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World Solar Challenge Post-Event Questionnaire
by Richard Rahders
created 7/29/2003
submitted 7/29/2003 11:16:01 AM

WSC '96 Post-Event Questionnaire regarding the performance of "Pumpkinseed", the first PV/Wind hybrid to cross a continent.

THE 1996 WORLD SOLAR CHALLENGE
TECHNICAL DEBRIEFING
QUESTIONNAIRE

TO: PHOTOVOLTAICS SPECIAL RESEARCH CENTRE
UNIVERSITY OF NEW SOUTH WALES, SYDNEY, AUSTRALIA

RE: "PUMPKINSEED" PERFORMANCE: finish 2nd U.S., 5th pb-acid/silicon, 30th overall.
Specifications: 16 ft. 10 in. (5.15 m.) long, 6 ft. 5 in. (1.98 m.) wide, 605 lbs. (275 kg) w/o driver.
Height: w/o wings, 34 in.(1.0 m. includes 6 in. fin); with wings, 1.5 m. max. reg.
Wings: 32 in. tall, chord length 17 in. to 13 in. (top).
Batteries/elec.: 60 V., 252 lbs. Johnson Controls SLI Group 65 flooded lead acid.

FROM: RICHARD R. RAHDERS, Australia Team Manager
Team New England @ SANTA CRUZ Solar/Electric Vehicle Racing Group
104 Moore Creek Road, Santa Cruz, California, USA 95060
Tel: (Intl.+) 408.426.3783; Fax: 2526; Email: FMJG65C@prodigy.com

The information provided for this questionnaire will be used to assist in preparation of the official technical report of
the 1996 World Solar Challenge. Your cooperation in answering the following questions in greatly appreciated. An
accurate and detailed response enables us to ensure that your team's efforts receive as much recognition as possible
in the report.

TEAM: TNE@SANTA CRUZ / ARIZONA STATE UNIVERSITY / UNIVERSITY OF
MASSACHUSETTS AT LOWELL
CAR NAME: "PUMPKINSEED"
CAR NUMBER: 69

Results

1. Where did your vehicle finish at the end of each day?

qualified: 26th place, 73 kph / 45.4 mph.
day 1: Katherine, 314 k./ 314 k. total / 33rd place. day 6: Marla, 397 / 2022 / 31st.
day 2: Dunmarra, 317 / 631 / 32nd. day 7: 91 k. S. of Coober Pedy, 243 / 2265 / 31st
day 3: 50 k. N. of Tennant Creek, 310 / 941 / 32nd. day 8: Glendambo, 162 / 2427 / 31st
day 4: 30 k. N. of TiTree, 348 / 1289 / 30th. day 9: Warnertown, 398 / 2825 / 32nd.
day 5: 135 k. S. of Alice Springs, 336 / 1625 / 30th. day 10: Adelaide, finish 12:54, 185 / 3010 / 30th.

Array Output

2. What was the peak power output of your array for each day of the race?
3. What was the average array power from 0800 to 1700?

day 1: peak power: 587 watts. average power: +/- 336watts. day 6: 730 / +/- 500
day 2: 644 / +/- 480 day 7: 630 / +/- 340
day 3: 600 / +/- 500 day 8: 650 / +/- 250
day 4: 600 / +/- 450 day 9: 670 / +/- 530
day 5: 590 / +/- 450 day 10: 415 / +/- 240

1996 WSC Tech Questionnaire page 2.

4. Was the array difficult to clean? NO.

5. Did you use any special methods for keeping the array cool?
YES, WE KEPT IT IN THE SHADE. Actually, no, we didn't.

6. Did the array perform as well as expected?
Yes, but the weather did not perform as we preferred.

Batteries

7. What was the maximum charge added to the battery:
a. In the morning, sunrise - 0800: 1.3 kWh (that's one point three kWh) on day 10.
b. In the evening, 1700 - sunset: 0.88 kWh (zero point eight eight kWh) on day 5.

