Go to Post Do what you do well and I'm sure there will be much hope in your future! - Collmandoman [more]
Home
Go Back   Chief Delphi > ChiefDelphi.com Website > Extra Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
Thread Tools Rating: Thread Rating: 2 votes, 5.00 average. Display Modes
  #1   Spotlight this post!  
Unread 07-12-2014, 10:23
Oblarg Oblarg is offline
Registered User
AKA: Eli Barnett
FRC #0449 (The Blair Robot Project)
Team Role: Mentor
 
Join Date: Mar 2009
Rookie Year: 2008
Location: Philadelphia, PA
Posts: 1,050
Oblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond repute
pic: 4464 Preseason Drive WIP

Reply With Quote
  #2   Spotlight this post!  
Unread 07-12-2014, 10:26
z_beeblebrox's Avatar
z_beeblebrox z_beeblebrox is offline
Custom User Title
AKA: Cal
FRC #4183 (Bit Buckets)
Team Role: Alumni
 
Join Date: Jan 2012
Rookie Year: 2012
Location: Cambridge MA
Posts: 811
z_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond reputez_beeblebrox has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

Nice design. I like the couplers which will make it easier to remove the gearbox.

Why did you choose to put the CIMs above the wheels? Is the belly pan space worth the significantly higher center of mass?

.25" birch plywood is a very good material for a belly pan. It's stiff, light and easy to cut or drill holes in.
__________________
2012 Utah Regional Rookie All-Star
2013 Phoenix Regional Judge's Award for "design process and prototyping"
2014 Hub City Regional Quality Award, Arizona Regional Excellence in Engineering Award
2015 Arizona East Regional Creativity Award, Winner
2016 Arizona North Regional Finalist, Arizona West Excellence in Engineering Award, Finalist
Reply With Quote
  #3   Spotlight this post!  
Unread 07-12-2014, 12:19
Andrew Lawrence
 
Posts: n/a
Re: pic: 4464 Preseason Drive WIP

It appears as if by delegating that much room to your wheel wells as well as supporting them on both ends that you are offsetting the advantage of the inverted CIM setup, and in the end are saving less room than possible. I'd actually argue that you would open up more chassis space just by having cantilevered wheels and non-inverted CIMs, which will also bring a lower CoG, and make maintenance far easier.

To answer your question, 1/4" plywood makes for a quick and excellent bellypan for those who want to save time and/or do not have the resources for a machined aluminum one. It can be argued that the aluminum ones provide more stiffness, but if you design your frame right the plywood will be perfectly acceptable.

Another question I will have to ask is why you chose 6 CIMs. Do you have mathematical proof of the advantages of the other two motors that you personally have done, or are you going off the anecdotes of other teams? I'm not saying 6 CIMs are a bad thing, but having once been a part of the hype that is built around them I now only design 4 motor drivetrains because after doing the math countless times I haven't found any advantages that outweigh the potential disadvantages.
Reply With Quote
  #4   Spotlight this post!  
Unread 07-12-2014, 13:14
Oblarg Oblarg is offline
Registered User
AKA: Eli Barnett
FRC #0449 (The Blair Robot Project)
Team Role: Mentor
 
Join Date: Mar 2009
Rookie Year: 2008
Location: Philadelphia, PA
Posts: 1,050
Oblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

Quote:
Originally Posted by Andrew Lawrence View Post
I'd actually argue that you would open up more chassis space just by having cantilevered wheels and non-inverted CIMs, which will also bring a lower CoG, and make maintenance far easier.
Possibly true on the points about space and lower COG. Not so much for easier maintenance.

I have two major gripes with WCD setups: belt/chain access and gearbox removal. This design specifically aimed to make both of those as easy as possible. The coupled output shaft design would be much harder to do with cantilevered wheels, as would keeping the belts outside of the gearbox.

Quote:
Originally Posted by z_beeblebrox View Post
Nice design. I like the couplers which will make it easier to remove the gearbox.

Why did you choose to put the CIMs above the wheels? Is the belly pan space worth the significantly higher center of mass?

.25" birch plywood is a very good material for a belly pan. It's stiff, light and easy to cut or drill holes in.
The center of mass for this gearbox really isn't that much higher than for a stock WCP 3-CIM shifter, actually - the gearbox is only about an inch taller.
__________________
"Mmmmm, chain grease and aluminum shavings..."
"The breakfast of champions!"

Member, FRC Team 449: 2007-2010
Drive Mechanics Lead, FRC Team 449: 2009-2010
Alumnus/Technical Mentor, FRC Team 449: 2010-Present
Lead Technical Mentor, FRC Team 4464: 2012-2015
Technical Mentor, FRC Team 5830: 2015-2016

Last edited by Oblarg : 07-12-2014 at 13:21.
Reply With Quote
  #5   Spotlight this post!  
Unread 07-12-2014, 16:01
Jared's Avatar
Jared Jared is offline
Registered User
no team
Team Role: Programmer
 
Join Date: Aug 2013
Rookie Year: 2012
Location: Connecticut
Posts: 602
Jared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond reputeJared has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

