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Sometimes, you get what you need...
Posted by Michael Betts.
Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.
Posted on 7/14/2000 10:49 AM MST
In Reply to: Enlightenment, It's Electrifying posted by Dodd Stacy on 7/13/2000 8:40 PM MST:
First, let me say that I am more than a little concerned at the revelation that this 3X30 was allowed by FIRST and implemented by several teams without any mention of it in the Q&A section of the updates. I will bring this up at the Team Forum in August.
Secondly, I agree completely with Dodd:
'I only know that we've used all the more powerful motors (2 drills, 2 F-P's, and 2 van doors) and never popped a breaker or blown a fuse. Maybe we're not trying hard enough...'
The Bobcat has not blown a 60A fuse in the last few years (except once, when an attempt was made to connect the battery backwards). In fact, we used every motor (11) in the kit two years ago (to get onto the puck, et cetera) and never blew a fuse.
Many teams have demonstrated that competitive robots and 60 amp fuses are not mutually exclusive.
The Bobcat design team has always opted to err on the side of reliability within the restraints of the contest rules. In the last four years, we have never failed to make the cut for the finals in any contest we entered (in or off season).
It all comes down to trade offs.
One of the great challenges in engineering is the trade-off. Design requires a balance of functionality, reliability, efficiency, speed and power. Execution requires a balance of design, quality of manufacturing and strategy.
If you want high reliability, you will sacrifice some speed and/or power. It's that simple.
It is normal for someone to become frustrated if they are blowing fuses and, in a contest this size, someone always will (regardless of the size of the protection devices). After the frustration passes, it's time to review the design (Dr. J's superb white paper on motors was required reading this year), take some measurements and take corrective action (find the source of friction, reduce gear ratios, et cetera).
In the end, reality does not care about your design calculations and a real-world engineer has to learn to deal with it.
'We're gonna vent our frustrations,
And if we don't we're gonna blow a 50 [60] amp fuse
You can't always get what you want...'
With apologies to Messrs. Jagger and Richards.
- Mike
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