large bearing

[pagheca]

Hi,
I have to rotate a disk weighting at about 4 kg, at 12 rev/sec, supporting it from the circunference (dia=300mm). I have to dissipate the minimum possible heat (less than a few W) and work at a temperature of ~ -200 C with dry lubrication. The rotation should keep going maintenance free for at least 1 year.

I found a reasonable design using wheels in Zirconia, but I'm worried about the differential speeds at the edges of the wheels supporting the axial load, that will slightly drag like the rotating wheels in a mill...

I wonder if there is any solution on the market, a sort of open bearing, that could do the job. Standard bearings cannot, as they dissipate far too much power in sliding friction.

Any help welcome - thank you.

 

[pagheca]

Reading my post, I understand I've probably been not clear enough...

My problem can be described in this way:
suppose you have to rotate a disk supporting it from the circumference (= nothing is permitted below or above the disk, except for a cm or so close to the circumference itself).

What I would like to find are sort of "sectors" of a bearing, large enough to support the disk but, as the radial and axial load are very low, not fully circular like in a standard bearing.

My question is:
is a solution like this commercially available?
If yes, which is its name?

Thanks again, and sorry for the (maybe) confused question

 

[dimjim]

I wonder if a large magnet would work or
series of them. Is this like a pancake
or a ferris wheel as to axis?
Is your od tapered? I am trying to visualize
the contact surfaces of the wheels or bearing.
Is the part thick enough to have a groove in
the od?

 

[dvd]

If you can grind the edge of the disk to a vee shape you could support the disk with v-groove wheels arranged around the disk. Graphalloy could make you some low-temperature v-groove wheels, similar to cam followers.

 

[pagheca]

Thanks for the reply and the advices. Some comments:

1) I can't use any magnetic field around this device as this is part of a detector very sensitive to magnetic fields.

2) If I understood dvd suggestion, what worries about grinding to a vee shape is the resulting dragging of the edges of the v respect to its center. A back of the envelope calculation give that at those speeds you would drag those edge about 1000 km/year, resulting in high wearing. Difficult to believe, but unfortunately true with reasonable assumptions.

Regards,

 

[MikeHalloran]

If you put a little crown in the v-roller faces or on the v-edge of the disc, there shouldn't be a problem with scuffing.


Mike Halloran
Pembroke Pines, FL, USA