DEWBOT X Design Philosophy

More so than in any past year, the team pursued perfection in executing DEWBOT X's design and construction. This can be best seen in the attention to detail, the modularity and serviceability of the robot. It is also visible in the repeated renditions of some parts, which we made over until just right.

Our inspiration

During 2013's Einstein Semifinal 2-2, alliance captain 303's (Test Team) battery cable failed, leaving us one robot down for the match. This is not a critique of 303, but of ourselves, for this failure could have been ours, had fortune been different. 3476 (Code Orange) and ourselves put up a determined fight, but lost this match 200-225. While it is impossible to say that we would have won (and moved on to finals) had this not happened, it made it absolutely clear that if we have the ambition to continue to play at this level of competition, then any failure could become (competitively) fatal and that there was no detail too small for attention.

This further reminded me of a 2012 visit the team made to sponsor UTC Sikorsky's Coatesville plant. I was very impressed by the attention to the processes which assured quality of the helicopters produced there. Of course, with any aircraft, quality is literally a matter of life and death. So impressed as I was, I did not immediately see how this focus on quality applied to FRC 1640. After all, we just make and compete with robots! No-one dies if our robot breaks.

Our 2013 Einstein experience, together with the team's hard goal to Go back to Einstein in 2014 and do it right crystalized the acute need for quality in our "product". Now that we finally get this, I hope we don't forget it.

4 Bolts

Quality is a tough thing to sell to Judges, and we did not do a good job of this. Quality doesn't look sexy, or technically intricate. It doesn't even look difficult. So how do you pitch quality?

Our pitch was 4 bolts. We could remove and replace any major mechanical system on our robot by removing and reconnecting 4 bolts. Why 4? Because it is a reasonable number for secure attachment for any small-scale (FRC scale) system. It shows that we've thought through service requirements and reduced service work to a minimum. It indicates that spares are either modular systems, or at worst ready spares.

Not a bad pitch. Didn't work, though, so it cannot be called a good one either.

What did work, however, was quality. Following our spectacular shooter failure at Hatboro-Horsham, DEWBOT X was the robot that very rarely broke, and when it did, was rapidly repaired. Our focus on quality resulted in reliability improving steadily throughout the competition season.

Modularity

Our pivots have been modular since 2011. This year, though, we went all-out for modularity to facilitate serviceability:

• Pivots: consolidated Anderson power connectors and PWM sensor connectors make for faster pivot changes (not needed, because no pivots failed during the competition season)
• Slingshot Elastics: originally attached directly through eyebolts, this was changed to threaded chain link connection to speed replacement time (not a common task, in practice)
• Winch: modular like pivots. Anderson power connectors. Winch replacement was a common task.
• Roller Frame: also modular. Anderson power connectors. Never actually replaced. Materials selection was critical to this system's reliability and success.
• Rivet Nuts: By-in-large, systems were connected to the chassis via permanent threaded connections provided by rivet nuts. These greatly facilitated system changes by eliminating the need to place wrenches on back nuts, and positioning back nuts for reconnection. We started using rivet nuts in 2013 and expanded the practice enormously this year. Requires good design before building.

Ready Spares

Spare parts in 2014 were ready to use. Spare cylinders included the appropriate pneumatic connections already in place. When designs changed and called for different connections, connections on spare were changed as well.

We still brought a lot of COTS to competitions: Bolts, nuts, washers, stock Al & polymers. But the expectation was that if we have a motor, actuator or sensor, it is in a form ready for use. Sensors have soldered connections and PWMs. We brought no loose CIMS, BaneBots or AndyMark motors: we brought Pivot, Winch and Roller Frame modules containing these motors.

Spare winch straps were cut to length.

We blew it, then recovered

We experienced a nearly complete failure of the Shooter system at Hatboro-Horsham, our first competition. The Shooter failed to fire on most occassions, relegating DEWBOT to a ground passing and low goal scoring role. This was a surprise because this system had, we believed, been thoroughly tested.

It turned out that the shooter release failed due to insufficient air pressure to release the winch's dog gear. Testing at the CCIU had been flawed in that we did not operate the Roller Frame actuation in practice as often as we did in competition and this Roller Frame actuation was the main air user. In addition, air use calculations (such as we had done for DEWBOT IX) had not been performed for DEWBOT X prior to Hatboro-Horsham. Frankly, DEWBOT X had not been identified as having large compressed air requirements and as a result, the compressed air system (VIAIR compressor and (2) 35 in³ storage tanks) were thought to be sufficient. Not nearly. Leaks in the pneumatic system exacerbated the problem.

Following Hatboro-Horsham, the air consumption analysis that ought have been done earlier revealed that we needed a Thomas compressor with (7) 35 in³ storage tanks. Video from Hatboro-Horsham helped to clarify the actual use patterns of the pneumatic actuators. Significant air leaks were also repaired.

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