Levitating a disk upwards / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Levitating a disk upwards

1 2 next

Move Thread

LAN_403

Tesladownunder

Mon Nov 13 2006, 04:36PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I cut down a 2kVA 230V to 110V transformer to get an open field the other day. Took a lot of arm work to get through the square inches of silicon steel.
I was thinking of a ferrofluid display or a maglev display. As a maglev it will suspend a magnet 17cm below it with about 450W. Much more than the 10cm of my previous large levitator.
I also tried levitating aluminium discs and managed to get a 15cm disk levitated over 15mm and shown below.
Of course it is not stable and will tend to slide off, hence there is a central drinking straw to center the disks.
I have wired the 110V winding in series with the 230V one and run it off 260V at about 1 A. I am using 74uF of power factor correction otherwise current flow is about 5A.
Now that I have a setup with reasonable power, I can look at stabilisation by shaping the disc or altering the central area at the expense of height. The Holy Grail being stable vertical elevation. It is feasible although I don't recall seeing a proper setup in a photo anywhere. Has anyone?
My longer term plan is to achieve stable vertical elevation using a maglev setup but this is a lot trickier than magnetic suspension.

Peter

Dr. Slack

Tue Nov 14 2006, 09:40PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Although Ernshaw's Theroem proves you can't do this feat with any array of DC magnets, with AC it's possible - the theorem hints that you need to use the AC nature of the field. Perhaps shading the central part of the pole piece and using a small disc would create a centrally acting linear-motor, and I'm sure there are other ways to do the same thing.

Not certain about the thread title, how would you levitate a disc *downwards*

Coyote Wilde

Wed Nov 15 2006, 12:12AM

Registered Member #175 Joined: Tue Feb 14 2006, 09:32PM
Location: Sudbury, ON
Posts: 111

I saw a video once of something at some World's Fair in the 1960s; it was something of an induction range, in a 'home of tomorrow' exhibit. An aluminium disk was levitated by eddy current repulsion, with the heat generated by these eddy currents being used to fry eggs.
No idea as to the internals, but I'd guess multiple transformers. The thing was spinning; I don't know if this implies if it was spin-stabalized, or what. I suppose that was entirely unhelpful.

Max Power

Wed Nov 15 2006, 02:25AM

Registered Member #490 Joined: Thu Nov 09 2006, 01:57AM
Location:
Posts: 1

Here is a video using an electromagnet to levitate a split tube made of aluminum. The poles look like they are shaped for this purpose. Go to Google Video and do a search for "Telsa, genius who lit the world". Its about 20 minutes into the video.

Tesladownunder

Wed Nov 15 2006, 08:41PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

hiTs_a_meloN wrote ...

Although Ernshaw's Theroem proves you can't do this feat with any array of DC magnets, with AC it's possible - the theorem hints that you need to use the AC nature of the field. Perhaps shading the central part of the pole piece and using a small disc would create a centrally acting linear-motor, and I'm sure there are other ways to do the same thing.

Not certain about the thread title, how would you levitate a disc *downwards*

I planned something along those lines although the central metal area is perhaps a bit small and square to complicate matters.

Title was trying to differentiate from the more common type of magentic levitation which is probably best referred to as magnetic suspension.

Peter

Simon

Thu Nov 16 2006, 01:53AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Tesladownunder wrote ...

Title was trying to differentiate from the more common type of magentic levitation which is probably best referred to as magnetic suspension.

Also, here downunder you have to be clearer about things like "upwards".

I take it you're levitating the aluminium disk by a Lenz reaction style effect. How hot does it get, out of curiousity?

Coronafix

Thu Nov 16 2006, 02:15AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

It's possible if you use a conductive sphere.
I read about it in an old Laithwaite text book.
Of course it also has to be AC, but you can also get the sphere to rotate.

Nik

Thu Nov 16 2006, 02:46AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

How bout this?

Tesladownunder

Fri Nov 17 2006, 12:53AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

[quote]
[i]
Yes, just eddy current induction and resulting repulsion. The temp rises to from 24C to 100C in 2 mins. This should be less if I use only one instead of 2 discs as it would have the the same surface area. Work coil running on 267V 0.95A (= 250VA) and 150W on my true KW meter. Work coil only slightly warmer.
An interesting aside about using an IR thermometer. I was wondering why the temperature didn't rise after one minute despite obvious heat. I put a bit of masking tape on the shiny aluminium and read the temp off that surface which seemed to be appropriate.
The thermometer has a fixed epsilon of 0.95. So it seems that you can't rely on Al measurements at all unless there is another surface on it. This would apply to heatsinks particularly I guess although the black anodised ones might be OK.

I still haven't seen a vertical levitation photo without anything above it. It shouldn't be too hard. I would really like to make Luke Skywalkers "car".

Peter

Nik

Fri Nov 17 2006, 12:56AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

If you have a BIG inverter and a parkinglot made of aluminum you could make a "hover car" of sorts.

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob