The aim of the present project was to quantify and compare differences in impact
performance and damping effectiveness among various off-road bicycle suspension
systems. Two experiments were conducted to compare suspensions. Fork impact
performance was tested by measuring peak antero-posterior braking forces and impulses
during impact with bumps of 6- and 10-cm height for five mountain bike suspension
systems. These results were compared to a rigid fork condition. Comparisons among
suspension systems showed small but significant differences in performance. While only
marginal differences in peak force were found for the suspension conditions, more
substantial differences in braking impulse were observed. Air-Oil design forks had the
lowest braking impulse for the range of speeds and impact characteristics of this
experiment. In another setting, an analysis of acceleration signals over a range of
frequencies on two surface conditions (gravel and trail) was conducted to assess the
damping effectiveness of the five suspension systems. The mountain bike was equipped
with accelerometers mounted at the axle and frame. A spectral analysis of the signal was
performed for each signal to provide a measure of fork effectiveness. Results showed
that accelerations ranged from -33 to +40 g at the axle and from -13 to +13 g at the
frame, while spectral analyses of the acceleration signals revealed two distinct frequency
regions from 0 to 100 Hz and from 300 to 400 Hz. The various suspension systems were
all effective in attenuating vibration over the first region. Vibration amplitudes at the
frame were considerably less than at the axle for the suspension conditions while similar
axle-frame vibrations were observed with the rigid fork. Lower frequency vibration
amplitudes were typically greater on the trail than on gravel. In the frequency region
between 300-400 Hz, the signal was attenuated at the frame for all conditions including
the rigid fork. The quantification and comparison process of the various suspension forks
using impulse provided an objective marker for performance, and allowed differentiation
between various suspension conditions. Moreover, the effectiveness analysis through the
use of accelerometers provided insight into the range of frequencies dampened by a
suspension. The lower frequency range dampening suggested that effectiveness of a
suspension fork can be quantified even though the experiment did not conclusively
differentiate between the forks. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32759 |
| Date | 08 May 2000 |
| Creators | Levy, Morris |
| Contributors | Smith, Gerald A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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