Rowing Computer Alternatives
Jonathan Dingwell
Now that school is out, I suppose I should stop lurking and post something...
My question is this:
Has anyone found anything in the way of a small computer to keep track of
stroke rates and times and so forth in a boat (i.e. a 1x), that does NOT
involve the expense of a Nielsen-Kellerman (NK) or other similarly expensive
toy? I want one for my 1x, but as a grad student, can't really afford the NK.
I know NK makes a great product (The new Stroke Coach now sells for $175),
bicycle computers which produce nearly the same information are available for
as little as $20, and decent ones can be bought for $40-$50. I realize rowing
is a MUCH smaller market, but that should not account for THAT big of a price
difference (I don't think).
I have thought of two alternatives using bicycle computers:
1) A friend of mine has mounted a cycle computer that keeps track of cadence
under his seat. It puts out a number equal to 2x the stroke rate (e.g. 60
instead of 30, etc.) since it counts each passing of the seat (twice/stroke).
It works pretty well, and except for stroke count, gives essentially the same
info as the NK Stroke Coach.
2) Many of these bike computers can also be programmed with the tire's
circumfrence to give accurate speeds (miles/hr) based on the wheel's size and
how fast it is spinning. It occurs to me that with a little numerical
fiddling, one could figure out what wheel circumfrence you would need to have
the thing output 30 mph when you were rowing 30 spm (my calculation gets me to
a circumference of 528in. or 1341cm - ask me if you want the whole thing).
Has anyone tried this?? Has anyone thought of this?? Has anyone thought of
something else, or even something better?? Hmmm...
If anyone from NK is peeking in, I'd be greatful for any comments you might
have as well. (on or off the record).
Jon Dingwell
Go Penn State Crew !!
A WARDLE
>From: jdin...@magnus.acs.ohio-state.edu (Jonathan Dingwell)
>Subject: Rowing Computer Alternatives
>Date: 15 Jun 1995 19:18:43 GMT
John Dingwell enquires (Condensed a bit):
>Has anyone found anything in the way of a small computer to keep track of
>involve the expense of a Nielsen-Kellerman (NK) or other similarly expensive
>toy? I want one for my 1x, but as a grad student, can't really afford the NK.
>
>I know NK makes a great product (The new Stroke Coach now sells for $175),
>bicycle computers which produce nearly the same information are available for
>as little as $20 It puts out a number equal to 2x the stroke rate (e.g.
60 >instead of 30, etc.).It works pretty well, and except for
stroke count, gives essentially the same >info as the NK Stroke Coach.>>2)
Many of these bike computers can also be programmed with the tire's>
circumfrence to give accurate speeds (miles/hr) based on the wheel's size
and>how fast it is spinning. It occurs to me that with a little numerical>
fiddling, one could figure out what wheel circumfrence you would need to
have>the thing output 30 mph when you were rowing 30 spm (my calculation
gets me to >a circumference of 528in. or 1341cm
The expense of such things as the NK unit is brought about by the
development cost of the software used and the fact that producing a small
number of application specific computers costs a lot lot more per unit
than producing very large numbers. Also, the NK units have a lot more
features than your average cycle computer such as memory and pre
programming of workouts. They also use larger and more expensive waterproof
cases and switches etc which all increase the cost. Finally, they use a
speed sensor consisting (as far as I know) of a mini turbine on an outrigger
or in the fin. This type of sensor is more expensive than the hall-effect
magnetic sensor used in bike computers.
A cycle computer (with cadence output) can be used as you say, and if you
wanted the proper stroke output, you can put a thing called a D type flip/
flop in the output line from the sensor which halves the frequency of the
pulses.
I think the 528inch wheel size will be out of range!!! So it's pretty hard
to get a useable output from a computer which doesn't have cadence.
In the UK we can buy strokemeters for about ś100 inclusive.
It is possible to make one but you need a bit of electronics knowhow. Don'
t read the next bit if you want to stay awake!! You can either use a good
integrator based one or, as I did, use an EPROM look-up table to get the
stroke rate for a particular frequency of seat movement. Then you put the
output into an LCD voltmeter module to get a visual output. It cost about ś
35 and registers immediately unlike some which take a while to settle on the
correct rate.
