Think I can make it? (electric 9-pole radial engine replica) - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: April 19, 2018, 08:12:50 pm
content: I have a small batch of ~1.5mm square cylinder re magnets. If coils are air wound, about how may turns, and volts, current could I plan for?Framing in aluminum or plastic, Y or D wiring...I haven't thought of any other use for them yet.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 19, 2018, 08:21:59 pm
content: Quote from: metrologist on April 19, 2018, 08:12:50 pmLow turns, high current with LiPo batteries. Look at some of the model aircraft motors with low number of turns. Love to see it in a small old-timer.

author: jmelson
author_rank: Super Contributor
timestamp: April 19, 2018, 10:17:27 pm
content: Motors generally need to have an EVEN number of poles. The magnets are arranged N - S - N - S etc., so it leaves a discontinuity of you have two N N in a row.Jon

author: GerryBags
author_rank: Frequent Contributor
timestamp: April 19, 2018, 10:36:14 pm
content: Quote from: jmelson on April 19, 2018, 10:17:27 pmYes, but I think the OP is talking about a solenoid motor, where each cylinder head on a radial engine is replaced by a solenoid. The crank/hub can be a direct copy of a radial that way.OP - Do you have enough magnets to do a Double Wasp, do you think? It's only 18 cyls.There are a few folks on Youtube that have made various solenoid motors, I'm pretty sure I've seen at least one radial, but most seem to be boxers/horizontally opposed for simplicity.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 19, 2018, 10:48:08 pm
content: If so, I want to hear it. My dad was with a B-29 squadron in WWII.

author: Stray Electron
author_rank: Super Contributor
timestamp: April 19, 2018, 11:14:30 pm
content: Quote from: jpanhalt on April 19, 2018, 10:48:08 pmI used to fly in the EC-121s (Super Constellations equipped with large RADARS). They used the same Wright R-3350 Duplex Cyclone engines as the B-29s. IIRC ours used triple Power Recovery turbines and were rated at 3400 HP each. NOTHING in the world sounds like a large four engine heavy aircraft up close and personal! I personally decommissioned six of the EC-121s and sent them to the bone yard in Az.The Super Constellations and the B-29s were both magnificent aircraft, it's a shame that so few of them are still flying.

author: metrologist
author_rank: Super Contributor
timestamp: April 20, 2018, 06:19:56 am
content: 3 phase, 3 coils per phase. not solenoid but that is a cool idea too. The coils would stay stationary and the magnets would rotate.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2018, 06:35:34 am
content: Quote from: Stray Electron on April 19, 2018, 11:14:30 pmThe Constellation is IMHO one of the most beautiful aircraft ever made, and those R3350's are incredible engines, I'd love to go up on one.IIRC the B29 used them in a conventional configuration without the power recovery turbines.

author: viperidae
author_rank: Frequent Contributor
timestamp: April 20, 2018, 06:39:47 am
content: With 3 coils per phase you'd probably want 12 magnets

author: metrologist
author_rank: Super Contributor
timestamp: April 20, 2018, 02:09:53 pm
content: I guess what I was thinking is that the energized coils would attract the magnets and pull the rotor assembly into radial alignment. I hadn't much though of the actual physics of how it would work, because will power...I'm now thinking I could wire all coils in series (or parallel) and use single phase AC, although that seems like I would need a sensor to time the phase to rotational position.Well, perhaps I have my fields 90° since the magnet N-S runs radially, but it seems that is the same orientation of the coil's field. If I rotated the magnets so N-S runs tangent to the circumference, then it seems I could use 12 magnets and still 9 coils - turning this inside out:http://www.bavaria-direct.co.za/info/images/Delta_diagram.gifAnd I guess this is an 18 or 24 pole motor if each N and S is a pole? What are we counting as poles?

