From: GT on
"Brimstone" <brimstone(a)hotmail.com> wrote in message
news:cpGdnZJvGoeLGNTRnZ2dnUVZ8vednZ2d(a)bt.com...
>
> <boltar2003(a)boltar.world> wrote in message
> news:i2brj4$ubu$1(a)speranza.aioe.org...
>> On Fri, 23 Jul 2010 10:43:17 +0100
>> "mileburner" <mileburner(a)btinternet.com> wrote:
>>>> What a load of drivel.
>>>>
>>>> Stop bike.
>>>>
>>>> Get off and stand next to wall/bush.
>>>>
>>>> Let cars past.
>>>>
>>>> See , not hard is it?
>>>>
>>>> B2003
>>>
>>>The only thing is that if you all-of-a-sudden stop, and get off you bike,
>>
>> Why would you do a sudden stop? Stick your arm out so drivers know you're
>> stopping and coast to a halt.
>
> Most car drivers don't know hand signals.

You have to know them to pass the driving test, so those car drivers without
a driving license and insurance should be arrested and given a prison
sentence. This does occasionally happen.

>>>It is far better to wait until there is an appropriate shoulder, lay-bay,
>>>side exit etc. where you *can* stop and get out of the way and let them
>>>pass. Even better, just wait for the road to widen (or otherwise be safe
>>>to
>>>pass) and pull over and wave them past. Then there is no need to hold up
>>>the
>>>traffic or put anyone at risk.
>>
>> In an ideal world yes. In a narrow road that you might be puffing your
>> way up for the next 10 minutes its only good manners to let other traffic
>> pass.
>
> Why should people sitting in nice comfy overpowered cars get precedence
> over people using muscle power?

No one gets precedence over anyone else - there are rules governing road
craft and conduct - everyone has to comply with the same rules. If a person
sitting in a nice comfy car is driving too slowly, then they will fail their
driving test and not be allowed to drive on the road unsupervised!


From: GT on
<boltar2003(a)boltar.world> wrote in message
news:i2buq3$491$1(a)speranza.aioe.org...
> On Fri, 23 Jul 2010 12:15:56 +0100
> Albert T Cone <a.k.kirby(a)durham.ac.uk> wrote:
>>> No it isn't. Cars have an optimum speed at which they use the least fuel
>>> for a given distance and its usually somewhere around the 50-60mph mark.
>>On the flat, without a headwind. And the peak can be anywhere from
>>25-60mph. On a hill, the optimum speed can be very different.
>
> Possible , I'm not an expert in this. But I was under the impression that
> IC engines have an optiumum rev range and if you keep within that range
> then no matter what the load you'll achive the best possible fuel economy.

True if maintaining a constant speed at a certain revs. If we take 2000 revs
as an example, one could be accellerating hard in 1st gear as you hit 2000
revs - this would not be very fuel efficient. You could be slowing down on
approach to lights in 4th gear as you hit 2000 revs - in a modern car this
will be using zero fuel at all!

56mph is supposed to be the most fuel efficient 'cruise' speed. The varying
example elsewhere does not take account of road conditions, gradient,
acceleration and other forces. At a constant speed, 56mph is the most
efficient if one is happy using mpg as a measure of fuel efficiency - I know
some people don't like this industry standard measurement of efficiency, but
lets not go there again!


From: boltar2003 on
On Fri, 23 Jul 2010 13:03:26 +0100
"Brimstone" <brimstone(a)hotmail.com> wrote:
>Why should people sitting in nice comfy overpowered cars get precedence over
>people using muscle power?

Well since you're so fond of quoting the highway code when it suits you:

http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_070314

"169
Do not hold up a long queue of traffic, especially if you are driving a large
or slow-moving vehicle. Check your mirrors frequently, and if necessary, pull
in where it is safe and let traffic pass."

It should be interesting to see you try and wriggle out of that.

B2003



From: Albert T Cone on
boltar2003(a)boltar.world wrote:
> On Fri, 23 Jul 2010 12:15:56 +0100
> Albert T Cone <a.k.kirby(a)durham.ac.uk> wrote:
>>> No it isn't. Cars have an optimum speed at which they use the least fuel
>>> for a given distance and its usually somewhere around the 50-60mph mark.
>> On the flat, without a headwind. And the peak can be anywhere from
>> 25-60mph. On a hill, the optimum speed can be very different.
>
> Possible , I'm not an expert in this. But I was under the impression that
> IC engines have an optiumum rev range and if you keep within that range
> then no matter what the load you'll achive the best possible fuel economy.

It's horribly complicated when you look at it in detail.

You are balancing the frictional losses in the engine (which increase
with rpm, and hence drop with higher gears) against the gravitational
(on a hill), rolling frictional and air-resistance losses (which
increase with speed (and hence drop with gearing.

Moreover, for a normally aspirated engine, the peak efficiency (energy
produced/volume of fuel) corresponds roughly to the peak of the torque
curve. However the peak of the torque curve depends on the throttle
position.
General wisdom suggests that you should run the highest gear you can
pull at any given speed to minimise engine speed, however running a
lower gear can result in you running closer to the peak of the torque
curve and getting better nominal efficiency.
Things get much more complicated if you have forced induction...

Finding the best speed for economy depends on the engine design,
gearing, frontal area, body shape, mass and gradient of the road.
The "56mph" rule is fine as a rule of thumb, as long as you bear in mind
that it can be out by more than 50%...
From: Mike P on
boltar2003(a)boltar.world wrote:
> On Fri, 23 Jul 2010 13:03:26 +0100

HC states.....

"........pull in where it is safe and let traffic pass."

> It should be interesting to see you try and wriggle out of that.

Mileburner says

"It is far better to wait until there is an appropriate shoulder, lay-bay,
side exit etc. where you can stop and get out of the way and let them
pass. Even better, just wait for the road to widen (or otherwise be safe to
pass) and pull over and wave them past. Then there is no need to hold up the
traffic or put anyone at risk"

Now, where's the difference?

*Safe to pass* being the main thing here..

Mike P