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#### Duncan

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6,653 Posts
Hi Zero

You can get a "car" to do 55mph on 900 watts BUT it will need to be a bit special!

This is Solar Racer territory!

It would need to be very light and "streamlined" - which does not mean "looks fast"

It would need to have the air flow over it without separation

This means it needs a loooong gently sloping tail

When we talk about electric motors being more efficient or more "powerful"

Energy out (useful power) / Energy In
an IC engine is about 30% - (absolute max)
An Electric motor is about 90%

A 100Hp (75Kw) IC engine only produces that at about 5000rpm - at 2000rpm it probably has 20 Hp (15Kw)

An electric motor with 100Hp has 100Hp at 1000 rpm and at 5000rpm

A car engine is not expected to run at full power for more than a few minutes

The DC motors from forklift we use are rated as continuous power

#### Duncan

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6,653 Posts
Hi Zero

You will have to bite the bullet and get your head around mathematics - if you can't use the numbers you are just going -WhaWhaWha

Go back to school - get a tutor - do what it takes but if you can't do the maths you can't do engineering

If you cant handle simple maths you cannot do engineering! - full STOP'

turbochargers nearly double ICE efficiency - COBBLERS!!
You can get double or triple the POWER - but not increased efficiency

For all of your - use the exhaust stream ....
you need to know the heat engine equation

(Temp In - Temp Out) / Temp In = Maximum Possible efficiency
(Temp in degrees Kelvin)

Temp in - 100C, 373K - Temp out 50C -323K - max efficiency 50/373 = 13%
And that is theoretical maximum with no losses of friction!!

i can totally understand how golfball dimples make a surface more aerodynamic than a smooth surface because i can picture air dragging on the surface where the turbulence of dimples makes a slippery "air to air" surface.

NO NO NO
the reason it works is because the turbulent air (which has more drag not less than laminar flow) stays attached to the surface longer reducing the form drag (the pocket of low pressure behind the ball)

You can do engineering with a small number of simple equations BUT you need to handle things in numbers -
Engineering = Quantitative

Art = Qualitative and works with people - but it doesn't work on "things" - they need engineering

#### Duncan

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6,653 Posts
Hi Zero

whoever replied about the golf ball, you're saying the EXACT same thing i did, but with different words. did i not say that the layer of air that clings to the dimples is more slippery than a smooth surface? maybe turbulence is the wrong technical word, but the dimples absolutely DO disturb the flow of air at the surface creating a sort of film over which the air that keeps flowing slides much more easily just like teflon does with surfaces, only in a gaseous form. the air in contact with the dimples is NOT static, hence the term turbulence, just like an air hockey puck sliding effortlessly.
NO NO NO NO NO

Read what I said ! There is MORE surface drag in turbulent air - MORE
There is also LESS Form drag which more than balances for the increased surface drag

Until you can handle numbers you can't tell diddly

If you are too lazy to do the maths you are just playing with yourself

#### Duncan

Joined
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6,653 Posts
Hi Zero

You are still wrong
You said - the turbulent air
the surface creating a sort of film over which the air that keeps flowing slides much more easily just like teflon does with surfaces

which is plain wrong

I said the effect is to keep the flow attached longer

On Zipp's smooth discs this was much higher than for the dimpled wheels and, suggesting the Recr is reduced by the presence of the dimples. It also suggests that the dimples make the flow turbulent at an earlier point so the more energetic turbulent flow may stay attached to the surface for longer

Stop getting annoyed and read other peoples posts before you fly off the handle

#### Duncan

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6,653 Posts
Zero
Forget what I said about learning some maths

When you have finished primary school - successfully I hope! you will be able to read other peoples posts and UNDERSTAND (a big word) them