheeler. He is
currently developing an ultra-lightweight folding
cycle using composites and other advanced
materials to get the overall weight below 2kg.
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