Aussie solar car fastest in world

[Phil Allison]

" Kym is so full of Horseshit - he is funny "

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).

** Read the article - sunshine.

The 4.8 kW motor was removed and replaced with one capable of 120kW short
term.

That's equal to 160 hp.

And the mad, pommy wankers even blew that up.




..... Phil

 

[[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&c
ntnt01returnid=15>

where Top Gear made a initally 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.

 

[terryc]

"terryc"


** Nonsense.

The speeds and input powers are similar.

Means the drag force must be too.

I sure hope your understanding of electrical matters isn't as poor.

 

[Phil Allison]

"terrycunt"

I sure hope your understanding of electrical matters isn't as poor.

** Power = Force x speed.

Most 12 year olds know this.

How old are you ?


..... Phil

 

[SFD]

"terrycunt"


** Power = Force x speed.

Most 12 year olds know this.

How old are you ?


.... Phil

Wot if they ate baked beens the nite b4 then lit a match upon take-off!

 

[fritz]

**See:

http://bigpondnews.com/articles/Technology/2011/01/07/Aussie_car_brea...

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

Congrats to Irving and the rest of the Sunswift team, awesome effort.
Hopefully I'll be doing a video blog tour of the Sunswift racer at the
end of this month.
If anyone wants me to show any particular area in detail, or ask any
specific questions, then let me know.

For those interested in some details, at 90km/h the aerodynamic drag
accounts for over 70% of the driving power. The rest of the required
power is directly proportional to the mass of the car. The base
chassis weighs only 50kg.
Also, the breaks can stop it from 50km/h in under 10m.
The whole car weights 165kg, including the 25kg battery pack, so the
record attempt car weighed only 140kg.
The wheel motor is over 97% efficient.
The tires are inflated to 90psi and are easy to puncture, so are
usually changed every day.

Dave.
----------------------------------------------------------------------------------------------------------

A couple of specific questions on the Sunswift..
What is the frontal area (A) of the car ?
What is the drag coefficient (Cd) of the car ?
How does the drag area (CdA) compare to a racing bicycle ?

 

[[email protected]]

....
For those interested in some details, at 90km/h the aerodynamic drag
accounts for over 70% of the driving power. The rest of the required

So air resistence is equiv to 840 W. The math then shows the
friction coeff is .05; an effective profile almost 10 times better
than my old electric kart project which was around that for a
bike + rider in race mode.

From the rough calcs before, it certainly seemed air resistance
was very low.

power is directly proportional to the mass of the car. The base
chassis weighs only 50kg.
Also, the breaks can stop it from 50km/h in under 10m.
The whole car weights 165kg, including the 25kg battery pack, so the

Rolling resistence around 360 W. My old formula with race tyres would
have it .05*m*v == .05*(165+80)*55 = 674 W. The tyres used were
apparently 2x better than Michilin "solars".

record attempt car weighed only 140kg.
The wheel motor is over 97% efficient.
The tires are inflated to 90psi and are easy to puncture, so are
usually changed every day.

Thanks for the details.

 

[Phil Allison]

"David L. Jones"

Here is the actual theoretical graph


** WTF does " actual theoretical " mean ??

It simply cannot be both things.


for the Sunswift car:
http://www.eevblog.com/images/projects/SunSwiftDragGraph.png
The rolling resistance and aerodynamic drag are equal at 60km/h
Drag is not a linear function of speed as you said. Rolling resistance
is linear.

** Rolling resistance is linear - in theory only.

Odds are it diminishes at high speeds since the tyres are subject to large G
forces thereby reducing contact area and hence loss of energy by deformation
PLUS that solar array looks like a wing and so it must have some lift.


...... Phil

 

[Phil Allison]

"David L. Jones"


For those interested in some details, at 90km/h the aerodynamic drag
accounts for over 70% of the driving power.


** Thanks for that confirmation of my original opinions.

The heretics here are seriously looney.


BTW

The actual drag force on the solar car from all sources at the record speed
( 88kph) amounts to no more than 5kg.

1200/24.4/9.8 = 5



..... Phil

 

[[email protected]]

It would have to be a lot less.

[...]

Suspicion seems to be confirmed.

The actual data indicates the streamlining was almost 10x better than a
race bike. No wonder the total power was comparable to just the rolling
resistance of other electric cars.

--
[Specific learning difficulties:]

Rolling resistance for a [80 kph] bike with average tyres is [...] 2.2 kW.
On a bike with rider in tuck position air resistance with no wind
is something like .4 * v^3 Watts [...] 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.
-- "[NPD?] Phil Allison" <[email protected]>, 9 Jan 2011 13:28 +1100

 

[Clifford Heath]

I doubt that has much effect actually, especially with the very high tyre
pressures used on this kind of vehicle.

