hubdynamo is a AC dynamo with a rotating magnet, of the same type as
in bottle dynamo's. However dimensioning is such that at low speeds
power is produced. Small size hasn't been pursued (there is plenty of
between the forklegs) but every effort has been taken to keep the
down. The characteristic of the dynamo is such that under load the
rises with speed upto a certain limit (eg 7.0v) An electronic
eg with current eating Zehner diodes is superfluous.
If you rotate the axle by
hand, you will feel the magnet poles attracting the stator, which gives
the impression of a maladjusted bearing. As long as no current flows,
losses are very small due to the hysteresis characteristics of the
chosen. First when the circuit is completed and current flows, the
will act as a electromagnet and mechanical energy will be transformed.
Another typical characteristic of the SON is the flashing of
lights at low speeds (upto ca 5 mph, 8 km/h). This is caused by the
low frequency of the current, at higher speeds the eye will see a
beam. In practice this isn't bothersome, and cosmetic solutions to get
rid of it will hurt efficiency. And it makes the cyclist more
at times when there isn't much light to start with.
The hub runs on two sealed
industrial bearings. One bearing is permitted to move axialy, so that
will never bind. This is a common practice in enginering design, but
which never seems to make it to bicycle parts! Another thoughtfull
is the very stiff axle and the extra gapseal. In the improbable event
a bearing needing replacement, the complete unit can be unscrewed from
the hub with a special tool. (with the previous model SON the
needed to be removed first).
The hollow axle is made from
high quality stainless steel. Standard the hub is supplied with a 5mm
axle, but a normal quickrelease can be substituted if required.
the dynamo always turns the
lights can be switched on electrically. The standard solution is to use
the Lumotec c.q. Lumotec oval plus headlights modified by SON with a
switch and heavy duty coax wiring and fitted plugs. This is very
and easy to fit. Coax wiring is used, as it is neat and strong. Two
4.8mm plugs complete the connection to the dynamo.
For a rear light we recommend
an efficient and reliable LED light, as the 4D-lite plus or Dtoplight
with 'afterburner' from B&M. The rear light is connected to the
with a 2.8mm plug. (note in Germany it is illegal to have a separate
for the rearlight, which prevents the other excellent solution of a
with a battery (use with a 3watt bulb)
in that market).
A Lumotec Oval senso plus
is also available, which switches on automatically in the dark.
power and current characteristics
of the SON are -as with any other dynamo- defined by the type-approval
regulations. The losses however are about a factor two smaller, which
the switching on of the lights hardly detectable. (we do recommend to
off the lights in daylight as bulblife is limited, and to stop fellow
from warning you all the time ;-) ).
drive hubdynamo's are
pretty old (eg Sturmey Archer built one in the fifties, which had 2.5v
output, and weighted 1.1 kg) Only in 1992 Wilfried Schmidt managed to
with modern materials a hubdynamo which could and deliver 3
wasn't much heavier than a conventional hub plus dynamo. In 1995
Schmidt started his own company to produce dynamo's, to ensure that his
high quality standards would be kept. Several other hubdynamo's are now
available, all cheaper, but also of lower performance. And SON's are
being improved, the latest version is smaller, lighter, and the
losses were halved!