Omniwheels (Kornylak wheels) decisions...

[dellagd]

Hello all-

A few questions on some onmiwheels from Kornylak

Here are the omniwheels I'm interested in-
1. http://store.kornylak.com/ProductDetails.asp?ProductCode=FXA308
2. http://store.kornylak.com/ProductDetails.asp?ProductCode=FXA108
Plus a different type
3. http://store.kornylak.com/SearchResults.asp?Cat=1 (All on this page minus the ones above $5.75)

Anyone with experience?
Which ones do I get?
How do I mount them?
Do I have to double them up on one axel?

Thx in Advance

                                                                                     -Dellagd

[Soeren]

Hi,

Do I have to double them up on one axel?

It would seem so, as they seem to have non-rolling bits hitting the ground otherwise, but I might not be the one to answer this, as I never understood the fascination with (wastefull) omniwheels.

[MechHead]

I assume the only difference between the two that look the same is the coefficient of friction and/or how tough the wheels are, but without knowing what the second one is made of it's hard to judge.
I guess the way to mount them is press fitting, but personally I've always just avoided plain bore wheels.
The ones with only 3 rollers would need to be doubled up, but I believe the other ones would work without being doubled up.

[madsci1016]

(wastefull) omniwheels.

This I don't understand. Care to enlighten?
Wasteful implies energy loss somewhere, but where do omni-wheels lose energy?

[dellagd]

wow...quick replies...Thanks Guys!

ok a few ends to clear up-

     The one transwheel that does not list a material that it is made of is Nylon. It said that somewhere else on the site.

     Omni-wheels are considered wasteful in some ways. Yes wasefull in terms of energy loss. Omni-Robots can move in any direction you want, starting at a stand-still. Forward, backward, left, right or a forward-left-ish direction. All 360 degrees. In order to move in some of these directions some powered wheels must rotate in a direction not exactly parallel to the line of motion (forward, ect.) thus creating a loss of energy

- Hope this helped 

[madsci1016]

in a direction not exactly parallel to the line of motion (forward, ect.) thus creating a loss of energy

- Hope this helped 

Not really.

 Law of conservation of energy. Where does it go? Heat? Noise?

I can see how non-parallel motion would create a gearing action and put more torque on the motor, but that's not a 'waste of energy' unless it's a huge jump in torque. So where does it go?

[dellagd]

Allow me to quote admin-

Disadvantages of Omni Wheel Drive
There are unfortunately several disadvantages to omni-wheel drive. Omni-wheels have poor efficiency because not all wheels rotate in the direction of robot movement. There are high losses from friction too.

you wonder where the heat goes? friction. The excess heat/energey is expelled through friction.

A picture might help-



In that picture a wheel must move in a direction not parallel to the line of motion. Just line if I glue a motor to the ground and stick a wheel on it. when I turn on the motor, the whell will turn, but the motor/wheel will stay put. friction is created. Heat is expelled via friction.


Can we get back to the helping me now, please?

[chelmi]

The excess heat/energey is expelled through friction.

My physics courses are long gone, but your explanation doesn't sound right. First of all, heat and energy are two different things and you seem to use them as synonyms. Moreover, friction is a force. friction can produce heat, but I fail to see how energy can be "expelled" through friction.

Chelmi.

[madsci1016]

Still not a good explanation, but I think I have an idea now.

Work is force over distance. When an omni bot to traveling at an angle, there are force vectors from different wheels acting against each other. If the bot wasn't moving, then it's not work. But since there is movment from the sum of wheel vectors, there is some work done by the wheels as an opposing force over the distance traveled by the robot. This work is useless, as it's a cost of energy that doesn't contribute to the over all motion of the robot. Heat and friction don't really have anything to do with it.

Am I on the right track?

Sorry for the hi-jack. Maybe Admin can split the thread, as id like to discuss this further.

i'd like to test this to get actualy energy loss figures. Can it really be as bad as 50% eff?

