[chbot] Chchrobotics Digest, Vol 69, Issue 15

[Mark Beckett]

Yes 1 m3 of air is heavier than 1 litre of milk, but its also 1000 times 
the volume.
I hate the use of m3 especially when talking about our water, as it 
gives everyone a false sense of the amount.


Your little 150cc (assuming 100% volumetric efficiency) is consuming 
0.18g of air, and having about 8.5g of fuel added to it.
At 1000rpm its 60mS/cycle but only half that is the intake, so 30mS to 
suck it in.
The other factor helping this is that Air is at 14.5psi (sea level) 
while the inside of the cylinder is less.

The 10.7cc of fuel gives around 0.3445MJ of energy, and if its consumed 
in the 30mS of the power stroke is around 11.48w
The higher the revs, the faster the stroke, the more energy.
The reality is that effeciencies start to reduce that, so somewhere it 
tapers off ...hopefully before the internals go bang.


You are right about the relative effectiveness of a low powered device.
I think Richard might have had another use for them....

Mark

Marshland Engineering wrote:
> After years of questioning how do planes fly, ok I know all the 
> equations, but until recently I came to realize air is much heavier 
> than you think. This all came about with motorbike racing. Sucking in 
> 150 cc or air into an engine in milli seconds takes a huge amount of 
> energy.
>
> 1 m3 of air is 1.2 kg or 1 m3 of air is heavier than a 1 litre of 
> milk!! Looking at it this way, planes now make more sense. AIR IS HEAVY
> Ok so how much energy does it take to move it in a vacuum cleaner. A 
> lot. Most cleaners are 1000+ watts. So how long will a 12 volt 
> rechargeable last at say 500 watts ??? Not long.
>
> Long live the  240 Volts.
>
> Another interesting 'fact', the brain is using 13 watts of energy 
> while running.
>
> Cheers Wallace
>
>
>
>
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