This morning I finally cracked the 4-minute mile (not by much!).
Not surprisingly, I was on the Coker. I have 5" (125mm) cranks. This was
towards the end of a long, fast ride.
I would bet that Rodger Davies has done this many times on his 110s.
Anyone ever pull this off with the 125s?
Here are some #s to help those of us who can’t read the cycle computer
while riding:
I have found that a tenth of a mile requires 57-58 revolutions on the
Coker. Some basic math tells us that this comes out to a bit over a mile,
but there is 1-3% inefficiency due to wiggle and possibly to
under-inflation.
Assuming you can measure a tenth of a mile, here are some more #s:
Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5 mph
24 sec 4 mins 15mph
Do these calcluations seem right (esp. the 57-58 revs)?
> I have found that a tenth of a mile requires 57-58 revolutions on the > Coker. Some basic math tells us that this comes out to a bit over a > mile, but there is 1-3% inefficiency due to wiggle and possibly to > under-inflation.
David, Congrats on your fast mile. Here are some other points to consider.
You talk of a “1-3% inefficiency”. If you know the true diameter of the
wheel & can count revs, why does it matter how much distance is actually
traveled? Give yourself a break & count a “crooked mile” as a
mile…unless we are actually talking about a mile long course for the
sake of competition. Otherwise, we get into an argument about how
much variance there is between different riders,etc. After all, a
Coker is not a proper surveyor’s wheel. It’s much easier to just
“attempt” to properly calibrate the computer & take it’s word for
speed & distance or use a stop watch over a “known” mile.
> Assuming you can measure a tenth of a mile, here are some more #s: > > Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5 mph > 24 sec 4 mins 15mph > > Do these calcluations seem right (esp. the 57-58 revs)? > > David
These calculations might be correct for you & incorrect for others. I’ve
found that the Coker tire (with my calculations) rolls out to under 112"
or less than 36" diameter for the tire…did you do a roll out or
just the math based on a 36" wheel?
Anyway, I’ll try to go as fast as I can for a “mile” on my Coker(w/125
cranks & a stopwatch) & get back to you.
cokerhead@gilby.com writes: >> I have found that a tenth of a mile requires 57-58 revolutions on the >> Coker. Some basic math tells us that this comes out to a bit over a >> mile, but there is 1-3% inefficiency due to wiggle and possibly to >> under-inflation. > >David, Congrats on your fast mile. Here are some other points to >consider. You talk of a “1-3% inefficiency”. If you know the true >diameter of the wheel & can count revs, why does it matter how much >distance is actually traveled? Give yourself a break & count a "crooked >mile" as a >mile…unless we are actually talking about a mile long course for the > sake of competition. Otherwise, we get into an argument about how > much variance there is between different riders,etc. After all, a > Coker is not a proper surveyor’s wheel. It’s much easier to just > “attempt” to properly calibrate the computer & take it’s word for > speed & distance or use a stop watch over a “known” mile.
Yeah, I don’t feel like counting to 580 everytime I decide to clock
myself. Luckily there are a few spots where I can use marked miles to
assist. As you noted, these distances don’t totally square with the size
of the Coker tire (no, I didn’t actually measure it – just used 36" to
get a rough estimate), due to wiggle and other inefficiency, but I’m ok
with just using marked miles in order to assess distance. I set the cycle
computer to reflect a true mile rather than going by the size of the tire.
I can’t recall the exact #s but can get them if you want. > > >> Assuming you can measure a tenth of a mile, here are some more #s: >> >> Tenth time Mile Time Approx mph 30 sec 5 mins 12mph 27 sec 4:30 13.5 >> mph 24 sec 4 mins 15mph >> >> Do these calcluations seem right (esp. the 57-58 revs)? >> >> David > >These calculations might be correct for you & incorrect for others. I’ve >found that the Coker tire (with my calculations) rolls out to under 112" >or less than 36" diameter for the tire…did you do a roll out or >just the math based on a 36" wheel?
