Shepard v2.0 Dev Log (Simplified Mount) Started: 06-17-13
All work done to create a simplified, yet stronger motor mount for the kitified version of Shepard.
In reviewing the Shepard 1.0/1.1 design it became clear that much of the complexity, cost, and build time was centered around both the slide and the structure necessary to pinch the pressure sensor between the slide and an immovable stop. When the sensor was upgraded to a single beam load cell, the need for the backstop went away. Since the slide was bolted to the load cell, and load cells generally have a mechanical failure point around 2.5 times their max sensor value, this would mean that the 5kg load cell shears at about 12.5kg or about 122.5 Newtons of force. Since this is a little over 3.72 times the max thrust of any engine made by Estes (32.9N is the highest it goes), it is safe to bolt a motor mount directly to the load cell, provided that both the mount and mounting hardware are able to withstand similar forces. Finally, if the slide and backstop are not used, it would be safe to vent the rocket motor's ejection charge forward rather than deflect it. This again simplifies the structure and assembly.