Think I can make it? (electric 9-pole radial engine replica)

[metrologist]

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.

[jpanhalt]

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.

Low 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.

[jmelson]

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

[GerryBags]

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

Yes, 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.

[jpanhalt]

If so, I want to hear it.   My dad was with a B-29 squadron in WWII.

[Stray Electron]

If so, I want to hear it.   My dad was with a B-29 squadron in WWII.

   I 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.

[metrologist]

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.

[james_s]

   I 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.

The 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.

[viperidae]

With 3 coils per phase you'd probably want 12 magnets

[metrologist]

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.gif

And I guess this is an 18 or 24 pole motor if each N and S is a pole? What are we counting as poles?

[hayatepilot]

With 3 coils per phase you'd probably want 12 magnets

This.
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

[Old Printer]

If so, I want to hear it.   My dad was with a B-29 squadron in WWII.

  The Super Constellations and the B-29s were both magnificent aircraft, it's a shame that so few of them are still flying.

When 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.

[ez24]

   I used to fly in the EC-121s (Super Constellations equipped with large RADARS).

So 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.

[Old Printer]

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.

[metrologist]

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.

[jpanhalt]

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. 

[jmelson]

If so, I want to hear it.   My dad was with a B-29 squadron in WWII.

There'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

[metrologist]

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. 

[Audioguru]

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.

[IanMacdonald]

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.

Had 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.

[james_s]

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.

[jpanhalt]

And my favorite, the F7F Grumman Tiger Cat.  Bit late in the war, but fast.

[james_s]

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.

[Gregg]

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. 

An 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.

[jmelson]

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