Quote:
Originally Posted by Oblarg View Post
I have two major gripes with WCD setups: belt/chain access and gearbox removal. This design specifically aimed to make both of those as easy as possible. The coupled output shaft design would be much harder to do with cantilevered wheels, as would keeping the belts outside of the gearbox.
I really agree with the maintenance comment. Being able to swap a gearbox in less than five minutes is a huge advantage.
Reply With Quote
  #6   Spotlight this post!  
Unread 07-12-2014, 16:18
JesseK's Avatar
JesseK JesseK is offline
Expert Flybot Crasher
FRC #1885 (ILITE)
Team Role: Mentor
 
Join Date: Mar 2007
Rookie Year: 2005
Location: Reston, VA
Posts: 3,632
JesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond reputeJesseK has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

Quote:
Originally Posted by Oblarg View Post
I have two major gripes with WCD setups: belt/chain access and gearbox removal. This design specifically aimed to make both of those as easy as possible.
IMO, both of these tradeoffs shouldn't cause a redesign that throws many other benefits of WCD out the window. In your design, the wheels are much harder to remove and it is far easier to mis-align the axles which then causes chain/belt woes. Your manufacturing and wheel decisions may make these concerns less of an issue, however.

Gearbox removal is definitely an Achilles heal of WCD. Yet it can be mitigated by making a more bulletproof gearbox. We've experienced a bit of this both years we've done WCD, and this year will probably do steel output shafts as a result.

WCP's WCD blocks make chain access for chain maintenance irrelevant (assuming proper sprocket spacing). Even replacing an axle with limited access isn't an issue.
Reply With Quote
  #7   Spotlight this post!  
Unread 07-12-2014, 16:53
Oblarg Oblarg is offline
Registered User
AKA: Eli Barnett
FRC #0449 (The Blair Robot Project)
Team Role: Mentor
 
Join Date: Mar 2009
Rookie Year: 2008
Location: Philadelphia, PA
Posts: 1,050
Oblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

Quote:
Originally Posted by JesseK View Post
the wheels are much harder to remove
I wouldn't call it "much" harder. For the outer wheels, you remove a nut and pull the bolt. For the inner wheels, you loosen one shaft collar and pull the shaft. It's not as nice as just pulling the wheel off the end of the shaft, but it's hardly a problem.

Quote:
and it is far easier to mis-align the axles which then causes chain/belt woes. Your manufacturing and wheel decisions may make these concerns less of an issue, however.
We manufactured this frame to very good tolerance, so misaligned axles really a problem at all. Wheel spacing is done with the stock VexPro delrin spacers (of which I am a huge fan), which remove any chance of having mis-aligned pulleys.

Quote:
Gearbox removal is definitely an Achilles heal of WCD. Yet it can be mitigated by making a more bulletproof gearbox. We've experienced a bit of this both years we've done WCD, and this year will probably do steel output shafts as a result.

WCP's WCD blocks make chain access for chain maintenance irrelevant (assuming proper sprocket spacing). Even replacing an axle with limited access isn't an issue.
I will agree that WCD is a very good solution (449 used it last year, and in all likelihood will use it next year).

This design trades a bit of convenience in wheel access and a bit of space for much easier gearbox and belt access. We think it's a worthy trade-off.

An aside: The wheel wells are as big as they are so that this design can fit either 1.5'' VexPro traction wheels or Colsons. We'll decide which we like better as we test the thing. I do wish that VexPro sold a live-axle colson hub with a standard bolt circle for mounting pulleys, though, as it would save us one hex versahub and one hex bearing per side in that configuration. It's a minor gripe, though.

Quote:
Originally Posted by Jared View Post
I really agree with the maintenance comment. Being able to swap a gearbox in less than five minutes is a huge advantage.
I have to thank you again for the hex coupler idea - it's a wonderfully simple and elegant solution.
__________________
"Mmmmm, chain grease and aluminum shavings..."
"The breakfast of champions!"

Member, FRC Team 449: 2007-2010
Drive Mechanics Lead, FRC Team 449: 2009-2010
Alumnus/Technical Mentor, FRC Team 449: 2010-Present
Lead Technical Mentor, FRC Team 4464: 2012-2015
Technical Mentor, FRC Team 5830: 2015-2016

Last edited by Oblarg : 07-12-2014 at 16:55.
Reply With Quote
  #8   Spotlight this post!  
Unread 30-12-2014, 13:39
Oblarg Oblarg is offline
Registered User
AKA: Eli Barnett
FRC #0449 (The Blair Robot Project)
Team Role: Mentor
 
Join Date: Mar 2009
Rookie Year: 2008
Location: Philadelphia, PA
Posts: 1,050
Oblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond reputeOblarg has a reputation beyond repute
Re: pic: 4464 Preseason Drive WIP

I just realized I never posted the CAD for this, which I should do if we're going to use this (or any derivative of it) during build season.

So, here it is. This is a slightly earlier version than the one that we actually built - the only major difference is the size of the wheel wells, which since been enlarged to allow us the option of using Colson wheels and to move the motors a bit back from the edge of the frame.

http://www.mediafire.com/download/t8...ssis_0.1.1.stp
__________________
"Mmmmm, chain grease and aluminum shavings..."
"The breakfast of champions!"

Member, FRC Team 449: 2007-2010
Drive Mechanics Lead, FRC Team 449: 2009-2010
Alumnus/Technical Mentor, FRC Team 449: 2010-Present
Lead Technical Mentor, FRC Team 4464: 2012-2015
Technical Mentor, FRC Team 5830: 2015-2016
Reply With Quote
Reply


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 23:10.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi