A little experiment

"Richard Bates" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

On Mon, 29 Mar 2004 13:15:18 GMT, in
<[email hidden]>,

Richard Goodman said:

If both ends of your bike arrive together, both wheels
will have

travelled

Quoted message said:

Quoted message said:

the same distance!

I assume your are jesting? Net distance-same. Gross
distance=front>rear (I hypothesise this to be the case
anyhow!)

Yes, it was partly in jest, but it also depends on what you
mean by 'the wheel' and what kind of travel you are
measuring. If you are measuring the displacement of the hubs
between start point and end point surely it will be the
same. If you are measuring how far each tyre has travelled
around its circumference then of course there could be a
slight difference, but to measure it accurately has all the
difficulties others have pointed out.

Ah, but I see you have also clarified what you wanted to
measure in a later posting 😉.

Rich

Richard Bates said:

Just had a mad idea whilst I was in the shower:

This year (May and June) I am doing a six week, very
indirect trip from John O'Groats to Land's End.

I thought it would be fun to measure the difference in
distance travelled by the front and rear wheels of my
bicycle.

I'm a knowledgaeable in scientific experiment construction
up to about A-Level standard. Apart from what is listed
below, can you think of any other important facts to make
it a valid setup?

1) Identical computers
2) Not wireless models (to avoid crosstalk)
3) Measure wheel circumferences independantly with bike
containing luggage with tyres pumped to my normal
pressure.

Easy to do, just line up the valve with the ground and roll
forward 4 or 5 revs and measure with a long tape, can get it
accurate to a cm or so. Do the same for both wheels (make
sure you're on the bike too!) but...

You will never get the circumferences to stay constant. IMO
the differences from the circumference changing will far
outweigh the actual difference in distance. Just roll your
bike along while sat on it, then while not sat on it to see
the difference. When you're riding I assume you'll be
moving your weight back and forward occasionally, and the
rear wheel may get slightly warmer and increase the
pressure and hence circumference. The tyres might well lose
a bit of pressure over the ride. Also, you better hope that
you don't ever lock your rear wheel for 6 weeks or that
will mess it up!

I'm sure you can come up with some experiments to measure
the error/variation in the points I mention, and how this
compares to what you expect the difference in distance to be
(do some simple geometry and predictions of corner speeds /
frequency...)

An interesting project!

Scott

Richard Bates said:

Just had a mad idea whilst I was in the shower:

Quoted message said:

This year (May and June) I am doing a six week, very
indirect trip from John O'Groats to Land's End.

Quoted message said:

I thought it would be fun to measure the difference
in distance travelled by the front and rear wheels of
my bicycle.

Quoted message said:

I'm a knowledgaeable in scientific experiment construction
up to about A-Level standard. Apart from what is listed
below, can you think of any other important facts to make
it a valid setup?

Quoted message said:

1) Identical computers
2) Not wireless models (to avoid crosstalk)
3) Measure wheel circumferences independantly with bike
containing luggage with tyres pumped to my normal
pressure.

Do a simulation or trial experiment to discover whether the
likely difference will be detectable within the limits of
error to which you can set wheel circumf, bearing in mind
gradually deflating tyres, etc..

--
Chris Malcolm [email hidden] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
["]http://www.dai.ed.ac.uk/homes/cam/]

Quoted message said:

Richard Bates said:

I guess this depends upon how the distance is measured. I
am not interested in the speed of each wheel. If the
computer calculates distance indirectly from speed and
time then the autostart function will interfere. (i.e. revs-->speed--

Quoted message said:

distance)

If however the computer calculates distance directly from
wheel revolutions (and subsequently calculates speed from
distance and time) then I think the auto start function
will not matter.

Anybody know whether computers primarly measure distance
or speed?

I would assume they measure distance, and then calculate
the speed.

Regardless of how they work out distance, if you're
carrying your bike up stairs for example, and you have one
wheel spinning around slowly, autostart could trip on,
record x revolutions of the wheel, and however it works out
distance it'll still add to the overall distance - and both
wheels could be spinning at different rates or one
spinning, one not, etc.

So you would have to make sure any revolutions of the wheels
aren't registered by the computer at all unless you're
actually cycling, and making sure the computer's won't
autostart in that situation (physical removal or switched
isolation from the sensors - just remember it's easy to
knock or forget to switch them back on again).

