# 350hp Electric Aircraft Motor



## dcb (Dec 5, 2009)

I'm skeptical, not really enough to go on in that article.

350hp @ 2500rpm is 734 foot lbs?!?

I don't see it.


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## brian_ (Feb 7, 2017)

Calling an electric motor an "engine" is nonsense - Siemens knows better (and refers to it as a "motor" within a "drive system"), so that would be the author's error.

The comparison of engine weight directly to electric motor weight would be sensible, if only batteries had the same weight as a fuel tank containing the same energy. Later in the original post, the reality of energy density is covered. As it is, the electric motor and controller could be entirely weightless and the battery-electric drive system is still far too heavy for most purposes. There's a reason that the demonstration aircraft is an aerobatic machine, and the speed tests are sprints.

75% power is used for cruise, but as much for fuel consumption as engine life... and you just need more power to climb than to maintain cruise speed. There's no reason to run the engine in a general aviation engine at max power after the initial climb. This is acknowledged in the Siemens material about hybrid drive systems (which is their interest, not battery-electric), which anticipates turbine engines sized for efficient cruise, and batteries used to handle the takeoff surge.

Still, the low weight of this motor is impressive. 



dcb said:


> I'm skeptical, not really enough to go on in that article.


A more informative article is this one, directly from Siemens:
Powerful Ultralight Motor for Electrically Powered Flight
This is from around the same time as the Flying Mag article.

One of the photos on Siemens's Electric Flight Takes Off page shows more of the complete configuration, with the battery pack.

The motor is a permanent magnet AC design, with liquid cooling and 580 volt input voltage; much of the effort seems to have gone into structural optimization for mass reduction.



dcb said:


> 350hp @ 2500rpm is 734 foot lbs?!?
> 
> I don't see it.


Yes, it is. 
(Power {in hp} / Speed {in RPM}) / 5252 {unit conversion factor} = Torque {in lb-ft}

or
Power {in watts} / Speed {in radians/second} = Torque {in Nm}
(no unit conversion needed in these coherent base units, so
260 kW / 131 rad/s = 993 Nm (Siemens says 1000 Nm)

Traditional light aircraft engines drive the prop directly, and so are slow-turning and have large displacement to develop the required power at that low speed. A typical certified aircraft engine putting out 350 hp peak would be a 540 cubic inch (8.8 L) turbocharged six-cylinder.

Siemens is currently testing this motor in an Extra 330, which normally has a non-turbocharged 580 cubic inch (9.5 L) six-cylinder AEIO-580-B1A


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## dcb (Dec 5, 2009)

brian_ said:


> Yes, it is.


I mean, I don't see that motor making 734 ft lbs...


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## brian_ (Feb 7, 2017)

dcb said:


> I mean, I don't see that motor making 734 ft lbs...


Okay, I now understand that it's disbelief rather than not believing the torque/power/speed combination.... but it does. 

I mean, either Siemens is lying and the aircraft performs in a miraculous fashion without the torque physically needed to drive the propeller hard enough... or that short motor really hammers out 734 lb-ft. Aircraft performance is so well understood that it would be hard to demonstrate any given level of performance and fool the aviation world about the power and torque required.

For a comparison, the Chevrolet Spark's motor puts out about 400 lb-ft of torque over a broad speed range (stall to 2000 rpm), in a design that went into production four years ago, and is much smaller in diameter. The somewhat newer and just-developed Siemens aircraft motor seems reasonable to me, after some consideration.


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## brian_ (Feb 7, 2017)

I understand the desire to build a high-torque low-speed motor for direct drive, because a gearset has substantial consequences in this application. Stuck on the front of a conventional aircraft with a huge box of battery behind it, the size and proportions work out well.

But to me, it's unfortunate that in a less conventional installation it would be all wrong: if one wanted to put twin props with their electric motors on the wings and the engine (or battery) in the fuselage, those large-diameter motors would force huge nacelles (fairings). They're like the old radial engines. It would be so much nicer to have more slim (even though they would be longer) motors so the electric power transmission could be used to enable new designs.

In a car, similar problems can occur. It can be pretty hard to package large-diameter motors, but different configurations can be used to suit different motor proportions.


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## dcb (Dec 5, 2009)

brian_ said:


> , in a design that went into production four years ago, and is much smaller in diameter.


Just curious, do you know the siemens vs sparks rotor magnetic area and radius?


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## brian_ (Feb 7, 2017)

dcb said:


> Just curious, do you know the siemens vs sparks rotor magnetic area and radius?


Sorry, no, but that would be interesting. All I've seen are photos, the stats mentioned in this discussion, and a description of the Siemens magnets... not even external dimensions of either motor, let alone internal.

If anyone knows of a collection of this sort of data - for these or other advanced motors - I would be interested.


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## dcb (Dec 5, 2009)

maybe they figured out how to largely nullify the air gap under smooth (i.e. propeller) loads? How much torque is that worth?

edit, maybe it has a lot of poles too?


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## brian_ (Feb 7, 2017)

dcb said:


> maybe they figured out how to largely nullify the air gap under smooth (i.e. propeller) loads?


They did seem to put a lot of effort into the structure, and a stiff structure might make a small gap more feasible. I had assumed the structural focus was primarily related to weight.

I'm not so sure that the propellor is a particularly nice and smooth load. Every time a blade goes past aircraft structure there is an aerodynamic interaction. It's worse on pushers than this puller configuration, and it would be worse on a wing than on the nose like this, but vibrations might still be an issue.

Aircraft engines which need to run faster than the propeller use reduction drives - traditionally gears but some are toothed belts for auto engine adaptations - and interaction of engine power pulses, propeller vibrations, and reduction drives are an issue.



dcb said:


> ... maybe it has a lot of poles too?


Since it is large in diameter, a high pole count would be practical.


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## WolfTronix (Feb 8, 2016)

From the pictures, it looks like they are either driving it 6 phase, or dual 3 phase.

My guess is dual three phase...
i.e. The motor has dual stators, and dual rotors on a common shaft.
And they power each with a separate controller for redundancy.

The aviation industry does like redundancy.


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## brian_ (Feb 7, 2017)

WolfTronix said:


> From the pictures, it looks like they are either driving it 6 phase, or dual 3 phase.
> 
> My guess is dual three phase...
> i.e. The motor has dual stators, and dual rotors on a common shaft.
> ...


They like redundancy, but particularly for components which are less trusted - such as electronics - and in larger aircraft. Something like that Extra has lots of single points of failure... but perhaps redundant inverters would be wise.

I didn't listen to the video (no patience for endless prattling free of any useful information, which describes most online videos) but apparently there was a mention of the dual sets of windings. It was also discussed in Reddit: Siemens 260 KW Electric Aircraft Motor. An article from Sustainable Skies mentions a hybrid aircraft from Pipistrel with Siemens electric machines which uses "dual-winding" generator and motor.

