On Wed, 13 Jan 2010 19:35:00 +0000, Orchid XP v8 wrote:

> Jim Henderson wrote:
>> On Wed, 13 Jan 2010 14:26:01 +0000, Invisible wrote:
>> 
>>> I still find it quite impressive that a CAR, which is made of METAL
>>> and powered by EXPLODING PETROL, can apparently be out-accelerated by
>>> a cheetah, which is MADE OF MEAT. Then again, an adult cheetah
>>> probably weighs significantly less than an Audi TT...
>> 
>> It's all about the power to weight ratio. :-)
> 
> Finally, somebody correctly identifies the issue... sheesh.

Well, the others had good ideas as well - grip seems an important thing, 
too - power on a ice vs. power on pavement end up with two vastly 
different results.. :-)

Or was that sarcasm? ;-)

Jim

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>> Finally, somebody correctly identifies the issue... sheesh.
> 
> Well, the others had good ideas as well - grip seems an important thing, 
> too - power on a ice vs. power on pavement end up with two vastly 
> different results.. :-)
> 
> Or was that sarcasm? ;-)

Power is nothing without control, 'tis true. But most cars (and animals) 
don't really have much of a problem with traction. The glaringly obvious 
thing about fast animals (including the cheetah) is that they weigh 
approximately nothing. Hell, fast cars tend to have the exact same 
property! Except they're made of metal, which is strong, but quite heavy.

Of course, a cheetah can out-accelerate most cars, but has limited top 
speed and severely limited endurance. But then again, if it doesn't kill 
something in 90 seconds or so, the animal it's chasing won't give it 
enough food to be worth continuing the chase anyway.

I gather the cheetah is limited primarily by overheating. Then again, it 
leaves in a freakin' desert wilderness, after all...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Eero Ahonen wrote:
> Stephen wrote:
>> Eero Ahonen wrote:
>>
>>>  - still having
>>> 150bhp/320Nm (upgradeable to 175bhp/370Nm with just a software) with
>> Let’s have an argument about the difference between hp and bhp, please. :-P
>>
> 
> Bhp is a more defined unit than hp - bhp is the actual power that comes
> out of the engine (and goes to the gearbox).
> 
> Well, actually bhp should be "braked" from the car itself - and they
> will be, after I'll upgrade the software.
> 
> -Aero

Do you call that an argument? LOL

 From my memory of mechanics at school, hp was more an advertising unit ;)
Bloody farmers couldn’t tell an erg from an egg :-)


-- 

Best Regards,
	Stephen

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scott wrote:
> Didn't the UK car tax depend on the displacement of your engine?

I don't know about the UK, but the USA both taxes and bases some
insurance off of displacement.

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On Wed, 13 Jan 2010 20:33:02 +0000, Orchid XP v8 wrote:

> Power is nothing without control, 'tis true. But most cars (and animals)
> don't really have much of a problem with traction. The glaringly obvious
> thing about fast animals (including the cheetah) is that they weigh
> approximately nothing. Hell, fast cars tend to have the exact same
> property! Except they're made of metal, which is strong, but quite
> heavy.

True - though many newer cars are lighter than older counterparts, what 
with using machined aluminium, carbon fibre, and other such composites 
(many of which come from the aerospace industry where high strength and 
low weight are absolutely necessary features), there's no doubt they 
still weigh more than the average cheetah. :-)

> Of course, a cheetah can out-accelerate most cars, but has limited top
> speed and severely limited endurance. But then again, if it doesn't kill
> something in 90 seconds or so, the animal it's chasing won't give it
> enough food to be worth continuing the chase anyway.

Yep, and often they'll abandon the chase when it becomes apparent that 
nothing useful comes from it.

> I gather the cheetah is limited primarily by overheating. Then again, it
> leaves in a freakin' desert wilderness, after all...

True. :-)

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Orchid XP v8 wrote:
> 
> Power is nothing without control, 'tis true. But most cars (and animals)
> don't really have much of a problem with traction. The glaringly obvious
> thing about fast animals (including the cheetah) is that they weigh
> approximately nothing. Hell, fast cars tend to have the exact same
> property! Except they're made of metal, which is strong, but quite heavy.
> 

Have you ever actually driven anything more powerful than the 1.6i? With
the traditional 1-wheel drive grip practically somewhere around 150hp
starts to make an effect (depending on the car, of course), even on
clean asphalt. Around 250-300hp you'll really start missing 4wd when
accelerating from standing position. Remember that the cheetah can take
practically ~full power to its legs right from the start (and to the
ground also). On nature films I've never seen a cheetah to "sping the
feet". Now, if the cheetah would be on clear ice, it would be a bit
different...

Yes. Even when you have the power-to-weight -ratio, to accelerate a car
like a cheetah you'll need enormous traction, an amount that actually is
incredible.

-Aero

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Eero Ahonen wrote:
> Now, if the cheetah would be on clear ice, it would be a bit
> different...

I must thank you for one of the most amusing mental images I've seen all week.

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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> Power is nothing without control, 'tis true. But most cars (and animals) 
> don't really have much of a problem with traction.

Have you seen cats on hardwood floors? (they slip a lot)

Or someone flooring it in a car from a standstill? (the wheels spin a lot)

I suspect the cheetah is so fast at accelerating because its claws can dig 
into the ground to get traction.

If you got a vehicle with spiked tyres and drove it on grass it would 
probably accelerate quicker too.  IIRC snow-mobiles have a similar drive 
system that digs into the ice and they can get phenomenal acceleration.

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> Nope. The 123d has two turbochargers. The 120d has a bigger
> turbocharger, different injectors, IIRC different crankshaft and some
> other differencies compared to 118d. 118d and 116d may possibly be the
> same engine, I haven't found theier differencies, but I'd guess that
> they too have different turbos.

I stand corrected! I assumed that as there seemed to be software upgrades 
available that the hardware was actually the same.

> I'd say that if it's done correctly, the reliability shouldn't be a
> major problem on that engine (especially 123d). But the software I
> referred to is a official software (by Hirch), so it won't trash the
> warranty of the car.

Yeh I saw that a lot of the more reputable companies will pay for anything 
if the OEM refuses to pay out.  It seems though that (at least for BMW) you 
do not automatically invalidate your warranty by changing the software, just 
that they reserve the right to refuse to pay out if they think it's because 
of you changing the software.

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scott wrote:
>> Power is nothing without control, 'tis true. But most cars (and 
>> animals) don't really have much of a problem with traction.
> 
> Have you seen cats on hardwood floors? (they slip a lot)

Or lino.

But then, domestic cats didn't evolve for that environment. There *are* 
in fact animals which regularly hunt on sheets of ice, and they have 
special adaptations to increase traction. (That said, none of them is 
anywhere near as fast as a cheetah. But you might argue that's due to 
lack of available fuel...)

> Or someone flooring it in a car from a standstill? (the wheels spin a lot)
> 
> I suspect the cheetah is so fast at accelerating because its claws can 
> dig into the ground to get traction.

And not because, oh, I don't know, it's 100x smaller mass has 
significantly lower inertia to overcome in the first place?

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