Rotary Racer - Car Performance
Kemble 2008-06-10 - Terry Barnaby
The Tests
The tests were carried out at Kemble airfield. The car was run slightly uphill into the wind (wind at 45 degees) turned around and then run down hill. Drivers took turns and various components were changed on the car to see the effect they would have. The Car Computer logged all of the results and a paper form was filled in with the peak speeds. The average of the uphill and downhill peaks was calculated to give a rough overal speed figure.
- Car in current form with rounded nose. Same as Goodwood but with lowered roll-bar, without foam and airfoils on front axle and with rounded nose
- Try Uplift nose cone as used in Goodwood race.
- Try Uplift nose, Screen
- Try Uplift nose, Screen, filling around driver
- Try Uplift nose, Screen, filling in behind driver (no fill around driver)
- Try Uplift nose, Screen, filling in behind driver (fill around driver)
- Try Uplift nose, Screen, rollbar airfoils
| Run |
Test |
Driver |
Time |
Avg Speed |
Peak Speed |
Current |
Notes |
| 1 |
1 |
DI |
|
41.94 |
46.44 |
19.96 |
Round Nose |
| 2 |
|
GB |
|
39.42 |
|
|
Round Nose |
| 3 |
1 |
GB |
18:25 |
41.4 |
43.56 |
0.60 |
Round Nose |
| 4 |
2 |
GB |
|
43.02 |
47.16 |
20.77 |
UpSweep Nose |
| 5 |
2 |
DD |
18:40 |
40.68 |
43.92 |
0.00 |
UpSweep Nose |
| 6 |
3 |
DD |
18:42 |
41.94 |
45.36 |
0.60 |
Screen |
| 7 |
3 |
AW |
18:45 |
42.48 |
46.08 |
0.00 |
Screen |
| 8 |
4 |
AW |
18:53 |
42.48 |
46.44 |
26.62 |
Screen, Driver Fill |
| 9 |
4 |
DI |
18:55 |
42.48 |
46.80 |
21.37 |
Screen, Driver Fill |
| 10 |
5 |
DI |
19:00 |
43.66 |
46.80 |
21.57 |
Screen, Behind Driver (No driver fill) |
| 11 |
5 |
GB |
19:03 |
43.12 |
46.80 |
21.37 |
Screen, Behind Driver (No driver fill) |
| 12 |
6 |
|
|
41.40 |
45.00 |
|
Screen, Behind Driver (driver fill) ? |
| 13 |
6 |
|
|
42.48 |
46.80 |
|
Screen, Behind Driver (driver fill) ? |
| 14 |
7 |
GB |
19:20 |
43.56 |
48.24 |
18.95 |
Screen, Rollbar AirFoils |
| 15 |
7 |
DD |
19:25 |
41.40 |
45.72 |
22.18 |
Screen, Rollbar AirFoils |
| 16 |
7 |
DD |
|
39.96 |
40.68 |
|
|
| |
|
|
|
|
|
|
Tom |
| |
|
|
|
38.88 |
44.64 |
|
Terry |
| |
|
|
|
33.12 |
|
|
Martin |
| |
|
|
|
38.88 |
43.20 |
|
Kevan |
| |
|
|
|
37.44 |
42.84 |
|
Garry |
Car Computer Log
Notes
- Drivers were: Dan Isles, Gareth Barnaby, Alex Ward, Dan Dando
- The computer data looks good. The first run was accidently done with samples every 8 seconds, the rest were at 2 seconds.
- There were no data glitches or computer dropouts at all.
- The graphs show the computer limiting the current to about 40Amps on the uphill bits. It was limiting untill close to 40Km/H. We could probably improve the software algorithm to increase the current at lower speeds for better acceleration. I notice that DD pushed the Turbo button on his last uphill run ! This altered the software to limit the current to a straight 50 Amps as it should.
Results
The performance changes were small and with windspeed and driver variations the results are not conclusive. However based on the results:
- The UpSweep nose code gave a 2% improvement over the rounded nose.
- The Screen gave a 2% improvement.
- The filling in around the driver did not have any effect (when the screen was in position).
- Filling in behind the driver gave a 2% improvement.
- The airfoils on the rollbar were almost as good as filling in behind the driver (questionable).
- An overal performance improvement of about 6% should be available (plus the underside covering).
These results appear to match the Virtual Wind Tunnel tests approximately.
Conclusions
Probably the best changes to make for Castle Coome, considering the time available:
- Add a screen (shape to shed air to side rather than upwards).
- Add long Aerofoils to rollbar (unless an easy way to fill in the rear section is found (hinged unit as Tom suggested ?) would need to check motor cooling)
- Cover the bottom of the car
- Add Airfoils to the rear axle and front axle heads.
Some Pictures