C
Another current thread on Slime tubes led me to waste an
hour happily playing with an upside-down bicycle, a
rear-wheel speedometer, and a stopwatch.
First, I cranked the tire with a normal inner tube twenty
times up to 35-40 mph and timed how long it took to spin
down from around 30 mph to around 10 mph.
Even with a speedometer reading in tenths of a mile per
hour, it's hard to start and stop because the speedometer
samples over a short time as the magnet spins past and then
shows the latest average.
Around 30 mph, the figures fall at about 1 mph or a little
more every time. By the time the speed has dropped to 10
mph, there are about two readings per mph.
Waiting for the wheel to spin down any further would
probably decrease even rough accuracy, since the magnet is
spinning slower and slower past the sensor.
Given the lack of precision and the length of time, I
rounded to the nearest second on the stopwatch.
After twenty spins, I pulled the normal tube out, stuffed in
a Slime tube, and did it all again.
http://home.comcast.net/~carlfogel/download/slime.txt
http://home.comcast.net/~carlfogel/download/slime.wk1
As expected, the heavier Slime tube took noticeably longer
to spin down, the greater mass having greater inertia,
averaging 1.96 seconds for each mph lost, versus only 1.67
seconds for the lighter normal tube.
This supports Jobst Brandt's prediction in the other thread
that the liquid Slime isn't so much sloshing around and
adding friction as plastering itself around the outer curve
of the tube.
What's curious is that about 70 grams of Slime smoothed
things out impressively. The seconds/mph-lost varied wildly
on the normal tube, producing a jagged graph compared to the
Slime tube's almost level graph.
I'm curious why a little liquid would smooth things out so
dramatically. It doesn't seem as if 70 grams would have much
of flywheel effect on what's probably a 2000 gram or more
wheel and tire, so maybe some kind of friction is involved?
Tomorrow, I'll probably weigh things, which might matter.
The plain text of the results is below.
Carl Fogel
plain tube
max 30.80 10.90 36.00 20.80 1.87
avg 29.81 10.04 32.95 19.77 1.67
min 28.70 9.60 29.00 18.60 1.40
start stop speed sec/
speed speed time range mph
#01 28.7 10.1 34 18.6 1.83
#02 29.4 9.8 36 19.6 1.84
#03 28.9 10.1 32 18.8 1.70
#04 29.1 10.3 32 18.8 1.70
#05 30.1 10.0 31 20.1 1.54
#06 30.6 9.9 29 20.7 1.40
#07 29.9 10.0 30 19.9 1.51
#08 29.2 10.0 30 19.2 1.56
#09 30.6 9.8 34 20.8 1.63
#10 28.9 10.0 32 18.9 1.69
#11 29.7 10.0 33 19.7 1.68
#12 29.1 9.9 32 19.2 1.67
#13 30.4 10.0 33 20.4 1.62
#14 30.6 10.0 35 20.6 1.70
#15 29.7 9.6 36 20.1 1.79
#16 30.8 10.9 32 19.9 1.61
#17 30.8 10.3 33 20.5 1.61
#18 30.4 10.3 34 20.1 1.69
#19 30.1 9.9 35 20.2 1.73
#20 29.1 9.9 36 19.2 1.87
slime tube
max 30.80 10.80 40.00 20.80 2.03
avg 29.78 10.24 38.20 19.54 1.96
min 28.90 9.80 36.00 18.30 1.83
start stop speed sec/
speed speed time range mph
#01 29.9 10.2 36 19.7 1.83
#02 30.4 10.0 38 20.4 1.86
#03 28.9 9.8 38 19.1 1.99
#04 30.1 10.2 38 19.9 1.91
#05 29.6 10.0 38 19.6 1.94
#06 29.4 10.1 38 19.3 1.97
#07 29.9 10.3 38 19.6 1.94
#08 29.4 10.3 38 19.1 1.99
#09 29.6 10.0 38 19.6 1.94
#10 30.8 10.0 40 20.8 1.92
#11 29.9 10.3 38 19.6 1.94
#12 29.1 10.8 36 18.3 1.97
#13 29.9 10.6 38 19.3 1.97
#14 30.1 10.6 38 19.5 1.95
#15 29.9 10.5 38 19.4 1.96
#16 29.4 10.3 38 19.1 1.99
#17 29.9 10.1 40 19.8 2.02
#18 29.7 10.0 40 19.7 2.03
#19 29.2 10.5 38 18.7 2.03
#20 30.4 10.2 40 20.2 1.98
hour happily playing with an upside-down bicycle, a
rear-wheel speedometer, and a stopwatch.