All the various external surfaces are aerofoil wings, mainly to reduce
drag and tail vortexes et.al. No lift figures are mentioned.

Highly unlikely they've designed-in any lift. You can't get lift without
drag. In fact the main figure of merit for sailplanes is L/D ratio,
because that tells you how much of your drag is actually producing lift.
It also happens to give you your sink angle.

Clifford Heath.

 

[Phil Allison]

"Clifford Heath"
"Phil Allison"

I doubt that has much effect actually, especially with the very high tyre
pressures used on this kind of vehicle.

** Really ??

90 psi is only 6 atmospheres.

88 kph results in about 250Gs on the surface of the tyres.

A = V squared / radius

G = A / 9.8

Highly unlikely they've designed-in any lift. You can't get lift without
drag.

** Not unlikely at all.

Even a small amount of lift would reduce rolling resistance as much as
removing the batteries did.


... Phil

 

[Clifford Heath]

"Clifford Heath"
"Phil Allison"
** Really ??
90 psi is only 6 atmospheres.
88 kph results in about 250Gs on the surface of the tyres.

From another post, the record attempt car weighed 140Kg.

The Michelin solar car competition tyres have a rolling resistance
coefficient of around 0.0025 - meaning the actual resistance force is
about 3.4N. To carry 140Kg across the three wheels at 88KPH requires
about 80 watts.

Assuming equal loading on the wheels of about 450N, at 90PSI, the
contact patch is about 7.5cm^2.

Estimating the total mass of each tyre at 250g, the diameter at about
60cm, and the width of the contact patch at 1cm, the mass of the tyre
in the contact patch is about 7.5 grams. At 250Gs, that's less than
20N - less than 5% of the 450N.

So you're proposing that the rotational speed at 88KPH can save about
4 watts. Big deal.

** Not unlikely at all.
Even a small amount of lift would reduce rolling resistance as much as
removing the batteries did.

It would increase the aerodynamic drag by much more, especially considering
that the aerodynamic drag is costing (1200-80) watts, or 93% of the energy
budget.

Clifford Heath.

 

[Phil Allison]

"Clifford Heath"

To carry 140Kg across the three wheels at 88KPH requires
about 80 watts.

** The graph posted by DL Jones shows rolling resistance consumes about 350
watts.

http://www.eevblog.com/images/projects/SunSwiftDragGraph.png

Very little energy is lost in ( presumably) ball bearings - else they would
become very hot.

It would increase the aerodynamic drag by much more, especially
considering
that the aerodynamic drag is costing (1200-80) watts, or 93% of the energy
budget.

** Wrong.

Aerodynamic drag is more like 70 % of the budget - as shown in the graph.

Any aerofoil section has drag, whether is produces lift or not. A simple
flat bottom, curved top aerofoil ( as appears in the pics) has lift even
with zero attack angle and so no additional drag.



...... Phil

 

[fritz]

"fritz the fuckwit lying pig ignorant **** "



** My god are one pig ignorant, lying fucking ****.

Then you better stop praying to your god(s), if you think so badly of them.
Or learn English.

Let's get the record straight here...Philthy has resorted to abusive language,
typical for him when he cannot formulate a logical argument - if you can't
beat 'em, use every foulmouthed word you can think of. Hint - it makes you
look REALLY stupid - you ain't fooling anyone with your abusive language.

Philthy said

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

I replied

It would have to be a lot less.

That is when Phithy went crazy and unleashed his boring-as-usual vitriolic spam, which he
always does when someone disagrees with his self-appointed majesty. Philthy really does
go nuts from time-to-time, resorting to infantile insults that belong in a primary school yard.

Anyway, Philthy got it wrong, as usual. The Sunswift has a substantially lower CdA figure than a
racing cyclist.

CdA for Sunswift III is 0.11
Optimised bikes seem to be typically around 0.7-0.8 at best?

Expect more foul-mouthed replies with no data.

 

[Grid Leak]

"David L. Jones"


For those interested in some details, at 90km/h the aerodynamic drag
accounts for over 70% of the driving power.


** Thanks for that confirmation of my original opinions.

The heretics here are seriously looney.


BTW

The actual drag force on the solar car from all sources at the record
speed ( 88kph) amounts to no more than 5kg.

1200/24.4/9.8 = 5



.... Phil

Who the **** cares?