Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

A different way of measuring bicycle speed

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

A different way of measuring bicycle speed

Old 11-25-17, 04:29 PM
  #1  
rollagain
Lopsided biped
Thread Starter
 
rollagain's Avatar
 
Join Date: Nov 2017
Location: NE Ohio
Posts: 603

Bikes: 2017 Day 6 Cyclone (the Buick); 2015 Simcoe Deluxe (the Xebec); Street Strider 3i (the not-a-bike)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 248 Post(s)
Liked 87 Times in 49 Posts
A different way of measuring bicycle speed

NOTE: Mods, feel free to move this if you think it belongs somewhere else.
--------------------------
To the best of my knowledge, all cyclometers measure bicycle speed by counting pulses from a magnet attached to a spoke. If someone does it differently, feel free to correct my ignorance.

I got to thinking about using a different method that would give more accurate readings, especially at low speeds, by using a light beam. Light source on one side of the wheel, photocell on the other side; the detector circuit would count the interruptions of the beam from each individual spoke. Compared to the magnetic-pulse method, this scheme would increase the precision of the reading by a factor equal to the number of spokes in the wheel.

Small details, of course; the light source would have to be modulated and/or color filtered to prevent interference and false signals from environmental sources. The assembly would need to read the spokes far enough inward from the rim to avoid being triggered by the valve stem. Probably other little problems; the pulse train would be a little uneven due to cross-pattern spoke spacing, but I think that one could be fixed with a corrective algorithm in the detector circuit.

BIG problems: mud, snow, ice, maybe even just rainwater or puddle-splashes. Not sure if a shield of some sort could solve those.

It got crazier from there--maybe. I was thinking of high-frequency-modulated light sources, coupled with little mirrors, and realized I've got one right in front of me--an optical computer mouse. What would happen if you pointed one of those at, say, the sidewall of your tire? I wouldn't be surprised if it would give a reading, but you'd have to have it awfully close or else rework the design of it. Same problems with fouling from mud, etc.

Thoughts?
rollagain is offline  
Old 11-25-17, 04:30 PM
  #2  
fietsbob
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,599

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,322 Times in 832 Posts
Furlongs per Fortnight?
fietsbob is offline  
Old 11-25-17, 04:32 PM
  #3  
rollagain
Lopsided biped
Thread Starter
 
rollagain's Avatar
 
Join Date: Nov 2017
Location: NE Ohio
Posts: 603

Bikes: 2017 Day 6 Cyclone (the Buick); 2015 Simcoe Deluxe (the Xebec); Street Strider 3i (the not-a-bike)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 248 Post(s)
Liked 87 Times in 49 Posts
Sure, or leagues per lunar cycle if you like. ;-)
rollagain is offline  
Old 11-25-17, 04:38 PM
  #4  
prathmann
Senior Member
 
Join Date: Nov 2008
Location: Bay Area, Calif.
Posts: 7,239
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 659 Post(s)
Likes: 0
Liked 4 Times in 3 Posts
It could give slightly faster response when your speed is changing but wouldn't really be different in accuracy from the standard method. The old Avocet models used a Hall effect sensor together with a special circular band at the hub that produced multiple pulses per revolution (20?) for the same effect
prathmann is offline  
Old 11-25-17, 04:42 PM
  #5  
europa
Grumpy Old Bugga
 
europa's Avatar
 
Join Date: Oct 2006
Location: Adelaide, AUSTRALIA
Posts: 4,229

Bikes: Hillbrick, Malvern Star Oppy S2, Europa (R.I.P.)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 370 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
The simple magnet triggered cyclometers are cheap and reliable. For those wanting a bit more, GPS units are now solid and reliable, though not cheap. I'm not saying "don't do it", just that you may have trouble finding a niche for the new system.

On the other hand, if all you're after is a fascinating project, go for it.

I'm reminded of car and motorcycle ABS systems which, I believe, use an optical system to read if the disc the sensor reads (don't know its name) is still spinning.
europa is offline  
Old 11-25-17, 04:50 PM
  #6  
HillRider
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 32,905

Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!

Mentioned: 38 Post(s)
Tagged: 0 Thread(s)
Quoted: 1687 Post(s)
Likes: 0
Liked 564 Times in 417 Posts
There is nothing so simple we can't complicate it.
HillRider is offline  
Old 11-25-17, 05:12 PM
  #7  
TimothyH
- Soli Deo Gloria -
 
Join Date: Aug 2015
Location: Northwest Georgia
Posts: 14,782

Bikes: 2018 Rodriguez Custom Fixed Gear, 2017 Niner RLT 9 RDO, 2015 Bianchi Pista, 2002 Fuji Robaix

Mentioned: 235 Post(s)
Tagged: 0 Thread(s)
Quoted: 6837 Post(s)
Liked 702 Times in 447 Posts
Originally Posted by rollagain View Post
all cyclometers measure bicycle speed by counting pulses from a magnet attached to a spoke.
Garmin wireless speed sensors using a magnetometer which references against the earth's magnetic field.

