Mendocino Motor Under Construction

[George_Race]

I am in the process of building a Levitating Mendocino Motor.

I got interested after finding a great German web site of a professor that actually teaches others to build the Mendocino at work seminars. It is all written in German, but using Babylon to translated some of the more interesting design stuff, I am making my version of his Motor.

Here are some links to his information. Everything you need to know about Mendocino Motors, in one location. But remember, much of it in German
http://www.bis0uhr.de/index.htm?http...t/english.html

Once you get there you can click to change some of the pages to English language, unless you can read German.

You can download his seminar lecture pdf paper from the site. It does contain all the design engineering details, but is all in German. Here is the address of the PDF:
http://www.bis0uhr.de/projekte/magne...ektseminar.pdf

Here are his original dimensions that I am working from.
http://www.bis0uhr.de/projekte/magnet/Motor_prev.gif
http://www.bis0uhr.de/projekte/magnet/Anker.gif

I do see a lot of interest in this kind of a project, and and I am thinking that I may end up offering a kit of the basic parts, making it much easier to build your own with minimal work. The kit prices that I have found on line, are really out of sight, price wise, and I think I can do much better. They run anywhere from $200 - $400 and there are not a lot of choices. Of course they are built and running.

I am thinking about offering the basic machined parts, as well as some of the more specialized parts like magnets, wire, and solar cells. It would be up to you to do the drilling and taping, wind the armature, solder the wires to the photo cells, and finish putting it together.

My goal is to do this with commonly available parts that I can purchase in quantities to keep the price reasonable.

What I am building is very similar to his, but to my own dimensions and style, based on easily obtainable materials. So far I have CNC cut the basic metal parts and assembled the basic frame. Next I am working on CNC cutting the core for the Armature using easily available high density foam material. I actually cut the first one today, but not happy with the overall design. Back to the drawing board and possibly tomorrow another prototype will be in hand.

Here is a picture of the Armature shaft in levitation! The brass weight in the middle is to simulate the finished armature weight and stabilize the shaft in the magnetic field. Really is kind of neat to see it just hanging there!

The magnets are all press fit into the .125 aluminum frame. The three magnets in the base are what will interact with the field created by the Armature. I will see if that is a practical way of doing it, rather than just mounting a magnet on the base like most do. As this is a fresh prototype, I am sure there will be changes as I move along and find out what works and don't work.

More to follow later as the project progresses.

 

[lazylathe]

Looking great George!

I was on that website about two weeks ago.
There seems to be a lot of interest in these engines lately!

I am sure you will get a lot of interest in the kits!
There are so many options for some of the components that I can get quite confusing.

Looking forward to your next stages!

Andrew

 

[Ken I]

Nice going George - my comment after building mine is to make the rotor complete before the base to determine the levitating centre height before finalising the support frame - 2c.

Ken

 

[George_Race]

Ken, I attempted to calculate the weight of the solar cells and wire to get an approximate weight of the finished armature. As I am going to make the armature core out of foam, I think I got it quite close. The brass weight is about twice the weight of what I calculate for the finished armature. I wanted to make sure the magnet strength was enough to support the shaft as high as possible, but heavy enough to put enough pressure on the magnetic field to keep the armature stable. Kind of a balancing act. I may actually need to add additional weight to the finished armature. My tests so far show that a much greater stability is obtained with a heavier weight on the shaft.

My end stop is a simple bolt on piece, so remaking it to a final new height will not be a problem, after I get the armature built. I also plan on putting a very small glass circle on the end stop, with a hole behind it, after all is designed and built.

Also I am going to try to put the end of a ball point pen cartridge at the end of the armature. That way I hope the armature shaft will not wear a hole in the end plate, what ever it is made of.

 

[Ken I]

I wanted to make sure the magnet strength was enough to support the shaft as high as possible, but heavy enough to put enough pressure on the magnetic field to keep the armature stable. Kind of a balancing act.

Yup - too high is unstable - I have seen some builds with a third "pulling" magnet between the two "repulsing" magnets to draw the rotor down to a more stable position - I found I needed to do this on my axle assmbly (I didn't put a dummy mass on it like you) - but once the armature was up to mass it was O.K (241g) it could easilly handle more - and yes heavier is more stable - so in retrospect I wouldn't lose too much sleep over keeping the weight down.

Ken

 

[George_Race]

Here is the next step in my process of building a Levitating Motor.

This is the Armature Core for the motor. I machined it out of rigid pink foam. Boy, does that stuff ever machine nice!

The notches in the corners are where the windings will go around. There are two milled out areas on each of the four sides. The upper "shelf" is where the 3" X 1" solar cell will be mounted. The deeper recess is where the hookup wires will terminate. Also will serve as a place to screw in a few small screws to balance the final assembly, if necessary.

