The Naked Scientists
  • Login
  • Register
  • Podcasts
      • The Naked Scientists
      • eLife
      • Naked Genetics
      • Naked Astronomy
      • In short
      • Naked Neuroscience
      • Ask! The Naked Scientists
      • Question of the Week
      • Archive
      • Video
      • SUBSCRIBE to our Podcasts
  • Articles
      • Science News
      • Features
      • Interviews
      • Answers to Science Questions
  • Get Naked
      • Donate
      • Do an Experiment
      • Science Forum
      • Ask a Question
  • About
      • Meet the team
      • Our Sponsors
      • Site Map
      • Contact us

User menu

  • Login
  • Register
  • Home
  • Help
  • Search
  • Tags
  • Member Map
  • Recent Topics
  • Login
  • Register
  1. Naked Science Forum
  2. Non Life Sciences
  3. Physics, Astronomy & Cosmology
  4. Why do bicycles have such big wheels?
« previous next »
  • Print
Pages: [1] 2 3 4   Go Down

Why do bicycles have such big wheels?

  • 70 Replies
  • 35796 Views
  • 0 Tags

0 Members and 1 Guest are viewing this topic.

Offline Geezer (OP)

  • Naked Science Forum King!
  • ******
  • 8314
  • Activity:
    0%
  • Thanked: 7 times
  • "Vive la résistance!"
    • View Profile
Why do bicycles have such big wheels?
« on: 05/09/2009 17:05:52 »
Well, most bicycles anyway. Is it a macho thing? "Hey, look at the size of my wheels!" or do big wheels serve a useful purpose?

(Lights blue touchpaper and retires.)
Logged
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.
 



Offline RD

  • Naked Science Forum King!
  • ******
  • 8883
  • Activity:
    4%
  • Thanked: 138 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #1 on: 05/09/2009 17:25:40 »
Not all do ...

 [ Invalid Attachment ]
http://www.treehugger.com/files/2007/11/marking_the_spo.php

Above smaller wheels have been used for portability.

The smaller tyres on smaller wheels will wear out quicker than larger tyres on larger wheels.
(ditto for hubs and spindles).

* X-bike.jpg (85.56 kB, 468x166 - viewed 5127 times.)
« Last Edit: 05/09/2009 17:36:30 by RD »
Logged
 

Offline syhprum

  • Naked Science Forum King!
  • ******
  • 4816
  • Activity:
    8%
  • Thanked: 56 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #2 on: 05/09/2009 17:29:20 »
Cyclists like to operate in a near vertical position so big wheels are needed to accommodate their legs also they have less rolling resistance and ride the bumps better.
Logged
syhprum
 

Offline Geezer (OP)

  • Naked Science Forum King!
  • ******
  • 8314
  • Activity:
    0%
  • Thanked: 7 times
  • "Vive la résistance!"
    • View Profile
Why do bicycles have such big wheels?
« Reply #3 on: 05/09/2009 17:33:26 »
Quote from: RD on 05/09/2009 17:25:40
Not all do ...

 [ Invalid Attachment ]
http://www.treehugger.com/files/2007/11/marking_the_spo.php

Above smaller wheels have been used for portability.

The smaller tyres on smaller wheels will wear out quicker than larger on larger wheels.

Wow! I'd like to see one of them in the Tour de France.
Logged
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.
 

Offline RD

  • Naked Science Forum King!
  • ******
  • 8883
  • Activity:
    4%
  • Thanked: 138 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #4 on: 05/09/2009 17:52:42 »
The bigger the diameter of the wheel the less the cyclists energy is lost to friction,
 so for maximum speed/efficiency the bigger the better.
Logged
 



Offline John Chapman

  • Hero Member
  • *****
  • 602
  • Activity:
    0%
    • View Profile
Why do bicycles have such big wheels?
« Reply #5 on: 06/09/2009 02:45:13 »
Presumably the frictional benefits are in the spindles. Larger wheels spin at slower RPM to cover the same distance.

There are also tranmission benefits to having a large driving wheel. Otherwise the front (pedal) sprocket would have to be enormous to gain the same benefit.
 
