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

Brandon Martus 21-01-2009 19:23

pic: 148 Follower Wheel Assembly
 

Jonathan Norris 21-01-2009 19:24

Re: pic: 148 Follower Wheel Assembly
 
Totally unnecessarily awesome... :cool:

Ice Berg 21-01-2009 19:30

Re: pic: 148 Follower Wheel Assembly
 
How is this going to measure ground speed if it can't touch the ground?

Joe G. 21-01-2009 19:32

Re: pic: 148 Follower Wheel Assembly
 
It can.

The GDC has ruled that similar devices do not count as "traction devices" in the Q and A.

NoahTheBoa 21-01-2009 19:33

Re: pic: 148 Follower Wheel Assembly
 
It was asked in the Q&A and they said that if it does not provide traction than it can touch the ground. The actual rule says that the rover wheels are the only thing that can provide traction, not the only thing that can touch the ground.

synth3tk 21-01-2009 19:34

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Ice Berg (Post 805477)
How is this going to measure ground speed if it can't touch the ground?

I'm no mechanical engineer (no, really, I'm not) but I'm assuming this will either touch the KOP wheels or somehow be attached along the route of the chains, without touching the ground.

NoahTheBoa 21-01-2009 19:43

Re: pic: 148 Follower Wheel Assembly
 
Here is a relevant Q&A on the subject
Quote:

Question:
Can any part of your robot...other than the FRC supplied wheels...make contact with the playing surface if their intention is not to provide traction to propel or stop the robot?

GDC:
Yes.
http://forums.usfirst.org/showthread.php?t=10919

Joe Ross 21-01-2009 19:45

Re: pic: 148 Follower Wheel Assembly
 
We were planning to do the same thing, but with all vex components, including the new encoders. Hadn't gotten to it yet.

Karthik 21-01-2009 19:55

Re: pic: 148 Follower Wheel Assembly
 
Fabulous use of VEX parts in a very elegant package. I think we'll be seeing a lot of similar assemblies this year.

Raul 21-01-2009 19:56

Re: pic: 148 Follower Wheel Assembly
 
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?

NoahTheBoa 21-01-2009 19:59

Re: pic: 148 Follower Wheel Assembly
 
If you are just using gravity to maintain contact with the ground have you tested to see if it slips at all when driving on the regolith?

danshaffer 21-01-2009 20:03

Re: pic: 148 Follower Wheel Assembly
 
Beautiful assembly!
Have you tested whether it will stay on the ground under its own weight? If not, may I suggest gas springs!

Akash Rastogi 21-01-2009 20:24

Re: pic: 148 Follower Wheel Assembly
 
Correct me if I'm wrong, but are those delrin sideplates? They look very nice. Good luck with this. =)

Greg Needel 21-01-2009 20:26

Re: pic: 148 Follower Wheel Assembly
 
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?

AdamHeard 21-01-2009 20:35

Re: pic: 148 Follower Wheel Assembly
 
Soo.... will Vexlabs be selling these?

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?

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.

=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.

martin417 22-01-2009 11:35

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by corpralchee (Post 805697)
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...

This what we are doing. Not because of the slipping issue, but for "smoothness" of rotation. The large Vex omnis have two sets of rollers, offset to the sides for a smooth roll. The small ones would tend to go bumpity-bump as it transitions between the rollers. We thought the smoothness would be better for the encoders.

Quote:

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
Why gear at all? ours is a direct drive set-up.

JVN 22-01-2009 11:43

Re: pic: 148 Follower Wheel Assembly
 
Wow, maybe this was NOT worthy of showing off. Sounds like almost every team in FIRST has something "identical" or better back in their shop. Color me corrected.

-John

PS - Of course I was joking about starting my own company and selling these.

Jonathan Norris 22-01-2009 12:01

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 that sounds like a lot of work for you... we all know Karthik isn't allowed to design anything that would actually go on a robot! :p

Chris Fultz 22-01-2009 12:05

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.

Do you want to forge a partnership with CollinChris?

