P plate training ...not

FWIW I have *heard* of that issue but it's one of those "mate of a
mate" stories so I wouldn't call it proven, a friend who used to drag
race professionally in the 70's and 80's (in the US but he's an
Aussie, no not Bray ) told me about that one quite a few years
ago, claimed to have had it happen to a drag car he built - can't
prove it either way though.

JL

 

It's not a design rule (how can you make a design rule about that ?)
it's a traffic law, and yes it used to be the case, no idea if it
still is - certainly no-one seems to get booked for it in Sydney.

No, I'm sorry, that's not even vaguely a pity, more like a cause for
celebration

JL

 

Well yessss... but I think Nev's point was that the alternator output is not
affected by headlights, accessories, etc,.. so that's not something you have
any control over.

 

Alternators with brushes do but modern bikes use brushless alternators that
aren't load-variable. (As far as I understand it)

 

Not if you're paying your local bikeshop to do the work!!

Yeah it offends me also but just like points ignition it's a thing of the
past now.
We've traded "runs forever with just a regular adjustment/replacement" for
"runs faultlessly for 3000 hours then fails irretrievably"...
Oh well.....

 

I've met someone who claims it happened to him at the end of the main
straight at PI. Front tyre inexplicably deflated. No damage to tyre.

He's not someone whose word I doubt, and having seen him ride he's not
one who needs to make up stories.

Says the problem was fixed by replacing the valve.

Moike

 

OK; I can accept the logic of centrifugal force causing the centre of the
valve to pull down (towards the outside of the tyre) at high speed and
letting the tyre deflate. (Sorry Nathan; I didn't understand the equation
and sorry Theo; I didn't understand the explanation.)

 

On the off chance that you _really_ want to know...

In your car, you've almost certainly got an alternator with the current
in the rotor windings controlled by the regulator - the regulator
detects how much electricity is actually being used at any time
(including whats required to charge that battery) by measuring the
voltage, and it adjusts the current in the rotor which changes the
strength of its magnetic field, which in turn changes the torque with
which it resists turning and hence changes the power consumption of the
alternator. The angular velocity is, as you point out, controlled
independently of the electrical requirements, but the torque is variable
and so the power output (and consumption) is variable. So you don't have
"left over" electricity "disappearing into the void" because you don't
have a constant load on the moving parts of the alternator. (think of it
as being like the difference in the engines output power at 5000rpm at
5% throttle compared to the power at 5000rpm at 100% throttle)

In your bike though, you probably have a permanent magnet alternator. In
these you do have the alternator generating power proportional to the
angular velocity, and you do in fact have "left over" electricity which
ends up generating heat in the regulator/rectifier - ask any VFR owner
about the cpu heatsink mod's they all do to their reg/rects... (It's
actually not always _quite_ as bad as that makes it sound, at least some
3 phase systems on some bikes will balance two phases against each other
to cut output by 66% when it's not needed so you don't end up with a
glowing red regulator whenever you ride around without your lights on -
my 99 Monster does this but the Monsters from a few years earlier only
ran two phase systems where this trick doesn't work...)

big

 

If I ever buy another Evo-powered H-D the electronic ignition will be
the first thing to go in the bin, to be replaced immediately with a
points setup. (As it was on the old Softy.)

Pity there's no points setups for the twin-cams, as far as I know.

Points used to cost me $8 and a few minutes once a year to replace
(whether they needed it or not).

Idled better, ran smoother.

 

However Nev has oversimplified.

An alternator will only produce the required amount of amps needed to run the operating electrical systems in the car (charging,
lights, stereo, heater/air-con fan, etc) up to the output capacity of the alternator. As the amp demand increases, so does the load
on the alternator, which in turn puts an added load on the engine running the alternator.

So yes the battery will stay charged provided the power demands of the alternator are not exceeded, but that does not mean there is
constant load on the alternator up to it's production limit.

 

Whether it's a "real world" effect or not I don't know, but that's the
marketing spin Ducati use to hype up the 90 degree valve stems they use
on the 99* and 74* range...

big

 

I can't say that my points bikes ran better than CDI equivalents ('specially
the two-smokes!) but I've never looked at a points system and said "I can't
get this home".

 

Yep; but you'd have to have the angle the right way or you'd suffer the same
[alleged?] effect under braking or acceleration!

 

In a car yes; but I think Nev was talking about the horrible constant-output
(dependent on revs) setups that bikes have these days.

 

Do Superbudgies come with radios these days?

 

So that's why the front end of your GS let go!

Boxer

 

so can i put my 25cc 2 stroke whipper snipper motor on a pully system to
turn over an alternator?

home made mini gen

 

I never heard of it before, although i did get dirt stuck into a tyre valve
which deflated it during a rally once.

this is something i got told im going to have to check in my upcoming silver
driver aka highspeed pursuit licence.

i dono how true it is..

 

all the new cars ive seen come so they can be on with any lights on,
including parkers.

which makes sence really because when your driving in fog, you turn them on
and your low beams, so the highbeams dont reflect off the fog blinding you!

 

That'll let you upgrade from the diesel Rodeo to the petrol model?

Nev..
'04 CBR1100XX