OT: What is acceleration? (it's got V8's in it.......honest!)

M

Mr.Nice.

Guest

• Jul 20, 2004

• #21

Twas Tue, 20 Jul 2004 14:42:46 +0000 (UTC) when "Neil Brownlee"
<[email protected]> put finger to keyboard
producing:

>Definition of Acceleration
>
>One Top Fuel dragster 500 cubic inch Hemi engine makes more horsepower than
>the first 4 rows of
>stock cars at the Daytona 500.
>Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro
>methane per second; a fully
>loaded 747 consumes jet fuel at the same rate with 25% less energy being
>produced.
>A stock Dodge Hemi V8 engine cannot produce enough power to drive the
>dragster's supercharger.


Not to put too fine a point on it.... sh1t!.


Regards.
Mark.(AKA, Mr.Nice.)
--
___________________________________________________________
"To know the character of a man, give him anonymity" - Mr.Nice.
www.mrnice.me.uk - www.markvarleyphoto.co.uk
1984 110 CSW 2.5(na)D
___________________________________________________________

 

B

Badger

Guest

• Jul 20, 2004

• #22

"Neil Brownlee" <[email protected]> wrote in message
news:[email protected]...
> Definition of Acceleration
>
> Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro
> methane per second; a fully
> loaded 747 consumes jet fuel at the same rate with 25% less energy being
> produced.

I'd like to see that proven. 747's have been fitted with RollsRoyce RB211
engines amongst others, which provide a spectacular thrust. Let's see some
power/ton figures for both the dragster and the 747.
I work daily testing RB199 engines, which in Combat setting provide approx.
70kN (7 tons) of thrust each, at a mass fuel flow of approx. 4800kg/hour,
the fuel s.g. for those who wish to convert to gallons is 0.798.
I've a sneaky feeling that the thermal efficiency of a jet engine is way
better than an internal combustion one.
Badger.

 

D

Dom J

Guest

• Jul 20, 2004

• #23

"Mr.Nice." <[email protected]> wrote in message
news:[email protected]...
> Twas Tue, 20 Jul 2004 14:42:46 +0000 (UTC) when "Neil Brownlee"
> <[email protected]> put finger to keyboard
> producing:
>
> >Definition of Acceleration
> >
> >One Top Fuel dragster 500 cubic inch Hemi engine makes more horsepower
than
> >the first 4 rows of
> >stock cars at the Daytona 500.
> >Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro
> >methane per second; a fully
> >loaded 747 consumes jet fuel at the same rate with 25% less energy being
> >produced.
> >A stock Dodge Hemi V8 engine cannot produce enough power to drive the
> >dragster's supercharger.
>
>
> Not to put too fine a point on it.... sh1t!.
>
>
> Regards.
> Mark.(AKA, Mr.Nice.)

Still not as fast as Sammy Millers Rocket car dragster of the early
1980's!.

Dom J

 

A

Austin Shackles

Guest

• Jul 24, 2004

• #24

On or around Sat, 24 Jul 2004 21:33:40 +0100, [email protected]
enlightened us thusly:

>On Sat, 24 Jul 2004 07:53:48 +0000 (UTC), Simon Birkby
><[email protected]> wrote:
>
>>Given that Mass x Acceleration = Force
>>
>>Vehicle Mass (kg) Best Accel (m/s/s) Force (Joules)
>
>'cept you confuse force (Newtons) with energy (Joules)
>
>It gets more complicated because the jet may be developing thrust
>(force) at the same rate throughout the take off (i.e. burning fuel at
>the same rate) but that does not result in a constant power because
>power is thrust times velocity, so the jet gets more useful conversion
>of heat to kinetic energy of the plane the faster it travels, I think
>;-).

also you get interesting results from varying the mass. the simple
equations of motion which are commonly used treat mass as a constant, and
say "F=ma" for example. in fact, F=d(mv)dt, rather than the F=m.dv/dt which
is implied by the former. In the case of both the dragster and the boing,
they may burn fuel fast enough that the mass change becomes significant.
Certainly is with rockets going straight up - initial acceleration is low
due to the heavy mass, then as the fuel is consumed the mass reduces so the
acceleration increases.

in fact, on the jet, it's probably not really significant; I don't think it
uses that much mass of fuel to take off, compared with the gross weight.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Quos deus vult perdere, prius dementat" Euripedes, quoted in
Boswell's "Johnson".