The Sustainable Skies article also mentions Diamond's HEMEP – Hybrid Electric Multi Engine Plane, which is more like what I see as a useful configuration than the swap-engine-for-electric-system test setup used for the latest big motor.

A Siemens presentation - _Electric propulsion components with high power densities for aviation_ - gives some recent history, and shows the new motor in the intended context of a hybrid propulsion system. They're looking at a 170 kW engine-generator set matched to this 260 kW motor, so the engine matches cruise requirements and the motor matches takeoff requirements.


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## Sunking (Aug 10, 2009)

Philly great for a airplane using s Constant Speed low RPM motor swinging a large prop or rotary wing. Not so great for an EV. You would need 6 or more gears.


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## brian_ (Feb 7, 2017)

Sunking said:


> Philly great for a airplane using s Constant Speed low RPM motor swinging a large prop or rotary wing. Not so great for an EV. You would need 6 or more gears.


Although the application is relatively constant speed, there's nothing constant speed about the motor. It is simply a permanent magnet AC synchronous motor - like most modern electric and hybrid vehicles - and will have the same torque-speed and power-speed characteristics as any other PM AC motor. 

In the very worst case it would need to be geared for 2500 rpm at the car's maximum speed; more likely the motor can safely run somewhat faster than that, even if it isn't needed in the aircraft. As with almost every other motor, this one would need to run through gearing to match the motor to the load, although less gear reduction than more typical motors in cars. As with almost every production electric car, there would be no need for a multi-speed transmission.

None of the specific details of this motor are suitable for cars; the mounting structure is for an aircraft, and the bearings are designed to take propeller loads. The advantage of being able to run without gearing is great, but only applies to a propeller and not the wheels of a car which rotate substantially more slowly. It wouldn't even work to directly drive a helicopter rotor; for instance, while a Robinson R22 light helicopter uses an engine which would suit directly driving a propeller (at about 2700 rpm), its rotor turns at only 510 to 530 rpm. What it does usefully demonstrate is that:

larger motor diameter can be used to suit lower operating speeds (which is already well known); and,
high power density (5 kW/kg) is possible.


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## WolfTronix (Feb 8, 2016)

It also looks like they have a variable pitch prop on the test aircraft...

More pitch at higher altitudes to keep the motor loading and RPM in the "sweet spot" of the torque curve.


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## Sunking (Aug 10, 2009)

WolfTronix said:


> It also looks like they have a variable pitch prop on the test aircraft...
> 
> More pitch at higher altitudes to keep the motor loading and RPM in the "sweet spot" of the torque curve.


That is what the motor is made for, Constant Speed Prop.


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## dcb (Dec 5, 2009)

brian_ said:


> None of the specific details of this motor


what specific details?!?



brian_ said:


> larger motor diameter can be used to suit lower operating speeds


we don't know anything about the dimensions though... you can double the torque by doubling the length as well (that is how servomotors keep inertia low).


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## brian_ (Feb 7, 2017)

WolfTronix said:


> It also looks like they have a variable pitch prop on the test aircraft...


Likely. I doubt it's possible to get this aircraft type (Extra 300) with a fixed-pitch prop.



WolfTronix said:


> More pitch at higher altitudes to keep the motor loading and RPM in the "sweet spot" of the torque curve.


The "sweet spot" is just the highest speed at which peak torque is still available. It's simpler with a PM AC motor than with an engine.

It's not entirely about keeping constant rotational speed, and there are airspeed changes to accommodate as well as altitude changes. Even if the motor could produce sufficient power at any prop speed, a variable-pitch prop would likely be chosen.


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## brian_ (Feb 7, 2017)

dcb said:


> what specific details?!?


The base/mount design, and the bearings. Those are the only design characteristics of the motor which are described in most of the Siemens material and press articles, presumably because the actual motor design (magnets, rotor and stator laminations, coils) features are nothing special. Those aircraft-specific details are the parts which are interesting to the application, and are important to the weight.



dcb said:


> we don't know anything about the dimensions though... you can double the torque by doubling the length as well (that is how servomotors keep inertia low).


We do know a little bit about the dimensions, because we can see in photos that this motor is large in diameter and not very long in axial length compared to electric car motors with half the power. It is true that length adds torque , but larger diameter allows the length to be kept down (important in the demo aircraft to allow room for the enormous block of battery). It also limits high-speed operation, which doesn't matter because this particular motor is designed to run a propeller which won't work at much higher speeds anyway.


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## brian_ (Feb 7, 2017)

Sunking said:


> That is what the motor is made for, Constant Speed Prop.


It seems to me that the characteristics on an AC PM motor would suit a fixed-pitch prop better than the characteristics of a engine would. The point of this motor is not likely to match a constant-speed prop, but rather just to direct-drive a prop in an aircraft.

A commonly available motor of the same power would be designed for a much higher speed (and so require a speed-reduction drive), would not have the redundant wiring scheme, and would likely be longer (taking too much room in this installation).


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## dcb (Dec 5, 2009)

rotor area/radius size isn't that different, accounting for length. not sure how you get to 734 ft lbs continuous from 400 is all. Or even if the 400 for spark is continuous or how much drag the seimens adds for cooling or?? I mean with enough cooling you can do all sorts of things with any motor. Not really sure why we are speculating so much on the siemens (because they didn't give any real useable data, so screw em)...

siemens (kinda looking like dual controllers fwiw, *possibly* 8? poles interleaved?)









spark


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## Karter2 (Nov 17, 2011)

Im sure this motor has many atributes which make it superior for Aviation use, but power and weight are not some of them.
Even the now aging Tesla designed motor exceeds its power capacity and undercuts the weight considerably. Some might also argue the compact dimentions of the Tesla would be more suitable for packaging in an aircraft.
However , i suspect the performance characteristics ( rpm, power, efficiency) may not be appropiate for conventional prop drives.
But the wide operating rpm (0-18k ) range of the Tesla does suit vehicle drive trains much better than the Siemens aero motor.
Horses for courses ...i guess . ?


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## brian_ (Feb 7, 2017)

dcb said:


> rotor area/radius size isn't that different, accounting for length.
> ...
> siemens...
> 
> ...


I was just going from photos, and the Spark motor didn't look as large in diameter, but they do look pretty close in those photos. That's a good one for the Spark stator. 

So, this Siemens is shorter but larger in diameter (not so suitable for high speed, but that doesn't matter for the aircraft application), so at least much of the torque difference must come from other differences.



dcb said:


> not sure how you get to 734 ft lbs continuous from 400 is all. Or even if the 400 for spark is continuous...


Siemens is pushing this thing with over 500 volts, presumably just using higher voltage to push more current is a substantial factor.

