Feasibility of spherical wheels.

[sganesh88]

We're trying to fit spherical wheels to move a prototype vehicle
rather than the circular one for our project. The
advantages we see are greater acceleration due to smaller M.I (for the
same mass of the wheels) and easy parking.
I suggested the conventional electric motor principle for giving drive to the
wheels. For steering, i think, by changing the orientation of the
field, we could bring about a change in the rotational axis.
Is this idea feasible? Im actually not sure about the steering part.

[Mech_Engineer]

I don't think that your perceived advantages of spherical wheels are entirely accurate, and they certainly don't outweigh the numerous disadvantages.

Perhaps you could explain in more detail how you plan to drive the wheels, it's not making much sense right now...

[sganesh88]

[QUOTE=Mech_Engineer;1798844]I don't think that your perceived advantages of spherical wheels are entirely accurate, and they certainly don't outweigh the numerous disadvantages.

QUOTE]

I dont know which advantage that i mentioned, you are referring to. If ou come with a point against it, i'd appreciate. Regarding the method of giving drive, i think of making the wheel just like the rotor of an electromagnetic motor.

[russ_watters]

The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?

And it does also seem to me that driving such a wheel (mouse ball style?) would be very problematic. If you do it mouse ball style, you vastly increase the rolling resistance of the wheel because your driving rollers have to dig into the wheel, creating friction. Regarding the method of giving drive, i think of making the wheel just like the rotor of an electromagnetic motor. That doesn't help us very much. You mentioned multi-axis motion, but a motor has only one axis. And it also has an axle! Would your wheels have axles or be magnetically suspended, or what?

If your wheel has an axle and a single axis of rotating, then making it spherical just adds a lot of rubber and steel to the wheel that never gets used.

[sganesh88]

"The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?"
M.I of a spherical wheel is lesser than that of a circular wheel of the same mass. Even with a decent increase in the mass in case of the spherical wheels, the M.I will turn out to be less.
http://en.wikipedia.org/wiki/List_of_moments_of_inertia (In the list, torus could serve as a close approximation for circular wheels i guess)
And yeah. i'm confused about the fitting of the wheels. One model i saw in the net has a small cylindrical wheel driving the spherical one through friction. But that was for some vacuum cleaner. That wouldn't do here.

[Mech_Engineer]

I don't think you should compare wheels of similar mass, because a sphere of the same mass as a cylindrical wheel will have a smaller diameter. Comparing wheels of the same diameter will give you a better comparison IMO.

You still haven't explained how you plan to drive the spherical wheel in the first place. Like Russ said, if it's driven about one axis (akin to having an axle through it), then there's no reason to use a sphere at all, since a cylinder of the same diameter will accomplish the same task with less weight.

[russ_watters]

"The first advantage you mentioned, better acceleration, doesn't make sense to me. A spherical wheel would have more mass than a regular one and therefore be tougher to accelerate, would it not?"
M.I of a spherical wheel is lesser than that of a circular wheel of the same mass. Even with a decent increase in the mass in case of the spherical wheels, the M.I will turn out to be less.
http://en.wikipedia.org/wiki/List_of_moments_of_inertia (In the list, torus could serve as a close approximation for circular wheels i guess)
I don't think you can really say either of those things. Wheels aren't easily reduceable to simple structures like that. You'll need to actually design one and calculate the mass of the wheel, tire, supporting spokes, etc. And what about contact area? How do you ensure you have enough tire touching the ground? And how do you support an inflated spherical tire?

Regardless, I still don't see how you would think that a sphere the same diameter as a torus or cylinder would have the same mass. I'm reasonably certain it would not.

[MIC]

I would like to see something like this, but you will have to develop a great way to manipulate the sphere. A sphere has many degrees of motion, you dont want it rolling in the wrong direction on mistake. I would like to see how you plan to make the various magnetic fields. The single rotor and stator design ( windings, teeth, disk shape ) wont be adequate, because you dont have the fixed axis in relation to the windings. Do you have some drawings of your "wheel", and a description of how the motion will be accomplished/controlled?