It's a family business. Right now we have no products, we just intend to steal good ideas from Chief Delphi posts and set up shop. Right now we are producing a cool wheel follower assembly that it appears you have copied... :) (our lawers will be contacting you for the patent infringement)

Tom Line 22-01-2009 12:26

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805846)
Wow, maybe this was NOT worthy of showing off. Sounds like almost every team in FIRST has something "identical" or better back in their shop. Color me corrected.

-John

PS - Of course I was joking about starting my own company and selling these.

Well, if it makes you feel any better, we don't have all that fancy-smancy vex stuff, so ours looks gargantuan compared to yours. :D

jgannon 22-01-2009 13:00

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805846)
Sounds like almost every team in FIRST has something "identical" or better back in their shop.

Just like all the roller claws "identical" to 1114's last year, right?

BenB 22-01-2009 13:07

Re: pic: 148 Follower Wheel Assembly
 
..

AdamHeard 22-01-2009 15:17

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805846)
Wow, maybe this was NOT worthy of showing off. Sounds like almost every team in FIRST has something "identical" or better back in their shop. Color me corrected.

-John

Aww. I'm sure this will be the coolest looking follower wheel I'll see all year, "identical" in function isn't really identical. Last year we were "identical" in function to 987, but they were clearly better (in design, looks and performance).

Quote:

Originally Posted by JVN (Post 805846)
PS - Of course I was joking about starting my own company and selling these.

Aww. lame. Sometimes we can blinded by awesomeness.

The Lucas 22-01-2009 15:37

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by JVN (Post 805846)
Wow, maybe this was NOT worthy of showing off. Sounds like almost every team in FIRST has something "identical" or better back in their shop. Color me corrected.

-John

PS - Of course I was joking about starting my own company and selling these.

Have you tested to see what percentage of your total robot traction the follower wheel represents? (like the GDC posted)

Quote:

Originally Posted by GDC
The TEAM must be prepared to provide test data verifying that the maximum sensor traction is not more than 5% of the maximum traction of the ROBOT (acceptable validation methods would include test data logging total drawbar pull both with and without the sensor in place).

I am not saying that I think this will represent >5% of robot traction, I would be surprised if it did. I am only curious because my team has yet to test our Way-Better, Uber-Awesome follower wheel we build out of Joe's spare Vex parts :rolleyes: :D

Ben Piecuch 22-01-2009 19:24

Re: pic: 148 Follower Wheel Assembly
 
John,

Are you running any sort of bushing on the vex shaft? Or, are you just letting it ride on the 1/8" hole in the ABS? (I'm having a hard time finding a flanged bushing for an 1/8" shaft)

Very pretty, thanks!

Bengineer
FRC1350

Andrew Bates 22-01-2009 19:32

Re: pic: 148 Follower Wheel Assembly
 
I bet they are just letting it ride in the hole. In the VEX system the bearings are just delrin with round holes so this plate essentially is the same thing.

Rickertsen2 22-01-2009 22:07

Re: pic: 148 Follower Wheel Assembly
 
I like it! Let us know what the accuracy of this turns out to be. A measuring wheel is something i always wanted to try. I'm assuming the remaining two holes are a pivot for this thing hang off of.

Just a word of warning about those greyhill encoders, they are very fragile and if subjected to remotely harsh conditions have a tendency to "go crunchy". Have a spare on hand.

JVN 23-01-2009 00:10

Re: pic: 148 Follower Wheel Assembly
 
Quote:

Originally Posted by Ben Piecuch (Post 806128)
John,

Are you running any sort of bushing on the vex shaft? Or, are you just letting it ride on the 1/8" hole in the ABS? (I'm having a hard time finding a flanged bushing for an 1/8" shaft)

Very pretty, thanks!

Bengineer
FRC1350

We're just running it in the ABS. VEX shaft is designed as a "rounded" square profile so it works great in that application.

-John

Dan Richardson 24-01-2009 09:46

Re: pic: 148 Follower Wheel Assembly
 
Every time I see a teaser/picture from 148 I feel like a tiny kitten who is lost in wonderment and amazement of the string spinning from the fan. I spend about 30 minutes pawing at the screen saying "I can haz?"

5n1p3r 30-01-2009 22:10

Re: pic: 148 Follower Wheel Assembly
 
wow,, thats awesome


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