21-01-2009 19:24

Jonathan Norris

Re: pic: 148 Follower Wheel Assembly

Totally unnecessarily awesome...

21-01-2009 19:30

Ice Berg

Re: pic: 148 Follower Wheel Assembly

How is this going to measure ground speed if it can't touch the ground?

21-01-2009 19:32

Joe G.

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.

21-01-2009 19:33

NoahTheBoa

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.

21-01-2009 19:34

synth3tk

Re: pic: 148 Follower Wheel Assembly

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.

21-01-2009 19:43

NoahTheBoa

Re: pic: 148 Follower Wheel Assembly

Here is a relevant Q&A on the subject

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

21-01-2009 19:45

Joe Ross

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.

21-01-2009 19:55

Karthik

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.

21-01-2009 19:56

Raul

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?

21-01-2009 19:59

NoahTheBoa

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?

21-01-2009 20:03

danshaffer

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!

21-01-2009 20:24

Akash Rastogi

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. =)

21-01-2009 20:26

Greg Needel

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?

21-01-2009 20:35

AdamHeard

Re: pic: 148 Follower Wheel Assembly

Soo.... will Vexlabs be selling these?

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.

21-01-2009 20:53

=Martin=Taylor=

Re: pic: 148 Follower Wheel Assembly

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

21-01-2009 21:00

artdutra04

Re: pic: 148 Follower Wheel Assembly

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

Edit: Yup, they're 24 DP.

21-01-2009 21:27

Brandon Holley

Re: pic: 148 Follower Wheel Assembly

wow JVN this looks VERYYYY familiar....ours looks almost identical...

21-01-2009 22:32

NoahTheBoa

Re: pic: 148 Follower Wheel Assembly

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

21-01-2009 22:35

DonRotolo

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

21-01-2009 22:42

NoahTheBoa

Re: pic: 148 Follower Wheel Assembly

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.

21-01-2009 23:52

JVN

Re: pic: 148 Follower Wheel Assembly

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.

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.

How much would you pay for one? I'm starting my own company KarthikJohn.
I think with some down-force this should get pretty good grip on the regolith.

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

21-01-2009 23:54

Andrew Bates

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...

22-01-2009 00:02

Travis Hoffman

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 00:27

JVN

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 01:18

AdamHeard

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 02:10

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 07:18

Jared Russell

Re: pic: 148 Follower Wheel Assembly

Looks strikingly similar to something we're making...

22-01-2009 08:03

Taylor

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 10:59

Kingofl337

Re: pic: 148 Follower Wheel Assembly

With a few modifications you could use the US Digital encoders that come in the kit.

22-01-2009 11:35

martin417

Re: pic: 148 Follower Wheel Assembly

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.

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

22-01-2009 11:43

JVN

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.

22-01-2009 12:01

Jonathan Norris

Re: pic: 148 Follower Wheel Assembly

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!

22-01-2009 12:05

Chris Fultz

Re: pic: 148 Follower Wheel Assembly

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)

22-01-2009 12:26

Tom Line

Re: pic: 148 Follower Wheel Assembly

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.

22-01-2009 13:00

jgannon

Re: pic: 148 Follower Wheel Assembly

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

22-01-2009 13:07

BenB

Re: pic: 148 Follower Wheel Assembly

..

22-01-2009 15:17

AdamHeard

Re: pic: 148 Follower Wheel Assembly

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).

Aww. lame. Sometimes we can blinded by awesomeness.

22-01-2009 15:37

The Lucas

Re: pic: 148 Follower Wheel Assembly

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

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

22-01-2009 19:24

Ben Piecuch

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

22-01-2009 19:32

Andrew Bates

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.

22-01-2009 22:07

Rickertsen2

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.

23-01-2009 00:10

JVN

Re: pic: 148 Follower Wheel Assembly

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

24-01-2009 09:46

Dan Richardson

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?"

30-01-2009 22:10

5n1p3r

Re: pic: 148 Follower Wheel Assembly

wow,, thats awesome