Automotive ratings are typically continuous, although in practice nothing in an automotive drivetrain operates at any of its peak conditions for very long because it doesn't need to... power to maintain speed in anything other than climbing a mountain is far less than the maximum provided for acceleration.



dcb said:


> ... how much drag the seimens adds for cooling or?? I mean with enough cooling you can do all sorts of things with any motor.


I don't understand what motor drag has to do with cooling. The stator is liquid-cooled; there's no liquid in the gap (which is still an air gap) in any motor I've seen, so no moving part of the motor sees the liquid.

There will be aerodynamic drag due to airflow through the radiator (which isn't shown in that photo of an incomplete installation, but you can see on the bottom of the nose in photos of the complete aircraft from below), but there would be aero drag for air-cooling of the motor anyway if it were not liquid-cooled.

Liquid cooling certainly works well, particularly for motors with high sustained power. I assume that the reason that many motors are not liquid-cooled is simply that the cost and complexity of the cooling system is not required, and not sufficiently justified.



dcb said:


> Not really sure why we are speculating so much on the siemens (because they didn't give any real useable data, so screw em)...


Well, the original post was about the Siemens motor, so that's the topic of this thread... 

I'm not surprised by the lack of specifics. The point of the Siemens material is to promote themselves as capable suppliers of complete aircraft electric power transmission systems, and that's not a retail market. The engineers who need detailed information to assess their products for actual paying customers (aircraft manufacturers) will get everything they need, but not from public websites.



dcb said:


> siemens (kinda looking like dual controllers fwiw, *possibly* 8? poles interleaved?)


Yes, some of the online material that I linked earlier described the configuration as having dual windings dual controllers/inverters; the three-phase wiring connection visible in that photo is repeated for the other set of windings on the other side of the motor.


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## brian_ (Feb 7, 2017)

Karter2 said:


> Im sure this motor has many atributes which make it superior for Aviation use, but power and weight are not some of them.
> Even the now aging Tesla designed motor exceeds its power capacity and undercuts the weight considerably.


A quick search shows the 362 horsepower Tesla motor at 70 pounds, which is 8.5 kW/kg. Yes, higher power density, but that's easy at much higher motor speed.



Karter2 said:


> Some might also argue the compact dimentions of the Tesla would be more suitable for packaging in an aircraft.
> However , i suspect the performance characteristics ( rpm, power, efficiency) may not be appropiate for conventional prop drives.
> ...
> Horses for courses ...i guess . ?


It would be easy to use a smaller and higher-speed motor (from anyone, of induction or PM type) in the aircraft, but it would require a speed reduction unit (gearbox). That's a big deal in an aircraft, which is why it's worth developing a high-torque / low-speed motor.



Karter2 said:


> But the wide operating rpm (0-18k ) range of the Tesla does suit vehicle drive trains much better than the Siemens aero motor.


Why are people are assuming that because the Siemens aircraft motor only needs to run at about 2500 rpm that it has a narrow operating range? It's normal for a PM AC motor to produce about the same torque all the way down to zero as it does at the peak torque speed, whether it needs to or not. Induction is not quite as good at stall, but the Tesla motor is still nothing special in that respect.


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## Karter2 (Nov 17, 2011)

Im sure the Seimens is the best motor for its intended application in aircraft.
But i was just responding to the OP where it was suggested that somehow this was some new development, moving motor development into new levels of power and low weight which could also be suitable for road vehicles.
The fact is, the Seimens is no better than the 10+ year old Tesla motor as far as power and low weight, and certainly does not have an rpm range that would readily lend itself to road vehicle use. (Unless you think that a motor designed to operate at 2500rpm, would be capable of reliable performance at 15+k rpm ?)


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## dcb (Dec 5, 2009)

here they are tweaked a bit for a swag based on the hands. I'd say the spark OD is ~ %70 of the siemens, and the spark slots are maybe %10 longer. Complete guesswork of course.


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## Karter2 (Nov 17, 2011)

There is obviously a smaller version of the Seimens motor as used in the Hamilton aEro aerobatic electric aircraft..
..100kW and 29 lbs inclusing controller !
https://cleantechnica.com/2017/04/10/final-frontier-electric-airplane-hamilton-aero-takes-off/


> The battery pack is made up of 108 battery cells that are designed with energy on instant demand. They were sought out in order to draw current at up to a maximum of 200 amp/hr at 450 volts. Demont went to great lengths to program a controller that can handle quick draws in less than a millisecond. All of this allows the aEro to fly an hour at 92 kts, roughly 110 MPH, drawing a mere 30 kW of energy to keep it in flight. It can fly 20 minutes of aerobatics mode with a two 10-minute transit capacity. And the aEro is efficient, since its minimum power required to keep it in flight is 40 hp. It can reach a maximum cruising speed of 146 kts, or 170 MPH. Its maximum range is 86 nm, close to 100 miles… so far.
> *
> The motor and control unit weighs only 29 lb, which is feather-weight for aircraft. The 100 kW/107 hp Siemens electric motor spins at 11,000 rpm, engaging a reduction gear that drives the propeller at around 2,900 rpm*. While the airframe weighs in at 308 lbs, the battery adds another 352 lbs, totaling around 683 lbs for this light plane......


 Now, a motor with 100kW and 11,000 rpm working range could be very suitable for a small car or eMoto conversion !
More info and pics etc on both motors here..
https://nari.arc.nasa.gov/sites/default/files/attachments/Korbinian-TVFW-Aug2015.pdf

Motor details...
The new GM Bolt motor is detailed here..
https://www.cnet.com/roadshow/news/deep-dive-2017-chevrolet-bolt-electric-powertrain/
It 204 mm dia (115mm rotor ?). compared to the Spark motor 213mm dia
Whilst the Seimens 260d is apparently 418mm OD..basicly double the dia of the GM motors.
This is the SPARK rotor...again i estimate about 150-175 mm dia
http://blog.caranddriver.com/wp-con...ding-the-permanent-magnets-into-the-rotor.jpg


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## brian_ (Feb 7, 2017)

I agree that the Siemens motor - although nicely constructed - does not represent a substantial advance for automotive use. On the other hand, it would work fine in a car.

The operating speed range of the Tesla motors is not an advantage - it's just what it is. Any motor has a maximum speed, and the vehicle will be geared so the motor hits maximum speed at the maximum design speed of the vehicle. The faster the motor needs to run to make enough power (and thus the less torque it has), the more gear reduction will be used. The only reason for choosing high speed is to keep motor size down for the same power. Since Tesla's motors are on the high-speed side, Tesla cars have high reduction ratios. Since the Spark motor's speed range is lower, it has a low reduction ratio. The rest are in-between... and they all work. 

