2583's Octocanum Modules
 

This year 2583 is using Octocanum for the first time ever

4x1.5" inch Colsons geared to 7 fps and 4" Vex mecanum wheels geared to 20.5 fps (around 15 fps forward after loss of top speed from mecanum)

Gears inside the module get the reduction without any belts or tensioning

One CIM per module
4.1 lbs per module without CIM (6.9 with CIM)

Each side of the octocanum is activated by one 1.0625 bore piston pushing in between them, total of two pistons

Traction wheels deploy on the outside to make it impossible to turn for straight driving in autonomous and to prevent being pushed while shooting

All comments and critiques are appreciated

Re: 2583's Octocanum Modules
 

Holy image size, Batman!

Is that a mounting hole for a CIM I see there in the side?

Re: 2583's Octocanum Modules
 

yes it is,
a CIM with a 14 T gear mounts to the side there
(fixed the image size)

Re: 2583's Octocanum Modules
 

Depending on gear reduction, frame and power (# of motors) you may be able to turn.

Our LogoMotion octanum, with a cim & 775 on each transmission, actually handled quite well in traction mode, even though it was in 'long' orientation with traction wheels on the ends.

Re: 2583's Octocanum Modules
 

These are pretty cool. They are also the first cantilevered meccanum wheels I've ever seen (not that there's anything wrong with that).

Re: 2583's Octocanum Modules
 

Cantilevered octacanum is far from impossible, but you've got to think seriously about how the module is supported and what moments you are putting on the pivot shaft. How is this attaching to the frame?

Re: 2583's Octocanum Modules
 

It pivots around the hole at the top of the module and the standoff on the mecanum side is where the piston will push/pull

I have attached a few screenshots of the side rail including two modules to help visualize it

Re: 2583's Octocanum Modules
 

I like your single piston switching method. Do you have a hard stop for the modules so that the piston doesn't take the path of least resistance and kick one module out, leaving the other un-switched?

Re: 2583's Octocanum Modules
 

Its hard to see but if you look at the side view, all the way on the outside there are two 1/2 inch holes and right above those there are two small holes next to the vertical line of three holes.
A bolt/standoff through that hole will act as a hard stop for the module

Re: 2583's Octocanum Modules
 

Here are some screenshots of the two positions that the hard stops will create when the piston extends/retracts

Re: 2583's Octocanum Modules
 

Have you done the math to make sure your modules will actually shift? We are moving to 4 1.5" diameter cylinders because our 4 1 1/16" were having problems. Our setup is different than yours but it seems like you will have a hard time lifting your whole robot.

Re: 2583's Octocanum Modules
 

I don't see why. We lift our robot onto traction wheels with two 1.5" cylinders with no problem.

It's hard to see how much mechanical advantage they have--looks like close to none--but 2 x pi x (1.5 in/2)^2 x 60 psi = 212 lbs; well more than enough.

Re: 2583's Octocanum Modules
 

The issue is that they are not using a 1.5 inch bore. Two 1.0625 inch bore will probably not be able to lift up the robot (and remember to take into account the added weight from battery and bumpers).

Re: 2583's Octocanum Modules
 

We've cantilevered mecanum wheels a few times.

Re: 2583's Octocanum Modules
 

Whoops, must have missed where they gave the bore, and was going by eye. (And not very well, apparently.)

2 x pi x (1.0625 in/2)^2 x 60 psi = 106 lbs, which is well below comfort without a 2:1 or better mechanical advantage.