Mind boggling logic required

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

The number means that fr every 2207 times the magnet passes the sensor,
the computer will register a single kilometer.

so if it's over-reading, then you need to tell it that there's more
clicks per k than it thinks at the moment. you're only out by 1.3%
though, that's not much, and is probably more influenced by tyre
pressure and ride path than you think.

[quote="Owen"]I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

It's a bugger to reset, so would like to do it once only


Owen

Assume your wheel circumference is 1,000 mm then it will turn 1,000 time in 1km.
The computer recorded that it turned 1,013 times
Therefore I would be entering a lower number into the computer being 1,000/1,013 of you current number.

Perhaps a mathematician could confirm or deny?

Mike

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

It's a bugger to reset, so would like to do it once only

TIA

Owen

Owen,

The wheel factor is actually the circumference of your tyre in mm, if you are observing a high reading over a known distance then you are not travelling as far as your computer thinks so the actual circumference must be lower than you have set.

Given that you record 1.013Km with a setting of 2207 then a setting of 2179 should give you a reading of 1.000Km. This of course assumes the same tyre pressure, rider weight, tyre wear, etc, etc.

1.013Km for 1Km is only an error of 1.3% which is probaply better than your average car odometer anyway (I know we all like to adjust everything bike related to within the tiniest fraction of a percent, just a pity the rider isn't as easily adjusted)

Geebs

Geebs said:

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer
reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today
among other riders was two bob each way so that only confused me more!

It's a bugger to reset, so would like to do it once only

Quoted message said:

The wheel factor is actually the circumference of your tyre in mm, if
you are observing a high reading over a known distance then you are not
travelling as far as your computer thinks so the actual circumference
must be lower than you have set.

Given that you record 1.013Km with a setting of 2207 then a setting of
2179 should give you a reading of 1.000Km. This of course assumes the
same tyre pressure, rider weight, tyre wear, etc, etc.

1.013Km for 1Km is only an error of 1.3% which is probaply better than
your average car odometer anyway (I know we all like to adjust
everything bike related to within the tiniest fraction of a percent,
just a pity the rider isn't as easily adjusted)

You should also be aware that the km markers at the side of the road
are not neccessarily exactly 1km apart. If there's a tree where the
marker should go or a bridge or a side road, the marker will be as
close as possible to the right place.
--
Regards.
Richard.

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

It's a bugger to reset, so would like to do it once only

TIA

Owen

Measure the circumference at operating weight and pressure of the wheel with the sensor.

1. Pump tyres to riding pressure

2. On a straight length of path, mark the start of measurement

3. rollout n revolutions of the wheel, sitting the bike.

4. mark the end for measurement.

5. measure between start and end marks in mm and divide by n

6. enter circumference in mm into bike computer.

A 5 m tape will measure 2 revolutions - divide measure in mm by 2
a 30m tape will measure 10 revolutions - measure in cm and enter as mm

I mark start and end of ten (10) revolutions of rollout and measure in cm for entry in mm - simple, easy, and no calculations needed

mikeg

On 2006-12-30, Bleve (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

The number means that fr every 2207 times the magnet passes the sensor,
the computer will register a single kilometer.

That's a small wheel, turning almost once per metre. An 11 inch
wheel, according to my calculations. Unlikely.

More likely, given that the majority of wheels I have come across have
a circumference around 2m (2000-2100mm or so depending on bike), he's
just got a bit of a high reading there for the circumference (maybe
used the 27" value from the table supplied in his speedo manual?).
I've never seen a speedo that inputs how many times you turn per km,
but I've seen plenty where you input the circumference in mm.

Now finally, measuring over 1km is a bit short for my tastes, as
others have said.

--
TimC
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

TimC said:

Now finally, measuring over 1km is a bit short for my tastes, as
others have said.

Yes, but we're not all comfortable / familiar dealing with light-years and such astronomer guy:eek:

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

Quoted message said:

On 2006-12-30, Bleve (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer
reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among
other riders was two bob each way so that only confused me more!

