21-12-2015 13:49

LeelandS

Re: pic: Mecanum 8 inch Iso

I like the design and I applaud your team's efforts to have some set designs ready for kick-off. Just remember you have to redesign the whole set-up after kick-off for it to be legal.

Just wanted to point out that when using Mecanum, you want to have an even weight distribution across all 4 wheels. It looks like most of your robot's weight is on the back wheels. This will cause your robot to strafe improperly (as if it were rotating around it's front). You can use a gyro to compensate for this rotation, but evenly spreading your weight is probably the easiest way to go.

Other than that, good job! I love all the designs you've put up.

21-12-2015 13:57

Ari423

Re: pic: Mecanum 8 inch Iso

Really? I don't remember that rule. Aside from any rule changes from year to year, I was under the impression that you could reuse chassis designs year after year after year if you want to. Many teams (esp. those that don't CAD their chassis) use the same chassis design each year because they're familiar with it.

21-12-2015 14:00

Chief Hedgehog

Re: pic: Mecanum 8 inch Iso

You may want to recheck that...

21-12-2015 14:05

Knufire

Re: pic: Mecanum 8 inch Iso

AFAIK, reusing the CAD would be illegal. I have reCADed nearly identical drive systems during build sesaon to maintain legality.

On the other hand, if the CAD is published and available to the entire community, it's legal.

See R13 from the 2015 Game Manual:

21-12-2015 14:39

GeeTwo

Re: pic: Mecanum 8 inch Iso

If I recall correctly, the 2014 bumper rules required that the bumpers be backed/supported by the frame every so many inches (8?). I don't see any frame backing down the sides apart from the corners.

21-12-2015 16:02

Anthony Galea

Re: pic: Mecanum 8 inch Iso

If you post the CAD files online before kickoff you should be okay. I think I remember an annual flood of CAD designs being posted in the two weeks before kickoff in order to keep the legality.

21-12-2015 17:02

GeeTwo

Re: pic: Mecanum 8 inch Iso

There's also a flood of syncs to teams' Github and other software source code control accounts during this period for the same reason -- sync up!

21-12-2015 23:50

cgmv123

Re: pic: Mecanum 8 inch Iso

Note that we currently don't know what, if any, parts/design reuse rules are in the 2016 Game Manual.

22-12-2015 09:13

suttonrc

Re: pic: Mecanum 8 inch Iso

Good point. I left it open (in each design) as the bumper rules are a bit different from year to year. Depending on this year’s rules I could potentially mount stand offs on the side, between the rear wheel and the front motor, also potentially sideways within the chain loop or if necessary I could move everything in and put a full length member (or plate) on each side, but I would prefer not to if the rules allow it.

I hope to have the CAD posted sometime tomorrow. Am I correct in thinking that Google Drive is the standard way of doing that?

As shown the drive base would definitely strife an arc. In the past though the mechanism, and game pieces (that we typically locate on the front) tends to involve a good amount of structure, motors, gearboxes etc. I'm thinking, picking up totes, climbing 3 rungs of a pyramid, shooting basketballs and a robotic arm to pick up inner tubes. They were all centrally located more or less in the front of the robot. The rear weight bias is intentional as in the past we've had issues falling over forward due to being too nose heavy after adding our upper structure.

22-12-2015 09:27

Ari423

Re: pic: Mecanum 8 inch Iso

NO. Please post CAD files on GrabCAD so people with any (or no) CAD software can look at it without downloading huge files. Also, if you get in the habit of using GrabCAD Workbench, it automatically does version control and file sharing for you.

23-12-2015 17:55

suttonrc

Re: pic: Mecanum 8 inch Iso

Below are links to the CAD files.

https://grabcad.com/library/mecanum-8in-wheels-1

https://grabcad.com/library/mecanum-4in-wheels-1

https://grabcad.com/library/skid-steer-2-speed-1

https://grabcad.com/library/skid-steer-1-speed-1

23-12-2015 20:17

GeeTwo

Re: pic: Mecanum 8 inch Iso

You can't be ready for every possible rule change, but that's no excuse for not being ready for rules that we expect to be carried from one year to the next with no change. I can't see the GDC deciding that designs posted publicly can be used by every team except the team that posted them; there's no exit strategy from those pitchforks.