2014-15 Design Notes.docx - General Information about Notes These notes are progressive and have been compiled over the course of the 2014-15 baja

2014-15 Design Notes.docx - General Information about Notes...

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General Information about Notes These notes are progressive and have been compiled over the course of the 2014-15 baja season. There will be contradictions as some solutions have replaced previous ones. The last information written in each section is the most recent. Front A-arm The upper a arms should have tabs that are aligned with the chassis tubes so that it is easier to cut the tabs to the correct length. (no grinding required if they’re water jet). The upper a arms could be connected with bushings not rod ends, this would be especially good if the a arms are designed like they were this year with no adjustability because we can’t put a set of testing a arms on anyway because we’d have to weld new tabs on. After building the a-arm it is clear that there is some amount of adjustability because of the very small change in angles when adjusting the rod ends. We can adjust camber so that shouldn’t be considered a negative in the design decision next year. When building the A arms, first cut tubes to approximate length, then notch tubes, then use jig to cut to final length, then use mill to slot tubes, then assemble on jig and weld. Do Kinematics First then analyze kinetics. I’ve made an excel Chart titled “shock points” that outputs the distance from the a arm rotating axis to the base of the shock. I’ve found data that gives us a motion ratio of about 1.45 (last year 1.8). We’ve decided to mount the shock to the center of the roll bar support tube triangle. The bending calcs have shown that with a 1000 lb load there is a factor of safety of 2.5 with a tube thickness of .095 wall as opposed to the rest of the chassis which is 0.065” wall. We don’t expect to be getting more than 750 lb though because with a spring constant of about 100 which is high and a max displacement of 8in we are getting max shock force of 800lb. the extra 200 comes from the potential to completely bottom out the shock. Jess helped to do the bending calcs assuming rigid-rigid supports and that the shock comes in at an angle of 60 degrees from the tube. Changed A arm to be a two force member Update: Found fox float manual has been found. It shows a maximum compression of 6”. The design will now use a maximum of 6” of stroke; the Final inch is much higher forces applied. We want about 10-11” of suspension travel. With a shock compression at ride height of about 3.92 Max length is 19.8 Min is 13.8. According to the Fox Manual, as general rule your vehicle’s sag should be 35-45% of total wheel travel. Last year we had 10.8 in of travel Designed the upper tabs to take into account the length of the weld nut and the length of the rod end Just moved the shock mounting points one inch forward relative to the plane of the a arm in order to make room for the tie rod.
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  • Fall '08
  • Yong,Y
  • rod, The Tubes, Spherical bearing

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