Framebuilders - Frame Stiffness Tester

As a racer and consumer of bicycles, I always thought the stiffness issue was made to be a bigger deal than it really is, mainly a selling angle, however there is nothing worse than a mushy feeling frame so I know it is a factor. As a new frame builder I am a bit curious as to the stiffness of my own frames and of different style designs and so forth. Can anyone give me an efficient way to test a frames stiffness or to build a frame tester. I haven't had an issue yet and I feel my frames are plenty stiff however I am curious as to what a steel fillet-brazed frame will withstand and how it compares to other style frames. Any ideas?

look on Sheldon Brown's site, he talks about a stiffness test. Bike quarterly did a different test. They said that the SB test was not repeatable.

http://www.sheldonbrown.com/rinard_frametest.html

http://www.biketesting.com/TestList.html

As a racer and consumer of bicycles, I always thought the stiffness issue was made to be a bigger deal than it really is, mainly a selling angle, however there is nothing worse than a mushy feeling frame so I know it is a factor.
Why do you think that "there is nothing worse than a mushy feeling frame?" Too stiff a frame can be just as unpleasant. The key is to design the frame for the rider, not some arbitrary number. In general, lighter riders will appreciate less stiffness while heavier riders prefer more. I weigh 140# can find I cannot comfortably ride super-stiff frames for long distances, particularly over rough roads. The wheels just don't feel like they want to stay on the road. A larger rider may well have a different preference, as would touring riders vs criterium riders, or off-road riders.

I agree with you totally about an overly stiff frame as well, especially with a 31.6mm seatpost, for a 140lb rider its like getting impaled.