Solar Freaks

Karo,

It certainly does appear that there was a significant improvement of the Moorebank cars between the state event and the nationals last year.

Please correct me if I'm wrong firefly, but I believe that a major change Moorebank made to "Stealth" was the replacement of the Dicksmith panel with one made up from 2 Scorpio car panels.

miseli

Karo wrote:Totally agree with firefly there. Jhg, did you mean a 300g car with NO maximizer and a 520g car WITH a maximizer. This then would probably be a tighter race...

Karo

PS. Hey firefly, was your car the same chassis weight at the state? Im guessing it was pretty major changes for the nationals...

300g car with no maximiser and a 520g car with a maximiser also cannot really be compared because of the variables that Mark has mentioned.

Chassis weight did increase, however no major changes were implemented because as i've stated earlier, the design was too heavily integrated to alter major changes.

firefly wrote:They were subtle changes, but yes panel choice was one of our changes.

I think you'll find that it was the panel change that brought about the major improvement in your performance.

miseli wrote:

firefly wrote:They were subtle changes, but yes panel choice was one of our changes.

I think you'll find that it was the panel change that brought about the major improvement in your performance.

Yes, without a doubt, in terms of efficiency and fill factor, it was a major improvement over the dicksmith cells which contributed to the increased performance. Old dicksmith cells read about 0.69-0.7 i think.

firefly,

It wasn't just the fill factor (a bad FF panel doesn't necessarily mean that it is no good). Last year's panel power to weight formula disadvantaged the lower powered cars. And that was even over just the 1 lap. Over 2 laps, the difference between a 6W and 12W panel was considerable.

This year's formula has been changed to hopefully even things out a little more again.

miseli

Thanks miseli. Maybe I should have made it more clearly, 'if everything apart from weight is a constant!' But yes your totally right!

miseli wrote:firefly,

It wasn't just the fill factor (a bad FF panel doesn't necessarily mean that it is no good). Last year's panel power to weight formula disadvantaged the lower powered cars. And that was even over just the 1 lap. Over 2 laps, the difference between a 6W and 12W panel was considerable.

miseli

Yes, we did the calculations with the ballast, which is why we did buy the scorpio.

firefly,

If you don't mind me asking, what type of panel and power will you be going with for this year? And will you give yourself the option of going without electronics?

miseli

Thanks Firefly but I disagree with your statement. If you run without a maximiser but have your gear ratio correct you will still be able to win over one which runs with a maximizer given your car is of the lightest weight possible! In regards to heavily integrated, I'm sure their are lighter substitutes. No offense! I only say this because for the past two nationals events I was able to produce cars which where under 300 but still able to support 4kg plus! But it will be interesting to see what you guy can bring to the national event this year! Main issue for this year will be keeping the car on the track especially in W.A.! Enjoy and Good Luck everyone! =]

jhg,

miseli wrote:If you run without a maximiser but have your gear ratio correct you will still be able to win over one which runs with a maximizer given your car is of the lightest weight possible!

Are you meaning this with the current power to weight ratio and with the 30% weight reduction for no electronics? If this is the case then, as has been mentioned in a previous post, there is an advantage there to be gained (if running without electronics), but only in the lower sunlights. This, of course, is only relevant if the correct car setup for the conditions is used.

In good sunlight, however, no electronics still has no chance. Even with the weight reduction.

miseli

When you come over to WA, I will show you what can be done to get around this! But only if I get a car together!

jhg wrote:When you come over to WA, I will show you what can be done to get around this! But only if I get a car together!

I'm going to have to disagree with you there. Physics is physics and that isn't something you can just get around.

jhg wrote:Thanks Firefly but I disagree with your statement. If you run without a maximiser but have your gear ratio correct you will still be able to win over one which runs with a maximizer given your car is of the lightest weight possible!

miseli wrote:jhg,

Are you meaning this with the current power to weight ratio and with the 30% weight reduction for no electronics? If this is the case then, as has been mentioned in a previous post, there is an advantage there to be gained (if running without electronics), but only in the lower sunlights. This, of course, is only relevant if the correct car setup for the conditions is used.

