29-07-2013 19:34

Re: pic: Crab/Swerve module using gears instead of belt /chain

Like the swerve module, really don't like the banebots drive wheels. I suggest some 4" performance/plaction/VEX traction/Versa wheels.

29-07-2013 19:41

Akash Rastogi

Re: pic: Crab/Swerve module using gears instead of belt /chain

Quote:

Originally Posted by Andrew Lawrence Like the swerve module, really don't like the banebots drive wheels. I suggest some 4" performance/plaction/VEX traction/Versa wheels.

29-07-2013 19:45

Re: pic: Crab/Swerve module using gears instead of belt /chain

Quote:

Originally Posted by Akash Rastogi Or some sweet sweet Colsons... http://www.chiefdelphi.com/media/photos/30599

29-07-2013 21:47

magnets

Re: pic: Crab/Swerve module using gears instead of belt /chain

What sort of bearing are you using for rotation, and how is the robot's weight supported?

Could we have a side view or an iso view?

If you're looking to save weight, you could move the gears to the outside of the module like 148 did. Also, you could replace the shaft collars with snap rings.

29-07-2013 22:00

Chris is me

Re: pic: Crab/Swerve module using gears instead of belt /chain

As others have implied, the Banebots wheels, especially the green ones, are just not suitable for a drivetrain. They will wear in a matter of minutes on carpet.

I don't know how your module is supported, but if it's just that piece of 1/4" plate hanging out there, through a single bearing, it's not going to cut it.

You may want to consider a VersaWheel for the module. This allows you to attach the gear directly to the wheel. The advantage of this setup is that it lets you use a dead axle instead of a live axle - which you can then use as a structural member of the module, increasing rigidity.

29-07-2013 22:16

jman4747

Re: pic: Crab/Swerve module using gears instead of belt /chain

The thrust bearings are mcmaster P/N 5909K34 rated for 8,000 rpm and 2,400lbs dynamic load. They sit on a quarter inch 7075 T6 aluminum plate (the weight of the robot being loaded on the bottom bearing and then the plate). The front view doesn't show it but the wheel shaft is hex so I use Vex hex collars unless someone makes a hex snap ring witch would be awesome. Other shafts use self locking retaining rings such as mcmaster P/N 98430A134 & 98430A138. Edit: Also the other photo I posted to the CD image gallary shows the whole system.

29-07-2013 22:24

Chris is me

Re: pic: Crab/Swerve module using gears instead of belt /chain

You can just use a round snap ring in a hex shaft. You cut the groove exactly as you'd cut a groove in a round shaft and then slip it over.

29-07-2013 22:36

jman4747

Re: pic: Crab/Swerve module using gears instead of belt /chain

Thoughts on Vex 4" traction wheel?

29-07-2013 22:54

apalrd

Re: pic: Crab/Swerve module using gears instead of belt /chain

The frame CAD posted is interesting. There is one large problem with that approach: Everything is essentially supported from one side, so loads will try to bend the chassis tube and flange plate (which should be fine as 6061, BTW).

I highly suggest you add inboard tubes or an alternate support system for the crab pods. While you'll probably be fine with the gearboxes as they are, the crab pod support plates will bend (or the tubes they are attached to will) under load.

I like the VersaWheels, but we do replace them every other competition, so design in a way to remove them for replacing them (you don't replace the tread, you replace the whole wheel). No experience with the non-Versawheels from Vex.