Braking Was : Best way to travel 5 miles to a train station?

Ok, the beer garden at your local pub where you're enjoying a pint with your
mates. Or anywhere where you're sitting outside.
And traditionally one doesn't chuck a motorbike out of a helicopter either,
but it's one way of doing what I'm proposing to do. (hint - the height of
250m was chosen).

cheers,
clive

 

There's always one that bites.

 

Maybe you think that motorbikes run on magic. Here is a clue. The people
that designed your motorbike are far better at maths than I am.

How do you know how quickly your bike stops? Have you measured it? No, you
guess. There is a simple way to prove your guess is wrong without having to
find
a motorbike, test track and ruler.

 

(v/h) * c, where v is the height of the centre of gravity of the bike
including rider, h is the horizontal distance between the contact patch
of the front wheel and the centre of gravity, and c is a constant[1].

Yes, you can stop the front wheel of a two wheeled vehicle faster than
that, but if you do the back wheel just goes over the top of it; so any
increase in braking power beyond that point doesn't help you any.

[1] The value of c is 1 if the unit of measurement is gravity; so the
above reduces to just v/h.

 

DavidR says...

I don't guess, I get my arse on the seat and ride the bike. I also drive
cars. In all I probably do something like 40K miles a year in cars and
another 15K miles on bikes, alot of them at high speed. I think I'm more
than qualified to make informed estimates on what a vehicle will or
won't do.

As an aside, I was also a contract test driver at Millbrook Proving
Ground, where I was involved in non-destructive testing of new vehicles.
So my driving skills are not to be discredited.

 

So how quickly does your bike stop? Any faster than 0.77G?

Do you actually have any *quantifiable data*?

You have, by your own admission, a motorbike, test track and ruler. How fast
can you stop?

How does this relate to the simple laws of physics?

Or will you go away in a sulk because you have supposition rather than real
data?

(BTW for the credentials, I am a scientist who knows a thing or two about
modelling, data and experimentation)

So will you put up or shut up?

...d

 

David Martin says...

I have practical experience gained over 26 years of riding fast
motorcycles and driving a huge variety of cars. You merely have books
and a calculator, no contest.

 

It's not how fast you pedal - it's how big a gear ring you use.


--
Cheers,
Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk) http://html.dnsalias.net/gawnsoft/smalltalk

 

I like to think a considerate driver is one who doesn't make another alter
their path or speed.

 

Except you claim to be able to brake from 150mph on a motorbike in a
shorter distance than a Mark 1 Cortina could brake from 70mph...

I guess someone else did all the measurement of braking distances for
you...


--
Cheers,
Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk) http://html.dnsalias.net/gawnsoft/smalltalk

 

Books listing the braking distances from 100mph of current motorbikes,
books listing the braking distances from 70mph of cars from the era of
Mark 1 Cortinas, and books detailing how increases in speed change a
given vehicle's braking distance.

What more does he need?


--
Cheers,
Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk) http://html.dnsalias.net/gawnsoft/smalltalk

 

Gawnsoft says...

Ok, maybe a small exageration, but there wouldn't be much in it.

How many times do you need telling, or are you terminally thick?
I don't measure, I get out and try for myself. I can tell how hard a
vehicle can brake by feel. I don't need a tape or a calculator, or a
degee in physics to tell me what I feel or know.

 

Gawnsoft says...

Funny how this book couldn't give you the data for a Yamaha Thunderace

 

Do keep up at the back.
Someone posted some test results earlier in the thread.
They showed that most sportsbikes can brake at just over 1G.

Why 0.77G? Precision without accuracy doesn't indicate any
understanding of the subject.

 

Looks like urc has been infected by clueless dweebs from urm who believe
that "big disks and good tyres" = "rapid braking".

We already get plenty of cyclists who think much the same, so **** off
back where you came from will you?

James

 

James Annan says...

I have good brakes, I'm not afraid to use them. As you're one of those
clueless wankers who hasn't discovered the delights of the internal
combustion engine and twin 4-pot calipers on 320mm discs, I wouldn't
expect you to understand. I mean, who the **** would pay over 5 grand
for a bike with no engine, especially one that has so little about it?

 

Not yet, its too much fun.

 

As we've gone through in detail already, there'd be a factor of four
in it.

If you go and try, but don't measure, how do you know what the results
were?

Oh? You can tell the difference between 1g and 4g?

Then why are you still claiming your bike stops at 4g, when patently
it's stopping at 1g?

--
Cheers,
Euan
Gawnsoft: http://www.gawnsoft.co.sr
Symbian/Epoc wiki: http://html.dnsalias.net:1122
Smalltalk links (harvested from comp.lang.smalltalk) http://html.dnsalias.net/gawnsoft/smalltalk

 

So that'd be a shut up then! Are you equally able to report on other facets
of physics? Perhaps you'd like to explain the secrets of cold fusion? Or do
you limit your ignorance to those areas where you have direct experience?



Jon

 

Funny how the Yamaha Thunderace is able to so completely defy the laws of
physics. Tell you what... prove that you're right.

Find a suitable brick wall. Mark a line an appropriate distance from the
wall (Using the stopping distances of a Mk1 Ford Cortina!). Accelerate hard
ensuring that you are travelling at 150mph when you cross the line and
begin braking.

Do be sure to let us know how you got on!

Jon