Next step, wind about 100 or more turns in the slots on the corners of the core.

 

[Ken I]

George,
Re my prior comments - I believe the final "optimal" position would be where the angle between the support magnets and the rotor magnet centrelines is at 90° - i.e. its sitting in a 90° "V" block.

Less than this makes it less stable horizontally and more than this less stable vertically.

I say "believe" based on logic & experimentation - you could probably come up with a theorum to prove / disprove this - based on physics.

Ken

 

[George_Race]

Hi Ken, yes, there are a lot of variables that one can play with on this kind of a project. But flying by the seat of the pants is a lot of fun too!

Well today I got a lot more done on the project. As winding the Armature is the next project, I started by making a stand to hold the roll of wire. As I did not want the wire to freewheel, ending up with a big mess, I ran it through a piece of tubing, squashed just enough to put tension on the wire, which also helped me to wind the wire tightly on the core.

Here is a picture of the setup. Very cheap and dirty, but it worked really well!

Next it was time to wind the core. I started by drilling a series of holes from the shaft opening into the wiring area of all four sides. I also drilled a pair of thru holes between the opposite sides of the wiring area.

Here is a picture of the first set of 120 turns, alternated 10 turns at a time on each side of the shaft.

Then on to the second side and 120 more turns of #30 wire. I did slip small pieces of 3/32 tubing over the center shaft to insulate the wires from the center brass shaft.

I finished up the armature by installing and spacing the magnets. Again, using small pieces of 3/32 tubing to hold the magnets in final position. Next I had to balance the assembly. I let it levitate and spun it between my fingers. When it stopped it was obvious that it was out of balance. If you look closely you will see several screws placed to balance the armature. I can not stop it an any position and it just sits there.

The next three pictures show the project as it is of of this afternoon.

Next I will be sorting out the wires from the coils and establishing some solder points in the wiring areas. As soon as the solar cells arrive, I will be ready to solder them in and see what happens.
George

 

[Ken I]

George,
Ballance is super critical for good working - below an extract from my build notes which I will place in the downloads shortly.

Static balance is dead easy - but it really needs to be dynamically balanced as well. I am did mine by sticking lumps of modeling clay to the rotor - static - then I bring a magic marker up to the free end magnet to make a mark at the high point of the "wobble" - add a small clay mass (a guess) to counter it (removing the piece from the static lump) - once I got that right I replaced the clay with bits of solder wire (mass for mass) bonded into the winding grooves.

The other reason balance is a bit fiddly is the "centre" is the magnetic centre - so bond the end magnets in place before final balance tuning (if you move them angularly after balancing you can throw the balance out significantly).

You cannot send the rotor for balancing – it must be balanced in-situ because it runs on the magnetic centerline – not the mechanical centerline.

Remove the field magnet during static balancing and work in low light conditions (to avoid the photocells / armature coils reacting with the levitation magnets)

Once I had achieved balance using modeling clay, I replaced the clay (mass for mass) with bits of bent solder forced into the armature grooves, which were then lacquered in place.

I made further final adjustments by lacquering further small pieces of solder and finally by adding drops of Glypal lacquer.

Obviously final balance tuning was done on the completed base frame and not the lash up rig.

Perform the fine balancing away from anything that will magnetically influence your set up. My workbench’s steel frame was a problem – I eventually did it on my wife’s kitchen counter – which cost me a few brownie points.

Since the set up is as near as dammit frictionless the motor will turn over in low light conditions but only if the static balance is spot on – the almost nonexistent torque must cause a frictionless rotor to turn but not if its defeated by an out of balance moment.

I also observed some curious problems during balancing :-

The motor seems to run better in one direction - if you turn the rotor around it still goes the same way but one way around is better than the other. Doesn't make any sense.

I reversed the field magnet - which reverses the motor - still the same - here there is also a difference which I suspect is constructive / destructive interference with the levitating poles.

That does make sense. But the difference on reversing the rotor remains.

Mine works best with the field pole upper face as the opposite pole facing inwards from the levitating magnets. Probably gives a better field shape for the rotor to turn in.

If you do “play” with the different pole configurations, do so before final balancing of the rotor – removing and replacing the rotor magnets will totally screw up any fine balancing you have done (guess how I know this).

Ken

 

[tel]

I'm getting very interested in doing one of these - waaaaay out of my comfort zone, but what's life without a new challenge now and then?

 

[b.lindsey]

I agree with Tel...I do much better with things I can see!! As such, I am both electronically and magnetically challenged ;D, but with that said, this is still fascinating to watch and I am looking forward to seeing one of these do it's "thing." George, the little wire spool fixture is elegant and the machining on the foam coreis very nice too!!