 

S

[email protected]

Guest

• Jul 25, 2004

• #25

On Sun, 25 Jul 2004 12:05:30 +0100, Austin Shackles
<[email protected]> wrote:

>hmmm. how much does an all-up 747 weight to start with though?

A google gives 377,800kg inc 196,515ltr fuel!

AJH

 

S

Steve Maloney

Guest

• Jul 26, 2004

• #26

I've read somewhere that the workshop manuals, spare parts books and "don't
touch that bit' bulletins for a 747 add up to more than the weight of the
aircraft.
Imagine the shelves in WH Smiths that could hold a Haynes Manual the weight
of a 110!

Steve
Durban
1984 110 V8

snip
> >On Sun, 25 Jul 2004 12:05:30 +0100, Austin Shackles
> ><[email protected]> wrote:
> >
> >>hmmm. how much does an all-up 747 weight to start with though?
> >
> >A google gives 377,800kg inc 196,515ltr fuel!

 

S

Simon Birkby

Guest

• Jul 24, 2004

• #27

In article <[email protected]>,
[email protected] says...
>
> I'd like to see that proven. 747's have been fitted with RollsRoyce RB211
> engines amongst others, which provide a spectacular thrust. Let's see some
> power/ton figures for both the dragster and the 747.
> I work daily testing RB199 engines, which in Combat setting provide approx.
> 70kN (7 tons) of thrust each, at a mass fuel flow of approx. 4800kg/hour,
> the fuel s.g. for those who wish to convert to gallons is 0.798.
> I've a sneaky feeling that the thermal efficiency of a jet engine is way
> better than an internal combustion one.
> Badger.
>

Being a Drag-Racing afficionado as well as a LR owner, I <love> the Top
Fuel/Acceleration story but the 747 part makes me raise an eyebrow too.

By my simple schoolboy math, the jet wins hands down on energy
production - employing something like 5.3MJ on a take-off run, compared
to the Top Fueller's 32KJ thusly:

Given that Mass x Acceleration = Force

Vehicle Mass (kg) Best Accel (m/s/s) Force (Joules)

Top Fuel 400 80 (av for 5sec 1/4) 32,000

747 200000 26 (30 secs/800M) 5,333,333

Stands to reason doesn't it? Doesn't each 747 engine make the equivalent
of around 125,000bhp?

However, because the Top Fuel has seven times the power to weight ratio
of the (admittedly very powerful) 747, even including the output from
all four turbines, it's specific fuel consumption in this context -
accelerative efficiency - is better than the jet I think:

Vehicle Force Fuel Consumed (Kg) Joules/Kg

Top Fuel 32,000 20 1,600

747 5,333,333 2000 1,333

Bear im mind this is all fag-packet math from a non-scientist ...

/Simon

 

Q

QrizB

Guest

• Jul 23, 2004

• #28

On Tue, 20 Jul 2004 20:05:50 +0100, "Badger"
<[email protected]> wrote:

>
>"Neil Brownlee" <[email protected]> wrote in message
>news:[email protected]...
>> Definition of Acceleration
>>
>> Under full throttle, a dragster engine consumes 1-1/2 gallons of nitro
>> methane per second; a fully loaded 747 consumes jet fuel at the same
>> rate with 25% less energy being produced.
>
>I'd like to see that proven.

Nitromethane has a density of 1.124 to 1.129 and a specific energy of
11.6 MJ/kg. Avtur comes in at 0.775 to 0.840 and a specific energy of
at least 42.8 Mj/kg.

From this it's clear to see that a gallon of nitromethane only
contains about a third of the energy that a gallon of avtur does. So
in raw terms the original statement is completely wrong.

Now, I don't have thermal efficiency figures for either dragsters or
jet engines, but seeing as how jet engines are designed with
efficiency in mind and dragster engines aren't, I'm not expecting the
dragster to be able to make up the ground it's already lost.

But I'm willing to be wrong on this one!

--
QrizB

"On second thought, let's not go to Z'Ha'Dum. It is a silly place."

