Re: i wanna look cute today...

On 2007-06-04, Rowland McDonnell <real-address-in-sig@xxxxxxxxxxxxxxx> wrote:
Whiskers <catwheezel@xxxxxxxxxxxxx> wrote:

[...]

I was getting £50 a month, gross, in my first real job.

And after the taxman had visited? ... ;-)

Noticeably less :((

Petrol prices
were going up alarmingly, and prophets of doom were saying that if it ever
got to 5/- a gallon (5.5p/litre) then people would be forced to give up
their cars. The first hole-in-the-wall cash dispensers, using single-use
punched cards, were being tried out - they dispensed one 10/- note (50p)
per punched card (you had to go into the bank to buy the punched cards, of
course ...).

Coo! Well, well, well.

It seemed pretty cool at the time, but looking back I can't help wondering
why anyone (me included) thought it was anything but a pointless gimick.

- and that was by no means the oldest car I'd
driven by then; pre-war relics were still in daily use, although in
dwindling numbers. Think no water-pump, no oil filter, side-valve,
3-speed gears with iffy synchro-mesh or none at all, starting-handles that
got worn out, 0-60 mph a possibility at best, etc.

Uhuh. The four wheeled equivalent of my old CZ, yes? Mind you - no
water pump? Air cooled, do you mean? Or do you mean gravity-fed liquid
cooling like old fashioned central heating?

'Gravity-fed'; tall radiators, often with steam coming out of the top.

Whee! Oh my word...

Easily distinguished from the smoke issuing from the oil-filler cap.
Usually.

<chuckle>

People sometimes really did drain the radiator in cold weather, and
re-fill it with hot water in the morning to get the car started. Slightly
more convenient for some was to use a small parafin heater (Halfords sold
them) under the engine compartment, with lots of blankets or bits of
carpet over the bonnet and radiator, to keep the frost off.

[...]

"My horse can do more than his 'one horse power' steam engine; he's
ripping you off, mate." If the people whose livelihood depended on
mines and workshops using horses could have done anything to besmirch the
image of steam power, they would have leaped at the chance.

Ah, but the point is that the actual number of horsepower wasn't
terribly relevant because no matter what your horse can do, it can't do
it for 24 hours without a break and without being fed anything but coal
and a dribble of water. They can say what they like, but the horse was
never up to replacing a stationary steam engine.

You would of course have a number of horses to take it in turns - and the
muscle-power lobby were keen to point out that you can't leave two
steam-engines alone for a bit and stand any chance of finding yourself in
possession of a third steam engine for 'free', and what comes out of the
back of a boiler is of little use at all on the fields or gardens. And
horses seldom explode.

So the `horsepower' measure was just for comparing different engineered
prime movers: you can't compare that sort of thing to an animal.

Surely the whole point of the 'horsepower' unit was precisely to compare
machines with animals? If you're only comparing machines by their own
characteristics then the 'pounds per foot per minute' or 'gallons per
hour' sort of measure is what's meaningful. With regard to motor
vehicles, the top speed or cruising speed or acceleration or the
load-carrying capacity are what customers are interested in (along with
the running costs and reliability); the 'brake horse power' and 'torque'
are just technical things of only indirect interest if at all, for most
people. (And we're supposed to use Watts not HP these days, aren't we?)

I don't think anyone knows precisely how he derived the figures he
used to create the unit of 'one horse-power',

The precise method is given by the link below, pretty much, isn't it?

It openly admits that 'it is not known' how Watt determined how much "pull"
a horse could manage.

Oh yes, but that's a trivial issue, isn't it? The outline of the method
is presented; the gaps are just `exercises for the student', surely?

I can think of a number of different ways that might have been available
to him; I'm sure they'd all give equally repeatable results - and equally
different. He also clearly 'rounded up' so as to make his horsepower unit
bigger rather than smaller. Why have the horse move at 181 feet per
minute instead of 180, for instance? That would make the horsepower unit
equal to 180² ie 32400 lbs/ft/min rather than 181*180=32580 as he made it
- and why round off to 33000 instead of 30000? He wanted that figure to
be credible but big, and using difficult numbers gives an aura of
'science'; that's marketing, that is.

It also doesn't say anything about the breed,
weight, age, feeding, etc, of the horse or horses he used for his
measurements, orwhat sort of machinery they were driving - there's a world
of difference between fast light things and slow heavy things, and between
steady loads and varying loads.

Well, yes, but one can assume that Watt used a steady load of a `decent
but not overlarge' sort. It's how to do that sort of thing - he was a
sensible engineer.

but it would have been wise
for him to make sure that few horse-dealers would be able to get more than
'one horse-power according to Watt' out of any normal horse.

