Computer math

Took the boy wonder out for an off-road adventure ride today. As I trailed
along somewhat bored watching boy wonder negotiate the trail ahead with the
speed of an overly cautious 10 year old, I started fiddling with my
computer.

Righ at the hour mark I managed to flip through the Cateye Endro 2's
functions and noted:
Time: 1:00
Distance 5.00 miles
Ave: 5.2 mph *-----------???????*

I know these aren't the most precise instruments in the world, but this one
struck me as odd. Given that the only two data points for the computer are
elapsed time and distance (as computed by distance/wheel rotation), how
would the average speed not equate to distance traveled in one hour of
elapsed time?

Tom

"tcmedara" wrote: (clip)how would the average speed not equate to distance
traveled in one hour of elapsed time?
^^^^^^^^^^^^^^
I can think of two possibilities, both rather unlikely:
1.) Your computer calculates a DISTANCE average, rather than a time
average.
2. If you stop, your computer continues to record and display elapsed time
from the start of the ride, but takes time out for computing the average.

"tcmedara" wrote in news:KMp3d.203740$4o.74833
@fed1read01:
I know these aren't the most precise instruments in the world, but this one
struck me as odd. Given that the only two data points for the computer are
elapsed time and distance (as computed by distance/wheel rotation), how
would the average speed not equate to distance traveled in one hour of
elapsed time?

Many computers record both elapsed time (total clock time) and ride time (not
counting time when the wheels are not moving). The average speed uses the
latter time.

On Mon, 20 Sep 2004 00:56:11 +0000, Ken wrote:

"tcmedara" wrote in news:KMp3d.203740$4o.74833
@fed1read01:
I know these aren't the most precise instruments in the world, but this one
struck me as odd. Given that the only two data points for the computer are
elapsed time and distance (as computed by distance/wheel rotation), how
would the average speed not equate to distance traveled in one hour of
elapsed time?

Many computers record both elapsed time (total clock time) and ride time (not
counting time when the wheels are not moving). The average speed uses the
latter time.

Howdy,

Assuming that you are correct, would that not cause the calculated
average MPH to be lower than 5 MPH in this example?

Thanks,

--
Kenneth

If you email... Please remove the "SPAMLESS."

Ken wrote:
"tcmedara" wrote in
news:KMp3d.203740$4o.74833 @fed1read01:
I know these aren't the most precise instruments in the world, but
this one struck me as odd. Given that the only two data points for
the computer are elapsed time and distance (as computed by
distance/wheel rotation), how would the average speed not equate to
distance traveled in one hour of elapsed time?

Many computers record both elapsed time (total clock time) and ride
time (not counting time when the wheels are not moving). The average
speed uses the latter time.

My understanding was that the time display on the Enduro 2 displayed actual
ride time (vice elapsed time, my error), i.e. time added only when the
sensor is picking up wheel rotations. As I was riding with my 10 year old,
there were several stops along the way. Total time (as read on the watch)
was well over an hour by the time the computer showed 1:00.

Obviously there's something I'm missing here. If this intelligent lot can't
figger it out, I might just have to email Cateye and get the company
approved reasoning. ......Perhaps I should do that anyway and see how that
compares to the answers here in RBT, eh?

Tom

On Sun, 19 Sep 2004 20:49:14 -0400, "tcmedara"
wrote:

Took the boy wonder out for an off-road adventure ride today. As I trailed
along somewhat bored watching boy wonder negotiate the trail ahead with the
speed of an overly cautious 10 year old, I started fiddling with my
computer.

Righ at the hour mark I managed to flip through the Cateye Endro 2's
functions and noted:
Time: 1:00
Distance 5.00 miles
Ave: 5.2 mph *-----------???????*

I know these aren't the most precise instruments in the world, but this one
struck me as odd. Given that the only two data points for the computer are
elapsed time and distance (as computed by distance/wheel rotation), how
would the average speed not equate to distance traveled in one hour of
elapsed time?