Velvet

Richard Bates <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

If however the computer calculates distance directly from
wheel revolutions (and subsequently calculates speed from
distance and time) then I think the auto start function
will not matter.

Anybody know whether computers primarly measure distance
or speed?

They count wheel revolutions and work out distance from the
circumference you provide, and speed from that and their
internal clock. The problem with the auto-start function is
that wheel revolutions within the start-up period may not
be counted.

--
Dave...

Following on from Colin Blackburn's message. . .

Quoted message said:

Sorry, I may be being extremely thick here or missing some
amazing joke but I'd still like someone to define what
they actually mean when they say the front wheel will
travel further.

SIMPLE The front wheel weaves more so takes a more sinuous
path than the rear which trails. Try a U-turn, the back
wheel travels inside the front so the result is a longer
path for the front. I presume that's what the OP meant.

HOWEVER
(a) I don't believe you can make accurate enough
measurements and maintain calibration.
(b) As great scientific experiments it rates alongside
getting up every hour through the night to see if the
light is still on inside the fridge.

INSTEAD Why not compare distances estimated / measured
from the map before each segment and the actual. Plot
your results X-Y to get a rule of thumb for future use.
eg It looks like 10 miles on the map but that works out
at 13 by the time all the twists in the lanes have been
taken into account.

--
PETER FOX Not the same since the deckchair business folded
[email hidden]
www.eminent.demon.co.uk/wcc.htm Witham Cycling Campaign
www.eminent.demon.co.uk/rides East Anglian Pub cycle rides

"Richard Bates" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

This year (May and June) I am doing a six week, very
indirect trip from John O'Groats to Land's End. I thought
it would be fun to measure the difference in distance
travelled by the front and rear wheels of my bicycle.

Superbly pointless. I'm sure you can get a grant for that
:-)

--
Guy
===
May contain traces of irony. Contents liable to settle after
posting. chapmancentral.co.ukchapmancentral.co.ukOpen ↗

88% of helmet statistics are made up, 65% of them at
Washington University

Peter Fox said:

Following on from Colin Blackburn's message. . .

Quoted message said:

Sorry, I may be being extremely thick here or missing
some amazing joke but I'd still like someone to define
what they actually mean when they say the front wheel
will travel further.

SIMPLE The front wheel weaves more so takes a more sinuous
path than the rear which trails. Try a U-turn, the back
wheel travels inside the front so the result is a longer
path for the front. I presume that's what the OP meant.

HOWEVER
(a) I don't believe you can make accurate enough
measurements and maintain calibration.
(b) As great scientific experiments it rates alongside
getting up every hour through the night to see if the
light is still on inside the fridge.

INSTEAD Why not compare distances estimated / measured
from the map before each segment and the actual. Plot your
results X-Y to get a rule of thumb for future use. eg It
looks like 10 miles on the map but that works out at 13 by
the time all the twists in the lanes have been taken into
account.

Or why not measure the length of the coastline between two
points ;-)

Please,

I have just wasted 5 minutes of my life reading this thread.

Will everyone stop wasting their lives worrying about how mch further the front wheel of a bike travels compared to the rear.

The overused phrase "get a life" will have to be deployed.

'I have just wasted 5 minutes of my life reading this thread.... The overused phrase "get a life" will have to be deployed.'

QED!

trembler50 said:

Please,

I have just wasted 5 minutes of my life reading this
thread.

No one forced you to.

Quoted message said:

Will everyone stop wasting their lives worrying about how
mch further the front wheel of a bike travels compared to
the rear.

Do you have no sense of curiosity?

Quoted message said:

The overused phrase "get a life" will have to be deployed.

Only for poster = self (or '== this' if you prefer.)

Colin
--

I have just wasted ten seconds of my life reading the above
post. I wondered why anyone bothers to complain about this
kind of thing, but then noticed that it came from
cyclingforums.com, home of the Sock Puppet, the Humour-
Impaired and the Troll.

--

The Pikey has risen from the Grave!

"Richard Bates" <[email hidden]> wrote

Quoted message said:

Anybody know whether computers primarly measure distance
or speed?

