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  #76   Spotlight this post!  
Unread 08-13-2018, 02:51 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Those were passive follower omniwheels that got sprung into the ground to provide odometry information. In practice there were a number of deflection and slipping issues which made them less accurate than just using standard wheel odometry (after switching to nitrile tread in the center + corner omnis).
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Unread 08-13-2018, 03:13 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by Brian Selle View Post
Does the Dyneema line on the elevator ever wrap up on itself on the drive tube or does it remain in a flat spiral?
It wraps at the extents of travel. The springs compensate for the variable rope lengths.
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Unread 08-14-2018, 07:24 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

We took your advice and added 0.05" to all our belt C-C's in the intake and also made room for 1/16 hex spacers between the wheels and the bearings and it seems to have fixed the issue. Thank you very much!
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Unread 08-16-2018, 11:34 AM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Are your joysticks for the base driver custom? From the rare images I can find of them, that's the assumption I can make. Could you post a better picture of your driver station setup?
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Unread 08-16-2018, 11:43 AM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by juju_beans View Post
We took your advice and added 0.05" to all our belt C-C's in the intake and also made room for 1/16 hex spacers between the wheels and the bearings and it seems to have fixed the issue. Thank you very much!
Did you add to the C-C or subtract from it? I was under the understanding that it would be ideal to remove from it to minimize friction.
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Unread 08-16-2018, 11:46 AM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by Schroedes23 View Post
Are your joysticks for the base driver custom? From the rare images I can find of them, that's the assumption I can make. Could you post a better picture of your driver station setup?
It is an off the shelf hall effect joystick (https://www.apem.com/int/hf-series-42.html) with a custom 3d printed handle. We really liked the feel of the bottom of a CH flight stick, but hated the analog circuitry and associated trim wheels for potentiometers. This is a nice compromise.

I was fairly certain we had put the most effort into joysticks in FRC until I saw 971's controller for this year...
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Unread 08-16-2018, 12:03 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by Big-b View Post
Did you add to the C-C or subtract from it? I was under the understanding that it would be ideal to remove from it to minimize friction.
Oops, that was a typo, we subtracted 0.05" from our belt C-Cs
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Unread 08-16-2018, 07:46 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Were your drive gearbox shafts custom sized? Our (7013's) WCP SS gearboxes showed 3/4" of backlash on a 6" wheel. Most of this from an undersized hex shaft mating loosely with its gear. I imagine it might rear its head over the long distances in a 3 or 4 cube auto.
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Unread 08-16-2018, 07:52 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Quote:
Originally Posted by christheman200 View Post
Were your drive gearbox shafts custom sized? Our (7013's) WCP SS gearboxes showed 3/4" of backlash on a 6" wheel. Most of this from an undersized hex shaft mating loosely with its gear. I imagine it might rear its head over the long distances in a 3 or 4 cube auto.
We mount our drive encoders directly to one of the wheel shafts, so this doesn't effect the accuracy of our odometry. There is a similar amount of backlash in our drive (much of which comes from the dog itself, to ensure smooth shifting).
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Unread 08-18-2018, 08:36 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

What size do you mill your bearing holes for 1.125" and .875" OD in your drive gearboxes?
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Unread 08-18-2018, 08:46 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Quote:
Originally Posted by josh341 View Post
What size do you mill your bearing holes for 1.125" and .875" OD in your drive gearboxes?
I believe it's 1.12480011222338483848828474828111838474 and .87480002837474928282919474749238. But you can round too.
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Unread 08-18-2018, 10:48 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by R.C. View Post
I believe it's 1.12480011222338483848828474828111838474 and .87480002837474928282919474749238. But you can round too.
Such precision. Much floating point.
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Unread 08-18-2018, 10:50 PM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

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Originally Posted by R.C. View Post
I believe it's 1.12480011222338483848828474828111838474 and .87480002837474928282919474749238. But you can round too.
I love machining in fantasy land.
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Unread 08-19-2018, 01:02 AM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Quote:
Originally Posted by josh341 View Post
What size do you mill your bearing holes for 1.125" and .875" OD in your drive gearboxes?
I target -.0005 to -.00025. Won't really go lower than -.0005, but occasionally they come out to nominal and we loctite them in.
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Unread 08-19-2018, 08:37 AM
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Re: Team 254 Presents: Lockdown Technical Binder 2018

Quote:
Originally Posted by R.C. View Post
I believe it's 1.12480011222338483848828474828111838474 and .87480002837474928282919474749238. But you can round too.
+/- 0.005" tolerance
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