need help picking out a bike

[James Annan]

Gawnsoft wrote:

>
> The fact that a force is applied normal to the direction of travel to
> achieve a component of travel normal to the previous direction of
> travel does not mean there is no work done, surely?

Well, it does actually. And the trivial energy losses in tyre scrubbbing
and sidewal deformation are surely an order of magnitude lower than the
proposed cost of turning a corner.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

 

[Simon Brooke]

in message <[email protected]>, Peter Clinch
('[email protected]') wrote:

> David Martin wrote:
>
>> I don't think 48 on a slick tyred MTB is unreasonable given the right
>> hill and enough weight.
>
> The more I think about this the more I'm prepared to agree with that
> aspect, but my doubts over 30 mph on near flat

30mph on the flat is a good club racer on a specialist time trial bike.
The best I can do on the flat on a light racing bike without hill or
wind assist is 27mph. I know people who claim to be able to do 40mph,
but I'll admit to being skeptical.

30mph for 25 miles would be 50 minutes; if you look at times for 25 mile
time trials on <URL:http://www.rttc.org.uk/> you'll see that the
winning times are more like 53 - 57 minutes. The people who really can
sustain 30mph for any length of time are mostly professionals (although
the leaders in this years Tour de France averaged 27 mph all the way to
the Alps).

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

'You cannot put "The Internet" into the Recycle Bin.'

 

[Sniper8052]

Sniper8052 wrote:


> Ie 32' p/ss as a terminal velocity

ahem

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

OK so I'll correct that then.
32.15feet p/s/s as acceleration due to gravity which is a constant for all objects on earth.
Sniper8052.

 

[David Martin]

On 1/10/04 5:47 pm, in article
[email protected], "Sniper8052"
<[email protected]> wrote:

> James Annan Wrote:
>> Sniper8052 wrote:
>>
>>
>>> Ie 32' p/ss as a terminal velocity
>>
>> ahem
>>
>> James
>> --
>> If I have seen further than others, it is
>> by treading on the toes of giants.
>> http://www.ne.jp/asahi/julesandjames/home/
>
> OK so I'll correct that then.
> 32.15feet p/s/s as acceleration due to gravity which is a constant for
> all objects on earth.
> Sniper8052.
>

Some more correction needed... (insert 'in a vacuum' and 'effectively' in
teh appropriate places).

...d

 

[Just zis Guy, you know?]

On Fri, 01 Oct 2004 06:26:40 +0900, James Annan
<[email protected]> wrote:

>Dave Larrington wrote:
>
>> Moreover, the additional effort required to turn bike and rider through 180
>> degrees has a significant effect; Robert calculates the extra effort
>> required knocks your average speed down from 63 km/h to 56.

>I don't believe that. What is the basis for that calculation? It sounds
>to me that some people don't realise that a centripetal acceleration
>does no work, being perpendicular to the direction of motion.

And there was I thinking you couldn't produce acceleration without
doing work

We are not talking electrickery, after all; the fact that it is normal
to the direction of travel does not make it imaginary.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

 

[Gawnsoft]

On Sat, 2 Oct 2004 02:47:48 +1000, Sniper8052
<[email protected]> wrote (more or
less):

>
>James Annan Wrote:
>> Sniper8052 wrote:
>>
>>
>> > Ie 32' p/ss as a terminal velocity
>>
>> ahem
>>
>> James
>> --
>> If I have seen further than others, it is
>> by treading on the toes of giants.
>> http://www.ne.jp/asahi/julesandjames/home/
>
>OK so I'll correct that then.
>32.15feet p/s/s as acceleration due to gravity which is a constant for
>all objects on earth.

Except it's not a constant for all objects on Earth. Although it only
varies slightly, depending on your latitude and height.


--
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

 

[the.Mark]

Whingin' Pom wrote:
>
> Any time you're down under, drop in on me for a cuppa and I'll
> show you some of the real monster hills round here. I hit 40(
> well, 70kmh anyway.) on my commute into work. Starts the day
> with a grin!

I've not been following this thread but I couldn't help seeing the claim of
40 going to work. I get over 40 on my commute. My best is 46.3 on my
Windcheetah going past Kingsknowe golf course in Edinburgh and I agree It is
the best way to start the day.
--
Mark

1x1 wheel, 3x2 wheels & 1x3 wheels.

