Aussie solar car fastest in world

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

** 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

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

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.

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.

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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 ?

David L. Jones wrote: ...

...

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.

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". :)

Thanks for the details.

--
[...] I want you to acknowledge that AGW is only one possible reason 
for temperature increase, out of a number of possible reasons.
 -- No Pressure , 7 Dec 2010 02:31:55 -0800

or

to

Here is the actual theoretical graph for the Sunswift car:

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.

Dave.

"David L. Jones"

Here is the actual theoretical graph

** WTF does " actual theoretical " mean ??

It simply cannot be both things.

for the Sunswift car:

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

"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

Of course, my bad. I meant that this is the theoretical power requirement graph from the actual Sunswift car used.

raph.png

e G

ion

All the various external surfaces are aerofoil wings, mainly to reduce drag and tail vortexes et.al. No lift figures are mentioned. The graph is the theoretical power required to drive the car based on total rolling resistance and aerodynamic drag figures. Presumably they are using known measured test data for both of these, and it kind of implies that in the document I have. It is stated they have measured these parameters and use them in a real-time simulator model to enable optimisation of the cars energy consumption vs performance etc.

From the documentation it sounds like the rolling resistance is not insignificant and is split into two components, tires and "bearings etc". In a formula provided, the tire rolling resistance and the wheels bearing resistance are both included. The tire rolling resistance term is: mass * gravity * rolling coefficient The bearing resistance term is: Number of Wheels * bearing coefficient

• velocity

Dave.

[...]

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:]

** For Christ's sake - go learn some basic physics, d*****ad. 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" , 9 Jan 2011 13:28 +1100

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

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.

"Clifford Heath" "Phil Allison"

** 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

** Not unlikely at all.

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

... Phil

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.

Michelin tyre data from .

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.

"Clifford Heath"

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

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

** 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 the f****it " <

** Good grief.

The speed and input powers are both known.

So the total amount of drag force is known = 49N.

** The data shows that the amounts of drag are similar.

The Sunswift uses about 900 watts (or 1.2 hp) to overcome aerodynamic rag - see graph.

A good cyclist outputs about that same figure when sprinting.

..... Phil

Here we go again, the latent abusive, probably psychotic trait of Phil emerges..... Philly boy, you have serious psychological problems. Why do you suddenly resort to calling me "fritz the f****it " when 99% of the people on this newsgroup would agree that YOU are the f****it, based on your previous posts ?

If you can't beat 'em, insult 'em is the Phil Allison way...........as usual................

What is the CdA for the Sunswift and a racing bike ? Please fill in the following ...

Racing bike CdA = Sunswift CdA =

coefficient (Cd)

Cd,

Fill in the CdA table above...if you don't know how to do it then shut up.

see graph.

The subject is air drag, CdA, specifically comparing the CdA of a racing bike to the Sunswift.

My latest document for the Sunswift 4 does not say, but from a document for Sunswift 3:

CdA for Sunswift III is 0.11 You could assume Sunswift 4 would be the same or marginally better.

Optimised bikes seem to be typically around 0.7-0.8 at best?

Dave.

My latest document for the Sunswift 4 does not say, but from a document for Sunswift 3:

-CdA for Sunswift III is 0.11

-You could assume Sunswift 4 would be the same or marginally better.

-Optimised bikes seem to be typically around 0.7-0.8 at best?

-Dave.

That's what I suspected. Looks like philthy phil has egg all over his face, yet again.

Who the f*ck cares?