author: hayatepilot
author_rank: Frequent Contributor
timestamp: April 20, 2018, 02:21:05 pm
content: Quote from: viperidae on April 20, 2018, 06:39:47 amThis.If you have the same number of magnets as coils, the motor will not work.You want a 9N12P Motor:http://www.bavaria-direct.co.za/scheme/common/Winding Scheme Calculator:http://www.bavaria-direct.co.za/scheme/calculator/This will work too if the coils are on the outside and the magnets inside.Greetings

author: Old Printer
author_rank: Frequent Contributor
timestamp: April 21, 2018, 02:15:22 am
content: Quote from: Stray Electron on April 19, 2018, 11:14:30 pmWhen you start adding up all the pistons, cams, valves and on and on and on, it's not hard to imagine why they are gone. Just the regular maintenance would keep a small city busy.

author: ez24
author_rank: Super Contributor
timestamp: April 21, 2018, 05:05:25 am
content: Quote from: Stray Electron on April 19, 2018, 11:14:30 pmSo how would you make the SC pitch up and down (not the crew)? I was on a SC and it pitched up and down. Can you guess how this was done? Very funny.

author: Old Printer
author_rank: Frequent Contributor
timestamp: April 21, 2018, 04:00:19 pm
content: This really looks like a basic brushless motor developing. Writing a PIC program for the ESC (electronic speed control) is a great way to become familar with writing code and programing.

author: metrologist
author_rank: Super Contributor
timestamp: May 10, 2018, 05:04:59 pm
content: I do not know why, but I made a rotor with 10 magnets. The plan was to saturate in superglue and wrap with the yellow thread, them machine down the excess aluminum, glue and thread. Maybe I'll need to start over with 12 magnets, or just make 7 coils?I still don't know how large to make the coils and turns, and wire gauge, but I'll probably just use what I have...That was the second one I made because the first was perfect, but for 12 magnets. I thought I was making it for 10 and whittled it down some and then the slot was too large.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 10, 2018, 09:05:53 pm
content: Do you have an indexing head? Very useful and can be cheap, if you don't need a lot of precision and are willing to go used.

author: jmelson
author_rank: Super Contributor
timestamp: May 10, 2018, 10:04:01 pm
content: Quote from: jpanhalt on April 19, 2018, 10:48:08 pmThere's a guy who built a REAL 18-cyl miniature radial! I saw it at the NAMES (North American Model Engineering Society) show a number of years ago. He did not run it, however. I did see a 5-cyl radial run, and it scared the HELL out of me. They erected a Plexiglas shield around it, and people were milling all around in line with the prop. I doubted the Plexi would stop a thrown blade. It sounded quite impressive.Jon

author: metrologist
author_rank: Super Contributor
timestamp: May 11, 2018, 12:10:57 am
content: I remade a new rotor out of steel and just one flange. I am having a problem bringing the 12th magnet into position - it will jump on top of an adjacent magnet.

author: Audioguru
author_rank: Super Contributor
timestamp: May 11, 2018, 03:13:58 am
content: I was 9 or 10 years old when I flew in a Super Connie. It had a lot of vibration and noise inside. Not much later Boeing 707 and DC-8 jets were much smoother.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: May 11, 2018, 06:10:14 am
content: Quote from: Audioguru on May 11, 2018, 03:13:58 amHad a flight in a DC-3 (Actually the C47 variant) some time back. Surprised how quiet it was compared to the average light aircraft. One advantage of radials was that they were better balanced than inline or V engines. A disadvantage was the large frontal area which made them less suitable for fast aircraft. Oh, and a 4-stroke radial always has an odd number of cylinders in each bank. If you think about the firing order, it becomes clear why.This one used the Wright R-1820 engines. Kinda awe inspiring to think this aircraft (which was still in regular commercial use) had taken part in the Berlin Airlift. Might have been involved in D-Day too, but not sure.Not the sort of plane to take if you're in a hurry, 180kt max operating speed and mostly cruises around at 120-140, but great for getting larger loads into short, rough fields. Which is why they're still used as there's no jet capable of a similar role.

