Bicycle-related science

D.M. Procida said:

Tomorrow night, our theme at Cardiff Woodcraft Folk:

<http://cardiffwoodcraft.org.uk/>

is "scientific curiosity".

I'll take in a bicycle wheel, to explore gyroscopic effects, but I
wondered if it's worth taking a whole bike. Is there anything else
surprising and hands-on to be discovered in the science of the bicyle?

The children are aged six to ten.

Thanks,

Daniele

The strength - to weight ratio of the wheel is remarkable, although I
don't know how you would demonstrate it.
I wonder if you could identify the tightest spokes on a heavily loaded
wheel by plucking them? That'll surprise most people.
The physics of the steering is interesting too. (see "countersteering,
discussed ad nauseam on this group). Maybe you could perform the
definitive experiment!
Get them to push a bike forward by the saddle and demonstrate castor,
then try it backwards.
Demonstrate lights and reflectors.
Dynamos.
Ball bearings.

roger Thorpe

(D.M. Procida) said:

Tomorrow night, our theme at Cardiff Woodcraft Folk:

Quoted message said:

<http://cardiffwoodcraft.org.uk/>

Quoted message said:

is "scientific curiosity".

Quoted message said:

I'll take in a bicycle wheel, to explore gyroscopic effects, but I
wondered if it's worth taking a whole bike. Is there anything else
surprising and hands-on to be discovered in the science of the bicyle?

Quoted message said:

The children are aged six to ten.

Seen once at a physics fun day: bicycle wheel with the spokes replaced by
rubber bands. Put wheel vertically so that it can rotate freely, and aim a
hairdryer at one side of the 'spokes'. The heat will relax the rubber
bands on that side, the wheel becomes acentric, and rotates.

Roos

Roos Eisma said:

Seen once at a physics fun day: bicycle wheel with the spokes replaced by
rubber bands. Put wheel vertically so that it can rotate freely, and aim a
hairdryer at one side of the 'spokes'. The heat will relax the rubber
bands on that side, the wheel becomes acentric, and rotates.

I'm sure something like that was done on one of the royal institute
Christmas lectures on telly a few years ago. I don't know if it
available on the internet anywhere.

Martin.

With derailleur gears you could demonstrate the principle of
mechanical advantage.

D.M. Procida said:

Tomorrow night, our theme at Cardiff Woodcraft Folk:

<http://cardiffwoodcraft.org.uk/>

is "scientific curiosity".

I'll take in a bicycle wheel, to explore gyroscopic effects, but I
wondered if it's worth taking a whole bike. Is there anything else
surprising and hands-on to be discovered in the science of the bicyle?

The children are aged six to ten.

Gosh yes!

Gear ratios may be 'obvious' to you but the fact you turn the
pedals (say) 14 times and the wheel goes round 32 times which
AMAZINGLY is the same number of teeth in the gears being used.
AND once you have a hypothesis you can test it with another
combination. The 'scientific method' at work.

Sound: Why do bells go 'ring' and spokes go 'ping'. I'd have a
loose/broken spoke ready to demonstrate after stretching an
elastic band say.

Dynamo?

Bearings. How can you keep a pedal 'flat' when the crank
goes round? It isn't obvious. (I've come across 14 yo. who
don't know how to use a spanner!) Now where else on a bike
are there bearings? Where in everyday life will children
ever get to see bearings? Hinges if you're lucky! Even a
crank - for example why why not just one - will never
have been explained to them.

(If your bike wheels are the same size then pi-D won't
make much sense.)

Inner tube. How does that work then? Hey! Look! - More air ->
more pressure.

Why are tyres rubber and not say wood, glass, plastic? It
is easy to demonstrate friction using samples of these
materials on the floor. More weight = more grip. (Eureka!
that's how brakes work) Now wet the floor for extra fun.
(Now add washing up liquid.)

Can little hands put the brakes on directly? No! They
need levers.

How clever is it to be able to pull round corners and through
pipes like gear cables and brakes do?

PS If you've got a good demo the parents will be fascinated
as well because chances are nobody ever explained the details
to them either.

FRICTION
GEAR
RATIO
LEVER
BEARING
PRESSURE
FORCE
CRANK

--
Peter Fox
Beer, dancing, cycling and lots more at www.eminent.demon.co.uk

On Jan 28, 9:47 am, [email hidden] (D.M.

