"Omni wheels" are wheels whose rims are made out of rollers, installed with their axles perpendicular to the wheel's axle.
If you install the omni wheels so their axles point out diagonally from the vehicle's chassis, as is the case in the above Lego construction, you get full 2D maneuverability, unexciting drive efficiency, and a vehicle that won't roll sideways down a hill.
If you install the omni wheels parallel to the sides of the chassis, then the vehicle will want to roll sideways down a hill. But you may be willing to accept this, in return for something that handles like this demented little beastie:
(Note the camera car, also made from Lego!)
It's called "Metal Grudge" (on account of having the same cartoonish proportions as the tanks in the Metal Slug games), and it's basically just a skid-steer machine, like a tank or "Bobcat" loader.
Plenty of motor power and those crazy flailing omni wheels make it a lot funnier than standard skid steer, though.
Metal Grudge was made by prolific Lego builder Peer Kreuger (so was the slow omniwheel platform).
He's here on Flickr, and here on YouTube.
4 January 2011 at 7:18 pm
Awesome! I want one, but in about the right size to have a racing bucket seat and powered by a big engine. Powersliding around fields in that thing would be my idea of a fun evening.
4 January 2011 at 7:56 pm
I'm having some trouble understanding exactly what advantage the arrangement of the wheels provide to the tank. Care to explain it for someone less well-versed in this kind of technology? :)
4 January 2011 at 9:10 pm
I'm having some trouble understanding exactly what advantage the arrangement of the wheels provide to the tank.
I could be wrong, but I think the key is that the wheels allow the momentum of the Metal Grudge to continue on sideways while it is spinning.
If you tried the maneuvers in the video in a vehicle with tracks or wheels orientated in the normal fashion, I expect the forward momentum of the vehicle would cause it to roll once it approached 90 degrees of the way through the 180 degree turn.
Instead, the sideways facing wheels allow it to continue to roll sideway.
Think of walking down a shopping aisle with a trolley, and spinning the trolley through 360 degrees while still moving forward, and then compare that with trying to do the same thing with something that has two or more wheels fixed in the direction of travel.
Which reminds me of why it is so hard to use those carts you find in libraries.....
5 January 2011 at 5:45 pm
Hi guys,
Like your creation. If you'd like to see more omni-directional wheels in action you might like to search under "rotacaster robotics" on youtube. Ready to go on the Lego Mindstorm NXT gear.
5 January 2011 at 9:52 pm
"This video is not available in your country"
Rant: [long list of obscenities]
Declaration: *sigh*
6 January 2011 at 1:02 am
Buckermann; here are the two videos mirrored on Flickr.
Omniwheel platform:
http://www.flickr.com/photos/28134808@N02/4793453871/
Metal Grudge:
http://www.flickr.com/photos/28134808@N02/5074735926/
Daniel; thank you for blogging me and the informative writeup. Being on 'How To Spot A Psychopath' is a great honor.
6 January 2011 at 8:08 pm
Thanks mahjga, very interesting indeed.
And just in case: my [long list of obscenities] wasn't directed at you, just generally at the current state of internet copyright nonsense.
8 January 2011 at 12:21 pm
Clayton: Sounds like your trolleys are a lot easier to use than american shopping carts (trolleys). Ours have fixed rear wheels, so we're acutely aware of the limitations on their maneuverability.
12 January 2011 at 1:38 am
Dan, are you okay? Just heard about the flooding. Hope everything is safe for you and your family.
12 January 2011 at 3:20 am
It's raining a lot here too, but, (a) I'm in New South Wales, not Queensland and (b) we're 1km above sea level here, with a few minor waterfalls but no rivers. So my inconvenience extends only to the feeding of damp cockatoos, instead of dry ones.
Thanks for worrying, but your worry is mis-aimed :-).
12 January 2011 at 4:23 am
Wasn't sure where you were located. Glad to hear you're doing well. Give my regards to the birds.
12 January 2011 at 3:17 pm
I'm intrigued by the diagonal wheels.
They could make my motorised wheelchair much more manoeuvrable, but they look like they'd rip up carpet.
Oh, I've been meaning to ask you for a while... you're not Paris Portingale are you? ...but then I guess you wouldn't answer honestly if you were.
25 February 2011 at 11:28 am
google.com
27 February 2011 at 3:56 am
Omni-wheels? Killough platform? That's grade-school stuff. If you're looking for brain-bending maneuverability, then you want Mecanum wheels:
Mecanum Wheel
Videos Mecanum drives being tested by some high-schoolers:
Bot2011_Test_110205_HD.wmv
Chop Shop team 166 Mecanum Wheel Drive number 3
Mecanums are theoretically 100% efficient. If your rollers aren't slipping, you only have losses from the bearings in the rollers.