author: james_s
author_rank: Super Contributor
timestamp: May 11, 2018, 09:37:11 pm
content: The large frontal area was long assumed to be a serious limitation in terms of fast aircraft but in reality once the aerodynamic cowling had been developed this proved to not be such an issue. The German FW-190, the American F4U Corsair and the British Sea Fury were some of the fastest planes in WWII, all powered by radial engines. Part of this is of course brute force, the enormous amount of horsepower available from such large engines but the aerodynamics are not that far off from the sleeker looking inline powered aircraft.I've always wanted to fly on a DC-3, it's probably the most versatile aircraft ever built, others since have been faster, bigger, sleeker, longer range, etc but nothing has quite captured that *perfect* balance of rugged versatility that has made the DC-3 so iconic.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 11, 2018, 10:28:42 pm
content: And my favorite, the F7F Grumman Tiger Cat. Bit late in the war, but fast.

author: james_s
author_rank: Super Contributor
timestamp: May 11, 2018, 10:37:59 pm
content: The Tigercat is a fantastic plane, I got to see an airworthy example named "Bad Kitty" up close at a local museum. Unlike most where everything is roped off, was able to walk right up and get my hand oily touching one of the engines. One of these days I need to go there on a day they fly it.

author: Gregg
author_rank: Super Contributor
timestamp: May 13, 2018, 04:03:23 pm
content: Quote from: metrologist on May 11, 2018, 12:10:57 amAn attempt to get back on the original subject:If you have the equipment to make it, I would suggest a three part (plus magnets, of course) rotor.The center or hub made out of steel, the middle ring made out of aluminum, brass, plastic or some non-magnetic material and a thin outer ring to retain the magnets against centrifugal forces.The middle ring would have radial holes to fit the magnets and made out of non-magnetic material wouldn’t bypass the magnetic flux but would keep the magnets apart.The center steel hub could be two parts screwed together like a tire rim with flanges to keep the middle ring located and tight so it wouldn’t slip. Some small screws would work to clamp the two halves together with suitable force to keep the middle ring from slipping. One half could be press fit on the shaft and the other a slip fit. Making the center form magnetic material will make it part of the magnetic circuit.The outer ring should be something thin like the brass drain pipe under a sink. It could be a light press fit or leave it a little wider and make some bend tabs to keep it from walking axially.I would probably start with the dimensions of the outer ring and build inward in CAD for real world dimensions.Another possibility would be to glue the magnets without the outer ring, but the magnetic forces combined with centrifugal forces of a working motor may cause catastrophic failure.Enclosed is a very rough sketch, if you want a better sketch just ask. My old AutoCAD only works on an old XP machine that is in storage and I don’t want to spend the $ for a new version.

author: jmelson
author_rank: Super Contributor
timestamp: May 13, 2018, 07:14:07 pm
content: When I was about 20 I worked for NASA for a couple years. They had a pair of C-47s with various sensing gear in them. We replaced a TV camera and they needed to start an engine to have AC power. It made an absolutely incredible sound from cranking up to the last cylinder rolling over TDC as it coasted to a stop. R-1830, I think.Jon

author: metrologist
author_rank: Super Contributor
timestamp: May 14, 2018, 02:28:48 pm
content: Gregg, thanks for the idea. That would work too. A lot of small parts I'm finding it hard to work with.Another try was to make a flat hub, more like a gear, so the magnets could be oriented with N-S facing poles and have some separation. My tool was a little small so the magnets will not quite fit into the slots. It's also kind of sloppy so I'll make another using a rotary table.I'm adding a pic ture with a US dime for size

author: Gregg
author_rank: Super Contributor
timestamp: May 14, 2018, 09:22:11 pm
content: I just reviewed a recent AvE video where he takes apart a Makita brushless drill. About halfway into the video he has a nice view of the rotor and stator. The rotor has 4 flat neodymium magnets inserted from the side. I thought it may give you additional inspiration. He showed less poles in the rotor than windings in the stator.You are making it smaller than I imagined. The thin brass hobby tubing may be useful. That small I would try making the rotor two piece and glue the magnets in with epoxy and machine the OD down after the epoxy has set. Maybe tap the holes in the non magnetic ring part way to help the epoxy bite, especially if using plastic.I don't envy you winding the coils; I don't see that well anymore. I used to fix clocks without magnification, but not anymore.Good luck on your project and post some pictures or a video of it running.

