pic: 148 Follower Wheel Assembly



This is the assembly team 148 will be using to measure ground speed of our robot. We thought this was pretty cool and worth sharing.

Totally unnecessarily awesome… :cool:

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

It can.

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

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.

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.

Here is a relevant Q&A on the subject

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

We were planning to do the same thing, but with all vex components, including the new encoders. Hadn’t gotten to it yet.

Fabulous use of VEX parts in a very elegant package. I think we’ll be seeing a lot of similar assemblies this year.

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?

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?

Beautiful assembly!
Have you tested whether it will stay on the ground under its own weight? If not, may I suggest gas springs!

Correct me if I’m wrong, but are those delrin sideplates? They look very nice. Good luck with this. =)

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?

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.

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 :slight_smile:

I’m [strike]about 95%[/strike] sure it’s 24 diametric pitch.

Edit: Yup, they’re 24 DP.

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

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

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