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Unread 11-09-2004, 21:29
Sean Schuff's Avatar
Sean Schuff Sean Schuff is offline
Year 18 in FRC!
FRC #0093 (N.E.W. Apple Corps)
Team Role: Teacher
 
Join Date: May 2003
Rookie Year: 2000
Location: Appleton, Wisconsin
Posts: 316
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Re: pic: 6 speed?? Great in theory - lets see how it works!

Couple of clarifications -

1. The drawings I have posted are for illustration purposes only. It was, more or less, a quick and dirty way to prove a concept. And, I'm pleased to say, it worked. At least in the theoretical universe of Autodesk Inventor 8 Pro.

2. The slots in the gears (the blue and red components that are missing actual gear teeth) are there so it is possible to see the rate of rotation of each gear as it steps down. Motion constraints have been applied to all of them so you can actually see the reduction taking place when the constraints are driven.

3. I am working on a four speed variation (can't imagine the need for 6 gears unless, as JVN pointed out, the field gets REALLY big!) of the same design using actual gears so the concept is a bit more clear. The assembly is about 90% complete and weighs in at just a shade over 8 pounds without motors or a shifting input device (pneumatics/lead screw/etc.). I'll post a pic after I submit this post.

This new design uses standard hubless spur gears (20 deg. pressure angle) ranging in size from 15T to 45T. Their face width is 1/2" and they are tied together in sets of two (face to face) using drilled holes and roll pins. I can probably reduce a fairly significant amount of weight by dropping down to 3/8" face width. I've tried to standardize as best I can for ease of component acquisition.

Tristan - thanks for the insight into the Lewis formula. I'll have to keep that in mind when selecting components that can withstand the abuse of FIRST robotics! $50 each - YIKES! I better find a more financially responsible solution!

Sean
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