The following was written a while ago after the recent Eurocycle at
Plymouth UK and i have only just got round to posting it, hope it is
not too long
Trev.
The eponymous Dave Mariner of DM Engineering has in his (very) sparse
spare time over the last nine years developed and built what I like to
call his “X project Unicycle” capable of measuring the pressure put onto
the pedals and saddle of a unicycle, and, with the inclusion of a sensor
for wheel position he has a system capable of monitoring the work put into
any unicycling skill by the rider, ie idling, hopping etc. The displaying
of this information is via a PC running a DM developed multichannel
interface card and software. This system while comprehensively covering
all relevant parameters had one slight drawback, the distance the X
project Unicycle could move away from the PC was severely limited by the
length of the sensor leads, this somewhat curtailed the number of skills
that could be recorded. With a bit of help from myself and limiting our
data to one pedal we were able to become mobile, plugging the pedal sensor
into a more mobile Laptop PC via a new battery powered interface built by
DM. With the original DM software installed and with the pressure
transducer mounted on one pedal of an otherwise ordinary 24" Ringmaster
Unicycle, it was possible to run alongside carrying the laptop PC and
interface box and capture the riders pedal “signature”. At this years
Eurocycle 2001 at the Tamarside College in Plymouth, England; we were able
to trial the new system and gain some fascinating insights into the way a
skilled unicyclist rides. The trace derived was setup to show a maximum
pressure of 125 Kg, just idling, the trace was a regular sawtooth shape
with peaks showing the maximum pressure and troughs the minimum with a
median level of about half the riders body weight. Riding in straight line
on a smooth surface (school corridor) the trace was much smoother with
reduced peaks and troughs (maximum to minimum) and a lower average
pressure. As a rider relaxed onto the uni and got more comfortable with it
the trace would smooth and drop towards the minimum pressure line. We
asked a number of riders to try out the system and people at Eurocycle
were probably a bit bemused to see myself running alongside various people
riding the uni, clutching a laptop connected to one of its pedals and
exhorting them to ride as smoothly as possible, pursued by DM and a small
group of interested onlookers. We found in our small sample a range of
signatures, the more skilled the rider the lower the pressure being put
onto the pedals and therefore the less work being done. Roger Davies and
Sarah Miller showed very low levels of work, riding very smoothly with
little pressure on the pedal, however it was Julian Monney who amazed us.
When Julian rode, the pressure sensor was unable to detect any pressure on
the pedal at all (in fact I had to check that the system was still
working). His balance is so perfect that he can ride without any
perceptible effort! Leo White tried some drops on the test system and even
here a difference could be perceived in landing “normally” and landing
“softly”, the pressure peak on a soft landing being up to 20 Kgs less than
a hard landing. Hopping and especially jumping onto pedals could generate
peaks as much as three times body weight.
Conclusion.
(a)The more skilled a rider the less effort they need to ride their
unicycle. This seems obvious of course but until now no one has been
able to actually prove it ! A possible new skill level might be to try
and obtain an increasingly lower and smooth a trace as possible on the
DM test rig 
(b)It is no wonder that hardened Muni riders need really tough cranks
and axles. DM’s splined ones are the best That was a blatant
plug. (grin)
Further experiments with Cokers and Muni’s will have to wait until I can
run at 10+ mph and throw myself down 10’ drops without injury 
We may
need a hardened test rig too.
(Disclaimer) The views expressed here are my own and not necessarily those
of DM Engineering.
Trevor Pearce-Jones
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Trevpj@globalnet.co.uk
Devizes. Wiltshire. England.
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