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Unread Yesterday, 02:50
Munchskull's Avatar
Munchskull Munchskull is online now
CAD Designer/ Electrical Consaltant
AKA: Anthony Cardinali
FRC #0997 (Spartan Robotics)
Team Role: CAD
 
Join Date: Jan 2013
Rookie Year: 2013
Location: Corvallis, OR
Posts: 538
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Climber help: thermal breakers.

Part of my teams strategy has been to have a fast climber. When I say fast I am talking sub 5 seconds. Our biggest factor on that is the thermal breakers.

We plan to use a two 775 pros, each with a 33.33:1 reduction. Using the tall robot size means that it would travel a little over 2ft to reach the top. On the 1.25in roller we are playing to use that ends up giving us a solid climb speed of about 7.5 seconds. CAD suggest that our worst case would be a 100lb robot. Across each breaker that would be 40.48amps assuming a gearbox efficiency of 90%.

I got 90% efficiency from some read I did on planetary gear systems and spur gears. I will admit that I choose that based on some hunch math. I was lead to understand that you would get roughly a 3% efficiency loss from every planetary stage. Using two per side that would equate to 94%. Then from there I plan to reduce using spur gears at a 2.1:1 ratio. It is my understanding standing from my reading that spur gears have a loss of 2-6% so I choose 4% loss for my happy medium. Putting that in to JVN got me my number of 40.48 amps.

Now I might be crazy but I would love a sub 5 seconds climb without adding motors. With a 20:1 gear ratio I would draw 67amps for for seconds, could the thermal breakers handel a spike of the current for that long. Also what would the main breaker risk be?
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“In theory, theory and practice are the same. In practice, they are not.” ― Anonymous
Anthony Cardinali
4th year of FRC
Class of 2017



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