[dellagd]

My apoligies. Maybe I have the wrong understanding.
Long story short omnibots can be somewhat ineffecieant because wheels may rotate in a direction not parallel to the line of motion. The wheels rotation is not used to its full potential to drive the robot. Energy is spent but not fully utilized. Clear enough?

I second splitting the topic.

Now which wheels should I choose?

[Admin]

What do you need omni-wheels for? My answer for which is best is dependent on your design requirements.


As for frictional losses . . . friction is a counter force. You'll need to apply X% more force to get work done to counter it. Extra energy is needed to generate that extra force, hence the efficiency loses. That extra energy that goes into the system is burned away as frictional heat.

[dellagd]

That is what I was getting at Admin, thank you

I am making a 4 wheeled omni-bot similar to your Fuzzy robot. (Same wheel positions)

[Admin]

I am making a 4 wheeled omni-bot similar to your Fuzzy robot. (Same wheel positions)

In that case, you'd want:
http://store.kornylak.com/ProductDetails.asp?ProductCode=FXA308

The reason is for the 'Synthetic rubber coated Polypropylene rollers'. Otherwise the friction would be so low that the wheels would spin yet the robot wouldn't move . . .

[TeslaHV9]

did you consider the other kind of omni-wheel as well Admin?

Just wondering because the omni-wheel listed below the transwheels looked pretty good as well.

[dellagd]

Yes what about these?

http://store.kornylak.com/SearchResults.asp?Cat=1 (All on this page minus the ones above $5.75)


I realize you would have to double them up.

[Admin]

Yes what about these?

http://store.kornylak.com/SearchResults.asp?Cat=1 (All on this page minus the ones above $5.75)

I realize you would have to double them up.

They won't work properly if the part that doesn't have a wheel touches the ground. Doubling up will result in thick wheels, double the cost, and the trig won't work quite right as there is an inch distance between both wheels.

[dellagd]

I see

Thank you Admin.

The ones with those polypropylene (or whatever plastic it is) coated rollers will give sufficient traction?

Are those the ones you used on Fuzzy?

[Admin]

The ones with those polypropylene (or whatever plastic it is) coated rollers will give sufficient traction?

Are those the ones you used on Fuzzy?

You didn't read my tutorial thoroughly enough if you're asking

(yeap)

[dellagd]

I clicked on the:
I used http://www.omniwheel.com/cgi-bin/plugins/MivaEmpresas/miva?plugins/MivaMerchants/merchant.mvc+Screen=PROD&Store_Code=KCWD&Product_Code=FXA309&Category_Code=Transwheel (It said 'this omni wheel' as the link) for my robot.

I couldnt tell because broken link

I think Kornylak recently renovated their site

[Admin]

I clicked on the:
I used http://www.omniwheel.com/cgi-bin/plugins/MivaEmpresas/miva?plugins/MivaMerchants/merchant.mvc+Screen=PROD&Store_Code=KCWD&Product_Code=FXA309&Category_Code=Transwheel (It said 'this omni wheel' as the link) for my robot.

I couldnt tell because broken link

I think Kornylak recently renovated their site

hmmmm ok I'll have to fix that.

Yeap, you want the rubbery type of wheel for the best friction.

[akornylak]

Hi guys,

Yes I think our site has changed a little but just to clarify the links:

Here is the store link: http://store.kornylak.com/SearchResults.asp?Cat=3

Transwheel page here http://www.kornylak.com/wheels/transwheel.html

there are lots of different types, look closely at the bore and you can see there are different keyways and so on. On the main Transwheel page there is also a picture at the bottom of wheels with threaded brass inserts. So that gives you another option (its $1 extra)

The ones you want to use are the rubber coated polypropylene versions, the "CAT-TRAK" versions http://store.kornylak.com/searchresults.asp?cat=31

We are always interested in coming up with new ways they could work for robots. The ones Ive seen at robotics competitions, etc almost always use double wheels sot he rolling action is smoother. They seem to work well on hard surfaces or carpet as long as its not too thick.

Feel free to contact me directly if you have any questions or need a different bore type

Andrew Kornylak [email protected]

[dellagd]

Thanks andrew!