View Single Post
  #18   Spotlight this post!  
Unread 07-10-2014, 13:05
Chris is me's Avatar
Chris is me Chris is me is offline
no bag, vex only, final destination
AKA: Pinecone
FRC #0228 (GUS Robotics); FRC #2170 (Titanium Tomahawks)
Team Role: Mentor
 
Join Date: Dec 2008
Rookie Year: 2006
Location: Glastonbury, CT
Posts: 7,718
Chris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond reputeChris is me has a reputation beyond repute
Send a message via AIM to Chris is me
Re: paper: Belt Driven VersaChassis WCD - Step by Step guide

Quote:
Originally Posted by asid61 View Post
From what I've read, you should put in tensioners regardless because of the tolerances required for belt engagement. Adding a cam tensioner is less than 0.1lbs anyway, so there's no reason not to have one.
If you put in tensioners, you could mess it up. If you don't, you can't. A very minor tradeoff, I know, but it's worth noting. It's surprisingly easy to overtension a belt.

You absolutely definitely do not need tensioners for a belt driven WCD, provided you can machine bearing holes in your drive tube with reasonably good accuracy. Our past three years of robots will attest to that.

Quote:
Originally Posted by M. Mellott View Post
I know that this system uses two 3-CIM transmissions but with only 2 motors each. Do you think that with the back-and-forth, high impact motion that a typical FIRST drive train will go through, the 9mm belts might not be strong enough? Would 15mm belts be a better choice for a drive train, especially for those who want to add on that third motor to each side?
We have had poor experiences with 9mm wide belts in the drivetrain using pulleys about this small. Last year several teams had belt failures doing this, though manufacturing issues at Vex may have contributed in addition to undersizing.

To me there's basically no benefit to not going 15mm, and the reliability is *much* higher. Even if it does work, why would you want to gamble on the edge of a safety factor with your drivetrain? All of our 15mm setups have been rock solid.

By the way, a good calculator for belt center distance is here. http://www.wcproducts.net/how-to-belts/ We have had good results with zero center distance added. Your mileage may vary based on your tolerances.
__________________
Mentor / Drive Coach: 228 (2016-?)
...2016 Waterbury SFs (with 3314, 3719), RIDE #2 Seed / Winners (with 1058, 6153), Carver QFs (with 503, 359, 4607)
Mentor / Consultant Person: 2170 (2017-?)
---
College Mentor: 2791 (2010-2015)
...2015 TVR Motorola Quality, FLR GM Industrial Design
...2014 FLR Motorola Quality / SFs (with 341, 4930)
...2013 BAE Motorola Quality, WPI Regional #1 Seed / Delphi Excellence in Engineering / Finalists (with 20, 3182)
...2012 BAE Imagery / Finalists (with 1519, 885), CT Xerox Creativity / SFs (with 2168, 118)
Student: 1714 (2009) - 2009 Minnesota 10,000 Lakes Regional Winners (with 2826, 2470)
2791 Build Season Photo Gallery - Look here for mechanism photos My Robotics Blog (Updated April 11 2014)

Last edited by Chris is me : 07-10-2014 at 13:19.
Reply With Quote