Others use accelerometers.


-Tim-
TimothyH is offline  
Old 11-25-17, 05:36 PM
  #8  
dieselrover
Senior Member
 
Join Date: Aug 2006
Posts: 59
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 24 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
If precision is your goal, then todays microelectromechanical sensors that you find in the wheel-hub devices of Wahoo and Garmin et al. will typically measure on the order of 12 bits of resolution (~4000 values) with maybe a conservative 8 bits of usable data (~250 values). These are based on accelerometers, measuring the force of gravity as the wheel spins around and around or magnetometers as stated before.

You'd need a lot of spokes to reach that level of precision.

https://support.garmin.com/faqSearch...Jd3Tnyif9jRSy6


s
dieselrover is offline  
Old 11-25-17, 06:10 PM
  #9  
bike_galpal
Banned.
 
Join Date: Jul 2015
Location: Oakland, CA
Posts: 415

Bikes: Swobo Sanchez 3x1

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 137 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
bike_galpal is offline  
Old 11-25-17, 07:19 PM
  #10  
Moose
Senior Member
 
Join Date: Jul 2001
Posts: 1,396
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 140 Post(s)
Liked 0 Times in 0 Posts
Originally Posted by rollagain View Post
NOTE: Mods, feel free to move this if you think it belongs somewhere else.
--------------------------
To the best of my knowledge, all cyclometers measure bicycle speed by counting pulses from a magnet attached to a spoke. If someone does it differently, feel free to correct my ignorance.

I got to thinking about using a different method that would give more accurate readings, especially at low speeds, by using a light beam. Light source on one side of the wheel, photocell on the other side; the detector circuit would count the interruptions of the beam from each individual spoke. Compared to the magnetic-pulse method, this scheme would increase the precision of the reading by a factor equal to the number of spokes in the wheel.

Small details, of course; the light source would have to be modulated and/or color filtered to prevent interference and false signals from environmental sources. The assembly would need to read the spokes far enough inward from the rim to avoid being triggered by the valve stem. Probably other little problems; the pulse train would be a little uneven due to cross-pattern spoke spacing, but I think that one could be fixed with a corrective algorithm in the detector circuit.

BIG problems: mud, snow, ice, maybe even just rainwater or puddle-splashes. Not sure if a shield of some sort could solve those.

It got crazier from there--maybe. I was thinking of high-frequency-modulated light sources, coupled with little mirrors, and realized I've got one right in front of me--an optical computer mouse. What would happen if you pointed one of those at, say, the sidewall of your tire? I wouldn't be surprised if it would give a reading, but you'd have to have it awfully close or else rework the design of it. Same problems with fouling from mud, etc.

Thoughts?
Your method would still rely on calculating speed using a formula relating to the tire's roll out distance. The system would be just as compromised by the the variations in circumference of tires as the system you are trying to improve. Doubtful that any accuracy achieved by counting spokes rather than the magnet's complete revolution would overcome the margin of error in the tire's actual roll-out distance.
Moose is offline  
Old 11-25-17, 07:24 PM
  #11  
pvillemasher
Senior Member
 
pvillemasher's Avatar
 
Join Date: Sep 2013
Location: Austin Texas USA
Posts: 343

Bikes: 1989 Trek 400, 2000 Lemond Buenos Aires, 2013 GT Attack, 2017 Lynskey R250

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 126 Post(s)
Liked 11 Times in 9 Posts
Solution looking for a problem
pvillemasher is offline  
Old 11-25-17, 07:37 PM
  #12  
rollagain
Lopsided biped
Thread Starter
 
rollagain's Avatar
 
Join Date: Nov 2017
Location: NE Ohio
Posts: 603

Bikes: 2017 Day 6 Cyclone (the Buick); 2015 Simcoe Deluxe (the Xebec); Street Strider 3i (the not-a-bike)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 248 Post(s)
Liked 87 Times in 49 Posts
Originally Posted by pvillemasher View Post
Solution looking for a problem
That's mostly what I expected. Fun to play with ideas, though, and thanks everyone for the contributions.
rollagain is offline  
Old 11-25-17, 07:42 PM
  #13  
sweeks
Senior Member
 
sweeks's Avatar
 
Join Date: Sep 2004
Location: Chicago area
Posts: 1,743

Bikes: Airborne "Carpe Diem", Motobecane "Mirage", Trek 6000, Strida 2, Dahon "Helios XL", Dahon "Mu XL", Tern "Verge S11i"

