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Energy Analysis Results

posted Oct 28, 2011, 10:27 AM by Greg Mills   [ updated Nov 5, 2011, 3:29 PM by Nate Delson ]
The energy analysis changes from year to year as we purchase kit components from different vendors.  And even from one vendor, not all rubber bands are made equally.  If your experimental values are wildly off from these suggested values, I would suggest redoing those spurious calculations before using it in future analyses. 

Sm  Rubber Band K = 40-70 N/m
Md  Rubber Band K= 80-110 N/m
Lg   Rubber Band K = 200-260 N/m

Sm Spring K= 130 -160 N/m
Md Spring K= 160-200  N/m
Lg  Spring K = 620-690  N/m

High Speed Motor
    Wno-load = 540-560 rad/s
    Tstall = 0.013-0.015 N*m
    Power =1.76-2.10 J

Geared Motor
    Wno-load= 14-17 rad/s
    Tstall= 0.040-0.044 N*m
    Power =0.14-0.19 J

Max Solenoid Force = 6-7 N



The large rubber band has the highest power, but its potential to do work is limited to the energy initially stored in the stretched configuration. Making it almost a "one time use" element.

The high speed motor has the most amount of energy available to it over the course of the competition and as such can do the most work.

The geared motor has the most readily available torque. (What would happen if you geared the high speed motor to have the same stall torque as the geared motor? Would one spin faster than the other or would they spin at the same speed?)

The large spring and large rubber band are relatively close for max force depending on what measurements for max length and k you use. The large spring is much stiffer and provides much more force per distance stretched but can only be stretched so far. The large rubber band is less stiff but can be stretched much further. Depending on the application one might suit the needs better than the other.


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