Aussie solar car fastest in world

[Phil Allison]

**See:

http://bigpondnews.com/articles/Tec...e_car_breaks_a_world_speed_record_561319.html

79kph on only 1200 watts of DC input is VEEERY efficient.

Reckon that is no more air drag than experienced by a racing cyclist on a
velodrome.




..... Phil

 

[fritz]

**See:

http://bigpondnews.com/articles/Tec...e_car_breaks_a_world_speed_record_561319.html

79kph on only 1200 watts of DC input is VEEERY efficient.

Sure is.
The rolling resistance must be very low - high pressure tyres and minimal suspension.

Reckon that is no more air drag than experienced by a racing cyclist on a velodrome.

Probably significantly less, the frontal area looks far smaller than a cyclist.

 

[Phil Allison]

"fritz"

Probably significantly less, the frontal area looks far smaller than a
cyclist.

** Huh ??

You looking at the same pic as me??

I see two front wheels with fairings, a large pod at the back with the
driver in it and a dirty great solar panel shaped like an aerofoil.

The trick is in the "streamlining" - a streamlined cyclist can go much
faster than a normal one.


..... Phil

 

[Phil Allison]

"Phil Allison"

**See:

http://bigpondnews.com/articles/Tec...e_car_breaks_a_world_speed_record_561319.html

79kph on only 1200 watts of DC input is VEEERY efficient.

** Oops - the new record is 88 kph.


.... Phil

 

[terryc]

Reckon that is no more air drag than experienced by a racing cyclist on a
velodrome.

It would have to be a lot less. This is why any serious human powered
vehicle speed attempt is undertaken by a bicycle(usually recumbent) with
fairings front and back if not a complete shell.

 

[Phil Allison]

"terryc"

It would have to be a lot less.

** Nonsense.

The speeds and input powers are similar.

Means the drag force must be too.



.... Phil

 

[[email protected]]

Sure is.
The rolling resistance must be very low - high pressure tyres and minimal suspension.

....

To overcome rolling resistance of a 1 tonne car 1 metre on normal tyres
on a road takes about 100 J. To get it to 80 kph therefore takes around 2.2 kW.

Using BMX tyres as per many solar cars is not quite a factor of 2 better --
so 1.1 kW.

 

[Phil Allison]

To overcome rolling resistance of a 1 tonne car 1 metre on normal tyres
on a road takes about 100 J.

** Even if true - it has got nothing to do with the car in question or
when travelling at speed.

To get it to 80 kph therefore takes around 2.2 kW.

** Absolutely nuts.

The drag experienced by the solar car or a cyclist is almost entirely due to
AIR resistance.

And that is not a linear function of speed.


..... Phil

 

[[email protected]]

** Even if true - it has got nothing to do with the car in question or
when travelling at speed.

....

It's not a bad rule of thumb as it turns out. Rolling resistance
can go higher than indicated as the tyres heat up.

Rolling resistance for a bike with average tyres is sometimes taken as around
.1 * m * v Watts.

Good racing tyres or "solars" might reduce the ".1" to ".05" or so.

So for m = 1000 kg, v = 22 m/s (80 kph) still gives 2.2 kW.
Very much in line with my original rule of thumb.

On a bike with rider in tuck position air resistance with no wind
is something like .4 * v^3 Watts. If possible to get to 80 kph
that would be 4.3 kW.

So a "car" going at 80 kph on 1200 W seems to not only out-perform
a good race bike but also seems to be meeting almost no air resistance
as per one comment.

 

[Phil Allison]

" Kym is full of Horseshit "

It's not a bad rule of thumb as it turns out.

** For Christ's sake - go learn some basic physics, dickhead.

The drag experienced by the solar car or a cyclist is almost entirely due to
AIR resistance.

And that is not a linear function of speed.


..... Phil

 

[[email protected]]

The drag experienced by the solar car or a cyclist is almost entirely due to
AIR resistance.
And that is not a linear function of speed.

I get it -- you can't read or understand anything that people write.

In the part you carfully clipped I showed the air resistance
at least for a bicyle is normally much greater than rolling resistance
and is a function of velocity cubed.

The rule of thumb in bike racing is the 2 are equal at around 20 kph.

A few years back a couple mates and I put a 10 kW electric motor in a
go-kart. It managed to do 1 km in around 17 sec. Luckily, we all survived.
Most of the go-kart didn't.

In any case, the report shows the car is "pretty good" with total power
comparable with just expected rolling resistance.

 

[Phil Allison]

" Kym is full of Horeshit and a raving NUT CASE "

In the part you carfully clipped I showed the air resistance
at least for a bicyle is normally much greater than rolling resistance
and is a function of velocity cubed.

The rule of thumb in bike racing is the 2 are equal at around 20 kph.

** Contradicts your previous claims now carefully snipped out of sight.

And backs mine up entirely.

At SPEED - the AIR drag is always way dominant.