The big Siemens motor is well-suited to the aircraft application because it doesn't need any gear reduction at all, so it avoids the reduction drive hardware (unlike the smaller Siemens motor mentioned above). No production car makes so without gear reduction, but the Spark motor is nice because it can be (and is) used with a single-stage gear reduction, while almost everyone else needs two stages (ratios from about 6:1 to about 10:1). The original Tesla Model S ratio of 9.73:1 (in two stages) is near the top of the range used, and later Tesla ratios are apparently even higher, simply because they have chosen a high motor speed.

If someone chose to use the Siemens 260d in a car, they would need to use a reduction drive, because 2500 rpm would be 300 km/h (190 mph) without gearing, and the motor can probably go much faster than that. Only a single reduction stage would be required, just like a Spark.


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## Karter2 (Nov 17, 2011)

Brian, i suspect you are overlooking the advantage of torque multiplication from the high ratio gearing the Tesla uses.
Their motor has been tested at 300+ kw and 600Nm torque.
With the 9.73 drive reduction that results in 5800 Nm at the wheels and a wheel speed range up tp 1850 rpm (~ 155 mph)
For the Seimens motor to have a similar wheel speed range ( from an assumed 6000 rpm max speed ?). It would require approx a 3.2:1 reduction drive.
That would result in 3200Nm torque at the wheels or 55% of the Tesla torque !
So , there is some advantage to a high rpm range motor for road vehicles...
...and likely explains why Tesla is the king of the production car 0-60 sprint.


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## PhantomPholly (Aug 20, 2008)

brian_ said:


> Later in the original post, the reality of energy density is covered. As it is, the electric motor and controller could be entirely weightless and the battery-electric drive system is still far too heavy for most purposes.


Too true. It is useful for illustrating the "weight budget" freed up by the motor, but sadly also points out as you say that we have a long way to go with battery tech before it really "takes off" for nonspecialized (e.g. trainers) aviation use.



> 75% power is used for cruise, but as much for fuel consumption as engine life...


I take it you're not a pilot? Most aircraft engines have a 2,000 hr specification for overhaul (a $25k+ cost for most 4 seaters); most never make it that far; and those that operate low enough to routinely operate at more than 75% power and actually choose to do so invariably must overhaul their engines even sooner. On the plus side, most people operate at or above 6,500' MSL where the engine really won't produce more than about 75% power due to thinner air (unless you have a turbocharger, which in aviation is a stiff price premium). 

Bottom line - many pilots prefer to cruise at 65% power rather than 75% to preserve the engine.



> There's no reason to run the engine in a general aviation engine at max power after the initial climb. This is acknowledged in the Siemens material about hybrid drive systems (which is their interest, not battery-electric), which anticipates turbine engines sized for efficient cruise, and batteries used to handle the takeoff surge.


That depends. Jetliners are typically speed limited by mach, so there isn't much advantage in trying to operate using sea-level takeoff power when cruising at 45,000'. A Cirrus 4-seat aircraft on the other hand is typically limited in power by motor weight, and you have the altitude-lapse issue for available cruise power. Since you can cruise about 3% faster per 1,000' of altitude on the same power, it would be great to cruise (with O2) at 25,000', but a normally aspirated engine is "out of steam" well before it reaches such altitudes. At 18,000', a 200hp motor is only cranking out 100hp on a very good day (rare), more likely 90hp. That's not much to move a 3,000lb airplane through the air.



> Still, the low weight of this motor is impressive.


Yes indeedee! Now, we just need better batteries...



> Siemens is currently testing this motor in an Extra 330, which normally has a non-turbocharged 580 cubic inch (9.5 L) six-cylinder AEIO-580-B1A


Perfect choice. The Extra is an airshow airplane, generally operated under 5,000' and an airshow is physically taxing so 20 minutes of power is probably plenty. Such a show generally does not operate continuously at 100% power, so 75-100Kwh of battery pack would be plenty.


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## PhantomPholly (Aug 20, 2008)

brian_ said:


> None of the specific details of this motor are suitable for cars; the mounting structure is for an aircraft, and the bearings are designed to take propeller loads.


The major factors of propeller loads on a traditional aircraft engine generally have to do with the piston power-pulses. That's why they need such large bearings. The pulses in an electric motor would be much smoother, with a relative reduction in the required size of the bearings. Propwash across the nose or wing for a tractor configuration really would not impact the prop itself, only the smoothness of airflow across the aircraft body. There are still some torsional forces from P-factor etc., so the bearing would still need to be bigger than for other uses but not enormous.



> The advantage of being able to run without gearing is great, but only applies to a propeller and not the wheels of a car which rotate substantially more slowly. It wouldn't even work to directly drive a helicopter rotor; for instance, while a Robinson R22 light helicopter uses an engine which would suit directly driving a propeller (at about 2700 rpm), its rotor turns at only 510 to 530 rpm. What it does usefully demonstrate is that:
> 
> larger motor diameter can be used to suit lower operating speeds (which is already well known); and,
> high power density (5 kW/kg) is possible.


All true. The major reason reduction is not used on most aircraft is weight and another point of failure - in other words, it would be more effective and safer just to install a bigger motor. Of course for helicopters there is no getting around it. However, electric motors do not have the power pulse magnitude of piston motors, and so if this same motor could produce twice the power by spinning twice as fast a reduction unit might make more sense ($/hp, lbs/hp, etc.).


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## PhantomPholly (Aug 20, 2008)

Karter2 said:


> Im sure the Seimens is the best motor for its intended application in aircraft.
> But i was just responding to the OP where it was suggested that somehow this was some new development, moving motor development into new levels of power and low weight which could also be suitable for road vehicles.
> The fact is, the Seimens is no better than the 10+ year old Tesla motor as far as power and low weight, and certainly does not have an rpm range that would readily lend itself to road vehicle use. (Unless you think that a motor designed to operate at 2500rpm, would be capable of reliable performance at 15+k rpm ?)


This is a common fallacy - to compare power density of aircraft motors to automobile motors. Literally hundreds of entrepreneurs have tried and failed to create a cheap, reliable aircraft motor out of automobile engines. 

Why? Simply this - an aircraft motor is designed to operate continuously above 50% power, while an automobile motor rarely spends more than 1% of its lifetime above 50% power. While I cannot prove it with the information I have with me ("proof" would require testing several Tesla motors to destruction), I can say with statistical assurance that a Tesla motor employed for aviation would not / could not be both lighter in total installed weight (once you add a reduction drive) and also equally reliable as a purpose-built motor.


