Brushless DC Motor for High Torque Experiments

[DMANN]

I am starting this thread with an interest in a motor that can provide usable torque for applications for ultralight craft, boats, race karts...etc. I have been researching this heavily and found at least four companies that are already providing these motors for high torque applications with at least one claiming efficiencies to 95%. I will name them here so that you can do your own research. Motenergy; Joby Motors; Golden Motor; Zero Motorcycles; Siemens They generally use a sophisticated controller unit to fire the coils at the right time by hall triggering or "sensorless triggering".

I have come up with a fairly simple but large 3D print file for experiments with this type of motor. I believe that the circuits found on this website can provide the current needed to power this motor. I am going to discuss the parts here first.

Part 1: This is a stator mold. It is nominally 6" in diameter and 2.15" thick. It should be filled using the #8 reloading steel shot method described somewhere on this site. You will have to grease all of the internal surfaces so that your end piece can be removed easily. The choice for adhesive is up to you. I am using white Gorilla Glue. It has claims of weather and reasonable heat resistance. The mold should be mounted to a flat smooth surface which should also be greased. Silicone lubricant may be a good option. There are 24 screw holes for mounting the mold to that surface. It will also be your choice on wiring. It is a 24 pole stator. It can be wired for 6-phase. There are six mounting positions that should use 1/8" threaded rod.

Part 2: This is the rotor file. It is for a quantity of 22 (2" X 1/2" X 1/8") neodymium magnets. They should be adhered to the 22 flat surfaces. A thin hollow cylinder can be printed and slide over the magnets for protection. They should be installed in the NSNS configuration. It has a 3/16" key stub included and 1/4" set screw hole. I am using a 3/4" shaft from BMI Karts for my shaft. It has a 3/16" key slot in it. It comes 36" in length and be cut to the length you need for this motor.

Part 3: This is the bearing ends. It is for 3/4" X 1 5/8" X 7/16" bearings.




This will be an open source project. It is at the ground level at this point. My hopes are to integrate multiple Bedini/Cole Window Motor Circuits and to stack an additional stator for a low-lenz generator to charge a second bank of batteries. If you need parts printed Tom Childs with Teslagenx has the files for distribution and is also set up to print upon request. I only wanted to share this with those on this site that are familiar with Bedini's technology so you will have to make an individual request to Tom for the files. Disclaimer: Build and experiment at your own risk. If you intend to use this on a mobile craft you will need to seriously consider exchanging the plastic parts for metal. You will also need to consider using premium bearings. The plastic motor ends and rotor is just for low voltage experimentation. Please share your build to include your circuit setup and any improvements made.

Doug Mann

[DMANN]

There was a request for the rotor to have the wall added around the magnets of the rotor. According to my measurements this is going to run the rotor as close as .04" or 1.16 mm to the stator ends. You can see that 11 mags will be slide in on one side of the rotor and the other 11 in the other side. There is a choice of three magnets that you can use here. This is the cheapest option for a 15 lbs pull force magnet. http://www.magnet4less.com/product_i...products_id=54

[DMANN]

I found the discussion for the core material. It was actually in a video. https://www.youtube.com/watch?v=WXMWvloZBgQ (discussion starts at 15:44) This video is an interview of Paul Babcock by Aaron Murakami in 2013 that was done shortly after the conference as a follow-up to that conference. It spells out the process to make the core and why it works well vs the laminated silicon steel ($). This is where I found #8. http://www.ballisticproducts.com/Ste...ductinfo/SH08/ It needs to be small to fit the detail of the form presented here.

So thanks to Mr Babcock and Aaron Murakami!

[Deuis]

Fantastic tip.

On the Monopole the welding rods penetrate the length of the coil.
I believe this is due to the fact that using multple pieces of iron reduces the transfer ability of the field through the coil. (junctions like a poly solar cell)
Try stacking washers on a magnet, then put the longest rod you can find on the same magnet. Measure the field strength at the end of the rod and washers.
I think the geometry of the monopole requires full penetration of single pieces of iron for maximum gain.
The other small issue is circles trying to fill an area. There will always be air gaps left by the multiple radius' reducing the actual amount of iron in the core.
Im sure these are all small 1% gains and certainly not worth the effort to buy silcon steel.
I do love a good hack.

1.Sheet Steel.
2.Silcon Steel.
3.Cast Steel.
4.Tungsten Steel.
5.Magnet Steel.
6.Cast Iron.
7.Nickel.
8.Cobalt.
9.Magnetite.

