The Optimist

(Stock Electric Propeller Vehicle Showcase): Bringing power to the people!

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Hey guys, what's the best way to maximize propeller speed? My propeller planes can't go above 30m/s for some reason.

AKA, what's the best way to mimimize friction and maximize lift for an engine, and keep this lift at high speeds?

 

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1 hour ago, quasarrgames said:

Hey guys, what's the best way to maximize propeller speed? My propeller planes can't go above 30m/s for some reason.

AKA, what's the best way to mimimize friction and maximize lift for an engine, and keep this lift at high speeds?

 

The science behind KSP propellers basically follows real life although it seems simplified just like NeoAero is compared with FAR or real life. Generally speaking: higher angular velocity (from now on called rpm) means more potential to convert it into thrust, just like the wing of an airplane produces more lift at higher speeds.

After rpm there is another crucial element which is a departure of the behaviour of airplane wings: angle of attack. In regular terminology: propeller pitch.

I'm assuming right now you have a fixed propeller.

A fixed propeller only works efficiently at a single airplane speed corresponding with its rpm. This means an efficient propeller is able to change its pitch. For taking off you use a "fine" pitch, compare it with an airplane with a low AOA. Great for building up speed at first but soon you discover the airplane won't accelerate anymore. This is because the airflow hits the propeller blades like you're trying to fly forward with the nose of the airplane pointing straight down. So we change the pitch in steps or fluently, always observing engine rpm. This can be compared with changing gears in a car. Every propeller has an rpm "sweet spot" for best thrust/drag ratio, you want to discover what speed that is and during powered flight, try to keep close to it. When changing the pitch to more "coarse" you'll immediately see two things: a drop in rpm and an increase in airplane speed.

If you're unable to accelerate your airplane beyond a specific speed it can be due to a number of things:

  1. The drag of your airframe is too high.
  2. The mass of your airplane is too high.
  3. Your engine is not powerful enough.
  4. The diameter of your propeller is too small.
  5. You don't have enough control authority for the pitch of your propeller or your standard prop pitch is too fine.
  6. You don't have enough propeller blades.
  7. Your propeller is going transonic.

Coming back to the subject of changing gears in a car: we use low gears for acceleration or when climbing a mountain. Same with airplanes. When diving or when trying to make best of a glide when the engine has died, we use a pitch as coarse as possible to minimize resistance.

I recommend installing V.O.I.D. for an angular speed readout of your engine/propeller in rad/s. Keep in mind KSP is unable to have speeds higher than ~50 rad/s (477 rpm). Above that speed physics go gaga, joints become spaghetti and you generally end up with a RUD, SMEF or giant explosion.

Hope this helps.

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I know no one's interested in getting propellers to space, but I can't resist posting this.

Here's Propeller-Nerv SSTO. No other kind of engines/propulsion systems are included.

Album https://imgur.com/a/xTCoY will appear when post is submitted

This can be improved further by adding things. For now too many parts of it is infrastructure like fairings, docking ports and service bays. I'm going to see how far this kind of craft can reach.

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49 minutes ago, TheFlyingKerman said:

Is there electrical propeller design that can fly (indefinitely) on Eve or Laythe? I still don't understand how these designs work.

Since you don't seem to understand how these designs work, it's pretty simple actually. Due to limitations of the game (in that being no parts that act like bearings) the spinning bit of the propeller itself is detached from the main craft to be able to spin freely. However, whilst the propeller itself is technically detached, it's still kept in the same space using some sort of housing (either using a fairing, structual fuselage, or a mix of RCS balls and thermometers) this is how it spins.

As for how the propeller is powered (I may get off topic);

Electrical propellers utilise reaction wheels and trim controls (Alt +  W/S/A/D/Q/E) to spin the propeller. As of now, it is the easiest, most powerful, and most practical way to power propellers. Because the propeller is powered by electricity, it's very simple to just clip several RTGs to generate power. This creates infinite electricity, which makes the plane have infinite range. A disadvantage of this kind of propeller is that you have pretty much no thrust control; it's either FULL POWER or no power.