For mine at least, it measures distance. Easy to check
because it won't show speeds below 2mph (returns to zero)
but still clocks up distance. Also still clocks up positive
distance with wheel spinning backwards. Starts up as soon as
wheel magnet passes sensor. Can't see how one would measure
speed without working out distance first because all they
really measure is wheel revolutions.

Quoted message said:

I have just wasted 5 minutes of my life reading this
thread.

Learn to skip a thread and/or the Joy of The Killfile. You
aren't forced to read any thread.

Quoted message said:

The overused phrase "get a life" will have to be deployed.

Quit moaning and get a life!

Cheers, helen s ;-)

--This is an invalid email address to avoid spam-- to get
correct one remove fame & fortune
h*$el*$$e*nd**$o$ts**i*$*$m*m$o*n*s@$*a$o*l.c**$om$

--Due to financial crisis the light at the end of the tunnel
is switched off--

On Wed, 31 Mar 2004 13:22:28 GMT, trembler50
<[email hidden]> wrote in message
<[email hidden]>:

Quoted message said:

I have just wasted 5 minutes of my life reading this
thread.

Then give up cycling forums and start using Usenet like
the grown-ups
do.

--
Guy
===
May contain traces of irony. Contents liable to settle after
posting. chapmancentral.co.ukchapmancentral.co.ukOpen ↗

88% of helmet statistics are made up, 65% of them at
Washington University

dirtylitterboxofferingstospammers said:

Quoted message said:

I have just wasted 5 minutes of my life reading this
thread.

Learn to skip a thread and/or the Joy of The Killfile. You
aren't forced to read any thread.

Quoted message said:

The overused phrase "get a life" will have to be
deployed.

Quit moaning and get a life!

...or work out out how much one climbs compared to
descending for a trip from LE to JoG and back.

John B

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

On Wed, 31 Mar 2004 13:22:28 GMT, trembler50 <usenet-
[email hidden]> wrote in message
<[email hidden]>:

Quoted message said:

I have just wasted 5 minutes of my life reading this
thread.

Then give up cycling forums and start using Usenet like
the grown-ups
do.

Usenet use and grown-up behaviour are surely mutually
exclusive ;o)
--
.paul

if at first you don't succeed... skydiving is probably not
the sport for you

On Wed, 31 Mar 2004 21:35:03 GMT, Simon Brooke <[email hidden]>

Quoted message said:

I strongly suspect that

(i) the inevitable internal errors in the computers (e.g.,
occasional missed pulses) and
(ii) variations in tyre diameter caused by wear and
pressure variation

will each exceed the difference in total distance.

Fit two computers to each wheel. Might help eliminate some
of the errors. Or at least make it look really scientific.

Tim

On Wed, 31 Mar 2004 21:35:03 GMT, in
<[email hidden]>, Simon Brooke

Quoted message said:

I strongly suspect that

(i) the inevitable internal errors in the computers (e.g.,
occasional missed pulses) and

Would you think this could be minimalised or overcome
by ensuring the smallest practical gap between magnet
and sensor?

Quoted message said:

(ii) variations in tyre diameter caused by wear and
pressure variation

This would affect the accuracy of the measured distance, it
is true, since an underinflated tyre will have a
circumference which does not equal what I have programmed
into the computer. However if I use the computer's distance
recording to calculate backwards and work out the number of
wheel revolutions front and rear (since afterall the
computer appears to be simply a rev counter and timer), I
will still end up with ratio F:R.

--
[email hidden] Personal Site: www.artybee.net (same
[censored], different layout) Sutton Brass :
www.suttonbrass.org.uk

In article said:

<[email hidden]>,
Simon Brooke

Would you think this could be minimalised or overcome
by ensuring the smallest practical gap between magnet
and sensor?

Quoted message said:

(ii) variations in tyre diameter caused by wear and
pressure variation

This would affect the accuracy of the measured distance, it
is true, since an underinflated tyre will have a
circumference which does not equal what I have programmed
into the computer. However if I use the computer's distance
recording to calculate backwards and work out the number of
wheel revolutions front and rear (since afterall the
computer appears to be simply a rev counter and timer), I
will still end up with ratio F:R.

Only if the front and back tyres wear and deflate at the
same rate. You could swap them over every day :-)