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## Karter2 (Nov 17, 2011)

^^. I agree ,... and previously said as such,... that the Seimens is the better motor for an aircraft.
but likewise i would suggest that the Tesla is a far better motor choice for a car application, not least because it has a much more suitable power delivery and rpm range.
Of course you cannot directly compare motors designed for different applications in an absolute judgement, but when someone throws down a simple metric like kW/kg without qualifying it, then its reasonable to respond in a like manner.
My comparison was purely on the comments regarding power and weight where much was being made of the 5kW/kg as some new achievement in motor design, when there are already several motors that exceed that figure.....Tesla being one of the more well known ones.
Repeating myself again ...."Horses for courses"


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## Karter2 (Nov 17, 2011)

Ahh !.. Maybe these guys have found the ideal combination of electric aircraft technology and car...
https://www.facebook.com/GlosAirport/videos/1664132510281385/
But, the real application is this..
http://www.electro-flight.com/electroflight-p1e

Seems ambitious, but their proposal claims a climb rate of 9000 ft/min !
...which is 4 time that of the Seimens record.
And a speed of 300 mph 
Whilst i know contrarotating props are a well established technology,..the shaft support and bearing configuration shown here would make me think twice before climbing aboard !..
? Dual Yasa motors ??


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## PhantomPholly (Aug 20, 2008)

Karter2 said:


> ^^. I agree ,... and previously said as such,... that the Seimens is the better motor for an aircraft.
> but likewise i would suggest that the Tesla is a far better motor choice for a car application, not least because it has a much more suitable power delivery and rpm range.


No argument there! Just trying to make it clear for folks who don't understand that airplanes are substantially different in their core requirements.



> Of course you cannot directly compare motors designed for different applications in an absolute judgement, but when someone throws down a simple metric like kW/kg without qualifying it, then its reasonable to respond in a like manner.


The devil is always in the details. Hundreds of defunct entrepreneurs because they thought they could convert car engines to aircraft use. I think they "kind of" succeeded with a low power Honda conversion, and of course there are all kinds of VW conversions used in very small experimental aircraft. But, for the higher horsepower applications it never seems to pan out.



> My comparison was purely on the comments regarding power and weight where much was being made of the 5kW/kg as some new achievement in motor design, when there are already several motors that exceed that figure.....Tesla being one of the more well known ones.
> Repeating myself again ...."Horses for courses"


There are all kinds of examples of insane hp/weight ratios for purpose built applications or just for show. One of my favorites was apparently a borderline scam (the motor might have worked, but probably not for very long). Called the MYT (pronounced "mighty") engine, the web site never goes away but the motor never materializes either. At one point I believe they "projected" something like 50:1 power to weight (better than a jet engine).


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## PhantomPholly (Aug 20, 2008)

Karter2 said:


> Ahh !.. Maybe these guys have found the ideal combination of electric aircraft technology and car...
> https://www.facebook.com/GlosAirport/videos/1664132510281385/


The same bombers I intercepted 32 years ago in Iceland have been flying for over 60 years now with counter-rotating propellers. They are not, however, more efficient - the only reason to use them is if a) your ground clearance is not sufficient to swing a bigger prop; b) you have insane hp compared to the size of the wing and so it would just spin your whole airplane like a top; c) a four or five bladed prop would be incapable of absorbing / transmitting all of the available power. Your best bet for efficient power delivery is a longer propeller turning slower (so the tips don't go supersonic). FYI flying alongside of them (or, as I am told, even inside of them) is "unpleasant" because of the tremendous amount of vibration caused by the props.



> But, the real application is this..
> http://www.electro-flight.com/electroflight-p1e
> 
> Seems ambitious, but their proposal claims a climb rate of 9000 ft/min !
> ...


That is 90mph straight up, so we are simply talking about an aircraft with a thrust to weight ratio approaching 1:1. On such a small airplane the Siemens motor would probably do fine, but you could only carry enough batteries to run for about 10-15 minutes. Another option would be to have a microturbine genset like in the Wrightspeed Fulcrum system (incidentally about 350hp of output) coupled to the Siemens motor - the combination would be about 250 lbs lighter than an IO-540 generally found in an Extra aerobatic plane, which can already "hang on the prop." That extra 250 lbs in a plane that small would allow accelerating straight up, and 90mph would not be unusual.


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## brian_ (Feb 7, 2017)

PhantomPholly said:


> There are all kinds of examples of insane hp/weight ratios for purpose built applications or just for show. One of my favorites was apparently a borderline scam (the motor might have worked, but probably not for very long). Called the MYT (pronounced "mighty") engine, the web site never goes away but the motor never materializes either. At one point I believe they "projected" something like 50:1 power to weight (better than a jet engine).


Ah, yes, one of the toroidal-cylinder designs. The Wikipedia page for Swing-piston engine is shaky in some areas, but contains an interesting introductory bit and one excellent related note:


> Swing-piston engines were initially introduced during the 1820s as alternate steam engine designs, prior to the widespread introduction of the steam turbine.





> In the 1990s, a number of inventors re-introduced the concept as if it were new. Examples include Angel Labs' "Massive Yet Tiny" engine, the Rotoblock, the Roundengine, the Trochilic Engine and designs by Tschudi and Hoose.



The Angel Labs setup is just a scam, or the product of someone's delusions, judging from their website.

The Siemens electric aircraft motor is a straightforward technical design to address a specific application scenario.


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## brian_ (Feb 7, 2017)

Karter2 said:


> Ahh !.. Maybe these guys have found the ideal combination of electric aircraft technology and car...
> https://www.facebook.com/GlosAirport/videos/1664132510281385/
> But, the real application is this..
> http://www.electro-flight.com/electroflight-p1e


When anyone asks the rhetorical question"


> Is this the most significant development in aircraft propulsion since Whittle's jet engine?


... the answer is "no"! 
I don't see anything radical or even new about what they are doing, with the motors, or the props, or the rest of the aircraft. Just like Siemens, they have chosen direct-drive (no gear reduction). The contra-rotating setup is just two motors and props, mounted coaxially. I can see doing this both for redundancy and to eliminate torque reaction, but it's not clear to me that there is any advantage over a conventional twin configuration.

I note that the Electroflight P1e uses fixed-pitch props, in contrast to the Siemens variable-speed prop.


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## PhantomPholly (Aug 20, 2008)

brian_ said:


> The Angel Labs setup is just a scam, or the product of someone's delusions, judging from their website.


Yep pretty much! And actually, as a steam motor it might have been fine (temperatures never much above 1200F, pressures never approaching that of compression ignition).

I was really hoping the Gemini Diesel (based on the Junkers Jumo) would finally appear - the design seems so ridiculously simple (no valves, inherently geared engine making best efficiency at propeller-friendly rpms on the output gear, good power to weight ratio for a diesel, and most of all successfully ran as a trans-oceanic motor for years). They made a splash at the airshows 2 years ago and then - nothing.

We need some smarter people to figure out batteries...


