I remember a teacher I had at school who told me that When she was a girl bicycles with small wheels were all the rage. She went on to say that it requires more effort to propel a bicycle with small wheels.
I appreciate that since a smaller wheel rotates about its axis faster, there'll be more friction but above this, will there be any difference?
2007-06-13 00:37:50 · 10 answers · asked by tuthutop 2 in Science & Mathematics ➔ Engineering
Obviously I was assuming that the bike had an array of gears and the optimum gear in each case could be selected.
Therefore the gearing is not the issue!
2007-06-13 00:48:38 · update #1
Here's an easy way to think about it. A wheel is like a continous inclined plane. The smaller the diameter of the wheel the steeper the incline. So a larger diameter wheel will always have lower rolling friction (between the wheel and the surface). Its not only the size but the material that matters. Because the wheel deforms slightly at the contact point. For pneumatic tires this deformation forms a contact patch which is flat. Thats why cars are not as efficient as rails.
The steel wheels on steel track deform very little and the rolling friction is very small for a train.
Rotating faster won't necessarily increase the friction at the wheel axle. The reason is rolling friction between the wheel and the surface supporting it.
2007-06-13 02:26:37 · answer #1 · answered by Roadkill 6 · 0⤊ 0⤋
In fact, there is no much differences... I explain myself
If you take the example of bicycles:
1) If the tyres have the same width, road friction will be the same as it depends on the distance you do and the friction of the tyre (which depends only on structure, width and material used to make it, not on diameter).
So, for example a 700x23 tyre using the same technology as a 600x23 will have the same friction even if the smaller rotates more because at the end, you will have done the same distance.
2) The effort (force) you need to pull your bike will not depend on the gear OR the size of the wheel, but on BOTH together!. In fact it depends on the distance per revolution of pedals. Therefore with a smaller wheel, you can take a longer gear.
With the same gear, you can pedal faster with a smaller wheel or harder with a bigger one.
3) A smaller wheel has less wind friction and is a bit lighter.
4) The same bike with bigger wheels has a better balance.
So in conclusion, if you want to put smaller wheels on your bicycle, change the cranks to inversely (and proportionally) bigger ones.
And it is the same for any means of transport...
2007-06-13 08:29:54 · answer #2 · answered by Rosamonte2000 2 · 0⤊ 0⤋
A small wheel and a large wheel will move around their axis at the same speed. It is nothing to do with friction.
If you think of a four spoked wheel and measure the distance between two of the spokes at a set distance from the axis, and then take another measurement at a distance further away from the axis, then the second measurement will be greater than the first.
If the total wheel size is equivalent to the first measurement then the circumference of that wheel will be smaller that the circumference of a wheel measured from the second measurement.
These differing sizes of circumference represent the distance travelled for the same movement of the axis for each wheel - the axis movement will be the same for each wheel, but the larger will propel you further for each single revolution.
So in fact the same effort is required (not taking into account any weight differences) for each wheel, but the large one will take you further, which means than for a set distance you will require fewer revolutions, resulting in less total energy output.
2007-06-13 07:55:57 · answer #3 · answered by sicoll007 4 · 0⤊ 2⤋
The business about size of railway wheels versus friction was something the 19thC engineer I.K.Brunel had a thing about. Sadly, this is one theory he was wrong about and the size of the wheel is virtually irrelevant. (The size of driving wheels on locomotives is not what he was talking about here)
Small wheels and large wheels on bikes is another matter. The use of either size wheel is compensated for by the gearing ratio in the chain drive design.
2007-06-13 07:47:15 · answer #4 · answered by efes_haze 5 · 1⤊ 1⤋
it is easier to keep your balance with larger wheels.
the Gyroscopic effect of a spinning wheel has a tendancy to keep itself upright. this effect is stronger when the wheel has more mass and better at keeping the bicycle level when the center of rotation is higher. (so a small but heavy wheel still wouldnt be as good).
2007-06-13 10:17:31 · answer #5 · answered by only1doug 4 · 0⤊ 0⤋
The same as on a car, the smaller the wheel (or more importantly, the tire) the less energy it will take to rotate it. There will be more friction on the hub and bearings, but it is virtually insignificant.
2007-06-13 07:43:27 · answer #6 · answered by sakotgrimes 4 · 1⤊ 2⤋
A smaller wheel requires more revolutions as a bigger wheel. Therefore you have to pedal further on a bike with smaller wheels.
2007-06-13 07:41:56 · answer #7 · answered by simon j 3 · 1⤊ 2⤋
in the same gear, it will take more effort to cycle with a bigger wheel. for each revolution of the pedals you will move furthur with big wheels though
2007-06-13 07:41:43 · answer #8 · answered by Anonymous · 0⤊ 1⤋
Smaller wheel = more revolutions to cover X miles.
2007-06-13 07:45:52 · answer #9 · answered by Dave 3 · 1⤊ 2⤋
because it has a much smaller circumference
2007-06-13 07:42:21 · answer #10 · answered by georgekb81 2 · 0⤊ 2⤋