author: metrologist
author_rank: Super Contributor
timestamp: May 14, 2018, 09:30:04 pm
content: I don't do much without magnification anymore either, but it is proving harder to hold things than see what I'm doing, because I have some optical stuff laying around. Those little magnets are about the size of broken off pencil lead.I got inspired by small things when a lady at work gave me a toothpick that she had whittled into a giraffe - with a tail and 4 legs standing on grass... I still have it somewhere.

author: metrologist
author_rank: Super Contributor
timestamp: May 15, 2018, 03:43:09 pm
content: I got all the holes milled to depth and may make an aluminum ring to press around the circumference to hold the magnets, or I may just super glue them.I have a good idea for the body now too, since the RT is set up...A question or two:I was thinking of using 4 transistors to swap voltage polarity across the windings (12 transistors total). I was going to wire them as Wye, but without the return lines connected together as neutral. The return lines would feed through transistors to ground. I would have pulsed AC square wave, each phase 120° degrees apart. This seems like it would work, but not sure. I attached one phase driver for reference where V2, V3 are out of square wave from mcu. I used an inductor for the winding with 0.1L and 2Ω series resistance. LTspice shows ~1.2A through the coil.If that would work, I have not yet seen how the motor could be wound Delta using the above driver. I'd need 6 connection points so separating each leg looks the same as above.I also have a regular RC speed controller with three wires. How would I convert my driver so it only has three connection points instead of 6?

author: metrologist
author_rank: Super Contributor
timestamp: May 17, 2018, 05:55:13 pm
content: Someone thought it might not work. I decided to use steel pegs shaped like a T for the cylinders, which will be pressed into the body and come closer to the rotor, then wrapped on the outside with motor wire. Then I drew the magnetic fields as I think they are at the start condition, with #1 at top going clockwise.

author: Gregg
author_rank: Super Contributor
timestamp: May 17, 2018, 09:14:00 pm
content: Those are very nice drawings; keep up the good work!I know this is just a novelty and basically just needs to turn and start by itself; maybe turn a small propeller for effect and some cooling.For possible inspirational purposes, I don't pretend to be an expert: If you could couple the outer coil cores together with magnetic material it will provide a better circuit for the magnetic flux. Even if the connecting material was looped toward the axis for appearance.

author: metrologist
author_rank: Super Contributor
timestamp: May 17, 2018, 10:03:57 pm
content: Now, that is a good idea to use small machine screws. Would it be better to make the body from steel instead of aluminum?I had considered it would be good to make the body from many layers of steel sheet, as pictured, with plates or endbells on each end.I loathe sheetmetal work

author: Gregg
author_rank: Super Contributor
timestamp: May 17, 2018, 11:03:04 pm
content: Your magnetic field of the sheetmetal as shown would only work for a motor with permanent magnets on the outside. The center ring will conduct the magnetic flux mostly between coils, leaving very little if any to turn the rotor. If you invert the design, it would have an outer ring that would take away the esthetics of a 9 cylinder radial engine.I guess it is back to the drawing board. I thought if the outer ring of magnetic materials was formed along the lines of the radial coils but far enough to not interfere with the coil magnetics too much, it would make your motor look more like an engine.(Motor and engine are often interchanged and therefore seldom used correctly on the internet)

author: metrologist
author_rank: Super Contributor
timestamp: May 18, 2018, 02:56:29 pm
content: I think it will be as such.(I added the wiring)

author: Gregg
author_rank: Super Contributor
timestamp: May 18, 2018, 07:04:14 pm
content: I may be wrong, it certainly wouldn’t be the first time, but I think you should re-think the ways magnetic flux work in a motor vs. a single magnet in free air. I believe that it is the flux between poles that gets the job done via the electromagnets pushing and pulling on the permanent magnetic fields. You certainly have the 3ph concept down.By the way, what are you using for CAD? It looks interesting

author: metrologist
author_rank: Super Contributor
timestamp: May 18, 2018, 07:32:51 pm
content: I am using Adobe Illustrator.Do you know if the flux would be the same as you've drawn it if there was no structure? Magnets and coils floating in space. I was considering it that way because I am using aluminum.