 

S

[email protected]

Guest

• Jul 24, 2004

• #29

On Sat, 24 Jul 2004 07:53:48 +0000 (UTC), Simon Birkby
<[email protected]> wrote:

>Given that Mass x Acceleration = Force
>
>Vehicle Mass (kg) Best Accel (m/s/s) Force (Joules)

'cept you confuse force (Newtons) with energy (Joules)

It gets more complicated because the jet may be developing thrust
(force) at the same rate throughout the take off (i.e. burning fuel at
the same rate) but that does not result in a constant power because
power is thrust times velocity, so the jet gets more useful conversion
of heat to kinetic energy of the plane the faster it travels, I think
;-).

 

A

Austin Shackles

Guest

• Jul 24, 2004

• #30

On or around Sat, 24 Jul 2004 21:33:40 +0100, [email protected]
enlightened us thusly:

>On Sat, 24 Jul 2004 07:53:48 +0000 (UTC), Simon Birkby
><[email protected]> wrote:
>
>>Given that Mass x Acceleration = Force
>>
>>Vehicle Mass (kg) Best Accel (m/s/s) Force (Joules)
>
>'cept you confuse force (Newtons) with energy (Joules)
>
>It gets more complicated because the jet may be developing thrust
>(force) at the same rate throughout the take off (i.e. burning fuel at
>the same rate) but that does not result in a constant power because
>power is thrust times velocity, so the jet gets more useful conversion
>of heat to kinetic energy of the plane the faster it travels, I think
>;-).

also you get interesting results from varying the mass. the simple
equations of motion which are commonly used treat mass as a constant, and
say "F=ma" for example. in fact, F=d(mv)dt, rather than the F=m.dv/dt which
is implied by the former. In the case of both the dragster and the boing,
they may burn fuel fast enough that the mass change becomes significant.
Certainly is with rockets going straight up - initial acceleration is low
due to the heavy mass, then as the fuel is consumed the mass reduces so the
acceleration increases.

in fact, on the jet, it's probably not really significant; I don't think it
uses that much mass of fuel to take off, compared with the gross weight.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Quos deus vult perdere, prius dementat" Euripedes, quoted in
Boswell's "Johnson".

 

S

[email protected]

Guest

• Jul 25, 2004

• #31

On Sat, 24 Jul 2004 21:57:53 +0100, Austin Shackles
<[email protected]> wrote:

>
>in fact, on the jet, it's probably not really significant; I don't think it
>uses that much mass of fuel to take off, compared with the gross weight.

IIRC a figure of 11tonnes to get a 747 to cruise speed and height,
perhaps we should convert these to 0.5MV^2+MGH and see how much work
that fuel did ;-).

AJH

 

A

Austin Shackles

Guest

• Jul 25, 2004

• #32

On or around Sun, 25 Jul 2004 14:32:00 +0100, [email protected]
enlightened us thusly:

>On Sun, 25 Jul 2004 12:05:30 +0100, Austin Shackles
><[email protected]> wrote:
>
>>hmmm. how much does an all-up 747 weight to start with though?
>
>A google gives 377,800kg inc 196,515ltr fuel!

hmmm. jet fuel is probably about .8 kg per litre... feckinell, that's about
half the all-up weight. Mind you, it goes a fair distance on that much.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"My centre is giving way, my right is in retreat; situation excellent.
I shall attack. - Marshal Foch (1851 - 1929)

 

A

Austin Shackles

Guest

• Jul 26, 2004

• #33

On or around Mon, 26 Jul 2004 20:33:04 +0200, "Steve Maloney"
<[email protected]> enlightened us thusly:

>I've read somewhere that the workshop manuals, spare parts books and "don't
>touch that bit' bulletins for a 747 add up to more than the weight of the
>aircraft.
>Imagine the shelves in WH Smiths that could hold a Haynes Manual the weight
>of a 110!

The maunals for DEC computers used to be impressive, great row of orange (or
grey, depending on model) folders.

inluded the immortal line about specifying the timeout for operator
intervention in the evnt of a power failure and subsequent auot-reboot. The
timeout, it says, is specified in microfortnights, which approximate to
seconds.
--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
"Festina Lente" (Hasten slowly) Suetonius (c.70-c.140) Augustus, 25