1-LA_Structural_Report_Addendum

耶鲁大学lux太阳能车队结构报告

Lux Aeterna

Addendum to Structural Report for Sunrayce ’97

June 11, 1997

Team Directors: John R. Frank

Lutz Berners Prepared by:

Bennett Sprague Lutz Berners

耶鲁大学lux太阳能车队结构报告

1. Purpose

This report updates the information given in the structural report submitted on January 13, 1997, and discusses some design changes.

2. Design Changes

Lux Aeterna performed well at Eastern Regional Qualifiers, prompting few major changes.

Between the time the original report was submitted and Eastern Regional Qualifiers, the following changes had been made in the car:

some frame members were omitted since the analysis indicated low stress

electronic systems were mounted to the frame instead of the body

the seat belt was attached to the frame instead of the seat

the battery box was redesigned to snugly enclose all batteries instead of strapping each battery

down to the frame

the steering was changed to a rack-and-pinion system

Scrutineering results prompted the following changes:

the front suspensions were rebuilt using smaller diameter (but same wall thickness) tubes and

double shear on all rod ends

efforts were made to obtain data on the frame material “as welded” condition

plugs were welded in to seal all open-ended aluminum tubes

the battery box straps were replaced with properly rated straps

mirrors were changed to achieve greater rear visibility

turn signals and brake lights were redesigned

the horn was replaced with a louder one

documentation for the power bus switches was obtained

all improperly used safety wire was replaced

Qualifying laps prompted the following changes:

wheel alignment has been fixed and improved since a tire blew in lap six

electrical array connections have been reexamined and reinforced

driver’s compartment was reorganized for more comfort and easier access to switches

the tinted canopy was replaced with a clear one because it shaded part of the solar array

the Wilwood Dynalite brake calipers have been replaced with Engenetics brakes to reduce

brake drag

all body openings were sealed as much as possible

new longer-range radios have been obtained to ensure continuous communication

overall efforts to reduce weight

The following is a discussion of the four major changes.

2.1 Omission of some frame members

The original analysis showed that many frame members were subjected to very low stresses in all

situations. We subsequently changed a cross in the top plane and a cross in the bottom plane of the frame to a simple diagonal.

The roll cage performed very well in the analysis. However, the diagonal member in the side planes

obstructed vision and, after additional analysis, was omitted. The stresses in the roll cage stayed below the maximum allowable stress of 20 MPa.

One thing that should be noted is bottom left corner which is shown as a high stress area. The actual frame is reinforced with a 1” aluminum plate into which the rear suspension rod end is threaded. The stress at this point should be much lower than indicated by the analysis. We believe that this change in the roll cage has no significant adverse effect on the safety of Lux Aeterna.

2.2 Re-examination of frame welds and material condition

耶鲁大学lux太阳能车队结构报告

The documentation for the frame material “as-welded” condition is attached. Note that the numbers are for the “beads off” condition. The slight weakening of the welds is incorporated in the safety factor of 1.4 which applies to all analyses of the frame.

Some frame welds have been examined and incomplete welds have been completed. After nearly 200 miles of road-testing, there are no signs of fatigue or structural weakening in the frame.

All frame tubes with open ends were sealed with aluminum plugs to avoid weak spots.

2.3 Redesign of front suspension

The front a-arm suspension was redesigned to incorporate double shear on all rod-ends. Also, additional professional advice was obtained from Alinabal, a rod end and parts manufacturer. Spacers were

incorporated to ensure that the rod ends rotate correctly, as well as the use of an anti-seizing compound.

2.4 Weight Reduction

Scrutineering revealed that the rear tire was loaded with 376 lbs whereas the front tires were loaded with an average of approximately 342 lbs. Therefore, the center of gravity proved to be slightly further back than anticipated, and the overall weight of the car was very high (1061 lbs with driver).

Weight Reduction efforts included cutting holes into body keel ridges, removal of redundant aluminum members, and moving electronic and other elements further forward to relieve the rear wheel specifically.

3 Conclusion

Few major changes had to be made from the original design. The car met our expectations by qualifying for Sunrayce 97 at the Eastern Regional Qualifiers with a comfortable margin (111 miles total). No major repairs had to be made during qualifiers or due to road testing, indicating that the car is ready for Sunrayce 97.

We believe that Lux Aeterna is a safe, roadworthy vehicle. However, no analysis is flawless, and we will stay alert for any problems that may arise during the remaining days of road testing and the race. We will conclude the series of technical documents after the race with a technical report summarizing Lux Aeterna’s performance in the race.

本文来源：https://www.bwwdw.com/article/pws4.html