Bill

 

[George_Race]

Thanks for all the comments guys, this has been a lot of fun so far. Don't be afraid to tackle a project like this, one piece at a time, it will come together.

Ken, yes, balance is going to be a challenge. I noticed that my magnets wobbled a bit on the shaft, even that threw the balance out of wack! It also made the pointed end of the shaft wobble on the vertical standard. It does not take a lot to make everything go astray.

Once I get the solar cells in place, I am sure I will need to do even more balancing of the armature. It is so neat to sit here and watch the thing just float in air! I really find it fascinating to simply push the floating end down, let it go, and then watch it bob up and down for about 5 minutes. Just thinking about how the shaft magnet is interacting with the intertwined magnet fields below it is overwhelming. It just seems to happen like magic.

Hopefully my solar cells will be in the mail box later today,
George

 

[George_Race]

Well gang, the learning curve continues and is very steep!

The armature shown in the pictures above was a complete failure, for many reasons. I had it perfectly balanced, or so I thought. You learn by doing dumb things. First dumb thing, DON'T USE STEEL SCREWS to balance the armature! Once I got the solar cells in and wired, it just would not run, no matter what I tried. Even though it was balanced, it kind of limped along as you would spin it. Finally figured out where the limp was coming from, the *&#.&% steel screws! Every time they came across the bottom of rotation, they would abruptly slow down the armature. They were passing above the three magnets in the base!

OK, now replace them with brass screws, and do the balance all over again. Put the solar cells back on the wires, only broke 2 of the 4, and try everything again.

Second dumb thing! No more rubber bands! Might as well glue the first two solar cells in place. So, take some super glue and carefully put it along the edge of the cells. Coming back in about 30 minutes....WOW....The super glue melts foam! The cells are held in a few places, but everywhere I put the super glue there are gaping holes in the foam!

Third dumb thing! Solder in the other two cells, this time use some Gorilla Glue to hold them in place. Forgot, Gorilla Glue expands when it dries. One solar cell is broken, the other three look like a Kindergartner was working on the project, really ugly! Icky brown gobs of glue everywhere!

Onward and upward, lets levitate it and add some light and see it run! But first, now with the cells and glue in place, lets check the balance. First turn off all the direct light so balance is not influenced by magnetic field of the coils with solar cell in light. Balance is like I had done nothing before. OK, now what, can't hide the brass screws under the cells. Forge ahead, poke screws in the areas between the cells, toward the windings. OK, it is kind of balanced! Will it run? Yes, Yes, Yes! So the proof of concept seems to be working, but I am so ashamed of how it looks, absolutely no pictures! Seeing I did machine several armature cores, tomorrow I will do a complete new one, hopefully without all the screw ups!

A new day!
Checked it out, still runs, but ugly! Try to salvage what I can. Only thing that can be saved is the shaft and magnets. And yes, break the core all apart and retrieve the brass screws for possible use later! Throw away the rats nest of wire! Start from scratch.

Wound the core with 150 turns in each coil. Next levitate the armature and check balance. Not to bad, a few BRASS screws here and there and it will set just about anywhere I stop it. Now to solder in the solar cells. This time hold all four in place with a couple of rubber bands. Glue can come much later, if ever! Again check for balance, not to bad. Three or four 2-56 short oval head brass screws in the right place, almost perfect balance again!

Time for the test, add some light, give it a light spin.....WOW.....it actually runs, and quite smoothly! Just a bit of a wobble at some speeds, and a bit of back and forth motion on the free end. Add a brass nut to the free end, sets it a bit deeper in the "magnetic V" and most of the back and forth motion stops.

I am pleased, it really runs great. Did not check the RPM, but will sit and run smoothly with just the light from the overhead florescent ceiling lights in the shop.

Now that I know how to build one that runs, Using the completed armature I am going to try different lower magnet spacings to see how I can improve the stability. I think that if I were to space the lower magnets farther apart, the armature magnets would set deeper into the "Magnetic V" and reduce the wobble and side play considerably. So tomorrow, I will probably design and cut a couple of new base uprights that hold the magnets with new spacing and see what happens.
I also want to try the base with only one magnet in the center, rather than the three that I now have. Maybe even a stack of several to see how it influences the operation.

As far as holding the solar cells in place, need some more ideas there. As they do sit nicely in the milled out pockets in the form, rubber bands, at least for now will have to do.

Below are two pictures of the new finished armature. The first shows one of the solar cells almost in it's niche. The other shows the armature spinning with just the room lights providing the illumination. As I make any improvements or new findings I will report back here with the details. This has been, and will be for a while, a very neat project.

 

[John Rudd]

George, Try your local r/c model shop for foam friendly cyano...