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## Karter2 (Nov 17, 2011)

Junkers Jumo !....
Now you have reminded me of my favorite engine design...the Napier Deltic.
Also based on the Junkers design but, this one was very successful in many applications
18 cylinders,
36 opposed pistons
3 crankshafts
Turbocharged, 2 stroke, diesel, 3000+ hp
And all that 70+ years ago !
http://autoweek.com/article/car-life/behold-napier-deltic-diesel-engine
http://atomictoasters.com/wp-content/uploads/2011/01/deltic_animation.gif


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## PhantomPholly (Aug 20, 2008)

Karter2 said:


> Junkers Jumo !....
> Now you have reminded me of my favorite engine design...the Napier Deltic.
> Also based on the Junkers design but, this one was very successful in many applications
> 18 cylinders,
> ...


I hadn't thought of it, but that's rather brilliant - simply make the central shaft the right size and put it in the center of an equilateral triangle, and you cut in third the length of crankshaft needed for the same power (if torque were the limiting factor for the crankshaft). Better yet, you could put a "central gear" both fore and aft (Gemini only has a drive gear in the front) with an actual shaft between them to reduce any torque asymmetry in timing between fore and aft banks. Only the central shaft need take the torque of the entire engine's output. Only real downside would be that the central shaft could not be positioned "above" the cylinders (a factor in some planes to get better ground clearance for the prop).

Wish I had enough capital to play with something like that...


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## Karter2 (Nov 17, 2011)

They (Napier) actually developed for the Navy a "Hybrid" version of the Deltic, with a gas turbine installed through the center between the cylinder banks , to help energy recovery and efficiency.
It made over 5000hp , but development was shut down in favour of just large turbines.


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## brian_ (Feb 7, 2017)

PhantomPholly said:


> I was really hoping the Gemini Diesel (based on the Junkers Jumo) would finally appear - the design seems so ridiculously simple (no valves, inherently geared engine making best efficiency at propeller-friendly rpms on the output gear, good power to weight ratio for a diesel, and most of all successfully ran as a trans-oceanic motor for years). They made a splash at the airshows 2 years ago and then - nothing.


Like the Electro-flight and Angel Labs cases, it only takes one statement:


> Gemini’s unique two-opposed-pistons-per-cylinder design...


"Unique"? Attempting to apply that term to an ancient design already produced by many companies earns an immediate and complete "fail" rating!

Piston-ported engines avoid the complication of valvetrains, but otherwise are typically undesirable in all but a few specialized applications.



PhantomPholly said:


> Wish I had enough capital to play with something like that...


"Play" would be the right term, and after a while you wouldn't have the capital any more.


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## Karter2 (Nov 17, 2011)

brian_ said:


> "Play" would be the right term, and after a while you wouldn't have the capital any more.


 But that is no different to many other hobby such as sailing, flying, horse riding, car racing, or even building EVs !
Actually, those Deltics are now very rare (in running order) , and i suspect will appreciate considerably as collectors items as time passes.


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## brian_ (Feb 7, 2017)

Karter2 said:


> They (Napier) actually developed for the Navy a "Hybrid" version of the Deltic, with a gas turbine installed through the center between the cylinder banks , to help energy recovery and efficiency.


When the turbomachinery is just a turbine in the exhaust, that's a turbo-compounding - that was Napier's Nomad. This was done on a few piston engines of various configurations by various manufacturers and became a routine Wright production design at the end of the piston-powered commercial flight era, but is challenging due to the high ratio of turbine and crankshaft speeds, and the mismatch in speed versus flow characteristics of positive-displacement machines and turbomachinery (gearing the turbo locks it to vary speed in step with the crankshaft, while a turbocharger's speed changes to suit gas flow independently of crank speed).

The E.185 Compound Deltic descriptions I've read are inconsistent, so I can't tell if this was a simply a highly turbocharged engine (as I suspect)... or a turbine engine bizarrely using a diesel engine for final compression, combustion, and initial turbine stages. It was only a prototype and failed, anyway. 

Despite the gear train needed, Detroit Diesel reintroduced turbocompounding a decade ago with the DD15 (although currently listed only as a feature for the DD16), getting up to 50 hp from the turbine on a roughly 500 hp engine, and improving fuel economy by about 5%. Apparently Scania and Volvo have done it in modern times as well, perhaps before Detroit Diesel (which is part of Daimler's truck operations).

To bring this back to electric power... the modern way to do turbocompounding would be to mount a generator on the turbocharger shaft, and size the turbine for power in excess of what the compressor needs. The net turbocompounding output would be power from the generator, and Formula One cars are now doing this. The generator can also be used as a motor to spin the turbo up for faster response, and some auto manufacturers are starting to do that. Electric motor-generators are a great match for turbine speeds.


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## brian_ (Feb 7, 2017)

Karter2 said:


> But that is no different to many other hobby such as sailing, flying, horse riding, car racing, or even building EVs !


Absolutely. Long ago I was involved in rally competition, and first heard the long-running joke:
Q: How do you make a small fortune in rallying?
A: Start with a large fortune! ​
A couple that only work for those on the water:
Meaning of "BOAT": "Bring On Another Thousand" or "Break Out Another Thousand" (dollars)
Definition of boat: a hole in the water that must be filled with money.​


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## Karter2 (Nov 17, 2011)

Yes, the descriptions of the E185 Turbo Compound do vary, but you are correct it was basicly a super turbocharger.
This is one of the more reputable descriptions..
http://www.startline.org.uk/slol74/deltic/deltic.htm


> The E185 Deltic Compound was designed in 1956 using the basic 18 cylinder engine. A 12 stage axial compressor was housed inside the triangle supplying compressed air to the cylinders and combustion chamber, with the exhaust gas driving a three stage axial turbine. Unlike the Nomad the gas turbine was not coupled to the engine and acted as a super turbo charger. This version of the Deltic produced 5,300 BHP and excellent fuel consumption. However the Admiralty decided to use gas turbines despite their high fuel consumption, and lost interest in the compound Deltic.


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## PhantomPholly (Aug 20, 2008)

brian_ said:


> "Unique"? Attempting to apply that term to an ancient design already produced by many companies earns an immediate and complete "fail" rating!


Perhaps literally correct, but it is also literally correct to say that either of these designs, if put into production (and I don't think Angel's ever will be), would be unique today. Personally I think the Gemini guys have the wrong idea - instead of scaling the engine UP, they should scale the components DOWN and use more cylinders as in the triangle design. I can easily imagine a design with 12 cylinders having 3 separate superchargers, turbochargers, and injection systems (each serving 1 side of the triangle) for virtually fail-proof operation. Lose the top injectors? Keep producing 2/3 power from the left and right side injectors. Lose one turbocharger or supercharger? You'll hardly notice it.



> Piston-ported engines avoid the complication of valvetrains, but otherwise are typically undesirable in all but a few specialized applications.


And one of those specialized applications would be aviation, where simplicity and lighter weight may outweigh considerations such as absolute efficiency, etc.



> "Play" would be the right term, and after a while you wouldn't have the capital any more.