The number means that fr every 2207 times the magnet passes the sensor,
the computer will register a single kilometer.

That's a small wheel, turning almost once per metre. An 11 inch
wheel, according to my calculations. Unlikely.

More likely, given that the majority of wheels I have come across have
a circumference around 2m (2000-2100mm or so depending on bike), he's
just got a bit of a high reading there for the circumference (maybe
used the 27" value from the table supplied in his speedo manual?).
I've never seen a speedo that inputs how many times you turn per km,
but I've seen plenty where you input the circumference in mm.

Now finally, measuring over 1km is a bit short for my tastes, as
others have said.

--
TimC
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

Of course, if you just want the value you need, set it to 2179 (~2207/1.013)

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

Quoted message said:

Of course, if you just want the value you need, set it to 2179
(~2207/1.013)

That would work......assuming that the km markers are exactly 5km apart.
From memory (and it has been a while since I had to set one), my speedo
manual states 2210mm for a 622-23 (ie. 700c) tyre and 2205mm for a 2.1 inch
wide mtb tyre (ie. 26"😉. I usually accept these values as being close
enough although I can remember a mate of mine some years ago spending a bit
more time in getting an accurate result....

The simple way to measure circumference is to draw a line on the ground and
line up the valve on your wheel with the line.....wheel your bike forwards
until the valve rotates around to the ground again....draw another
line....distance between lines is what you enter into the
speedo.....simple!! But this was not accurate enough for my mate.....he
insisted that he had to be on the bike as this would compress the tyres,
effectively reducing the circumference. He also had to buy a speedo that
used the rear wheel as it is less prone to wobble about and travel further
than you have actually gone. Finally, he wasn't happy with measuring one
rotation and so I got roped into helping him measure 10 rotations,
effectively reducing any measurement errors by a factor of 10. At the time
I can remember being tempted to ask him how much confidence he had in the
tape measure that we were using but I didn't want to spoil it all for him!!!
I can't remember the final figure that he entered but I do remember that
when we rode side by side we would have the same speedo measurement!!!

For a 1.3% error at say 30km/h, you are only going to be out by 0.39
km/h......do you need it to be more accurate than this??

Gags

TimC said:

That's a small wheel, turning almost once per metre. An 11
inch wheel, according to my calculations. Unlikely.

On those assumptions, I make the wheel diameter 144.23 mm
(5.68"😉.

In mm, 1000000 / (2207 * pi)

John

Resound said:

Of course, if you just want the value you need, set it to 2179
(~2207/1.013)

Agreed.

John

TimC said:

On 2006-12-30, Bleve (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today among other riders was two bob each way so that only confused me more!

The number means that fr every 2207 times the magnet passes the sensor,
the computer will register a single kilometer.

That's a small wheel, turning almost once per metre. An 11 inch
wheel, according to my calculations. Unlikely.

Mea Culpa, you're quite right.

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

Quoted message said:

TimC said:

On 2006-12-30, Bleve (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Owen wrote:
> I set the wheel factor of my odometer to 2207
>
> Today I rode past three 1 Km markers in a 5 Km stretch and the
> odometer reads high, ie for every Km I do, the odometer reads 1.013
> Kms
>
> Do I increase or decrease the wheel factor. A big discussion today
> among other riders was two bob each way so that only confused me more!

The number means that fr every 2207 times the magnet passes the sensor,
the computer will register a single kilometer.

That's a small wheel, turning almost once per metre. An 11 inch
wheel, according to my calculations. Unlikely.

Mea Culpa, you're quite right.

I rather suspect that it's the circumference in mm. 2207/pi being 702½ which
is a quite reasonable diameter for a bike wheel.

Richard Sherratt said:

Geebs said:

Owen said:

I set the wheel factor of my odometer to 2207

Today I rode past three 1 Km markers in a 5 Km stretch and the odometer
reads high, ie for every Km I do, the odometer reads 1.013 Kms

Do I increase or decrease the wheel factor. A big discussion today
among other riders was two bob each way so that only confused me more!