Logged
 

Offline lightarrow

  • Naked Science Forum King!
  • ******
  • 4605
  • Activity:
    0%
  • Thanked: 12 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #6 on: 06/09/2009 03:00:29 »
Quote from: John Chapman on 06/09/2009 02:45:13
Presumably the frictional benefits are in the spindles. Larger wheels spin at slower RPM to cover the same distance.

There are also tranmission benefits to having a large driving wheel. Otherwise the front (pedal) sprocket would have to be enormous to gain the same benefit.
 
Also, the equilibrium on the bicycle is more difficult with little wheels because of little gyroscopic effect.
Logged
 

Offline syhprum

  • Naked Science Forum King!
  • ******
  • 4816
  • Activity:
    8%
  • Thanked: 56 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #7 on: 06/09/2009 11:59:31 »
Do the gyroscopic effects play any part in the equilibrium of bicycles ?
I thought that tests had been made with bicycles fitted with contra rotating wheels that were found to be little if any more difficult to ride than regular ones.
Logged
syhprum
 

lyner

  • Guest
Why do bicycles have such big wheels?
« Reply #8 on: 06/09/2009 12:48:30 »
The Moment of Inertia of a bicycle wheel is pretty small (particularly a light weight racing wheel)  so is it really likely to have much effect?

Surely the biggest advantage of big wheels is that the footprint is longer for a given tyre pressure. This will mean that the distortion , and hence the losses / internal friction will be less. The better efficiency of the transmission with big wheels will also be a factor, natch, but tyre friction is sure to be a major factor.

btw, does anyone know of any work done cycling on rails / steel track, with steel wheels. (Obviously, stabilisers could be needed). There may be a world record out there for someone.

There is also the issue of ironing out bumps in the road but neither this nor any (possible?) balancing help would not be relevant for competitive cycling on high quality cycle tracks. Pros would cycle on 10cm wheels if there was a speed advantage.
Logged
 



Offline LeeE

  • Naked Science Forum King!
  • ******
  • 3382
  • Activity:
    0%
  • Thanked: 1 times
    • View Profile
    • Spatial
Why do bicycles have such big wheels?
« Reply #9 on: 06/09/2009 17:55:24 »
Quote from: RD on 05/09/2009 17:52:42
The bigger the diameter of the wheel the less the cyclists energy is lost to friction,
 so for maximum speed/efficiency the bigger the better.

Hmm... on a hard surface, a smaller wheel will have a smaller area of contact than a larger wheel, so a smaller wheel should offer less rolling resistance than a larger wheel.

A smaller wheel would impose a higher pressure upon the surface it's traveling across though, so if you're traveling across an unmetalled surface you'll sink further into it with a smaller wheel than with a larger wheel, which will raise the rolling resistance.  The larger wheel, with it's larger contact area, will sink less on a soft surface, so it's rolling resistance will be more constant across hard and soft surfaces.  This was an issue when the first bicycles were invented, as many 'roads' were unmetalled.

Smaller wheels are also more susceptible to bumps, irregularities and even stones on the surface.  Obviously, a wheel cannot roll over an obstacle unless the height of the obstacle is less than the radius of the wheel, so larger wheels can roll over larger obstacles than smaller wheels, but even when the obstacle is small enough that both large and small wheels can roll over it, the larger wheel, with its reduced curve, will intercept the obstacle sooner than a small wheel and result in a lower vertical acceleration as the wheel passes over it; in short, a larger wheel is more comfortable than a smaller wheel.
Logged
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!
 

Offline Geezer (OP)

  • Naked Science Forum King!
  • ******
  • 8314
  • Activity:
    0%
  • Thanked: 7 times
  • "Vive la résistance!"
    • View Profile
Why do bicycles have such big wheels?
« Reply #10 on: 06/09/2009 18:02:44 »
Quote from: sophiecentaur on 06/09/2009 12:48:30
btw, does anyone know of any work done cycling on rails / steel track, with steel wheels. (Obviously, stabilisers could be needed). There may be a world record out there for someone.

No data. But these guys might have some. (Note very small front wheel). There are several kits available to convert a regular bike into a rail bike.

http://www.railbike.com/buying.htm
Logged
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.
 