Perhaps. There is risk in any endeavor. On the other hand these engines routinely flew across the ocean 60-70 years ago. It seems far-fetched that the idea couldn't be made to be both economical and reliable with today's technology. A reliable diesel that has the same power to weight ratio as a gasoline engine? Worth something to someone.

Well tomorrow I head to Florida to get familiarity training in another innovative contraption called a Velocity. Engine is typical Lycoming, but it flys backwards. It is my hope that by the time I retire I can get a used one and convert it to electric, or perhaps an electric hybrid using something like the Wrightspeed microturbine generator. 350hp in a design intended for 200 ought to be inspiring...


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## RIPPERTON (Jan 26, 2010)

edited to reduce content


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## brian_ (Feb 7, 2017)

RIPPERTON said:


> Theres so many things wrong with this photo.
> ...
> The die cast alloy motor mounts should handle about 100N of thrust ...


Did you read any of the articles? That structure is the result of an extensive structural study, and has proven capable in actual flight, taking the entire weight of the aircraft in axial thrust in a vertical climb.



RIPPERTON said:


> Then theres the over educated corporate smiley face, I mean shit.


Just what are the educational credentials of that person, and in what way was some portion of his education unnecessary or harmful? Or is there no factual basis to the comment?


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## themotorman (Jan 7, 2010)

Just an FYI on motors and weight etc... I have just designed and built a new motor . It is an axial field PMAC and size is 6 " x 6 " x 12 " and weighs 35#. It puts out 50 HP at 5000 RPM at 95% efficiency. Biggest problem with such a small motor is cooling so forced air is needed if running at full power.


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## brian_ (Feb 7, 2017)

I drafted a post for this thread long ago, then forgot about it. Perhaps it's still of interest...



PhantomPholly said:


> ...
> Personally I think the Gemini guys have the wrong idea - instead of scaling the engine UP, they should scale the components DOWN and use more cylinders as in the triangle design. I can easily imagine a design with 12 cylinders having 3 separate superchargers, turbochargers, and injection systems (each serving 1 side of the triangle) for virtually fail-proof operation. Lose the top injectors? Keep producing 2/3 power from the left and right side injectors. Lose one turbocharger or supercharger? You'll hardly notice it.
> 
> And one of those specialized applications would be aviation, where simplicity and lighter weight may outweigh considerations such as absolute efficiency, etc.


Yes, aviation may be that narrow application... but engines like this have already been tried there and abandoned. One of the challenges of cylinder wall ports is getting seals (piston rings) to work reliably while sliding across them, and reliability is everything in aviation; another is to get complete scavenging, and that's important to efficiency and emissions management. General aviation in North America has had a nearly free ride for decades - allowed wildly excessive noise and barely constrained pollutants while burning high-octane leaded gasoline - but hopefully that will end and aircraft engines will logically converge toward many of the same design features as highway vehicles.



PhantomPholly said:


> ... There is risk in any endeavor. On the other hand these engines routinely flew across the ocean 60-70 years ago. It seems far-fetched that the idea couldn't be made to be both economical and reliable with today's technology. A reliable diesel that has the same power to weight ratio as a gasoline engine? Worth something to someone.


The fact that something worked long ago could indicate that it would work even better now, but it can also indicate that it proved to be inferior to the technology which became mainstream. Perhaps - as is now occurring with battery-electric cars - better technology will fix the biggest problems with the long-abandoned tech and changing circumstances will make it more desirable; however, I'm not aware of either technical improvements or changed circumstances which would now favour ported cylinders.

Again on the theme of converging technology, I note that in automotive engines spark-ignition gasoline engines have evolved very close to diesel, by adding direct injection, higher compression ratios enabled by that direct injection, and broader use of turbocharging. At the same time, diesels have evolved very close to modern gasoline engines, abandoning prechambers, adding multiple valves per cylinder run by overhead cams, applying electronic management, lowering compression ratios, and adding catalyitic exhaust treatment for emissions control. Gas and diesel reliability and power-to-weight are getting pretty close, without radical changes in engine configuration.

Remembering that we are in an EV forum, perhaps any powerplant design should be considered in the context of a hybrid application - that's the way Siemens clearly sees near-future aircraft development - and so the major constraints of matching a prop speed and accommodating take-off power demands are relaxed.


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## brian_ (Feb 7, 2017)

PhantomPholly said:


> Well tomorrow I head to Florida to get familiarity training in another innovative contraption called a Velocity. Engine is typical Lycoming, but it flys backwards. It is my hope that by the time I retire I can get a used one and convert it to electric, or perhaps an electric hybrid using something like the Wrightspeed microturbine generator. 350hp in a design intended for 200 ought to be inspiring...


How did the Velocity training go?

I think the composite pusher canards are great - although I've never had an opportunity to fly in one - and my mental design for a hybrid aircraft follows that pattern: with at least two props driven by electric motors mounted on pylons off the wings (like a HondaJet) it would look much like a Velocity V-Twin less the big nacelles (and with one engine in the tail). A tiny turbine would be cool, but just not very efficient; a more practical choice of engine would be whatever billions of dollars of automotive development has produced for hybrid car use... currently that might be from a Prius, in a few years it might be Mazda's HCCI.

But again, the innovation occurred long ago - the 1903 Wright Flyer was a canard, and the rest of the key design features of these aircraft were established by Burt Rutan in the 1960's with the VariViggen, although his VariEze of the 1970's became the archetype. I was sad to see all the Beech Starships destroyed when that variant of the pattern failed commercially. Now aircraft of this pattern are just unusual, not innovative or novel.


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## Terrence (Jan 27, 2019)

PhantomPholly said:


> ..." which could of course be used in an automobile. Capable of continuous operation at full power, this motor weighs only about 100lbs / 45kg.
> 
> Considering that an aviation motor rated at 350hp today weighs about 500lbs / 225kg, and that that motor is only rated to operate at 75% power continuously, that is rather incredible.
> 
> ...


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## brian_ (Feb 7, 2017)

Terrence said:


> PhantomPholly said:
> 
> 
> > ..." which could of course be used in an automobile. Capable of continuous operation at full power, this motor weighs only about 100lbs / 45kg.
> ...


_Edit note: more of this was PhantomPholly's original post than I realized, due to Terrence's omission of the closing quote tag._

It's not incredible - it's a nonsensical comparison. The function of an electric motor is minimal compared to an engine, since the motor can only take electricity rather than fuel. The comments which follow about batteries demonstrate that comparing an engine to an electric motor is useless, and that the only valid comparison is a complete powertrain:

fuel + engine + accessories (exhaust, etc), vs
battery + controller/inverter + motor + accessories
On that basis, for any useful range, battery-electric is heavy compared to decades-old aviation fuel and engine technology.



Terrence said:


> But that assumption is for flying at sea level, and also that the propulsion unit needs to power a slow (2500 RPM) propeller. A private aircraft might take advantage of the Tesla's high RPM to spin a fan, which is much more efficient that a propp at high subsonic speeds; and at altitude much less power is needed for high speed.