In good sunlight, however, no electronics still has no chance. Even with the weight reduction.

miseli

My statements are in an agreement to what mark has said..

firefly wrote: Last year's winning car did have the possibility to reduce some weight, however the design was too heavily integrated to alter major changes.

jhg wrote:In regards to heavily integrated, I'm sure their are lighter substitutes. No offense!

You've taken my statement out of context, i can't take offense to that.
I did mention "the possibility to reduce some weight".

Thanks Marc for your definite answer about the use of Maximiser in this years competition. For all those students which werent sure, hope they read this post and know what to do. On another note, I did like the carbon fiber sheet at the front of the chassis Firefly. Are you still in this years competition?; if so good-luck!

jhg wrote:I did like the carbon fiber sheet at the front of the chassis Firefly. Are you still in this years competition?; if so good-luck!

Thanks, the CF was actually leftovers which was previously used for other purposes. It is very dear and we were lucky to have some to use. Are you helping WA schools?

jhg wrote:Thanks Marc for your definite answer about the use of Maximiser in this years competition

No problem jhg. I'm just trying to give everyone a heads up. No one out there should be turning up to an event without being able to switch to electronics.

By all means, teams can have a play around with going without, but have the electronics there as a safety net.

miseli wrote:In good sunlight, however, no electronics still has no chance. Even with the weight reduction.

I will concede that this statement does not does take one thing into account and that is wheel slip. At the start of a race, a car with electronics (especially a lighter and lower powered one) is prone to wheel slip in high sunlight and this means it won’t accelerate (initially) as quickly as it should be doing.

This therefore means that if a car has a particularly low (and it would have to be low) drive wheel slip coefficient (N/kg), and the sun level is very high, then going without electronics may in fact (and I say may) be slightly advantageous (for that particular car). If this does happen to be the case then as soon as the sun drops off a little, wheel slip will lessen or disappear and electronics will take over. This will then continue until the sun drops low enough for the advantage to swing back to no electronics.
If this low drive wheel slip coefficient scenario is taking effect then get a tyre or do something else to improve the traction as this will easily better the performance over trying to switch to no electronics.

Drive wheel slip is dependent on several things. It depends on weight distribution in the car, 3 or 4 wheels, tyre or no tyre, track surface, etc. The likelihood of wheel slip will also depend on what panel power is being used. I think that most cars using a tyre should be alright. If no tyre is being used, I suggest that one be made available in the better sunlights.

Ian Gardner has performed some wheel slip tests on the national track and found it to provide considerably less traction than the Victorian track.

miseli

Can wheel spin be minimized by putting the drive wheel at the back/front/middle/side? Also by having a tyre on your drive wheel, would that improve traction?

Karo

Hello Karo,

Yes, a tyre on the drive wheel should increase your traction. If you are using one of the nylon wheels from RI gear in Victoria then I would definitely suggest to use one in the good sunlights (especially on 4 wheeled cars).
I have video footage from the 2009 national event where one of the Syndal South cars went without a tyre in the first race of the plate event final. You can clearly hear the wheel slip at the start of this race.

http://www.youtube.com/watch?v=N-oDCEw9XZM

I will see if I can get it online as well, but they then added a tyre to their car for the second race and there was a significant improvement in their acceleration. This reduced the losing margin from the previous race of about 4 to 5 track sections to a little over one track section.
I don't think you could have any evidence more conclusive.

Adding a tyre will however increase your rolling resistance and so you may then like to remove it in the lower sunlights. I never bothered back when I was still racing, but things seem to be a little tighter these days and so everything counts.

Three wheels will give you more drive wheel traction than four if the end with the single wheel is being driven. Having the drive wheel at the rear should also help although not by a great deal in a model solar car. Ever wondered why a drag car has its drive wheels at the back?

miseli

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On another note, 50% power reduction will be interesting to see next year! The connections for the automax and easymax are ideal! The dean plugs can connect to each other in the right terminal to finish the connection. Tony were they designed to do this or was it the luck of the draw? Unfortunately the engelec maximizer is somewhat harder to be interchangeable for the use of a maximiser or not.

Question: When schools decide to race without a maximizer they don't need to carry the weight of the maximizer (roughly 40-50grams). No-one tried I don't believe, so it was never an issue. From memory (just checked) from the NSW spreadsheet of car data they had maximiser and without max weight. The without maximiser weight did not adjust for no maximizer there! This should be taken into consideration for next year right?