pic: Unique drive concept
 

Re: pic: Unique drive concept
 

That looks interesting......Can I assume the vertical 'big' CIM is used to turn the table for steering?

duh.....of course it is. I got to read your caption first. Please post any refinements. I'm going to bring this to my team's resident VEX expert for a prototype.

Shawn???? Are you reading this.

Re: pic: Unique drive concept
 

I think that is how it works...

Re: pic: Unique drive concept
 

thats really cool

I'm going to try that with VEX

Re: pic: Unique drive concept
 

I'm not sure, but ball casters might have less friction than omniwheels

Re: pic: Unique drive concept
 

we had a bad history with casters this year. i wouldn't recommend it. that design is sort of present in our 05 bot. its not multi directional http://www.chiefdelphi.com/media/photos/20299
it shows it with
ball casters but. later we switched them out with omnis and personally its my favorite bot to drive. its a great idea i might want to try that out.

Re: pic: Unique drive concept
 

The Champion Lightning Bots of Team 2010 built a somewhat similar drive system this year, but instead of both drive modules on a single turntable, they were on separate pivot points driven by a Globe motor chained to them via a 2:1 sprocket reduction. When pointed straight ahead, the system was laid out the same as in your concept drawing. The four corners of the frame had ball casters instead of omniwheels. Each drive module had 180 degrees of rotation limited by potentiometer feedback.

2010 used 2 A-M traction wheels for their driven wheels, each of which was powered by a custom 2-CIM motor single speed transmission. The wheels were mounted 16" apart, center to center. It proved to be a very maneuverable and reliable design, although the casters did make it next to impossible for them to climb ramps.

The drive modules were inspired by those used on Team 48's 2002 robot. This style of module requires plenty of clearance for the motors to freely rotate.

2010's 2007 Drive Module

Steering Linkage Overhead View

Globe Motor Mounting

Drivetrain Side View

Your solution is definitely unique - If you decide to attempt to build it, best of luck attempting to solve its particular design challenges!

Re: pic: Unique drive concept
 

Thats a really cool idea... I would also have to agree that ball casters would be a better idea then omni wheels.
My main concern with this idea is the torque required to move the center 'module', because most of your contact with the ground will come from those two middle wheels... and if they provide too much friction you may just end up turning the whole body of the robot. So instead of having a crab drive you have your robots body turreted.... with your center two wheels staying put...

To solve this you would have to either program the wheels to turn the direction your are trying to move the middle module, basically running the wheels in opposite directions helping the big CIM turn your center module. Or you may want to use omni wheels over the kit wheels...

This is defiantly something you would want to do some calculations and small prototyping to see if it would actually work, cool idea thou!

Re: pic: Unique drive concept
 

Very interesting concept, a nice simplified swerve concept. I think I may also try and find the parts/money to try and test it with Vex (although the bushing around the base of the drive will probably be hard to reproduce, I might have to prototype it without it).
Some thoughts to consider:
As it stands, this drive will have difficulty climbing ramps/inclines/large(r) steps. When the leading set of wheels starts to go up the incline, the drive wheels will be lifted off the ground, and the bot will roll back down. If you added some form of suspension to the omnis, this could possibly fix the situation, but that increases the weight/complexity. It's really a game/strategy dependent decision.
You're going to have to consider your wire runs carefully (but that is true for pretty much any swerve).
It might not be possible, but it would save a considerable amount of chain (and space that cannot be used to mount because chain is there) if the steering motor is moved to the central support.

Re: pic: Unique drive concept
 

What makes it so that the wheel bogey in the middle turns across the carpet rather than the frame rotating around the wheels?

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Yeah, I was thinking that omniwheels might be needed in the middle, but normal wheels are obviously preferable for traction reasons if it dosen't push backwards like you suggested. A prototype is really the only way to find out for sure. It'd probably have some programming compensation like you said too.

I agree with Lil' Lavery that ramp climbing is a problem, omniwheels or casters, but I have a few concepts to play around with for some kind of suspension.

Re: pic: Unique drive concept
 

Last year when we were throwing around ideas for drivetrains and such, we came up with a concept similar to one drawn. We tossed it for the very reason that lavery posted, and also for the reason that if we ever got into a pushing match, the slightest bit of lift would lose it for us.

Re: pic: Unique drive concept
 

almost as maneuverable as my off season idea; spherebot:)

Re: pic: Unique drive concept
 

I think everyone else have covered most of the things about that base. The first thing that caught my eye was the 1x1 that is holding the powered module up. What is the thickness on that? Also... what is the thickness of the shaft that is coming out (going into that 1x1) to connect to the sprocket (in order to turn)? I am assuming its 1/2". Are you worried about that 1x1 bending/sheering? How much does it weigh as is in the picture?

Very interesting concept. I hope after some modifications on the drawing you will be able to manufacture this and share the outcomes. Good luck.

Re: pic: Unique drive concept
 

http://www.firstroboticscanada.org/site/node/372

http://www.firstroboticscanada.org/site/node/323

Im guessing you already knew about these when comming up with the design, but my advice is to try to contact whoever did these and discuss the pro's and con's with them.

There used to be more pictures of similar drive methods but they seem to have been lost when waterloo moved all its info to FIRSTroboticsCanada

-Simon