Of course you can if you drive 'em a bit harder - but for how long and
so on and so forth?

Yers, well, you can flog a beam-engine too ;))

... hurting you more than the engine, I'd expect.

Not with a bit of luck; weighing down the safety-valve and fiddling with
the speed governor and valve-timing were not unknown.

[...]

So my VFR750 (84hp when the magazine stuck one on a dyno) has an RAC hp
rating of:

70mm bore = 2.76", four pots, so:

2.76^2 x 4
---------- = 12hp (near enough).
2.5

Which is a considerably bigger number than many middle-sized cars would
have scored in the '50s and '60s. Long stroke accounted for the total
'capacity' of those old engines being in the 1-litre range

(my VFR's engine is, would you believe it, rather short stroke?)

"Over-square" was a term used at one time, I think. A shorter stroke
results in a narrower range of engine speeds with useful torque,
necessitating more gear-changes and ideally more gears to choose from, but
the trade-off is likely to be a higher engine speed being available and
thus greater 'maximum power'. You also need less metal in the cylinder
block and con-rods, thus saving weight (some of it oscillating or rotating
weight, which can make a big difference to efficiency and vibration).
Your bike is probably a lot more "fun" to ride than a "12hp" bike with an
old-fashioned long-stroke engine - and possibly a lot more controlable and
economical too. Most current petrol engines for cars and bikes have a
stroke that is less than the bore diameter.

Modern mopeds with continuously-variable automatic transmissions have
engines with a very narrow 'torque band', so their engines are mostly
spinning at a near-constant rate with the belt-drive pulleys changing
size constantly to adjust to road-speed. They seem to have
speed-governors too to keep the speed below 'a bit more than 30mph', and
deliberately restricted carburettors. My Vespa could go up quite steep
hills at 30mph just as easily as along the flat - but absolutely would not
go much above 30 in any circumstances.

(and meant that
low-speed torque and a widish torque 'curve' made a 3-speed transmission
perfectly practical).

Uhuh. Righto.

[...]

But if something could be done to get people to drive according to the
highway code, I'd be happy around town with 20hp, and if they *were*
driving properly, 30mph mopeds would be great fun to ride on the road
rather than deeply frustrating and annoying.

I think that's another way of saying that if no-one else was going so
fast, you wouldn't feel the need to go so fast either.

Well, yes. When you've got folk shooting past in a 30mph zone at
40-60mph (typical round here), a moped doesn't look at all like a good
idea. And the way people drive - well, it's handy to have 84hp on tap
to get you out of trouble, you know?

I'd rather not have to do all that stuff, but it's what's needful given
the state of driving. And yes of course I know I've made myself part of
the problem, but there are tens of millions of others who are more
problematic. The solution does not involve individual action at the
outset.

Legislation and enforcement are required. Not popular with motorists.

So getting more
power to keep up, is at least no better an answer than taking some of the
excess power off all the others ;))

Ah, but too little power is a problem - if you slowed 'em down *enough*
by reducing available peak power, they'd never be able to do sensible
motorway cruising, you know?

Many high-performance road cars have speed-governors fitted already, in
the form of engine rev-limiters. The world didn't come to an end when we
had a national speed-limit of 50mph - and journey-times were less affected
than you might think. I think that in some US states they have a similar
blanket speed limit still (not that the USA is a particularly good example
of road safety).

One of the major causes of traffic hold-ups is the act of someone slowing
down, not the actual speeds involved; if one car brakes at 70 mph, the
following driver will brake more sharply and in heavy-enough traffic you
get a sort of 'wave' of braking travelling back up the line of cars until
someone is forced to stop completely, thus making everyone else in that
stream of traffic have to stop too. That sort of thing in fog or rain can
cause nasty accidents - with the driver who originally slowed down miles
away and oblivious, but giving drivers going on the opposite direction a
temptation to slow down 'for a look' and thus setting off another such
sequence of events.

[...]

That's why loadsapower is handy. Okay, okay, there wasn't actually any
excuse for the cruising speed of 90mph, but you get the idea. Hell, the
road was almost empty except for us. Sunday evening in Wales.

At least once upon a time the chapels would be open in Wales on a
Sunday, but they seem to have mostly given up even on that.

Some parts of Wales still don't have so much competition for the chapels on
a Sunday.

I think it depends on where you go. The part of south Wales I'm most
familiar with seems to have a good supply of active busy places of worship
to choose from. The one my mother frequents has a nice working
arrangement with the neighbouring supermarket; the Methodists park in the
supermarket car-park for services, and pop in to the shop on the way home.
That's pretty revolutionary, but it seems to work.

--
-- ^^^^^^^^^^
-- Whiskers
-- ~~~~~~~~~~
.

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