Impact testing on Bike Frame Materials.

Impact Test Fixture

Oak, Aluminum, Steel, Titanium

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

Frame Stiffness

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.

Kestral TalonFrames 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 Triangle Stays



Material Material
Stiffness
Stiffness



Front Stays Defl. % of Defl. % of
No. Frame Size Triangle Stays inch Soloist inch Soloist
1 Renovo R4 54 Wood Wood 0.38 107% 0.215 98%
2 Renovo R3 56 Wood Wood 0.39 104% 0.203 103%
3 Cervelo Soloist 54 Carbon Carb 0.407 100% 0.21 100%
4 Kestral Talon 48 Carbon Carb 0.409 100% 0.228 92%
5 GT ZR 1.1 58 Alum Alum 0.414 98% 0.199 106%
6 Colnago Dream 56 Alum Alum 0.418 97% 0.224 94%
7 Trek 2100 56 Alum Carb 0.425 96% 0.252 83%
8 Renovo R2 54 wood Carb 0.425 96% 0.264 80%
9 Renovo R2 54 Wood carb 0.437 93% 0.293 72%
10 Calfee Custom 56 Carbon Carb 0.525 78% 0.157 134%
11 Surly Steamroller 56 Steel Steel 0.533 76% 0.225 93%
12 Trek Madone 5.2 60 Carbon Carbon 0.505 81% 0.29 72%
13 Renovo R4 61 Wood Wood 0.458 89% 0.232 91%

Notes:

1. Less deflection is stiffer.

2. All else being equal, smaller frames are stiffer.Jatoba over bamboo

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.