Impact testing on Bike Frame Materials.
The butted metal tubes are: Easton 7005 Aluminum down tube, Dedaccia steel top tube and a titanium top tube. The wood is a top tube section of oak. The impact is a 4" dia. steel pipe weighing 8 lbs. at point of impact, dropped from 12 inches. Clearly the thick wall and fibrous structure benefits the wood. Oak is about the middle of our hardness and strength scales.
Lateral frame stiffness numbers are meaningless for most people without a comparison to known bicycles. So, in addition to the Renovo frames, we have tested a variety of frames of various materials so an objective comparison is possible. The test setup we use is pretty standard and allows separate testing of both the main triangle and the stays.
Frames are bolted to a stanchion on a steel table through the bottom bracket shell. A weight is suspended from the rear dropouts which are fixed together at the correct spacing. Deflection is then measured at the dropout with a dial indicator reading in thousandths of an inch. The process was repeated for the main triangle by suspending the weight from a tube extended a fixed distance from the head tube.
Main triangle stiffness is extremely important because it determines stability and handling quality during stressed turning, such as turns in high speed descents. This stiffness is also minimizes flex or torsion at the bottom bracket for efficient delivery of power to the rear wheel.
The stays are responsible for keeping the rear wheel in plane during hard pedaling, but they also contribute to the comfort of the ride, so their stiffness profile is more complex and not fully explored with the lateral test alone.
The Cervelo Soloist (S2) is our gold standard in this test, considered by many to be one of the best all-round racing bikes made.
|Front||Stays||Defl.||% of||Defl.||% of|
|5||GT ZR 1.1||58||Alum||Alum||0.414||98%||0.199||106%|
|12||Trek Madone 5.2||60||Carbon||Carbon||0.505||81%||0.29||72%|
1. Less deflection is stiffer.
3. Frame #1, wood main triangle, wood stays.
4. Frame #3: Cervelo Soloist. This is the same as the current Cervelo S2 which has revised cable routing.