Procida) said:

wondered if it's worth taking a whole bike. Is there anything else
surprising and hands-on to be discovered in the science of the bicyle?

Friction (tyre-to-road, brakes). Perhaps introduce oil to demonstrate
the effects of losing friction?

PhilD

--
<><

"Peter Fox" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Even a
crank - for example why why not just one - will never
have been explained to them.

I was amazed when I discovered the reason James Watt used sun and planet
gearing was that the crank had been patented!

(gets lego out to make one. now I even understand it! equal gears gives 2
revs of wheel for one up/down of piston. )

cheers,
clive

Clive George said:

Quoted message said:

Even a
crank - for example why why not just one - will never
have been explained to them.

You mean, why not just one pedal crank? Does that need to be explained?

Quoted message said:

I was amazed when I discovered the reason James Watt used sun and planet
gearing was that the crank had been patented!

The crank had been used for at least two thousand years prior to that.
How on earth could anyone patent it?

Daniele

D. M. Procida said:

You mean, why not just one pedal crank? Does that need to
be explained?

It seems obvious to me too, but according to Jobst Brandt it
escaped the designers of the Alenax reciprocating-lever
bicycle:

The early models had fully independent pedal levers that
could be pedaled singly or in parallel or only only one if
you wanted. This made the return stroke difficult because
the leg and crank had to be pulled back to the top. What
was worse is that in the event of a bump in the road, the
rider could not stand up, because both pedals would go to
the very bottom, fully extending the legs which prevented
rising from the saddle.

(http://draco.acs.uci.edu/rbfaq/FAQ/8i.4.html)

--
Gareth Rees

"D.M. Procida" <[email hidden]> wrote in
message
news:[email hidden]...

Quoted message said:

Quoted message said:

I was amazed when I discovered the reason James Watt used sun and planet
gearing was that the crank had been patented!

The crank had been used for at least two thousand years prior to that.
How on earth could anyone patent it?

Possibly in the context of steam engines.

cheers,
clive

D.M. Procida said:

Clive George said:

Quoted message said:

Even a
crank - for example why why not just one - will never
have been explained to them.

You mean, why not just one pedal crank? Does that need to be explained?

Quoted message said:

I was amazed when I discovered the reason James Watt used sun and planet
gearing was that the crank had been patented!

The crank had been used for at least two thousand years prior to that.
How on earth could anyone patent it?

Daniele

Sorry Daniela I deleted your first message after reading it and before I
replied

Cycle science....

bike pumps getting hot...

why tyres go flat

triangulation for strength , used in pioneering ( do woodcraft folk do
pioneering)

energy used in cycling compared with driving a car

I have used all of these with Cub Scouts and they worked well.

D.M. Procida said:

Clive George said:

Quoted message said:

Even a
crank - for example why why not just one - will never
have been explained to them.

You mean, why not just one pedal crank? Does that need to be explained?

Yes. Consider the following hypothetical exchange:

Q: Why are there two pedals - can't there just be one?
A: It's obvious.

One of the first and worst mistakes teachers make is to
assume 'the obvious'. It is a small thing - but vital. Can you
cycle if you've only got one leg? If so, why is it difficult
and what would make it easier.

--
Peter Fox
Beer, dancing, cycling and lots more at www.eminent.demon.co.uk

In message <[email hidden]>

marc said:

Cycle science....

How screws and wedges work.

How the nuts get hot when undone.

Streamlining.
--
Charles
Brompton P6R-Plus; CarryFreedom -YL, in Motspur Park
LCC; CTC.

"POHB" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

With derailleur gears you could demonstrate the principle of
mechanical advantage.

A difficult concept for the young ones to grasp.

In article <[email hidden]>, vernon
[email hidden] says...

Quoted message said:

"POHB" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

With derailleur gears you could demonstrate the principle of
mechanical advantage.

A difficult concept for the young ones to grasp.

Why? Bottom gear: one pedal revolution = one wheel revolution; top
gear: one pedal revolution = three wheel revolutions. Liken it to going
up stairs one at a time or three at a time, one being easier and the
other being quicker.