 

[Steph Peters]

Paul Rudin <[email protected]> of ntl Cablemodem News Service wrote:
>Can't you get someone else with a cycle computer to ride with you for
>a bit? That way you can at least discover whether your speed readings
>are similar to theirs or not.

Which proves precisely nothing. DH and I have 3 bikes with computers fitted
with computers between us. No two of them give exactly the same readings.
But as they give only about a 4% spread in distance traveled, and we've
never been able to work out which one is most accurate, we just leave them
alone.
--
If at first you DO succeed, try not to look astonished!
Steph Peters delete invalid from [email protected]lid
Tatting, lace & stitching page <http://www.sandbenders.demon.co.uk/index.htm>

 

[Whingin' Pom]

On Fri, 1 Oct 2004 09:40:21 +0100, "Clive George"
<[email protected]> () wrote:

>"Whingin' Pom" <[email protected]> wrote in message
>news:[email protected]...
>> On Thu, 30 Sep 2004 17:42:31 +0100, "Clive George"
>> <[email protected]> () wrote:
>>
>> >"Sniper8052" <[email protected]> wrote in
>> >message news:[email protected]...
>> >>
>> >> I refer you to a good physics book.
>> >
>> >I refer you to a better one.
>> >
>> >(btw who are you talking to?)
>>
>> Refer them to a newsreader.
>
>Charlotte Green?

Charlotte Green is people! People, dammit!

Errm, I've got this wrong, haven't I...


--
Matt K.
"And on the seventh day, He exited from append mode."

 

[Whingin' Pom]

On Fri, 1 Oct 2004 20:57:39 +0000 (UTC), "the.Mark"
<[email protected]> () wrote:

>Whingin' Pom wrote:
>>
>> Any time you're down under, drop in on me for a cuppa and I'll
>> show you some of the real monster hills round here. I hit 40(
>> well, 70kmh anyway.) on my commute into work. Starts the day
>> with a grin!
>
>I've not been following this thread but I couldn't help seeing the claim of
>40 going to work. I get over 40 on my commute. My best is 46.3 on my
>Windcheetah going past Kingsknowe golf course in Edinburgh and I agree It is
>the best way to start the day.

Having serious hills helps.
I'm lucky to hit 4mph on the way home!


--
Matt K.
"And on the seventh day, He exited from append mode."

 

[James Annan]

Just zis Guy, you know? wrote:


> And there was I thinking you couldn't produce acceleration without
> doing work
>
> We are not talking electrickery, after all; the fact that it is normal
> to the direction of travel does not make it imaginary.

I'm not sure what point you are trying to make. Of course a force
perpendicular to the direction of travel does no work. Thats why the
moon keeps going round the earth without slowing down.

(yes, it slows down marginally due to energy dissipated in tides - there
is no true perpetual motion machine. But the presumed 10% speed loss
through a bicycle turning a corner is obviously due to something rather
substantial, and obviously wrong.)

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

 

[Martin Wilson]

>
>Beyond that, we don't actually know if Babylon Hill is the "right hill".
> The only one of the name Streetmap turns up in the UK is good, but but
>not good enough IMHO (70m descent over a kilometre) on the A30 just
>outside Yeovil). Martin, is that the one, or am I looking in the wrong
>place?
>
>Pete.

Yep you've got the right hill. When I look out of the bedroom window
at night over a basically flat landscape the only thing in the
distance that can be seen is the lights of cars and lorrys going
up/down Babylon Hill as if driving to and from space. This is the hill
alright. Sounds quite impressive to me too, 70m descent over 1000m+

The actual peak reading of 48.1mph I realise now is because of testing
my gears. I have a small workstand that takes the rear wheel of the
ground and my cycle computer is connected to the rear wheel not front
so I can use a Tacx trainer with it. Obviously when I was testing the
gears the 48.1mph was achieved then when I used my arms to pedal with
no load at all.

Right I've just done some tests.

At 80rpm cadence on f3,r6 the speed of the cycle computer reads
21.7mph

At 100rpm cadence on f3,r6 the speed of the cycle computer reads
26.7mph

Logically I would need to momentarily hit a cadence of 112 rpm cadence
or my own slight downhill momentum to get to 29.7mph.

Obviously doing an exact consistant cadence is hard but I managed to
hit 20 at quarter past, 40 at half past and 60 at quarter to, so I was
fairly accurate at 80rpm. Same is true of 100 as I hit 25,50 and 75
pretty well.

