View Single Post
  #5   Spotlight this post!  
Unread 20-12-2011, 16:57
Garret's Avatar
Garret Garret is offline
Standing on the Shoulders of Giants
AKA: Garret Smalley
FRC #0691 (Hart District Robotics)
Team Role: Mentor
 
Join Date: Dec 2009
Rookie Year: 2008
Location: Goleta, CA (UCSB)
Posts: 203
Garret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond reputeGarret has a reputation beyond repute
Re: pic: I was bored... so I designed this.

Thanks for all the complements about the render and design.

Quote:
First, your modules. Yes, cantilevered wheels offer easier access, but they are not the end-all be-all most important drivetrain feature in FRC. The reason my team cantilevers wheels is mainly for simplicity and weight. Cantilevering wheels in a swerve drive saves negligible weight (maybe a half pound?) and makes the whole wheel and module significantly worse supported.
I cantilevered the module just for fun and aesthetics of the module.

Quote:
In 2008, team 148 built modules much like yours, but with a fully supported wheel. Even then, the modules wore through bevel gears, I'm assuming due to the modules twisting causing excessive tip loading. You'll notice teams like 1625 and 1640, two popular coaxial swerve teams, go to great lengths to make their bevel gear setup rigid. 1625 used a "puzzle piece" method of connecting 1/4" plates while 1640 uses gussets to connect a piece of U-shaped extrusion together.

It also looks like your module support is a bit lacking. It looks like you have a single thrust bearing mounted to a piece of 1/8" metal plate supporting all of the forces on the module. That's a pretty extreme cantilever. A lot of teams use a lower support for at least extreme loading, or they support their modules in multiple places / over a wide area. Think carefully how you want to do this.
I have attached a section view of the module (not mounted to frame and without bolts). There may be support issues still but I did try to take into account as many of the load issues as possible.


(the image is a little squashed so it looks a little off)
About the module itself:
The main body of the module is machined out of a 3" long piece 5"x3"x1/2" Aluminum Angle. The top of the main body of the module is adapted from my teams current swerve drive module design. Also I did not want to cantilever the bevel gear so I went ahead and supported the bevel gear shaft on both ends. (This module was designed just for fun really so there may be issues I am unaware of). I welcome any advice and comments about the design.
__________________
7 Years of FRC
"You students are at the top of the mountain, at the pinnacle of success, and what is it that you do?
You become the future guides to help others climb the mountain."

Last edited by Garret : 20-12-2011 at 17:03.
Reply With Quote