I found the discussion for the core material. It was actually in a video. https://www.youtube.com/watch?v=WXMWvloZBgQ (discussion starts at 15:44) This video is an interview of Paul Babcock by Aaron Murakami in 2013 that was done shortly after the conference as a follow-up to that conference. It spells out the process to make the core and why it works well vs the laminated silicon steel ($). This is where I found #8. http://www.ballisticproducts.com/Ste...ductinfo/SH08/ It needs to be small to fit the detail of the form presented here.

So thanks to Mr Babcock and Aaron Murakami!

[Deuis]

Here's a question that may have been answered in the past.

Is the point of twisting the 8 filar coils together merely cosmetic or does the twist serve some purpose?
Has anyone measured the differance between twisted coils and non twisted coils?
Can you fit more winds on without the twists?

[Faraday88]

Here's a question that may have been answered in the past.

Is the point of twisting the 8 filar coils together merely cosmetic or does the twist serve some purpose?
Has anyone measured the difference between twisted coils and non twisted coils?
Can you fit more winds on without the twists?

Yes, by twisting the wires the coupling between them increases and would in effect have a common Magnetic Structure.
Rgds,
Faraday88.

[DMANN]

My parts are on the way from Teslagenx!! They look great!
Thanks Tom!

[DMANN]

https://www.youtube.com/watch?v=n-KcUztjarc I saw this video today. It looks like a simple way to get the motor up and going without halls/reeds (sensorless). You could parallel several of these together on each phase to maximize torque. The washer motor videos seem to be a dime a dozen but this particular one stood out with a circuit made from parts that most of us probably have laying around already.

[DMANN]

just a couple of pictures of the core molds. I have the #8 shot coated and dry poured into the forms. I was able to get about 3.5lbs in the form w/o the adhesive. It will probably be closer to three with the adhesive. So, you should be able to get three stators per 10 lb bag of #8 shot. I have settled on using Bondo resin epoxy to bond the stator. I will be doing this in 5 to 6 stages. Hopefully this will keep my 3d printed mold from turning into a lump of molten plastic. My prep will include coating the entire inside with masking tape and then using petroleum jelly over that.

[DMANN]

Where was I when this video came out???!!!! 5-6 amps rms with no heat from something soo small?? Am I missing something? This is what I am going for!!!!!
https://www.youtube.com/watch?v=sbUbIRcVxnI

[DMANN]

I have all of the prints before me and it looks like some changes to the design are in order. There will need to be an increase in the width to each of the parts where the shot will be placed to build on integrity. At the current diameter (6"), that would mean a reduction of stator poles from 24 to 12.

I am going to be switching from AutoCad 2014 to Fusion 360 shortly. My hopes are that this can become more of a coordinated effort among others.

I am still pushing forward with a modified version of the original build file and will post my results. My biggest hurdle right know is removing the mass of steel shot/resin from the mold. I am having to build a jig to fit in a vice to see if I can push it out without damaging the 50 hour 3d print. If all else fails, even if I have to cut it out I should still have a piece to test core saturations.

* The take-away from this. Design a casting mold where the piece can be removed more easily.

Input is welcome.

Doug

[DMANN]

Okay...The vice idea did not work...neither did the cut to remove. So, it is back to the drawing board altogether. If you were to ask "What did work"? The Bondo brand fiberglass resin worked great to adhere the steel shot. Coating the masking tape to the inside then rubbing petroleum jelly over it worked good. The areas that just had petroleum jelly did not work as well. I used pla filament for my first bout and it actually held up great. The heat caused by the reaction of the 2-part epoxy did not distort the plastic a bit. It was conveyed to me to try splitting up the print more to make it easier to remove so that is what I am going to work on. I am open to other suggestions.

Thanks
Doug

[DMANN]

For the new design the total outer diameter should be set to 8". This should accommodate the added thickness of the workpiece and still allow for a 4" diameter rotor (for torque). I think that the outer wall should be printed in 4 parts and printed separate from the rest of the print. Tabs for those parts should be made to bolt those parts together. Removable spacers would have to be printed to ensure the inner wall is lined up correctly in this case. Here is a picture (X2) of an example of 1/4 of the 8" outer wall.

This is a start. It was tough getting back on this horse.

[DMANN]

And here is a new proposed inner portion of the stator. It is in a puzzle piece design. There are twelve pieces.

[DMANN]

Update: The new prints are coming along beautifully. I should be able to have another go at the resin tomorrow. The 10" mdf that it is sitting on will serve as the mounting base. It will be painted and have the mounting bolts installed through the bottom.