Turboprops use a jet engine's (or multiple) thrust to spin a propeller. In my opinion, turboprops are WAYY cooler, but have limited range, are bigger and bulkier, and less easy to build. They're much better with something like a helicopter though, since they have control (somewhat) over the thrust the propeller produces.

Tip jets use jet engines to spin a propeller, but unlike a turboprop, the jet engine is directly attached to the propeller (these kinds of engines were the first to fly propeller/helicopters in KSP). A disadvantage is the propeller itself has to carry all the fuel, instead of the fuel being on the plane. Designs are also quite bulky, and like an electric propeller, there's pretty much no throttle control (unless you are extremely quick with switching craft).

Hope you learned about propellers in KSP, and how they work. As for making the most optimum blade, I'm not the best for this, other people are much better at this than I.

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This thread is getting a bit stale, isn't it?

 

Don't care - I just flew my first ... well, second ... successful prop plane from KSC to the island.  Suchel very much enjoyed her first joyride around KSC, but Haldun's trip was more fraught with danger.  Suchel's joyride topped out at 65 m/s in a wide-gapped, open-air, rattle-trap that nonetheless had zero issues.  Haldun's trip to the island topped out at 105 m/s but started out with about a dozen false starts where the motor dashed itself to pieces against the fairing or departed the aircraft entirely, or the prop pitch adjust sent the motor into shock which required the fairing be dumped to allow a go-round back to KSC.  I've found that a perfectly balanced electroprop is a nightmare to glide once it's lost all of the nose-forward weight of the engine, but due to the extremely low speeds involved, nearly any landing (crash) is survivable.

Edited by HalcyonSon
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I built my first rotor, based on a microbearing I got as a craft file, 2 small reaction wheels and 6 blades. It lifts 2 tons (including itself).

Is there an optimum blade/reaction wheel ratio?

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Hello all,

Made a simple 3 speed electric plane and thought you guys might be interested. 

Ta6xejs.png

To change speed. Ive set action groups to the two reaction wheels that power the 2 blade prop. From the plane switch to the prop using either [ or ]. Now press either 1 or 2 to slow the motor. Press both 1 and 2 to set the motor to idle for landing. Switch back to the plane with [ or ]. It does takes a few times to get used to but soon becomes second nature. 

https://kerbalx.com/Avro_500/AV-3-Speed-Electric-Plane if anyone wants to try it out.

Cheers.

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On 4/30/2018 at 4:40 AM, Avro_500 said:

Hello all,

Made a simple 3 speed electric plane and thought you guys might be interested. 

 

<Very interested.  I'm glad you posted here on the forums because I didn't catch it on kerbalx.

 For a single engine this seems like a fantastic way to allow throttle control on electric.  Control gets tougher on multi engine stuff with so many craft to switch to, and sometimes has to be done quickly to hold back yaw effects.

 So I been tinkering on @erasmusguy 's Flugzeug d2.  I REALLY want to be able to control a motor without switching craft.

 

Begin experimentation (all this was over a bunch of evenings)-

 

Let's try 2 clutch plates.  So 3 craft - the frame, the motor, and the props w/shaft.

i5Or9nx.jpg

Force that fuel tank (that's connected to the prop) hard against the motor after the motor has been run up.  Makes the bearings really janky, but feels like it transmits almost 1/2 the motor's power.  Got airborne once for a few seconds.

 

Forget plates, let's try ball-in-a-socket to help with jankyness.

gFB2Oci.jpg

Not any better..  I had high hopes for this one.

 

I know, let's try wheels as the clutch surface.  

AOD9IRr.jpg

 Way smoother, but no matter how many wheels or what type, or strength of brakes, etc, I can only get 1/2 the RPMs thru them, and maybe 1/4 of the power.  Tried lots of suspension settings too.

 

K, skip the clutch.  Run up the motor and mesh 2 gears for straight-thru power.

lbDcKbS.jpg

NOPE.  Big badda boom.

 

Would you believe a grabber works, even at full RPM?

0RVX2yX.jpg

One grabbed, everything shuts off though, like when you dock.  Not exactly what I wanted :( 

 

If you use flaps to put pressure on the motor to slow it down you'll just end up just connecting the motor to the plane and rolling.

