View Single Post
  #26   Spotlight this post!  
Unread 11-10-2009, 00:54
artdutra04's Avatar
artdutra04 artdutra04 is offline
VEX Robotics Engineer
AKA: Arthur Dutra IV; NERD #18
FRC #0148 (Robowranglers)
Team Role: Engineer
 
Join Date: Mar 2005
Rookie Year: 2002
Location: Greenville, TX
Posts: 3,078
artdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond reputeartdutra04 has a reputation beyond repute
Re: pic: 6 Wheel Drivetrain

Quote:
Originally Posted by joeweber View Post
If you layout your sprockets and chain flat on a table you can get the dimensions center to center of the axels and you will not need tensioners. We did this on our test bot and it worked pritty good.
Unless you plan on pre-stretching it, 25-pitch chain will "stretch" under a high enough load to the point where it will start skipping. Over very short chain runs (a few inches, max), it often won't be enough of a problem. But over anything longer than a few inches it'll be noticeable enough to cause the chains to pop off.

This past season I experimented with super lightweight floating idlers to much success. The floating idlers I used were polycarbonate sprockets (milled from 1/8" sheet) that were inserted into the roller chain. The tension of them kept them in place. I made several sizes, so that over the course of the competition season the chain could be re-tensioned as it stretched by either moving the sprockets closer to the end sprockets, or by replacing it with a larger idler sprocket.



After our first or second competition, the chain stopped stretching and the sprockets have remained untouched since, where they've lasted through a half dozen competitions. They've worked flawlessly, and have never popped out of the chain or failed in any way, all with a tensioner that weighs a fraction of an ounce.
__________________
Art Dutra IV
Robotics Engineer, VEX Robotics, Inc., a subsidiary of Innovation First International (IFI)
Robowranglers Team 148 | GUS Robotics Team 228 (Alumni) | Rho Beta Epsilon (Alumni) | @arthurdutra

世上无难事,只怕有心人.
Reply With Quote