Re: pic: FRC488 Octocanum.
 

Rapid direction changes + Short wheel base + tall manipulators = Tipping

The longer the wheel base, the less likely you are to tip when accelerating hard or coming to a hard stop.

Re: pic: FRC488 Octocanum.
 

However, mecanum is not at all like full blown swerve. The bot tends to drift a little bit as the rollers spin which should help remove some of the problems typically associated with rapid direction changes and tall manipulators. That being said, I still would not change direction at full speed (or even drop those traction wheels) if I had any sort of large mass up top. But knowing what I know about 488 they will have thought that out already (this ain't their first rodeo with mecanums).

Cool system, glad to see someone went with it, hopefully the ability to strafe will be beneficial.

Re: pic: FRC488 Octocanum.
 

I'm very curious as too why you put the traction wheels on the inside as to opposed to the outside. As of now it appears that you are not really taking full advantage of switching wheel base sizes. Why not put the traction wheels in the longer wheel base configuration to make it that much more difficult to turn as opposed to the mecanum wheels which could be made to preform equally well on the shorter (inner) wheel base?

Otherwise, really cool.

Re: pic: FRC488 Octocanum.
 

We prefer to call them über-mecanums..... ;)

Re: pic: FRC488 Octocanum.
 

Well team 1708 did a very simalar design

http://www.chiefdelphi.com/media/photos/34890

Re: pic: FRC488 Octocanum.
 

I like the idea. If the execution can be made perfectly reliable, it should be a formidable drivetrain. The trick comes in ensuring theres no problems with throwing chains etc.

Re: pic: FRC488 Octocanum.
 

Team 1708 actually did something like this last year..

Check it,
http://www.chiefdelphi.com/media/photos/34890

Re: pic: FRC488 Octocanum.
 

We anticipate using the mecanum wheel set most of the time, so we wanted that to be our most stable configuration. The traction wheels are not really intended to prevent others from turning us in place, but to kindly remove defense from our path when the mecanum wheels can't get us around it.

Re: pic: FRC488 Octocanum.
 

Well said. Never know when you'll need to gently escort someone across the field.

I really like this drive, I feel like it negates the majority of the disadvantages of a Mecanum Drive in a relatively simple and elegant method.

Re: pic: FRC488 Octocanum.
 

When you guys assembled those mecs, did you do anything special, like grease the washers at the end of each roller and/or replace the washers with nickel plated ones?

Re: pic: FRC488 Octocanum.
 

We checked that each of the rollers is spinning freely, but did not do anything otherwise special to them. As we run the chassis in, we'll see how they behave and make adjustments as necessary.

Re: pic: FRC488 Octocanum.
 

Hi Madison,
Looks good. The Robowranglers built an octocanum platform this fall. Do you mind my asking -- what are you geared at for the mecanum drive?

-John

Re: pic: FRC488 Octocanum.
 

It's geared at 8.9:1 right now.

Re: pic: FRC488 Octocanum.
 

Interesting. That is much faster than I expected.
I look forward to seeing video of it in action so I can recalibrate my mental picture of performance. :)

-John

Re: pic: FRC488 Octocanum.
 

I think it's a bit faster than I expected, too. We're going to get a bit more weight onto it soon and test it again under more realistic conditions to get a sense of whether or not it's something we can handle.

We've got rookie drivers this year and haven't found an area large enough to let it run at full speed for more than about a second, so necessity may require that we slow it down.