8. What was the battery capacity at the end of each day? Remaining charge, end of race day (5:00 pm):
approximate percentages, based upon 100%= 5kWh:

day 1: 50% day 4: 15% day 7: 10% day 10: 60% (12:54 pm)
day 2: 20% day 5: 15% day 8: batts reverse polarity 10:15 am; replace; 80%
day 3: 5% day 6: 20% day 9: 60%

9. What was the battery capacity at the race finish? 60%.

10. Did the batteries perform as well as expected?
Yes. Johnson-Controls Group 65 lead-acid batteries by K. Jones were perfectly balanced. Bad weather, no sun
at end of day 7, rain and no sun during the morning of day 8, plus excessive discharge by driver led to failure of
first battery pack on day 8.

11. If you entered the World Solar Challenge again, would you change the type and/or capacity of your battery?
We prefer real-world, available, EV-related batteries. If chemistries other than lead-acid are readily available to the
general public in the next race we may test those, especially to minimize weight. With the drive system we use we
will probably run a higher bus voltage than we did in this race.

12. Would your battery management strategy be different? How?
Instead of starting with a constant-speed strategy and switching late on day 2 to a constant-current strategy,
we would start with a constant current strategy.

Tyres

13. If known, what is your tyre rolling resistance coefficient and how was this determined?
Unknown. We used Avocet Fasgrip 20x1.75 tires and Pacemark tubes on custom Team New England / UML carbon
wheels by Nelson, Garrison & Zappa on days 2 through 10, and on steel spoke wheels day 1.

14. How many flat tires did your car have?
We had two before the start on day 1, necessitating a 22-min. late start; we had three more on day 1 before the
spoke scratching the tubes was discovered; we switched wheels in the morning of day 2 and then we had no flats
until 30 km. before the finish in Adelaide, when we had one more flat. We did change three tires at the ends of
race days as precautions.

1996 WSC Tech Questionnaire page 3.

15. How long did each flat tyre change take?
Flats 1 & 2, rear, 20 min. each; 3, 4, & 5, rear, 10 min. each; 6, front, 8 min.

16. see above.

Strategy

17. What method of weather prediction did you use and how could this be improved?
We obtained good weather data from the governments of the Northern Territory and South Australia, detailing
typical weather at 20 stations down the Stuart Highway for October and November, for between 15 and 45 years,
which we used to develop our race strategy. For daily race tactics during the race we relied on public radio broadcasts
& observation. Next time we will get better daily data, perhaps through a weather fax.

18. Please describe your race strategy. To what extent did your chosen race strategy influence your result?
We started with a constant speed strategy for maximum motor/controller efficiency, but with the heavy headwinds,
scattered afternoon clouds, and wheel/tire problems on day 1 we used too much energy. Thereafter, we switched to
a constant-current strategy, running to a target of 600 watts per hour, which gave us a speed of between
32 kph (20 mph) and 96 kph (60 mph) depending upon wind and terrain. The historic westerlies which we relied
upon for our pre-race strategy only occurred in isolated instances, making our wings less effective than expected.
Our wings were able to reduce our aerodynamic drag in a cross wind substantially and significantly when crosswinds
did occur, sometimes reducing our energy consumption by as much as 50% even at 40 kph, or, in the alternative,
allowing a 50% increase in speed at the same energy consumption. Sideloading was far less of a problem than
some people predicted, but our typical speed was far less than expected also. Our main problem throughout the
race was inappropriate weather and lack of power, not strategy, although better reading of weather patterns might
have given us a slightly better result.

Overall performance and problems

19. During the race, at what speed did your vehicle travel with 1000-watt input to the motor, on a flat surface with no
wind? 20. With 1500 W input?
As mentioned above, we generally traveled at 600 watts average input, with speeds from 32-96 kph depending upon
wind and terrain. We NEVER traveled with 1M or 1.5M W input to the motor on a flat surface with no wind.

21. Alternatively, for a given speed on a flat surface with no wind, what was the power consumption?
We have not crunched the data yet. Here are some anecdotal numbers:

During one 1.5-hour period on the morning of day 4, with a cross-wind and no wings, we averaged 39.4 kph (24.6 mph)
using 13.6 Wh/km (21.8 Wh/mi.). That same afternoon, during a 2-hr. period slightly uphill with the wings up and an
+/- 18 kph (11 mph) crosswind, we averaged 56.2 kph (35.1 mph) on 13.4 Wh/km (21.5 Wh/mi.).