I've already stated that the 30mph was achieved on a slight gradience
in my favour. Near flat but not flat. So I find it amazing that some
will accept my 40mph speed and not my 30mph speed claims. I mean the
gearing takes me upto at least 20mph and possibly 24mph with normalish
cadence so if I'm on a slight downhill section (very slight) and I'm
cycling with a much faster cadence than normal is it really that
amazing that I get a peak reading of about 29.7mph?

 

[Jon Senior]

Martin Wilson [email protected] opined the following...
> I've already stated that the 30mph was achieved on a slight gradience
> in my favour. Near flat but not flat. So I find it amazing that some
> will accept my 40mph speed and not my 30mph speed claims. I mean the
> gearing takes me upto at least 20mph and possibly 24mph with normalish
> cadence so if I'm on a slight downhill section (very slight) and I'm
> cycling with a much faster cadence than normal is it really that
> amazing that I get a peak reading of about 29.7mph?

Only that 112rpm is a pretty good cadence to hold. I used to aim for 90
and was pleased when I hit 100. The fastest I ever managed was 115 and
that was down a hill and I was basically adding nothing to the speed of
the bike. (I may since have managed more going downhill on the fixer but
I no longer have a cadence meter and quite frankly I was too scared to
look anywhere but the road in front!)

If you did / do manage it, then good for you. Get a tight range racing
cassette on the back and give it some!

Jon

 

[Just zis Guy, you know?]

On Sat, 02 Oct 2004 07:34:22 +0900, James Annan
<[email protected]> wrote in message
<[email protected]>:

>I'm not sure what point you are trying to make. Of course a force
>perpendicular to the direction of travel does no work. Thats why the
>moon keeps going round the earth without slowing down.

I'm just having trouble understanding how we can apply the force
necessary to produce the angular acceleration, without doing any work.
In the case of the moon the force is provided gratis by Old Sir Isaac,
but when riding round a velodrome on a bike, all the force comes from
the legs (through a system which incorporates certain mechanical
losses).

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

 

[James Annan]

Just zis Guy, you know? wrote:


> I'm just having trouble understanding how we can apply the force
> necessary to produce the angular acceleration, without doing any work.

By applying it perpendicular to the direction of travel. work = force x
distance.


> In the case of the moon the force is provided gratis by Old Sir Isaac,
> but when riding round a velodrome on a bike, all the force comes from
> the legs (through a system which incorporates certain mechanical
> losses).

No, in this case the force (to turn a corner) is the lateral reaction
force of tyre on ground. You can still turn a corner when freewheeling!

It should be obvious from everyday experience that turning a corner does
not cause the bike to screech to a halt. I accept that there may be a
slight slowing due to tyre scrubbing effects, but nothing like the
ludicrous figures quoted.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

 

[Just zis Guy, you know?]

On Sat, 02 Oct 2004 19:20:26 +0900, James Annan
<[email protected]> wrote in message
<[email protected]>:

>> I'm just having trouble understanding how we can apply the force
>> necessary to produce the angular acceleration, without doing any work.

>By applying it perpendicular to the direction of travel. work = force x
>distance.

Nope, still not with you. We have to do work overcoming mechanical
friction and such just to get the force to the wheels. When turning
it looks like only part of the power produced is resolved into forward
motion, which looks like a loss to me.

>in this case the force (to turn a corner) is the lateral reaction
>force of tyre on ground. You can still turn a corner when freewheeling!

That doesn't help; you can go in a straight line when freehweeling,
but you slow down due to drag. I don't have a way of measuring,
empirically or otherwise, the difference in deceleration, if any,
while cornering.

>It should be obvious from everyday experience that turning a corner does
>not cause the bike to screech to a halt. I accept that there may be a
>slight slowing due to tyre scrubbing effects, but nothing like the
>ludicrous figures quoted.

Well that's my point, really - there must be some slowing effect.

I don't have an opinion on the scale of the effect, I just find it
hard to believe that cornering is "free" when it is achieved by means
of some of the tractive effort is being diverted into providing
lateral acceleration.

I have a very literal mind. Help me out here

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

 

[Just zis Guy, you know?]

