Axles and cranks under pressure

Axles and cranks under pressure

Post by Trevor Pearce-Jon » Sun, 30 Sep 2001 07:05:44


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

? ,o`o,?? ,o`o,?? ,o`o,?

    Devizes. Wiltshire. England.
`o,?? ,o`o,?? ,o`o,?? ,o

 
 
 

Axles and cranks under pressure

Post by Klaas B » Tue, 02 Oct 2001 08:52:23


<interesting stuff snipped>

Quote:
>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!

Riding without any pressure is theoretically the same as coasting.
Wasn't it Julian who was mentioned some time ago in this newsgroup as
being able to coast, and also to manage the incredible feat of doing
standstills without touching the pedals for 30 seconds?

Klaas Bil
--
"To trigger/fool/saturate/overload Echelon, the following has been picked automagically from a database:"
"7 August, 1998, Iraq, MI-6"