This is very intriguing to me. I’m assuming the middle (omni) wheel is offset lower than the traction wheels. This would mean the chassis is always sitting on 2-traction wheels + 2-omni wheels at any given time.
The weird thing is… I imagine the turning point of the robot would drastically shift from the front to the back depending on which set of wheels the robot is sitting on. (At least, this is what physics tells me).
Have you driven it yet? How does it handle?
Is there a reason you didn’t go with front/read omnis and middle traction wheels? This would result in the same 2+2 configuration, but you’d have a consistent (centered) turning point.
-John
Silly John…
That IS the whole chassis!
The game this year is obviously going to be a scooter-like thing!
I tend to agree with JVN’s comments, with this addition: Seems to me that by putting the omni’s in the middle (presumably dropped the obligatory 1/8"), you lose your resistance to sideways pushes.
And are we looking at the outer part of the chassis? I see two sprockets on the middle wheel and one sprocket on each outer wheel, so I’m wondering where the motor goes…
Is it realy strong, i would like to do something like this because our normal chassis is extremely heavy, but strong :yikes:
I’m guessing the center wheel IS DROPPED so it will function as a normal 6WD chassis. This is so because we all know on most 6WD there are only 4 wheels on the ground so it can rock and turn? right? so the middle wheels act as the turning point so its like a 4WD with omni’s in front.
Do i make sense? Because it was a little hard to explain trough the 'net
If the CG is fairly balanced front to back I don’t think the traction wheels would get enough grip to greatly affect how the robot turns in place. I suspect you could probably pull some of those fun maneuvers from Lunacy though, like the sideways slides and the backwards-180-forwards whip around. Looks like fun to play with!
The middle wheel will simply make it so only a front set and middle set or back set and middle set are on the ground at a time. Thus, it’s treated like any four wheel drive, except the issue with this 4 wheel drive will be that half of the mass is located beyond the sliding wheel. It certainly appears that resistance to rotation from robot-to-robot contact will be reduced, but this may be intentional (It’s an interesting concept that could be explored, IMO).
This is great 
I put this up to see what kind of comments i would get … 
to clarify things up… we can swap all 3 wheels and I think we were also looking at going for all 6 wheels to be plaction style wheels. we are going to run it on friday soooo we’ll see
Jun,
Try it in the configuration shown! If nothing else I’m extremely curious how it performs. I don’t know if it will perform well (in fact I suspect it won’t)… but you’d be my hero if you tried it out and took some video…
I bet if nothing else you could teach some students a cool lesson on drivetrain turning (the video would also be giving me a tool I could use to teach the same things).
-John
I think this is really cool. Imagine a robot that could shift its CG at will by moving an arm or a weight. You could pivot among whichever axis you chose, if for whatever reason you didn’t want to rotate about your center.
I am with JVN, give it a spin (pun intended) and shoot some video. I would suspect it would have a very crazy behavior if you had a slightly rear biased CG. Take the 2008 game, where you are trying to do laps. If the weight is rear biased, going into the turn I would suspect the robot to initially push (understeer), but then as the weight shifts to the front, and those wheels grab, it would have crazy snap oversteer. With a lot of practice, you could probably make an “FRC Tokyo Drift” video…:yikes:
Interesting, I think this wheel configuration would be handy in a way. If you ended up pinned, you could shift CG and slip out of it in a lot of cases. My old team designed mechanisms to make the robot ‘slippery’ in '09 and it worked fantastically. If you can shift CG and need to escape pinning this could be viable.
Unless theres some sort of optical illusion going on here, it seems that the omni wheels are smaller than the traction ones. The sprockets on all the wheels appear to be the same size as well, meaning the ground speed of the omni and traction wheels will be different. I still think its worth a shot at trying and showing everyone here your results, just wanted to point that out.
-Brando
I measured the wheels and the omni wheel seems to bee about 6/7x the size of the outer wheels. Good observation.
here’s the video a day early.
Well that’s unexpected. It looks like it’s driving exactly like any other drivetrain. Is the omniwheel touching the ground at all? Is it dropped lower than the other wheels, or are all the wheels collinear?
its the dropped 1/8 center. it rocks just a little bit:p eventually I would like to put on supershifters and run it with that.
But it’s on a hard surface. Most any drive will work well on that. Carpet will tell the real tale!