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I am considering a feather weight with 4 wheel holonomic drive. I have looked around a bit and the only omni wheels with sufficient grip seem to be only in the usa. I cant buy stuff from the usa so i really need to find some in the uk. Or even better does anyone have any for sale ?
Omniwheels have no traction whatsoever. What you'd want to use are Mecanum wheels, which provide more efficient use of power and resistance against being pushed. I'm not sure if they've been used in a robot though - you'd definitely have to keep them away from anything which spins.
Surely omni wheels like this: http://www.superdroidrobots.com/images/TD-022-002.jpg
can only slide sideways easily and mechanum wheels like this: http://ysserve.int-univ.com/Lecture/Fujisawa1/img5.gif
can allow all four wheels to point forwards and by rotating the front and back wheels in opposite directions, move sideways.
Just like this thing: http://www.youtube.com/watch?v=k8pguDSEl5k
I think some robots have used mechanum wheels before like alcoholic stepfather.
I looked into this a while back. The only place you can get them is the US.
Problem with them is that you are supporting the entire weight of a featherweight on a very thin shaft ie a single roller which makes them very fragile for combat use. I got the omni drive board off robotmarket place and tested it with 3 drills and 3 blue wheels. It worked fine on a piece of wood similar to that used in a lot of arenas and yeah its not the most efficient form of movement but it works well because theres so much dust and other crap already on an arena floor.
A little known fact. We made a set of 2 omni wheels for typhoon 2 and used them during qualifying for series 7. We never made it through qualifying and I asked for the wheels (which took a good few hundred hours to make) to be taken off when we got through on a bi. Not sure what happened to them but I believe they somewhat fell to bits.
trevor uses omni wheels on the front of megga mouse.... i believe he could only get them from the US.
I dont think he can decide if they are good for his machine or not, but they are big and strong ones !
John
www.RoamingRobots.co.uk
the person to speak to about this is andy hibbard of anticide fame, hes designing a ant with these macanum wheels :D
I supplied these wheels to Trevor. They come from the US based Kornylak Corporation. http://www.omniwheel.comQuote:
Originally Posted by roamingrobots
Wonder if Mecanum wheels are any better?
http://www.youtube.com/user/HIBBERDAR#p ... yMeaLBVhHA
Mecanum wheels are the way forwards. Or is it sideways? :D
I have had several discussions with andy befor ei even posted this about mecanum wheels :P, my origional plan was to use 4 mecanum wheels , but they are a lot more fragile than omni wheels and cant support nearly as much weight , they are mega mega expensive and theres no way to build them efectively . and also a system with 4 omni wheels is a lot easier to ontrol with out designing your own controller or using a4 channels. So i definitely want to sue omni wheels :D .i have found some really grippy ones in america so i might just have to get them off ebay or something.
And my plan for the omni wheels is to use 4 in a square configuration , so 1 on each side but not on 45 degrees. Ill find a picture :).
You can get omniwheels from RS, but they are only plastic and are only suitable for feathers - and would definitely not take a hit from anything spinning. I bought 2 pairs of 50mm to put in Mini Mighty Mouse, not got round to it yet though
Here is a link - http://uk.rs-online.com/web/search/sear ... &x=25&y=13
The omniwheels on Meggamouse are aluminium and very tough, thanks to Leo, who saved me a few quid. As to their efectiveness, they replaced rubber wheels and has improved the turning ability and are a better setup than castors as they are chain driven from the rear wheels.
If anyone is interested is looking at them I will put them in the toolbox for Maidstone.
Trev
I wouldn't trust those 48mm ones. A loading of 50N (just under 5kg)? I wouldnt trust that one a featherweight even if you have them doubled up.
The 80mm ones doubled up might work well, a load of 250N each, doubled up and id be happy to run them (protected of course) in a feather
thanks trev, The 80 mm wheels siund great :). One thing though, as youve used tehm, do you need to double them up to get smooth turning ?
They will not work unless they are paired, they lock together 60degrees apart and this gives a full smooth diameter. If you try one on it's own it will give you a lumpy ride.
The 2 pairs of 50mm I bought are well made but cannot comment on their strength as I have not used them yet, but as long as they are protected they should be suitable for a feather.
Ultimately one day I may use 4 banks of 6 or 8 in a cross formation driven by 4 motors. No idea whether it would be effective or not, but should be fun to drive.
I just lo9ve the idea of evading opponents side ways :P. As soon as funds are sufficvient i shall begin buying bits and start a build diary :).
Aussie bot Sidewinder is an omnibot
http://i34.photobucket.com/albums/d1.../4-6-06004.jpg
There is a lot of information in the builders thread on the RoboWars forum, especially with testing different wheels and designs.
http://robowars.org/forum/viewtopic.php?t=428
thanks :). Very helpfull but iam building a 4 wheeled bot for ease of driving.:)