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 684 Post(s)
Liked 194 Times in 150 Posts
Originally Posted by prathmann View Post
The old Avocet models used a Hall effect sensor together with a special circular band at the hub that produced multiple pulses per revolution (20?) for the same effect
I still have one of these! Simple by today's standards, but it worked well.
Steve
sweeks is offline  
Old 11-25-17, 07:44 PM
  #14  
Dean51 
Senior Member
 
Dean51's Avatar
 
Join Date: Feb 2016
Location: Olympic Peninsula, WA
Posts: 502

Bikes: '83 YKonno Allez, '82 Ron Cooper, '87 Ciocc Designer 84, '95 Trek Saturn, '86 Tommasini Racing, '98 S-Works Hardtail Mtn., Klein Quantum Singlespeed

Mentioned: 32 Post(s)
Tagged: 0 Thread(s)
Quoted: 177 Post(s)
Liked 101 Times in 53 Posts
Originally Posted by pvillemasher View Post
Solution looking for a problem
+1

Dean
Dean51 is offline  
Old 11-25-17, 09:44 PM
  #15  
HillRider
Senior Member
 
Join Date: Aug 2005
Location: Pittsburgh, PA
Posts: 32,905

Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!

Mentioned: 38 Post(s)
Tagged: 0 Thread(s)
Quoted: 1687 Post(s)
Likes: 0
Liked 564 Times in 417 Posts
Originally Posted by sweeks View Post
I still have one of these! Simple by today's standards, but it worked well.
Steve
I had Avocet cyclometers starting in 1986. The early ones were very good, the later ones not so much.
HillRider is offline  
Old 11-25-17, 09:58 PM
  #16  
sweeks
Senior Member
 
sweeks's Avatar
 
Join Date: Sep 2004
Location: Chicago area
Posts: 1,743

Bikes: Airborne "Carpe Diem", Motobecane "Mirage", Trek 6000, Strida 2, Dahon "Helios XL", Dahon "Mu XL", Tern "Verge S11i"

Mentioned: 18 Post(s)
Tagged: 0 Thread(s)
Quoted: 684 Post(s)
Liked 194 Times in 150 Posts
Originally Posted by HillRider View Post
I had Avocet cyclometers starting in 1986. The early ones were very good, the later ones not so much.
Mine was on my first "new" bike, a Motobecane Mirage I bought in 1975. After all this time, I'm restoring this bike because I like it. I could use the old Avocet computer... it would match the Avocet saddle.
Steve
sweeks is offline  
Old 11-25-17, 10:03 PM
  #17  
gregf83 
Senior Member
 
Join Date: Jun 2008
Location: Vancouver, BC
Posts: 9,202
Mentioned: 11 Post(s)
Tagged: 0 Thread(s)
Quoted: 1185 Post(s)
Liked 286 Times in 174 Posts
Originally Posted by rollagain View Post
I got to thinking about using a different method that would give more accurate readings, especially at low speeds, by using a light beam.
Your solution would have higher resolution but be no more accurate than a system counting wheel revolutions.

The challenge in either system is to determine how far you travel per wheel revolution.
gregf83 is offline  
Old 11-25-17, 10:09 PM
  #18  
KD5NRH
Senior Member
 
KD5NRH's Avatar
 
Join Date: Jul 2010
Location: Stephenville TX
Posts: 3,697

Bikes: 2010 Trek 7100

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 697 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by TimothyH View Post
Garmin wireless speed sensors using a magnetometer which references against the earth's magnetic field.

Others use accelerometers.
Others do neither: https://www.walmart.com/ip/Bicycles-...eter/401844238
KD5NRH is offline  
Old 11-25-17, 10:36 PM
  #19  
TimothyH
- Soli Deo Gloria -
 
Join Date: Aug 2015
Location: Northwest Georgia
Posts: 14,782

Bikes: 2018 Rodriguez Custom Fixed Gear, 2017 Niner RLT 9 RDO, 2015 Bianchi Pista, 2002 Fuji Robaix

Mentioned: 235 Post(s)
Tagged: 0 Thread(s)
Quoted: 6837 Post(s)
Liked 702 Times in 447 Posts
Originally Posted by KD5NRH View Post
That thing doesn't make sense.

The inner scale goes from zero to 400+ and is either RPM or km/hr.
TimothyH is offline  
Old 11-25-17, 11:39 PM
  #20  
79pmooney
A Roadie Forever
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 9,666

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 103 Post(s)
Tagged: 0 Thread(s)
Quoted: 2989 Post(s)
Liked 1,587 Times in 1,051 Posts
Originally Posted by europa View Post
The simple magnet triggered cyclometers are cheap and reliable. For those wanting a bit more, GPS units are now solid and reliable, though not cheap. I'm not saying "don't do it", just that you may have trouble finding a niche for the new system.

