
28-02-2016, 22:02
|
 |
 |
Technical Director
AKA: Gus Michel II
 FRC #3946 (Tiger Robotics)
Team Role: Mentor
|
|
Join Date: Jan 2014
Rookie Year: 2013
Location: Slidell, LA
Posts: 3,570
|
|
|
Re: STEM Quiz #1
Quote:
Originally Posted by MechEng83
The lower limit as Sun Gear diameter approaches Ring Gear diameter should be 2:1, as the ratio for a planetary gearbox as described is R/S+1.
The upper limit requires some geometry constructions of 3 equally spaced tangent inscribed circles. My literal back of the envelope derivation got messy, but the result came out to 1/(1-6/(3+2*sqrt(3)))+1 or 13.928203235:1
I'll try to post a coherent derivation when I get it worked out nicely on something more legible.
I should point out that these are the limits of the ratio, rather than achievable ratios under the stated conditions, as you would have gears or rollers moving in opposite directions in direct contact.
|
Correct on the limit of large sun gear is 2:1. On the lowest gear ratio, you're quite close but not quite right.
__________________
If you can't find time to do it right, how are you going to find time to do it over?
If you don't pass it on, it never happened.
Robots are great, but inspiration is the reason we're here.
Friends don't let friends use master links.
|