Keith and Tony B,

Good thoughts. I'll reserve some small areas for disagreement. What we all realize is that the approach that I've described has it's limitations, maybe major limitations. An experiment based on first principles.

I think that a benefit of this experiment and discussion is to draw attention to the chassis floor pan is a major contributor to the MINI torsional rigidity. One look at MINI cut away diagrams shows the effort the BMW structural engineers put into the chassis floor pan portion of the overall structure. To the extent that this is true, accessories like the rear stress bar and other bars and strut systems have relatively little to offer.

Detailed analysis of the chassis floor pan suggests a number of small ways that the rigidity of the structure could possibly be improved. I am troubled by my piecemeal approach of creating a series of 3 tubes. The series of tubes aren't ideally linked together. Not the best solution. I have been thinking of building an underchassis "X" brace that links together the jacking points and the exhaust tunnel tube. This approach might offer much more rigidity than my current hodgepodge series of tubes. Have purchased the materials but the weather is too good right now to spend days laying under the car. Some day.

Regards,
John Petrich in Seattle

 

Did you notice any difference with the plate in place? It can always be made stiffer by adding some L-braket to it with little added wieght.... Or take it out and have some beading done to it at a body shop. Maybe even your name in cursive?

Matt

Ps, I'll be up your way with the family June 10th-12th for a nephews graduation from HS and becomming an Eagle Scout. I'll try to track you down for a beer!

 

Matt,

Making the aluminum plate "stiffer" with trusses or "L" brackets isn't where I am headed. The whole idea is that creating a tube adds torsional rigidity to an "open" channel like structure . Tubes by definition are open at both ends. While not as rigid as boxes, enormously more rigid than a channel.

"Differences": I don't really know. The car responds to my local 'benchmark' bumps - railroad crossings and huge road seams- more like a single unit post tube system, not like the wet noodle that characterizes my wife's Z-3 chassis. At the track, I am now back to the stock rear anti-roll bar and the car rotates fine. A lot of subjectivity and interplay of other variables here. What I would like to say that I "see" is the results of removing the undamped spring of chassis distortion under load. For instance, I'd like to think that my car settles more quickly and predictabily at turn entry and that it is easier for me to "catch it" if I overdo it mid-turn. And the like. I feel good about the handling but really cannot claim anything for sure.

Would love to see you in mid-June. Actually don't like beer, but am crazy about coffee. There is a Starbucks near the High School and we can visit there. Keep my phone number (425) 868-1256 and call me ahead of time so we can make plans.

Regards,
John Petrich in Sammamish

 

hijack away, i dont mind, especially when it about a topic as good as this one. The idea itself is old as cars, people have been boxing their frame rails since prewar days, but this is the first example i have seen on a monobody car. Goodwork!

Beecher