During one six-hour period on day 9, from Glendambo to Port Augusta, with the wings up and a +/- 24 kph (15 mph)
crosswind, we averaged 50 kph (30.8 mph) on 6.8 Wh/km. (10.9 Wh/mi), our best performance. Our best segments
of that day were: (a) one 20-minute period where we went +/- 50 kph (30 mph) on 6.4 Wh/km. (10.3 Wh/mi.); and
(b) one 45-min. period where we went 58 kph (36 mph) on 10.1 Wh/km. (16.2 Wh/mi).

1996 WSC Tech Questionnaire page 4.

22. What were the handling characteristics of your vehicle in buffeting side winds?
In general, the vehicle was quite stable in sidewinds. When the wind was from the west and the wings were up,
road-trains passing would cause a slight pull toward the west. When the wind was from the east or from straight
ahead, with the wings up or down, road-trains passed without effect.

23. If the average speed of your vehicle for the entire race was less than expected, what do you see as the reasons
for this?
The main reason was that we did not get the weather we preferred. We had too little crosswind, and too much overcast. Other reasons included having an undersized solar array and having problems with wheels early in the race.

24. If you entered the World Solar Challenge again, what would you do to improve the result?
Change the weather! And increase solar power; improve aerodynamics slightly; run higher voltage; have alternative
cross-section wings, different shapes for different speeds. Plus some secret stuff.

25. Please list any major mechanical [or other] problems experienced during the race:
On day 8 the batteries failed, costing us 80 minutes in penalties and battery-swapping time. We had no other major
problems even driving in the rain. BRLS PM motor, controller by Bohn & Bleck were perfect.

26. What do you think is the best feature of your car?
The aerodynamic design and the construction of the body; the design and construction of the wings; and the car's
relatively low cost (US$15,000, not including borrowed array and motor/controller).

27. What other features about your car or race strategy do you think are relatively unique and/or interesting?
(a) The Photocomm/ASU solar array, built by ASU students and A. Chuzel, is attached to the hatch/substrates with
hot-glue "rivets" developed by Chuzel which are secure even at Outback temperatures but which can be melted at
higher temperatures so that the array can be removed and affixed to other substrate shapes.
(b) The monocoque kevlar/nomex body designed and built by Bassano, Wirtanen and Tuttle is very fair, light and
strong.
(c) The interior carbon bulkheads and tubes are recycled: flat panels from D. Cloud were originally used as floorboards
in Boeing jetliners, and tubes were originally windsurfer masts.
(d) This is a tricycle design, one wheel front and two back, which allows a less blunt front end, improving aero &
handling, but limits solar array area.
(e) The elegant, unique front wheel assembly by Leeds drives the car and steers it.
(f) Steering is by footle bars, rather than handle bars or steering wheel. Accelerator and rear go-cart disc brakes are
operated by a stick and pot in the left hand; wings and gauges are operated by the right hand.
(g) Wings by Wirtanen and Francis are adjusted by reference to telltales on the windscreen, consultation with the
chase car observing telltales on the wings, and driver experience.
(h) Both the body and the wings are NACA 64[2]-015 Basic Thickness Forms, per Bassano. The car was designed to
perform best in crosswinds; the purest NACA shape in the body is a cross section at 15 degrees off the centerline,
which is the apparent wind angle at design speed and wind speed. Also, the leeward rear wheel is in the wind shadow
of the front wheel at that apparent-wind angle, giving a two-wheel wind shadow.
(i) Excellent electronics by Bohn & Bleck.
(j) Carbon wheels by Nelson were light, strong, cost-effective.
(k) We will have an unusual motor energy consumption vs. speed graph when we are done crunching the numbers.
Our main surprises were how much of a contribution the wings made to reduction of drag in significant crosswinds at
the rather low speeds we were going; and how minimal the effect of sideloading was on suspension, wheels, tires
and driving.

28. In what area do you think the most improvement could be made to your vehicle?
If we had a lot of money we could get more efficient (non-Sunrayce spec) solar cells; lightweight batteries; and
wheel-motors. And the more you know, the more you know you don't know: more knowledge, better teamwork.

Best regards,
Richard R. Rahders

07/28/03 notes:

The "Pumpkinseed" and its mule (first parts from the molds), the "Packaging Material", were donated
to an Arizona high school district where interested teams have been trying to get funding to rebuild and race again.

We installed wings on the Solar Motions WSC '99 car but conditions did not allow the team to utilize the wings effectively
during the race.

3178 words | dickr

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