Not many private aircraft fly at high subsonic speeds and high altitudes. For those business jets, I agree that something that looks like a turbofan but has an electric motor instead of a gas turbine engine is plausible. Of course the power and energy requirements make that very far from current reality for any useful range.



Terrence said:


> What is the time TEMPERATURE limit for various torque levels for the Tesla; can't yet find that info. Aircraft need the high power only to takeoff, and altitude extends the time available for (current) battery technology.


Aircraft are worse than cars in this respect. While the car rarely uses peak power and the aircraft only briefly uses peak power (but at every takeoff), the car cruises on a much lower fraction of its peak power.


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## Terrence (Jan 27, 2019)

brian_ said:


> It's not incredible - it's a nonsensical comparison. The function of an electric motor is minimal compared to an engine, since the motor can only take electricity rather than fuel. The comments which follow about batteries demonstrate that comparing an engine to an electric motor is useless, and that the only valid comparison is a complete powertrain:
> 
> fuel + engine + accessories (exhaust, etc), vs
> battery + controller/inverter + motor + accessories
> ...


Brian. DO you have a source for a Tesla motor time-temperature-torque limits?


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## PhantomPholly (Aug 20, 2008)

I suspect most people don't realize how quickly battery tech is now advancing. While Tesla batteries today certainly cannot make up for the difference in energy density even with a 400 lb savings in engine weight, some that can are getting very close. One approach in the works promises up to 10x better energy density. That would be enough, including the motor weight savings, to achieve 65% of the "fuel" on board as the same weight in Lycosaurus + 100LL gas. Shorter hops unless you use cargo allowance for more batteries yes, but with "fuel" that cheap it might be worth the extra stops.


If range is an absolute requirement, an Aluminum Air flow battery under development may produce even better energy density than Jet A. This solution would require actual servicing (replacing the spent electrolyte with reprocessed solution, and sometimes replacing the catalyst part of the system). Cost at this point is unknown, but if it can be made competitive with carbon neutral synth fuels we could replace airliner turbines with electric motors also.


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## brian_ (Feb 7, 2017)

Terrence said:


> Brian. DO you have a source for a Tesla motor time-temperature-torque limits?


No, but in any car with significant power you reach the maximum legal highway speed in a few seconds, so full power is inherently very brief. Attempts to run Tesla cars on racetracks typically show power reduction as the car protects itself from overheating in a very small number of laps. For a practical exploration of motor temperature issues, I suggest reading this thread:
Tesla Powered Cobra Race Car
Keep in mind that this race car is light compared to an actual Tesla, so the Tesla would overheat its motor sooner.


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## Terrence (Jan 27, 2019)

Brian, thanks for the info and llnks. 
I'm still looking for temperature vs. torque test data for the motor.
Suspect the motor is the temperature choke point, as Jack Rickard showed me that its cooling is through the shaft and back out; also that the controller cooling is an issue, but maybe solvable using a custom controller, simpler for an experimental aircraft. Looking for a motor sans the car's gear reduction, as it would be driving a fan directly. The one I saw at EVTC was welded to the differential-reducer... but I think it could be cut off. 
But first, what temp vs torque of the motor at motor RPM?


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## brian_ (Feb 7, 2017)

Terrence said:


> I'm still looking for temperature vs. torque test data for the motor.
> ...
> But first, what temp vs torque of the motor at motor RPM?


I can't help there. Given that people who own and operate Tesla motors don't have this information, I think you'll have trouble finding an authoritative source.



Terrence said:


> Suspect the motor is the temperature choke point, as Jack Rickard showed me that its cooling is through the shaft and back out..


That would be the rotor cooling. It appears that both the rotor and the stator are liquid-cooled.


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## brian_ (Feb 7, 2017)

Terrence said:


> Looking for a motor sans the car's gear reduction, as it would be driving a fan directly. The one I saw at EVTC was welded to the differential-reducer... but I think it could be cut off.


Did you mean "EVTV" (rather than *EVTC*)? I don't have the patience to watch and listen to those videos, but I understand that they include a Tesla drive unit teardown.

I understand wanting to go *without gear reduction*, but that "welded" description seems strange: do you mean that the motor you are considering shares part of its case with the case of the transaxle? Yes, that does seem to be how Tesla drive units are constructed, and probably some others as well. Conversions using Tesla motors are generally based on using the complete drive unit, and that makes sense in a car; I've never heard of anyone using just the motor, although that doesn't mean it can't be done or hasn't been done.

Nissan Leaf motor housings and some others are distinct from the transaxle housing: they are bolted together, so the motor can be readily used without the transaxle.

What *rotational speed* are you planning for this fan? A major point of the design of the Siemens motor was to suit the low speed of a propeller; at a higher speed, an automotive motor might be suitable, although still not ideal.

While the requirements for *redundancy* in an experimental aircraft are not stringent, and electric motors are extremely reliable due to their simplicity, I would be concerned about having an electronic controller/inverter in the chain of single points of failure for aircraft propulsion. Another aspect of the Siemens design is two sets of stator windings, each driven by a separate inverter, for electronic redundancy in a single machine. Are you considering two fans, or two motors coupled to one fan, or just one motor and one fan? While not available as salvage from production EVs, there are "pancake" format motors which can be stacked on a single shaft, such as those from YASA.

The YASA motors have power density (kW/kg) at least comparable the Siemens motor. The YASA P400R would be workable at propeller speeds and possibly in their sweet spot with a fan; the larger YASA 750R would match a prop well, if you can stand the large motor housing diameter. Coaxial YASA motors were mentioned back in post #34, but that was in what appeared to be a counter-rotating coaxial configuration, so the motors would not provide full redundancy (a single motor or controller failure would leave only one propeller operating, rather than both propellers at half power).


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## Terrence (Jan 27, 2019)

brian_ said:


> Did you mean "EVTV" (rather than *EVTC*)? I don't have the patience to watch and listen to those videos, but I understand that they include a Tesla drive unit teardown.
> 
> I understand wanting to go *without gear reduction*, but that "welded" description seems strange: do you mean that the motor you are considering shares part of its case with the case of the transaxle? Yes, that does seem to be how Tesla drive units are constructed, and probably some others as well. Conversions using Tesla motors are generally based on using the complete drive unit, and that makes sense in a car; I've never heard of anyone using just the motor, although that doesn't mean it can't be done or hasn't been done.
> 
> ...


Brian, thanks for your comments.
Still looking for a Tesla motor without the gear reduction and controller needed, as I have talent in my aerospace-engineer-sons to assist here. 
Guidance to ... what location ... to see a prospective unit possibily still on a damaged assembly with or without the inverter. I'm in Illinois near St. Louis, but could go see the prospective unit.


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