First, I cranked the tire with a normal inner tube twenty
times up to 35-40 mph and timed how long it took to spin
down from around 30 mph to around 10 mph.
Even with a speedometer reading in tenths of a mile per
hour, it's hard to start and stop because the speedometer
samples over a short time as the magnet spins past and then
shows the latest average.
Around 30 mph, the figures fall at about 1 mph or a little
more every time. By the time the speed has dropped to 10
mph, there are about two readings per mph.
Waiting for the wheel to spin down any further would
probably decrease even rough accuracy, since the magnet is
spinning slower and slower past the sensor.
Given the lack of precision and the length of time, I
rounded to the nearest second on the stopwatch.
After twenty spins, I pulled the normal tube out, stuffed in
a Slime tube, and did it all again.
http://home.comcast.net/~carlfogel/download/slime.txt
http://home.comcast.net/~carlfogel/download/slime.wk1
As expected, the heavier Slime tube took noticeably longer
to spin down, the greater mass having greater inertia,
averaging 1.96 seconds for each mph lost, versus only 1.67
seconds for the lighter normal tube.
This supports Jobst Brandt's prediction in the other thread
that the liquid Slime isn't so much sloshing around and
adding friction as plastering itself around the outer curve
of the tube.
What's curious is that about 70 grams of Slime smoothed
things out impressively. The seconds/mph-lost varied wildly
on the normal tube, producing a jagged graph compared to the
Slime tube's almost level graph.
I'm curious why a little liquid would smooth things out so
dramatically. It doesn't seem as if 70 grams would have much
of flywheel effect on what's probably a 2000 gram or more
wheel and tire, so maybe some kind of friction is involved?
Tomorrow, I'll probably weigh things, which might matter.
The plain text of the results is below.
Carl Fogel
plain tube
max 30.80 10.90 36.00 20.80 1.87
avg 29.81 10.04 32.95 19.77 1.67
min 28.70 9.60 29.00 18.60 1.40
start stop speed sec/
speed speed time range mph
#01 28.7 10.1 34 18.6 1.83
#02 29.4 9.8 36 19.6 1.84
#03 28.9 10.1 32 18.8 1.70
#04 29.1 10.3 32 18.8 1.70
#05 30.1 10.0 31 20.1 1.54
#06 30.6 9.9 29 20.7 1.40
#07 29.9 10.0 30 19.9 1.51
#08 29.2 10.0 30 19.2 1.56
#09 30.6 9.8 34 20.8 1.63
#10 28.9 10.0 32 18.9 1.69
#11 29.7 10.0 33 19.7 1.68
#12 29.1 9.9 32 19.2 1.67
#13 30.4 10.0 33 20.4 1.62
#14 30.6 10.0 35 20.6 1.70
#15 29.7 9.6 36 20.1 1.79
#16 30.8 10.9 32 19.9 1.61
#17 30.8 10.3 33 20.5 1.61
#18 30.4 10.3 34 20.1 1.69
#19 30.1 9.9 35 20.2 1.73
#20 29.1 9.9 36 19.2 1.87
slime tube
max 30.80 10.80 40.00 20.80 2.03
avg 29.78 10.24 38.20 19.54 1.96
min 28.90 9.80 36.00 18.30 1.83
start stop speed sec/
speed speed time range mph
#01 29.9 10.2 36 19.7 1.83
#02 30.4 10.0 38 20.4 1.86
#03 28.9 9.8 38 19.1 1.99
#04 30.1 10.2 38 19.9 1.91
#05 29.6 10.0 38 19.6 1.94
#06 29.4 10.1 38 19.3 1.97
#07 29.9 10.3 38 19.6 1.94
#08 29.4 10.3 38 19.1 1.99
#09 29.6 10.0 38 19.6 1.94
#10 30.8 10.0 40 20.8 1.92
#11 29.9 10.3 38 19.6 1.94
#12 29.1 10.8 36 18.3 1.97
#13 29.9 10.6 38 19.3 1.97
#14 30.1 10.6 38 19.5 1.95
#15 29.9 10.5 38 19.4 1.96
#16 29.4 10.3 38 19.1 1.99
#17 29.9 10.1 40 19.8 2.02
#18 29.7 10.0 40 19.7 2.03
#19 29.2 10.5 38 18.7 2.03
#20 30.4 10.2 40 20.2 1.98