I'm still thinking of a cheap and non-mechanical way of measuring boat speed.
Hope this is of some use.
If you want any more info, email me.
Andy W.
Ken Young
>In article <3rq12j$c...@charm.magnus.acs.ohio-state.edu> jdin...@magnus.acs.ohio-state.edu (Jonathan Dingwell) writes:
>>From: jdin...@magnus.acs.ohio-state.edu (Jonathan Dingwell)
>>Subject: Rowing Computer Alternatives
>>Date: 15 Jun 1995 19:18:43 GMT
>John Dingwell enquires (Condensed a bit):
>>Has anyone found anything in the way of a small computer to keep track of
>>involve the expense of a Nielsen-Kellerman (NK) or other similarly expensive
>>toy? I want one for my 1x, but as a grad student, can't really afford the NK.
>>
>>I know NK makes a great product (The new Stroke Coach now sells for $175),
>>bicycle computers which produce nearly the same information are available for
>>as little as $20 It puts out a number equal to 2x the stroke rate (e.g.
>60 >instead of 30, etc.).It works pretty well, and except for
>stroke count, gives essentially the same >info as the NK Stroke Coach.>>2)
>Many of these bike computers can also be programmed with the tire's>
>circumfrence to give accurate speeds (miles/hr) based on the wheel's size
>and>how fast it is spinning. It occurs to me that with a little numerical>
>fiddling, one could figure out what wheel circumfrence you would need to
>have>the thing output 30 mph when you were rowing 30 spm (my calculation
>gets me to >a circumference of 528in. or 1341cm
I Have been using a bike computer for years. Although an unsuspecting
person using my boat will wonder about the 60!!! The programming to
the large wheel diameter for speed display or miles rowed doesn't fit in
the allowed sizes of the Cat Eye bike computer.
I have fiddled with the prop driven speedometers. They work pretty well
at almost constant speed. However, the 30% varition in hull speed of a
rowed shell makes these things work kinda badly. [although it does
distort the speed consistently if the shell oscillates in speed about
the same way for different speeds so that you can get comparitive
readings.]
I have been awaiting the cost of GPS receivers to come down to the $150
level. It's already down to $250 for a pocket sized one made by
Magellan when it's on sale. The GPS should measure speed to 1/10 knot
which should be enough.
There was some discussion about the accuracy of GPS speed in an earlier
discussion here. The civilian band GPS has an absolute position
resolution of about 50 m. This makes it sound as if the speed
measurement should be useless for our purpose. The catch is that the
relative position for short time intervals is much, much better. The
especially good sets can measure relative positions to cm accuracy and
is used for monitoring earth movement!! For the civilian band GPS,
the military guys distort the clock output readings . However, the
distortion in NOT completely random with an equivalent rms 50 m. It's
more like random for a few m and a syste...periodic distortion to rms
50m. Thisprevents you from aiming your missiles and having them guided
to strike the silos directly!!
When I get one, I'll report the actual measured accuracy. Till then, I
hope others will report their experiences.
Regards,
Ken Young
>Andy W.
--
Ken Young Tel: 206 543 4186
Dept of Physics Box 351560 FAX: 206 685 9242
University of Washington Email: yo...@phys.washington.edu
Hamilton Richards Jr.
jdin...@magnus.acs.ohio-state.edu writes:
>Has anyone found anything in the way of a small computer to keep track of
>toy?
My Sachs Rowtronic displays
current stroke rate
stroke count since last reset
duration of workout since last reset (not counting rest periods)
and it cost me US$78. Sadly, I haven't seen it advertised for some
years.
--Ham
Moneywatch
what is the american name for the flip/flop piece that will halve the freq
output of a cycle computer cadence? can it be bought at a radio shack?
also, if anyone reads this who is currently using a cycle computer, which
one are you using?
Are they all equal when it comes to waterproofing andf length of life?