Design News for Mechanical and Design Engineers

Father knows best?

Jean Pryor

Zirkle's response: Your CRV is safer than the average SUV. The NHTSA gives it a Static Stability Factor of 1.17 for the 2 wheel drive version and a 1.14 for the 4 wheel drive version. Even though the SUVs have more of a tendency to roll, you may be safer in one in a head-on or other non-roll collision than in a smaller, lighter, shorter car. This is due to the fact that you are sitting up higher with respect to the usual main impact area, and the vehicle is usually heavier and stronger. (Of course stronger does not always mean safer.) All in all, I would think favorably about buying one for a family member, since a non-roll collision is more likely to occur than a roll. However, I would look for one with a higher SSF. Several manufacturers are also coming out with SUVs that are not on a truck chassis and handle a little more like a car. These will probably have a higher SSF, again similar to a car. You can compare the SSF with other vehicles (cars, trucks, SUVs, etc.) at the NHTSA website— www.nhtsa.dot.gov/hot/rollover/fullWebd.html . They also have crash data on various vehicles so that you can make comparisons in this respect. When looking at the NHTSA data on frontal crashes you should realize that they are rating vehicles in a crash with a vehicle of the same type. This makes light vehicles look safer than they really are, because when a heavy vehicle hits a lighter vehicle, the lighter vehicle loses. Of course one of the most significant factors is to drive safely, i.e. defensively, carefully, and smartly. Good luck!

I'm curious! In Dr. Zirkle's Z-files column (10.15.01), you ran a photo of a Montero Sport. It appears that you are implying that the Montero Sport has the 1.15 = µ. Is this true or is it the much Bigger Montero, in which case µ> t/(2h) is typically much less than 1.0, that you refer to?

John Sullivan

Zirkle's response: The photo is incorrect. As noted in the article, the Consumer Reports (CR) study was with respect to the Mitsubishi Montero Limited, the larger Montero. Mitsubishi reported to CR a static stability factor (SSF) for the 2001 Montero Limited of approximately 1.15. The National Highway Traffic Safety Administration has tested the 2001 Montero Sport, and reported a SSF of 1.07 for the rear wheel drive model and 1.11 for the four wheel drive model. This would indicate that the Sport would be more susceptible to rollover than the larger Montero. The narrower wheelbase would contribute to this difference. Center of gravity information on the two vehicles is not generally available.

Thanks for the informative and entertaining editorial on "Oldies but Goodies" (DN 11.05.01). I, too, am somewhat typical of several of the engineers you mentioned. I am an older engineer (57) who thoroughly enjoys doing my own maintenance and repairs. Just like Mr. Fry and Mr. Clausen, I have had some bad experiences buying new cars—especially in the mid-1970s and early '80s. However, I think the respondents mentioned in your editorial should take another look at new car quality. Perhaps they would be pleasantly surprised, as my wife and I have been.

We took delivery of a 2001 Nissan Pathfinder in July, 2000. What a pleasure to own, and what a pleasant surprise this has been! The vehicle goes back to the dealer for the first time in two weeks, but only to have the tires rotated and balanced. That is only because I can't do that myself. But there have been no quality issues. No fit and finish problems. No leaks. What a pleasure to drive.

Several of my associates have had similar experiences with a Dodge Durango, a Jeep Grand Cherokee, and two Ford F-150 pick ups. Maybe this says something for improved truck and SUV quality!

I thoroughly enjoy Design News and read each issue.

Michael L. Noll, P.E. Manager, Interiors Engineering, International Truck and Engine Corp.

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