Tom

And I bet you kept that average speed till the time registered 1 hour
2 minutes and 24 seconds.

wrote:
On Sun, 19 Sep 2004 20:49:14 -0400, "tcmedara"
wrote:

Took the boy wonder out for an off-road adventure ride today. As I
trailed along somewhat bored watching boy wonder negotiate the trail
ahead with the speed of an overly cautious 10 year old, I started
fiddling with my computer.

Righ at the hour mark I managed to flip through the Cateye Endro 2's
functions and noted:
Time: 1:00
Distance 5.00 miles
Ave: 5.2 mph *-----------???????*

I know these aren't the most precise instruments in the world, but
this one struck me as odd. Given that the only two data points for
the computer are elapsed time and distance (as computed by
distance/wheel rotation), how would the average speed not equate to
distance traveled in one hour of elapsed time?

Tom

And I bet you kept that average speed till the time registered 1 hour
2 minutes and 24 seconds.

Hmm, didn't think to check. If that were the case, then I guess you're
saying that the average computation is only performed every few minutes
rather than a continuous display of distance over time. I guess that could
be the case, though I seem to recall a much greater rate of change on the
ave display during the early part of several rides. I can't dispute your
suggestion -- I'll have to check it out next time I ride (and remember to
look....I normally don't obsess on the computer, just keep track of
distance). I did email Cateye just out of curiosity. I'll post their
response when I get it.

Topm

On Sun, 19 Sep 2004 20:49:14 -0400, "tcmedara"
wrote:

Took the boy wonder out for an off-road adventure ride today. As I trailed
along somewhat bored watching boy wonder negotiate the trail ahead with the
speed of an overly cautious 10 year old, I started fiddling with my
computer.

Righ at the hour mark I managed to flip through the Cateye Endro 2's
functions and noted:
Time: 1:00
Distance 5.00 miles
Ave: 5.2 mph *-----------???????*

I know these aren't the most precise instruments in the world, but this one
struck me as odd. Given that the only two data points for the computer are
elapsed time and distance (as computed by distance/wheel rotation), how
would the average speed not equate to distance traveled in one hour of
elapsed time?

Tom

Dear Tom,

If your external figures show 1:00 hours, 5.00 miles, and
5.2 mph average time, then you need:

a) a badly programmed speedometer, or . . .

b) an internal distance of 5.2 miles (unlikely), or . . .

c) an internal time around 3462 seconds (138 seconds less
than a full hour), or . . .

d) an "average" that skips certain periods, or . . .

e) a speedometer that reads in odd-looking increments such
as 4.7, 5.2, 5.8, 6.3,6.9, and so forth (that is, a speedo
whose average-speed function will show only odd-looking
roughly half-mph points

f) a more accurate speedo that reads in tenths of an
mph--4.9, 5.0, 5.1, 5.2--but which still rounds up or down
along with c), a hidden internal time being slightly
different

I expect that the real answer will be g) something that
doesn't occur to me, but you might look into e) and see if
your speedometer reads 5.0, 5.1, 5.2, and so forth by
spinning the wheel and watching the numbers. If it switches
from 5.2 to 4.8, you've probably found the answer.

Carl Fogel

wrote:

I expect that the real answer will be g) something that
doesn't occur to me, but you might look into e) and see if
your speedometer reads 5.0, 5.1, 5.2, and so forth by
spinning the wheel and watching the numbers. If it switches
from 5.2 to 4.8, you've probably found the answer.

Carl Fogel

Bike is on the stand right now. I'm going to now have to leave my cozy
computer chair and meander out to the garage in the interest of science.
Perhaps I'll just forget about it and get one of these!

http://www.schwinnbike.com/products/...tail.php?id=53

If it's good enough for the likes of a tried and true racing bike, then
surely it won't be out of place on my generic, mass produced, cookie cutter
mountain bike..

Tom

"Kenneth" wrote: Assuming that you are correct, would that not cause the
calculated average MPH to be lower than 5 MPH in this example
^^^^^^^^^^^^^^^^
No, say you stopped riding for a couple minutes during the ride, so the
total elapsed time was 1 hour, but the time spent moving was, say, 58
minutes. 5 miles in 58 minutes is 5.17 MPH.