author: Gregg
author_rank: Super Contributor
timestamp: May 18, 2018, 08:59:45 pm
content: If all the coils are mounted independently it would be much better than the ring of magnetic material near the rotor. Air has some magnetic permeability; about the same as aluminum, wood or many plastics. Iron has many orders of magnitude better permeability which would cause the magnetic flux to follow along the path of greater permeability rather than interact with other magnetic fields like the permanent magnets. A quick Google search for magnetic permeability will show some interesting results.The problem with aluminum in close proximity to changing free magnetic flux (flux not being directed by a medium of much greater permeability) is that aluminum is such a good electrical conductor that eddy currents will be generated in the aluminum by the changing fields of the electromagnets which will cause heating because they are essentially short circuit and will need more current to overcome this loss. To demonstrate this, try dropping one of your small magnets through a similar ID copper tube and note how long it takes to fall.Plastic would be a better material; using something like Delrin you wouldn’t need shaft bearings.

author: metrologist
author_rank: Super Contributor
timestamp: May 18, 2018, 09:06:26 pm
content: I have black Delrin. I think I'll still give it a whirl with the aluminum body and later compare with Delrin. The aluminum is already chucked and the roughing started a couple days ago. Hope I have some suitable screws.

author: Gregg
author_rank: Super Contributor
timestamp: May 18, 2018, 09:19:00 pm
content: Nails cut to length may make good cores for the coil and they are cheap, easy to chuck up and power wind the wire prior to cutting them to length. The sheetmetal laminate plates you mentioned earlier may be a little more efficient, but what a pain for winding coils

author: metrologist
author_rank: Super Contributor
timestamp: May 18, 2018, 09:44:53 pm
content: I was thinking 16 turns. But I would need a continuous wind between 3 cylinders. I was just going to wrap the single wire manually, but I think to get the wires to lay down nice, I'd need to wind all three runs at the same time, from cyl to cyl...

author: Gregg
author_rank: Super Contributor
timestamp: May 19, 2018, 12:36:02 am
content: I probably thought you were using more than 16 turns since the magnetic field is proportional to ampere-turns. More turns at lower current equals the same magnetic flux and usually less heat.But just getting it to work is the first step, take some measurements and modify if necessary. The magnetic field doesn’t care if the wiring is neatly wound. You do need to make all the coils wound the same direction.I believe you have a lathe. You could wind the first coil, put some heat shrink or tape around to keep it from unravelling; hold the first wound nail against a chuck jaw with tape while you wind the second, repeat for the third. You probably don’t want to wind it very fast so you can count turns.This is a great project; you do all the work and I just observe.

author: metrologist
author_rank: Super Contributor
timestamp: May 21, 2018, 01:53:25 pm
content: Not much else to do but put it together now. I'll see how many turns feels write when I start rapping.

author: metrologist
author_rank: Super Contributor
timestamp: May 25, 2018, 03:02:46 pm
content: I got as far as winding the first set of 22 turns. I decided to test for a magnetic field by running an amp through the circuit, and could not detect any field with ferrous objects or magnets. I set a small magnet on top of one of the nails and reversing current had no effect on the magnet.I recall an elementary school exercise involving a 6V alkaline lantern battery, some speaker wire, and a nail. I should go back and study my notes.This is 28ga wire and can only handle about 1.5A, so I'm sure this design will not work.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 25, 2018, 03:36:33 pm
content: Your magnet wire looks used and could have multiple shorted turns. Try the test with ordinary, vinyl insulated hook-up wire (stranded or solid).

author: Gregg
author_rank: Super Contributor
timestamp: May 25, 2018, 06:02:29 pm
content: I don’t envy your task of winding wire in such a tight configuration. Maybe it is time to bench test your theory. Maybe three nails through a block of wood to try more windings, different voltages etc. and test the magnetic fields with a lot less hassle and if a meltdown occurs it won’t ruin all your hard work. For a bench test you could wire coils with separate lengths of wire to make things easier and possibly test three phases.I’d start by drilling holes in the wood so that the nails are a tight fit but not split the wood and grind off the nail points flush with the back. Then during your tests you can put a suitable steel washer or sheet of steel across the bottom of the nails and see how much it enhances the magnetic fields and what it does to the current draw of the coils.