On the other hand, if all you're after is a fascinating project, go for it.

I'm reminded of car and motorcycle ABS systems which, I believe, use an optical system to read if the disc the sensor reads (don't know its name) is still spinning.
I never thought of this before but I wonder if the circuitry in ABS is similar to that of the SawStop, a system that detects a change in electrical resistance from flesh contacting a power saw blade developed for chop saws used by lumber mills. (I spent a little time working for an engineer designing chopsaws for one of the early outfits to buy a license for the stop. In those days you would draw blood from a small nick. Apparently they stop the blade even faster now.) One significant difference - the blade and stop get destroyed but we get to use out ABS repeatedly.

Ben
79pmooney is offline  
Old 11-25-17, 11:41 PM
  #21  
europa
Grumpy Old Bugga
 
europa's Avatar
 
Join Date: Oct 2006
Location: Adelaide, AUSTRALIA
Posts: 4,229

Bikes: Hillbrick, Malvern Star Oppy S2, Europa (R.I.P.)

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 370 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by TimothyH View Post
That thing doesn't make sense.

The inner scale goes from zero to 400+ and is either RPM or km/hr.
You can't ride at 400 km/hr? All you need is a decent hill
europa is offline  
Old 11-25-17, 11:46 PM
  #22  
KD5NRH
Senior Member
 
KD5NRH's Avatar
 
Join Date: Jul 2010
Location: Stephenville TX
Posts: 3,697

Bikes: 2010 Trek 7100

Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 697 Post(s)
Likes: 0
Liked 2 Times in 2 Posts
Originally Posted by TimothyH View Post
That thing doesn't make sense.

The inner scale goes from zero to 400+ and is either RPM or km/hr.
Wheel RPM makes sense. OTOH, that would mean the gauge can only read an accurate speed with one wheel size somewhere around 24".
KD5NRH is offline  
Old 11-26-17, 01:46 AM
  #23  
alias5000
Senior Member
 
Join Date: Apr 2016
Location: Ontario
Posts: 532

Bikes: HP Velotechnik Streetmachine GTE, 2015 Devinci Silverstone SL4, 2012 Cannondale Road Tandem 2, 2007 Trek 6000, Circe Morpheus

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 169 Post(s)
Liked 9 Times in 8 Posts
Originally Posted by rollagain View Post
Light source on one side of the wheel, photocell on the other side; the detector circuit would count the interruptions of the beam from each individual spoke. Compared to the magnetic-pulse method, this scheme would increase the precision of the reading by a factor equal to the number of spokes in the wheel.
You can have that much easier with existing technology. Mount a magnet on each (/every other) spoke and divide the wheel circumference in your bike computer by the number of magnets installed.
alias5000 is offline  
Old 11-26-17, 06:52 AM
  #24  
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,192

Bikes: Catrike 559 I own some others but they don't get ridden very much.

Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1558 Post(s)
Liked 561 Times in 326 Posts
The way that you improve precision is by reducing measuring errors. Success can only be achieved by minimizing the biggest errors.

I'm thinking the greatest measuring errors in a wheel driven odometer come from inaccurate wheel circumference input measurements and riding an inconsistent path.

It doesn't matter how many wheel pulses you count per revolution if your circumference measurement is off.
It doesn't matter how accurately you count each revolution of the wheel if repeated rides don't exactly follow the same path.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.

Last edited by Retro Grouch; 11-26-17 at 06:57 AM.
Retro Grouch is offline  
Old 11-26-17, 08:05 AM
  #25  
wphamilton
Senior Member
 
wphamilton's Avatar
 
Join Date: Apr 2011
Location: Alpharetta, GA
Posts: 15,280

Bikes: Nashbar Road

Mentioned: 71 Post(s)
Tagged: 0 Thread(s)
Quoted: 2932 Post(s)
Liked 333 Times in 223 Posts
The optical switch speedometer has been tried, usually with a spinning disk with holes mounted on the wheel, and has the great advantage of more frequent data, and more precise data. Which is a big "don't care" for the usual speedometer usage but can be useful otherwise. I think it may be possible but tricky to use the spokes, but if you're going to have a shield anyway for environmental factors why not just use the perforated disk in the first place?

Using an optical/laser mouse seems like a shortcut until you have to place it right up against a surface and try to make that work. If you're going to have to buy a few high quality lenses and experiment to make a mouse work it defeats the purpose of using the mouse. Expensive, extra trouble. Your first plan with a laser with detector is more practical.
wphamilton is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.