In any case, the report shows the car is "pretty good" with total power
comparable with just expected rolling resistance.

** Wot absolute BOLLOCKS !!

You are totally BESOTTED with your stupid, wrong math.




....... Phil

 

[[email protected]]

[...]

--
[Read before writing:]

On a bike with rider in tuck position air resistance with no wind
is something like .4 * v^3 Watts. If possible to get to 80 kph
that would be 4.3 kW.

** For Christ's sake - go learn some basic physics, dickhead.
The drag experienced by the solar car or a cyclist is almost entirely due to
AIR resistance.
And that is not a linear function of speed.
-- "Phil [dill?] Allison" <[email protected]>, 9 Jan 2011 13:28 +1100

 

[Phil Allison]

" Kym is so utterly wrong he is entertaining "


"To overcome rolling resistance of a 1 tonne car 1 metre on normal tyres
on a road takes about 100 J. To get it to 80 kph therefore takes around 2.2
kW."

** For Christ's sake - go learn some basic physics, dickhead.

The drag experienced by the solar car or a cyclist is almost entirely due to
AIR resistance.


BTW

On what planet does a solar race like the one in question weigh 1000 kg ?

Jupiter ??

What planet is Kym from ???

Pluto ??



..... Phil

 

[Phil Allison]

" Kym is full of Horeshit and a raving NUT CASE "

In the part you carfully clipped I showed the air resistance
at least for a bicyle is normally much greater than rolling resistance
and is a function of velocity cubed.

The rule of thumb in bike racing is the 2 are equal at around 20 kph.

** Contradicts your previous claims now carefully snipped out of sight.

And backs mine up entirely.

At SPEED - the AIR drag is always way dominant.

In any case, the report shows the car is "pretty good" with total power
comparable with just expected rolling resistance.

** Wot absolute BOLLOCKS !!

You are totally BESOTTED with your stupid, wrong math.

DICKHEAD !!!!!!!!!!



....... Phil

 

[T.T.]

snip>

A few years back a couple mates and I put a 10 kW electric motor in a
go-kart. It managed to do 1 km in around 17 sec. Luckily, we all survived.
Most of the go-kart didn't.

snip

Fast car.
Is there a mixup between seconds and minutes, or kilometres and metres, or a
missing decimal point or something?

 

[Phil Allison]

"T.T."

Fast car.

** Like 211 kph !!

Is there a mixup between seconds and minutes, or kilometres and metres, or
a missing decimal point or something?

** The fastest class of Go Karts are the "Superkarts".

Fitted with a 95hp engine and being fully faired means they can reach over
250 kph.




...... Phil

 

[[email protected]]

snip>
Fast car.
Is there a mixup between seconds and minutes, or kilometres and metres, or a
missing decimal point or something?

It was pretty informal measuring, and we maybe were scared +/- a
couple seconds (10%) on the total time, but it's around there.
An avg of around 200 kph although it felt like Mach 1+.

You no doubt know electric motors have good torque at low revs
so you tend to get off the start line really well but then (at
least in our case) quickly hit a wall.

I have some notes as well as twisted metal out in the garage.
I looked at them before poor ol' NPD Phil got involved . It's
definitely 17 and not 27. Some other numbers show the accel
maxed around 1G -- 0 to 60 kph in well under 2 sec -- levelling off
well before 10 sec into the best km. Snapped a few bolts that day.

As I said before, it was pretty scary even for bystanders. And that's on
a good day when the motor wasn't making loud noises and trying to screw
the 1/2 the vehicle up into a ball from the inside.

If you look around on youtube there is one neat vid from
a few years back with some mech eng academic in cal who built
what looks like a 50s classic racecar (something like
<http://housebroad.com/SpeedClassic/Blue_race-car.jpg>)
with an electric motor I think much less than the 10 kW Lynch (100V/100A)
we were using and he was using it to blow away motorheads at trafficlights.

--

My sig lines fall into 2 broad categories: either wise or silly.
I rely on the reader understanding which is which.

Congratulations. You must be a very special boy or girl.
-- tg <[email protected]>, 1 Dec 2010 12:35:45 PST

 

[T.T.]

"T.T."



** Like 211 kph !!



** The fastest class of Go Karts are the "Superkarts".

Fitted with a 95hp engine and being fully faired means they can reach over
250 kph.




..... Phil

I came to mock and I left better informed and astounded.
Thanks.

 

[[email protected]]

[email protected] wrote:
[...]

While my little project was a few years back, I noticed this:

<http://www.lmcltd.net/index.php?mact=News,cntnt01,detail,0&cntnt01articleid=2&cntnt01returnid=15>

where Top Gear made a 48v (!!) 4.8 kW Lynch motor-based quadcycle
beat a Mustang upto 100 mi/hr (for those what forget -- that's 166 kph).

Yea. There's a lot you can do if you don't give a damn how well
the batteries work after the first 20 seconds.