Offline lightarrow

  • Naked Science Forum King!
  • ******
  • 4605
  • Activity:
    0%
  • Thanked: 12 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #11 on: 06/09/2009 18:25:08 »
Quote from: syhprum on 06/09/2009 11:59:31
Do the gyroscopic effects play any part in the equilibrium of bicycles ?
I thought that tests had been made with bicycles fitted with contra rotating wheels that were found to be little if any more difficult to ride than regular ones.
I don't know of those tests; anyway gyroscopic effect should play some part: it's not easy to stay in equilibrium on a bicycle which is not moving, but as soon as it moves it's much more easy; why?
Logged
 

Offline LeeE

  • Naked Science Forum King!
  • ******
  • 3382
  • Activity:
    0%
  • Thanked: 1 times
    • View Profile
    • Spatial
Why do bicycles have such big wheels?
« Reply #12 on: 06/09/2009 19:06:44 »
Quote from: lightarrow on 06/09/2009 18:25:08
Quote from: syhprum on 06/09/2009 11:59:31
Do the gyroscopic effects play any part in the equilibrium of bicycles ?
I thought that tests had been made with bicycles fitted with contra rotating wheels that were found to be little if any more difficult to ride than regular ones.
I don't know of those tests; anyway gyroscopic effect should play some part: it's not easy to stay in equilibrium on a bicycle which is not moving, but as soon as it moves it's much more easy; why?

When a bicycle is stationary you can only keep it in balance by moving your weight from side to side to keep your CoG over the wheels.  This isn't an ideal solution because you're moving the larger of the two masses instead of the smaller to maintain balance.  Moving the larger of the two masses also requires more force to be used.  When the bicycle is moving though, this is reversed and instead you steer the smaller mass of the bicycle to keep it beneath the larger mass of yourself, with consequently less force being required to do so.

The steering process is also more progressive than than simply moving your body from side to side because the bicycle follows the sum of the forward and steering vectors, instead of just the sideways vector, giving a finer degree of control.
Logged
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!
 



Offline John Chapman

  • Hero Member
  • *****
  • 602
  • Activity:
    0%
    • View Profile
Why do bicycles have such big wheels?
« Reply #13 on: 06/09/2009 19:36:48 »
That was well explained LeeE.

You'd make a good teacher  [:)]
Logged
 

lyner

  • Guest
Why do bicycles have such big wheels?
« Reply #14 on: 06/09/2009 20:14:50 »
Quote from: lightarrow on 06/09/2009 18:25:08
Quote from: syhprum on 06/09/2009 11:59:31
Do the gyroscopic effects play any part in the equilibrium of bicycles ?
I thought that tests had been made with bicycles fitted with contra rotating wheels that were found to be little if any more difficult to ride than regular ones.

I don't know of those tests; anyway gyroscopic effect should play some part: it's not easy to stay in equilibrium on a bicycle which is not moving, but as soon as it moves it's much more easy; why?
I thought we'd been here before. You can make a bike which is impossible to ride by having the front forks so that the line of the top bracket hitting the ground behind the point of contact with the wheels. Gyroscopic action is the same in both cases. It has to be the castor action which steers the front wheel to produce a moment to push you upright. I have done diagrams which satisfy me but they wouldn't work on a post here cos I need to wave arms at the same time! [;)]
Logged
 

Offline syhprum

  • Naked Science Forum King!
  • ******
  • 4816
  • Activity:
    8%
  • Thanked: 56 times
    • View Profile
Why do bicycles have such big wheels?
« Reply #15 on: 06/09/2009 20:37:49 »
Research has also been done on this matter, bicycles fitted with gearing that causes the forks to rotate in the reverse manner to the handlebar's can be ridden with practice but it is not as instinctive as riding a normal machine.
With a zero castor angle the steering would be heavy but could be learnt.
As a boy I practiced riding a bicycle with ropes tied to the handlebar's like reins, by crossing the ropes you could produce the same effect as the reverse geared steering.
Logged
syhprum
 

Offline Geezer (OP)

  • Naked Science Forum King!
  • ******
  • 8314
  • Activity:
    0%
  • Thanked: 7 times
  • "Vive la résistance!"
    • View Profile
Why do bicycles have such big wheels?
« Reply #16 on: 06/09/2009 20:48:58 »
Wasn't there something called the Moulton bicycle produced in the 60's? It had much smaller wheels. I think Raleigh produced something similar, but it had wider tires. As I seem to recall, they actually worked quite well, certainly on well paved surfaces.

