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-   -   pic: 148 Follower Wheel Assembly (http://www.chiefdelphi.com/forums/showthread.php?t=72609)

=Martin=Taylor= 21-01-2009 20:53

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by NoahTheBoa (Post 805490)
Here is a relevant Q&A on the subject
http://forums.usfirst.org/showthread.php?t=10919

Well... one could argue that the friction in the side-ways direction from this device COULD be used to stop the robot from sliding sideways...

But it would be one anal inspector to call you for that :)

artdutra04 21-01-2009 21:00

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Greg Needel (Post 805547)
I like the fact that black gear is an ABS rapid prototype. Want to clue the world into the right pitch for interfacing with a vex gear?

I'm about 95% sure it's 24 diametric pitch.

Edit: Yup, they're 24 DP.

Brandon Holley 21-01-2009 21:27

Re: pic: 148 Follower Wheel Assembly
 
wow JVN this looks VERYYYY familiar....ours looks almost identical...

NoahTheBoa 21-01-2009 22:32

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Hachiban VIII (Post 805568)
Well... one could argue that the friction in the side-ways direction from this device COULD be used to stop the robot from sliding sideways...

But it would be one anal inspector to call you for that :)

I think that since it's an omni wheel the sideways friction won't be enough to slow a 120 lbs+ robot.

DonRotolo 21-01-2009 22:35

Re: pic: 148 Follower Wheel Assembly
 
Very nice! But why such a big green gear? I'd have used a smaller gear and a similar green gear on the encoder. I am curious.

Also, I think we'll be stealing the idea! (kinda sorta) Thank you!

Don

NoahTheBoa 21-01-2009 22:42

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Don Rotolo (Post 805638)
Very nice! But why such a big green gear? I'd have used a smaller gear and a similar green gear on the encoder. I am curious.

It looks to me like it's a 1:1 ratio. Would make programming a bit easier without the extra math to account for the gear ratio.

JVN 21-01-2009 23:52

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Raul (Post 805507)
Humm - how much bigger than the green gear is that omni wheel? The reason I ask is because on the carpet, the wheel may sink in enough to allow the gear to grab some carpet fibers.

Also, is it just pivoting off the robot frame from that empty set of holes, and thus using gravity to keep it in contact with the floor?

It's 1/8" bigger radially. It should be okay, if there are problems during testing I'll tweak things a bit. We plan to spring load it down. Spring tension, TBD. Surgical tubing, of course.

Quote:

Originally Posted by Joe Ross (Post 805494)
We were planning to do the same thing, but with all vex components, including the new encoders. Hadn't gotten to it yet.

The electrical engineers on our team say I have an "encoder mental block" where I refuse to model them into the final design. I had a heck of a time cramming them into Tumbleweed last year. This year we knocked em out almost immediately so they'll keep their mouths shut.

Quote:

Originally Posted by AdamHeard (Post 805557)
Soo.... will Vexlabs be selling these?

How much would you pay for one? ;) I'm starting my own company KarthikJohn.
Quote:

Originally Posted by AdamHeard (Post 805557)
We had a similar plan, and were thinking if gravity wasn't sufficient, a rubber band to add a slight amount of tension would be easy enough.

I think with some down-force this should get pretty good grip on the regolith.

Quote:

Originally Posted by artdutra04 (Post 805571)
I'm about 95% sure it's 24 diametric pitch.

Edit: Yup, they're 24 DP.

Yes, 24DP. We just modded the VEX 60t Gear Model to make the coupler piece. Works pretty well.

The side plates are laser cut ABS, 1/8" thick (cut on our small 12x24" laser, not the big one that does the sheet-metal.) The coupler is 3D printed ABS on our Dimension SST. I feel pretty darn spoiled.

Probably could have gone with a smaller package, but we've got plenty of room in the drivetrain to mount it. Like Raul said, if the 60t gear catches some carpet we may change it. I'm not real concerned. *Shrug* This was done quickly and the design group moved onto other things.

-John

Andrew Bates 21-01-2009 23:54

Re: pic: 148 Follower Wheel Assembly
 
Why not use the larger omni wheel? It would get the wheel away from the gear more. Also the larger omni probably has a less likely chance of slipping...

Travis Hoffman 22-01-2009 00:02

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805695)
The electrical engineers on our team say I have an "encoder mental block" where I refuse to model them into the final design. I had a heck of a time cramming them into Tumbleweed last year. This year we knocked em out almost immediately so they'll keep their mouths shut.

"Knocked out"....the encoder models or the EE's? :p

JVN 22-01-2009 00:27

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Travis Hoffman (Post 805700)
"Knocked out"....the encoder models or the EE's? :p

This year the encoder models... but thanks for a good 2010 plan.

AdamHeard 22-01-2009 01:18

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805695)

How much would you pay for one? ;) I'm starting my own company KarthikJohn.

-John

Not counting the cost of the encoder, I'd say $25-30 probably.

CraigHickman 22-01-2009 02:10

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by AdamHeard (Post 805726)
Not counting the cost of the encoder, I'd say $25-30 probably.

Ditto on this. With encoder, depends on the accuracy/type of the encoder.

Jared Russell 22-01-2009 07:18

Re: pic: 148 Follower Wheel Assembly
 
Looks strikingly similar to something we're making...

Taylor 22-01-2009 08:03

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805695)
How much would you pay for one? ;) I'm starting my own company KarthikJohn.

Where would you put this company? Halfway between Toronto and Greenville is...I dunno...Kokomo?

Kingofl337 22-01-2009 10:59

Re: pic: 148 Follower Wheel Assembly
 
With a few modifications you could use the US Digital encoders that come in the kit.


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