It's a bugger to reset, so would like to do it once only

Quoted message said:

The wheel factor is actually the circumference of your tyre in mm, if
you are observing a high reading over a known distance then you are not
travelling as far as your computer thinks so the actual circumference
must be lower than you have set.

Given that you record 1.013Km with a setting of 2207 then a setting of
2179 should give you a reading of 1.000Km. This of course assumes the
same tyre pressure, rider weight, tyre wear, etc, etc.

1.013Km for 1Km is only an error of 1.3% which is probaply better than
your average car odometer anyway (I know we all like to adjust
everything bike related to within the tiniest fraction of a percent,
just a pity the rider isn't as easily adjusted)

You should also be aware that the km markers at the side of the road
are not neccessarily exactly 1km apart. If there's a tree where the
marker should go or a bridge or a side road, the marker will be as
close as possible to the right place.

Borrow or arrange for someone to measure out a long distance between two
points on a straight section of road with a GPS. The further the
distance the more accurate it will be.

Friday

Richard Sherratt said:

You should also be aware that the km markers at the side of the road
are not neccessarily exactly 1km apart. If there's a tree where the
marker should go or a bridge or a side road, the marker will be as
close as possible to the right place.

As close as possible? My experience is that they vary by as much as 200
metres.

Theo

Theo Bekkers said:

Richard Sherratt said:

You should also be aware that the km markers at the side of the road
are not neccessarily exactly 1km apart. If there's a tree where the
marker should go or a bridge or a side road, the marker will be as
close as possible to the right place.

As close as possible? My experience is that they vary by as much as 200
metres.

Fairly close? :-)
--
Regards.
Richard.

Richard Sherratt said:

"Theo Bekkers" wrote

Quoted message said:

Quoted message said:

As close as possible? My experience is that they vary by as much as
200 metres.

Quoted message said:

Fairly close? :-)

Before we went metric we used to put up signs saying "Gnangara Road - 200
Yards", the 200 yards being a number approximating the distance to the
intersection within 50 yards. It was replaced by a sign saying "Gnangara
Road - 173 Metres".

I suppose that was "fairly close".

Theo

Theo Bekkers said:

Richard Sherratt said:

"Theo Bekkers" wrote

Quoted message said:

Quoted message said:

As close as possible? My experience is that they vary by as much as
200 metres.

Quoted message said:

Fairly close? :-)

Before we went metric we used to put up signs saying "Gnangara Road - 200
Yards", the 200 yards being a number approximating the distance to the
intersection within 50 yards. It was replaced by a sign saying "Gnangara
Road - 173 Metres".

I suppose that was "fairly close".

I think that's "pretty close".

I remember the TV news reports where the news reader said that "the
witness said he was about 182.88 cm tall".

The road engineers, btw, were spitting chips. If the posts were more
than 1cm out of place, they wanted them put where they should be. 1
metre out of place was a hanging offence. Some of the REs had to be
persuaded that a 1mm variance was not a catastrophe.

--
Regards.
Richard.

Richard Sherratt said:

Theo Bekkers wrote:

Quoted message said:

Quoted message said:

It was replaced by a sign saying "Gnangara Road - 173 Metres".

I suppose that was "fairly close".

I think that's "pretty close".

Somebody with more interest than myself also thought the sign was a bit off
and measured the distance. I think, from memory, that it was actually 195
metres to the centre of the road reserve. The sign was eventually changed to
say 200 metres.

Quoted message said:

The road engineers, btw, were spitting chips. If the posts were more
than 1cm out of place, they wanted them put where they should be. 1
metre out of place was a hanging offence. Some of the REs had to be
persuaded that a 1mm variance was not a catastrophe.

I always thought road engineers were [censored], you've now confirmed it for
me. Roads and road trips are measured in kms, very short road trips in 100s
of metres. What does it matter if a road sign is a few metres out?

Theo