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Journal 4.1 Make Detail Design Decisions BEFORE Building

Dizzy’s Journal Entry (Caught a mistake BEFORE prototyping)

History:

-the game is Gatekeeper
-Our team strategy focuses on collecting sticks and inserting them into collection bins. The sticks begin in an upright position. Some collection bins require the stick to be inserted vertically from the top. Some collection bins require the stick to be inserted horizontally.
-Eve and I were assigned the function “collect sticks.” (Function #2 in Journal Entry 1.4)
-We brainstormed and came up with 18 ideas and presented our favorites to the team (Journal Entry 2.2)
-The team helped us complete a design matrix to choose the best one (Journal Entry 2.3)
-As another group (the arm team) was analyzing their embodiment design, they made discoveries that influences our design. (Journal Entry 3.0)
-Based on the design principle, “Self-Help,” (Journal Entry 3.1) we combined our function (Function #2) with Function #4 and modified our design to have a passive element (Journal Entry 3.2).

The moment we entered the detailed design phase (adding precise dimensions and such), we realized a gross oversight…Specifically,

YOU CAN’T PUSH ON A ROPE!!!!!

 Conceptually, we had settled on a “gripper/collector” that used a half-cylinder with a passive constraints to capture the sticks. In the embodiment design phase we focused in and decided a brake cable would act to tilt the collector AND to release the passive constraint mechanism. Today, we remembered that it is impossible to push a load with a rope (ropes are made for pulling). In other words, a brake cable can apply a little pushing force…but not much. It may not be enough to release the passive constraint.

Fortunately, we documented all our design alternatives along the way and have plenty to choose from. We’ve elected to replace the passive-constraint with a servo motor. It won’t add much weight and is a straight forward design change…probably a lot easier than the passive constraint was going to be anyway.

sketch 4-1

We’re going to put a short arm on the servo and a half-cylinder on the end of that little arm. Basically, we are back to idea #14 from our brainstorming session (Journal Entry 2.2 and Journal Entry 2.3).

I’ll do the engineering sketches tonight and pass them on to the build team next meeting. I’m not sure if it is worth passing on to the CAD team yet…not until a little prototyping.

 

This article demonstrates how thinking through the details can reveal oversights even before prototyping.

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