Nice job btw....

Might have a go at one myself..I have a nice slab of pink foam in the garage that would do just fine for the rotor.

 

[George_Race]

Thanks John, did not realize that. Probably just exactly what i need to hold the cells in place permanently.

Your web picture, looks like a T6. Just had a good friend and his wife crash a T6. He will be OK, but lost his wife. That makes two of my friends have lost their T6's this past year.

George

 

[John Rudd]

Slightly off topic-
George, sory to hear you lost a friend....
Yes it is a T6, it belongs to the Warbirds museum at Kissimee Fla.
I went up in it as a treat for myself for my 50th birthday, Sean the instructor is a great guy who also flies at Reno with a self build....

Off to cut some pink foam....

 

[Ken I]

George,
There are foam friendly adhesives available.

Sorry about your tribulations - I didn't dwell on mine too much the learning experience is a fun part of this.

It's like banging your head on a wall - It's so nice when you stop (or succeed).


it does look good just ticking over for no apparent reason and with no apparent support.

Ken

 

[George_Race]

You are right Ken, will always be a work in progress, probably right into the next model. And I do love the challenge of doing it better, building new experience with every step of the process, forward or backward, the goal is always in sight.

Today I really did a lot. I started by widening the end pair of magnets. Went from a center to center of 1.5 inches to 1.875. My idea was to bring the armature down closer to the end magnets as well as the base magnet. What a difference, almost immediately it started running, all by itself, in just the light in the shop. I got rid of the brass nuts (weights) on the both ends of the shaft and did a really fine balance of the armature. Made a new base with only one magnet, as the three were influencing the armature magnets to some degree. It immediately started running much smoother, and of course it sets deeper in the "Magnetic V" due to the wider spacing. Incidentally, after all the changes today, my armature weights a whole 2.5 ounces. After all the changes the armature sets just over .5 inches lower as well. The only thing left to finish is the gluing on of the photo cells. That will complete the build. The last thing I will add will be a list of materials that can be purchased to build a similar motor in your own shop. This is really a fun project! Anyone who sees it does not believe what they are seeing.

Follows, a series of pictures of how the unit looks after doing a complete rebuild of the base frame work today.

Here is how it looks running.

Here is a full side view, and yes I did polish all the aluminum plate!

Another side view, favoring the back end.
The small holes you see in the foam are where I have pushed in #80 brass screws while balancing the armature.

Here is a picture of the rear end rest. I machined it out of a piece of smoke lexan. It is bolted to the base with 2-56 screws in threaded holes.

In the picture above, notice the way I am now holding the rotor magnets in place. As the shaft is .125 brass, the .125 milling tool stops are an ideal way to hold the magnets vertical and in place. The stops really press on hard, and will not move once in place. Just getting both end magnets to turn without a wobble is a giant step in getting the armature to run smoothly.

The next picture shows the "floating" end of the armature shaft. Note the tool stops holding the magnet in place.

Here is a pictures of the front of the frame with pressed in magnets.

Here is a picture of the rear of the frame, showing the end stop for the shaft.

Here is a close up of the 1" X 3" .5VDC 250MA solar cell. Hopefully tomorrow I will have them all in place with some rubber cement, and the rubber bands will be gone for good.

And the last picture is of the bottom magnet that attracts the armature coil that drives the rotation. You are looking at the reflection of the armature in the base place. It really polished up very nicely.

I did use my optical tachometer to check the speed today. Sitting under the shop ceiling lights it ticks over at about 215-220 RPM. I exposed it to blue sky this afternoon and was amazed when it consistently showed 2180-2190 RPM, and running very smoothly at that speed. For this unit, I believe that is the maximum speed it will achieve.

For this to be a declared finished project, I will be adding a list of materials and links to the DXF files of the base unit and foam cutouts. I will also be writing up a list of dimensions for those that would like to have a starting point and do their own thing. I do think that my final dimensions are ideal, and will be very easy to duplicate. This is really a great running little motor!
George

 

[dsquire]

George

I have been following along with your build (also Ken I) and am fasinated by their simplicity. I may try to see what I can find in the goodies drawer to see if I can duplicate your effort. You have certainly given enough detail so that anyone should be able to follow along if they wish. Thanks George. :bow:

Cheers

Don

 

[George_Race]

Hi Don, it is really surprising that there are not hundreds of these under construction. Ken and I both started around the same time, incidentally, on opposite sides of the world. I think that both builds show not only how simple the overall project is, but how versatile you can be with the building materials and construction style.

I do plan on getting the suggested parts list on line later today, along with some dxf drawings that will give you a better overall picture of the details and size. The project is only 6 X 3 inches, a nice table top toy!

Good luck on your build, it is a very neat project.
George