Poor Man's FEM

[rwstevens59]

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[rwstevens59]

And not a comment to be had. :(

I thought I could at least get a laugh from someone. Although I have found that for a qualitative first pass at an idea the hot melt glue and sticks or drinking straws as described in the second RCVD workbook works very well. It is very instructive to have something you can hold in your hands and twist and bend. :cool:

[Edward M. Kasprzak]

It is very instructive to have something you can hold in your hands and twist and bend.

This. Nothing to laugh at here, except perhaps the thread title.

[rwstevens59]

A little background seems in order. A local race car constructor designed, intentionally, a very torsionally soft front clip for his tube framed cars. Certainly nothing close to a space frame. His reasons for this design are his own and I won't comment on that. After a season of racing all of the cars built developed cracking consistently at one particular joint. I was asked for an opinion on the problem and the proposed fix. Unable to gain access to a full car for torsional testing I took some measurements, fixed a scale and built about six of these rough models representing the front clip from the engine plate forward in two evenings. The rough models very quickly qualitatively revealed the cause and direction of the forces causing the weld failures as well as demonstrating the consequences of the builders proposed fix. These little models also made talking with the builder extremely more productive as he had something to hold and twist as I gave my opinions.

Bottom line don't neglect the simple qualitative models, they are very quick to make and can very quickly confirm or uncover faults in your thinking.

[BillCobb]

It is very common in the industry to use miniaturized (1/4, 1/8, 1/10 scale) models to study potential stress and strain relationships in body and chassis structures. They are even strain gaged when specific details are wanted.

The effect of strains on compliance steer and camber deflections are studied carefully and managed to produce acceptable (or desirable) values. Twist axle rear suspensions are a good example. This guides the mega construction of finite element models and the selection of normal mode participation in ride and handling analysis.

The use of such models for aero work is probably more well known.