Well, whatever method, if a person can reliably measure a tenth of a mile,
then the chart above works. The question is whether 57 or 58 revs per
tenth is accurate. I would bet it’s pretty close. > > >Anyway, I’ll try to go as fast as I can for a “mile” on my Coker(w/125 >cranks & a stopwatch) & get back to you. > >-Mark
Great. Good luck, and be safe. David
I measured the Coker circumference at 2.776m which converts to 35.345
inches in diameter. This was with a 160lb rider at 40psi, measured over 3
revolutions, I forget how many measurements, but I threw out the high and
low and averaged the rest. I was supported by a friend and pedaling
straight and smooth and slow. As always, YMMV!
nathan@movaris.com writes: >I measured the Coker circumference at 2.776m which converts to 35.345 >inches in diameter. This was with a 160lb rider at 40psi, measured over 3 >revolutions, I forget how many measurements, but I threw out the high and >low and averaged the rest. I was supported by a friend and pedaling >straight and smooth and slow. As always, YMMV! > >—Nathan >
Don’t forget that the circumf of the wheel does not change just from
compression. A rider will compress the wheel, of course, and this affects
height a tad, but the full sheel still has to go around, even if some of
it is compresed…so you should not try to convert diameter to circumf.
It definitely makes a difference, tho, if your wheel is a bit more or
less pumped.
The important info to me is that the circumf was measured at 2.776m –
this can be usued to calculate other data. I just would throw away the
diameter part.
Yes, the effective circumference is all that matters. You have to get the
cyclometer setting just right. I seem to remember measuring the diameter
of the wheel unweighted at 35.5", so even that is not a full 36". Right
now my tire is bald with threads showing, so that has a little affect too.
—Nathan
“David Stone” <dstone@packer.edu> wrote in message news:fc.000f4e6700519311000f4e6700517472.519321@packer.edu… > nathan@movaris.com writes: > >I measured the Coker circumference at 2.776m which converts to 35.345 > >inches in diameter. This was with a 160lb rider at 40psi, measured over > >3 revolutions, I forget how many measurements, but I threw out the high > >and low and averaged the rest. I was supported by a friend and pedaling > >straight and smooth and slow. As always, YMMV! > > > >—Nathan > > > > Don’t forget that the circumf of the wheel does not change just from > compression. A rider will compress the wheel, of course, and this > affects height a tad, but the full sheel still has to go around, even if > some of it is compresed…so you should not try to convert diameter to > circumf. It definitely makes a difference, tho, if your wheel is a bit > more or less pumped. > > The important info to me is that the circumf was measured at 2.776m – > this can be usued to calculate other data. I just would throw away the > diameter part. > > david
Yes, the effective circumference is all that matters. You have to get the
cyclometer setting just right. I seem to remember measuring the diameter
of the wheel unweighted at 35.5", so even that is not a full 36". Right
now my tire is bald with threads showing, so that has a little affect too.
—Nathan
“David Stone” <dstone@packer.edu> wrote in message news:fc.000f4e6700519311000f4e6700517472.519321@packer.edu… > nathan@movaris.com writes: > >I measured the Coker circumference at 2.776m which converts to 35.345 > >inches in diameter. This was with a 160lb rider at 40psi, measured over > >3 revolutions, I forget how many measurements, but I threw out the high > >and low and averaged the rest. I was supported by a friend and pedaling > >straight and smooth and slow. As always, YMMV! > > > >—Nathan > > > > Don’t forget that the circumf of the wheel does not change just from > compression. A rider will compress the wheel, of course, and this > affects height a tad, but the full sheel still has to go around, even if > some of it is compresed…so you should not try to convert diameter to > circumf. It definitely makes a difference, tho, if your wheel is a bit > more or less pumped. > > The important info to me is that the circumf was measured at 2.776m – > this can be usued to calculate other data. I just would throw away the > diameter part. > > david