(I just Googled Moulton - still seems to be going strong.)

http://www.moultonbicycles.co.uk/index.html
Logged
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.
 



lyner

  • Guest
Why do bicycles have such big wheels?
« Reply #17 on: 06/09/2009 22:17:07 »
syphrum
Did you run away and join the circus?
Logged
 

Offline that mad man

  • Hero Member
  • *****
  • 724
  • Activity:
    0%
    • View Profile
    • My music
Why do bicycles have such big wheels?
« Reply #18 on: 06/09/2009 22:24:00 »
Sir Clive Sinclair developed a portable folding bike with small wheels called the A-Bike and was described by some as a bit "wobbly" because of the size of the wheels.

I remember a science lesson at school when we had several sized bicycle wheels each mounted on a small axle that we could hold in outstretched arms. We sat on a desk type chair (one on wheels) and held the bicycle wheel out in front of us. Someone then spun the wheel and then we were asked to tilt the wheel from the vertical and also simulate it turning like a bikes front wheel.

The outcome was the chair, with you in it, spun round a bit. The different sized wheels produced different sized effects with the larger wheels producing greater effects. Unfortunately that was years ago and I cant remember exactly what that lesson was about but I think it was something to do with the gyroscope effect. [:I]

Logged
 

Offline Turveyd

  • Jr. Member
  • **
  • 25
  • Activity:
    0%
    • View Profile
Why do bicycles have such big wheels?
« Reply #19 on: 06/09/2009 23:40:33 »

As a Mountain Biker who's messed with wheel sizes and has been running a 29" wheel on the front of a standard normal 26" wheel for 2years,  I can safely say the main advantage is it takes longer from contact to highest spot therefore the peak bump force is lower,  therefore they ride smoother over rough ground which makes them more efficent as they stall less,  which leads to going over the bars and pain and maybe even a broken kneck!!

There is a slight drop in rolling resistance,  the foot print becomes slightly longer but narrorow and the narrower part helps in short,  for the same air pressure though the overall size is unchanged.

Logged
 



  • Print
Pages: [1] 2 3 4   Go Up
« previous next »
Tags:
 

Similar topics (5)

Can water be lifted using electrical equivalents of ancient water wheels?

Started by newrobertBoard Technology

Replies: 22
Views: 13208
Last post 04/12/2014 22:40:14
by syhprum
Why do car wheels seem to spin backwards, when at high speed?

Started by SeanyBoard General Science

Replies: 13
Views: 37307
Last post 07/07/2007 18:30:36
by Soul Surfer
Why do car wheels seem to go backwards when illuminated by street lights?

Started by Dan HoltonBoard General Science

Replies: 7
Views: 8113
Last post 09/03/2015 13:34:49
by larrylee
Is a 3-wheeled car more stable if two of the wheels are at the front?

Started by JPBoard Physics, Astronomy & Cosmology

Replies: 19
Views: 16349
Last post 02/07/2008 18:42:53
by Bored chemist
Why can wheels appear to be turning backwards at certain speeds?

Started by thedocBoard Physiology & Medicine

Replies: 1
Views: 1312
Last post 12/10/2016 19:36:26
by chris
There was an error while thanking
Thanking...
  • SMF 2.0.15 | SMF © 2017, Simple Machines
    Privacy Policy
    SMFAds for Free Forums
  • Naked Science Forum ©

Page created in 0.212 seconds with 83 queries.

  • Podcasts
  • Articles
  • Get Naked
  • About
  • Contact us
  • Advertise
  • Privacy Policy
  • Subscribe to newsletter
  • We love feedback

Follow us

cambridge_logo_footer.png

©The Naked Scientists® 2000–2017 | The Naked Scientists® and Naked Science® are registered trademarks created by Dr Chris Smith. Information presented on this website is the opinion of the individual contributors and does not reflect the general views of the administrators, editors, moderators, sponsors, Cambridge University or the public at large.