On Sat, 2 Oct 2004 10:12:44 +0100, Jon Senior
<jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message
<[email protected]>:

>112rpm is a pretty good cadence to hold

Doable, though. I regularly sustain 110 for minutes at a time, riding
on the flat. Not in high gears, though.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

 

[Jon Senior]

Just zis Guy, you know? [email protected] opined the following...
> Doable, though. I regularly sustain 110 for minutes at a time, riding
> on the flat. Not in high gears, though.

Hmm. May need to invest in a new cadence meter and go back to monitoring
it!

Jon

 

[James Annan]

Just zis Guy, you know? wrote:

> On Sat, 02 Oct 2004 19:20:26 +0900, James Annan
> <[email protected]> wrote in message
> <[email protected]>:
>
>>By applying it perpendicular to the direction of travel. work = force x
>>distance.
>
>
> Nope, still not with you. We have to do work overcoming mechanical
> friction and such just to get the force to the wheels. When turning
> it looks like only part of the power produced is resolved into forward
> motion, which looks like a loss to me.

Where does the rest of the energy go?


> That doesn't help; you can go in a straight line when freehweeling,
> but you slow down due to drag. I don't have a way of measuring,
> empirically or otherwise, the difference in deceleration, if any,
> while cornering.

That in itself should tell you that the diffference is not close to the
magnitude that would be required to make your average speed drop from 63
to 56kmh

> I don't have an opinion on the scale of the effect, I just find it
> hard to believe that cornering is "free" when it is achieved by means
> of some of the tractive effort is being diverted into providing
> lateral acceleration.
>
> I have a very literal mind. Help me out here

I don't dispute that cornering will cause a small amount of slowing due
to some extra scrub of the tyre. This is the quote that I think is absurd:

> Moreover, the additional effort required to turn bike and rider through 180
> degrees has a significant effect; Robert calculates the extra effort
> required knocks your average speed down from 63 km/h to 56.

At these speeds, the vast majority of power dissipation is due to air
resistance, certainly 80% and maybe 90%. Yet according to Robert, the
_total_ resistive force increases by 40% just through going round in
circles (56^3x1.4 = 63^3). Since the air resistance does not change,
that's a trebling of the rolling resistance component, which would be
easily noticeable just riding around at lower speeds. Without seeing the
basis for the calculation I can't say for sure what the mistake is, but
I strongly suspect some cod physics from someone who does not realise
that a centripetal acceleration does essentially no work, and who isn't
sufficiently clued in to give his results an elementary reality check.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

 

[Just zis Guy, you know?]

On Sat, 02 Oct 2004 20:29:25 +0900, James Annan
<[email protected]> wrote in message
<[email protected]>:

>> Nope, still not with you. We have to do work overcoming mechanical
>> friction and such just to get the force to the wheels. When turning
>> it looks like only part of the power produced is resolved into forward
>> motion, which looks like a loss to me.

>Where does the rest of the energy go?

Eh? Let us say that I am putting in effort E and turning at angle A,
it seems to me that effort cos E will go into maintaining speed (in
the scalar sense) and sin E into producing a turning component. The
difference between E and cos E, assuming I keep E constant, means that
speed (scalar) will reduce in the turn. Is that wrong?

I accept that A is small, so the difference is likely to be small.

Of course, it could be that the real consideration should be the force
required to maintain forward speed against the wind, and the resolved
centripetal force required to produce the turn at that speed.

I quite see that the forces alone do not account for the observed
reduction in average speed. Actually I'd be prepared to bet that was
at least partly due to running outside the black line, but what do I
know?

>> That doesn't help; you can go in a straight line when freehweeling,
>> but you slow down due to drag. I don't have a way of measuring,
>> empirically or otherwise, the difference in deceleration, if any,
>> while cornering.

>That in itself should tell you that the diffference is not close to the
>magnitude that would be required to make your average speed drop from 63
>to 56kmh

Not disputed, as noted before.

>I don't dispute that cornering will cause a small amount of slowing due
> to some extra scrub of the tyre. This is the quote that I think is absurd:

Well, I am not sure whether it is tyre scrub alone, you see. But I'm
not disagreeing (with anybody), just trying to find out more.

>At these speeds, the vast majority of power dissipation is due to air
>resistance, certainly 80% and maybe 90%. Yet according to Robert, the
>_total_ resistive force increases by 40% just through going round in
>circles

Which does, on the face of it, sound absurd.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University