Re: A new drivetrain Idea?
 

How about instead of using casters, which can be a little problematic as people have mentioned above, use plastic nubs. We used them on our robot, as you can see in this
photo. They slide really easily and you don't have to worry about them ever getting stuck.

Re: A new drivetrain Idea?
 

The more I think about this idea, the more I wish I had more Vex omnis. It would be easy to prototype on Vex. Anyone got 6 omnis?

Re: A new drivetrain Idea?
 

(I'm quoting Kevin as a starting point, not because he's wrong. He's not.)

The idea is that the chassis will rotate about the point where lines, drawn perpendicular to and from the center wheel on each side, intersect. This is true of how traditional tank-steer robots operate as well, except that they typically lack the ability to move that point as this design allows.

Typical drives can spin in place because, by moving each side opposite the other, the translation vector of each -- that is, the force that would move it forward or backward -- is cancelled by the other. When each side is no longer parallel with the other, some of that translation escapes, as it were, and the chassis starts to behave as an inefficient holonomic platform. Thus, running each side in the 'opposite' direction will result in sideways translation. Driving them in the same direction will result in forward or backward movement. The only exception would be when they sides are again parallel, but collinear, as would occur when opened 90*. In this instance, driving them in opposite directions would do nothing at all (except break your robot, perhaps), while driving them together would result in the most efficient sideways translation possible because you've effectively changed which direction represents 'forward'.

Without a fixed point about which to rotate, all this design seemingly allows is a way to vary the efficiency at which a holonomic platform operates. That's not without merit, necessarily, but it doesn't seem to me that it would work as advertised. All of this assumes, of course, that it uses omniwheels. Other wheels would effectively function the same, but it would be even less efficient.

Re: A new drivetrain Idea?
 

Here is a thought starter;

Imagine a traditional mechanum drive arrangement. Now imagine it translating sideways, except that the rotational velocity of the front 2 wheels is less than the rotational velocity of the rear 2 wheels. Wouldn't it have exactly the same motion that your trying to get?

Re: A new drivetrain Idea?
 

I see one big flaw in it... when the bot is extended out for side-to-side motion (Crabbing) it is totally vulnerable to being pushed back and forth because of the omni-directional wheels. I think the drive train design, while pretty cool and original, would be so poor defensively that it would be almost useless in a FIRST game.

Maybe another application could be in order? It would be cool if you could use it in an off-road vehicle so it could snake through obstacles. Modification would be needed, but it has potential.

Re: A new drivetrain Idea?
 

Plastic Nubs are simple and pretty slick, but they make driving the bot a little harder and there is the small chance that you'll tear something on the field or snap one off.

I like doing teflon "scrub" wheels. They are mounted inline with tank-style wheels and give it good stability driving in a stright line, but slip when you're turning.

Re: A new drivetrain Idea?
 

I agree with James. While the drivetrain has potential for outside uses, if you look at the way defense has been coming back to FIRST, it would be pretty much useless, due to easily being pushed, and the great possibility of jamming the system.

Re: A new drivetrain Idea?
 

But if you use mecanums in a 4 wheel drive like above, that is greatly diminished.

Re: A new drivetrain Idea?
 

I agree with what has been said a few times, that an idea along these lines might be cool for non-FIRST purposes. But for FIRST, I think it invests too much weight, spaces, motors, and compelxity (especially for either the driver and/or programming). Secondly, it would do as Madison suggested, and perform similar to a holonomic system (which could be beneficial in other ways).
There are other ways that your desired arc could be achived. The mecanum suggestion earlier is one.
Another could be a standard holonomic drive.

By moving the wheels as such (with the "NW" and "SE" wheels driving at different rates) you can acheived the desired arc motion.

Re: A new drivetrain Idea?
 

There are few posts in this thread that just explains how this idea would never work and how other kind of drive trains will work better (basically asking him to give up on this). I think that is pretty obvious that this design is in the very early stage, and it definitely has some potentials. Has any of you seen a drive train like this before? Team 47, Chiefdelphi designed the first swerve drive and over the years teams have come up with stronger swerve drive. I bet one of the robots could have pushed around chiefdelphi's first swerve drive easily at that point but it has been developed and modified by many teams over the years. Rather than telling Cody that this idea would never work, why not help him and give him ideas about how to make this new idea a reality?

Are there people here who wants to think outside the box and come up with new designs that has never been done in FIRST?

Keep in mind the first transmission I ever designed weighed 13 pounds, the second one I designed weight weighed 5 pounds. Designs can be reviewed and modified for the better. I am going to propose to all the chiefdelphi designers to come out here and post how can this design become a product. Thank you.

Re: A new drivetrain Idea?
 

cromat44 is exactly right about the kind of advantage I was originally looking for, although some people have mentioned a couple of others that are now seeming VERY interesting to me. Please don't take the drawing with the omni-wheels as set in stone... because as Arefin or Tytus have said, It is more a way to get my Idea across than an actual design. I'm taking into consideration everything that everyone is saying, and I just don't get how this wouldn't work. When coming up with this Idea, I was mainly thinking of roller blades or Ice skates, and how the athletes that wear them turn in arcs; it seems to work for them... I will try and build a prototype tomorrow or the next day. Until I can do that, please continue as you are.... I find this VERY helpful :D


P.S. Sorry if I don't have the Prototype tomorrow, I have to go to a wedding.
P.P.S. Thanks Arefin and Tytus:D

Re: A new drivetrain Idea?
 

This is fascinating. Any idea on how you would wire it?

Re: A new drivetrain Idea?
 

Oh! I see what you are saying.

That would be a very fun demo bot based on what you have designed so far.

But do the wings need to be so massive?

Imagine a robot with 4 wheels. Rear wheels remain parallel to the sides of the chassis, and the front two are independantly rotated, and all four are independantly driven. You could achieve the same effect without dealing with bumper zones and appendages and all that stuff. Also, you wouldn't be pushed forward and backward so easily.

Also, looking at what cromat44 said. This would be incredible, however I remember watching a video team 88 made with a holonomic robot that did the same thing using a gyro and a holonomic drive. I'm not a programmer so I have no idea how it worked, but that's how they described it.

I forget where I saw the video though...

Re: A new drivetrain Idea?
 

I was planning on making a prototype of this as well. It will be posted in a month or so because I need to get some stuff from vexlabs and make some mecanums (I made ona while back similar to the "vexanum" wheel posted a while ago). Hopefully I can help you prove this design useful for this kind of game.

Re: A new drivetrain Idea?
 

I remember that video.

This could be done on the software side of things, BUT it would give your programmer a headache, and you would have to do some R&D before and during the season. Basically, it'll take a while to troubleshoot all of the kinks out of the system.