 Long story short -- @Avro_500 's hotkey control is good.  Grabber works for emergency shutdown.  And my clutches can't transmit enough power yet.  Gonna keep tinkering.

 

 

 

 

 

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I don't mind switching to be honest but I thought I'd have a look at your stuff. The issue with this type of solution is the part count and mass.

3EQOkAL.png

The bearing is directly attached to the motor on the right but it it still rotates as if was on a clutch (its starts to rotate on its own). The control surfaces act as a brake on the rcs wheel and are controlled by action groups 1 and 2 (1 being only slightly touching and 2 locked).  My kraken tech is awful though and the whole thing explodes at any speed :( but I think the idea is sound. Ill work on it a bit more before Ill post it on kerbalx.  

qSy8aEu.png

latest

Edited by Avro_500
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Kraken tech gives me a headache......... My [snip] poor bearing is so bad its acting as a clutch! Cant spin the motor fast enough to move anything. I give up. 

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21 hours ago, Avro_500 said:

I give up. 

Just take a break and come back to it later. Sleep on it and a solution may present itself.

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Sucky screenshot, but I had a go at an electric propeller driven craft for use offworld, interestingly, it has no bad torque habits, it is slow to take off though, mainly because I am not using deploy on the props, 8-10 small reaction wheels

1plN5LX.png

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It's evolving, it now has unlimited engine range, carries three Kerbals, Solar power recharging of main craft (i want to redock the engine but so far the claw has had krakenesque consequences), it sports a relay and also an antennae on the engine, this is supposed to be for exploring other worlds. Landing in water is hard, but once landed it floats nice and high, has parachutes for emergency landing (I am beginning to think this should be the standard way). Top speed of about 80ms, on take off it likes to break free of the ground suddenly and soar upwards, you need to be ready to intercept it, I am working on the wing placement to curb this.

Ducz3FL.png

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Finally released a version, here you can see it in it's grounded configuration gears up and everything deployed on an arctic science expedition, if you use the emergency chutes you also have a ladder to the top of the wing. It has a relay antennae but the commutron antennae on the probe core still seems to go out of range if anyone knows about comms.

I wanted to make it as easy and useful to use as possible, on Kerbin and other worlds. Some variations of props gave mean torque effects on take off. This takes off without input, which is as easy as I can make it! ;) and still reasonably fast.

S7BGsgg.jpg

PS: I also need to work on the docking so it can be timewarped.

Edited by selfish_meme
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Testing on Duna

5trHlck.png

So I made a little video on Reddit of flying this on Duna. I have come to realise that besides it lacking directional authority (which I will fix). The terrain does not really suit planes. I have had lots of issues because of the comparatively long take-off required compared to Kerbin, and the terrain grade changes on Duna. But shortening that take-off impairs its ability on higher atmosphere world's. I think I will continue this research in another type of craft.

Edited by selfish_meme
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Ubsurdly proud of this non succesful ubsurdity - it was made to see if there was a solution to the problem of twin engine startup torque on light gravity worlds. When you have two engines driving contra-rotating blades (obviously to counter torque issues) when you spin up the first engine, your craft is subject to the torque from just one engine for a while. I thought maybe if I drive both blades from the first engine, I may lose some power, but at least I have distributed the torque. then when I start up the second engine, both sets of blades will then spin up to nearly full power. The losses through this particular setup are more than 50% on both engines and what could fly easily without now barely generates any lift at all. Still it's one of the most complex gears I have ever built and it worked so........ win!

PS: I think a lot of the problem is that the middle gear is too small, I need to make it bigger and slower, then the fast gears are the top and bottom ones

 

PPS: yes that alleviated the problem, now it is much faster, still not fast enough, and size is now becoming an issue because I had hoped to shrink that stack down a bit

Edited by selfish_meme
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I made a high speed propeller plane! Capable of exceeding 400m/s in level flight.

Craft file: https://kerbalx.com/akash_rawal/Propeller-plane-07. Handling is horrible at high speeds and it will lose stability and disintegrate after 400m/s.

Album a/of9AhTG will appear when post is submitted

Edited by akash_rawal
Fixed a software gore with imgur album.
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Hey guys, though I'd share a project I've been working on. 

Album https://imgur.com/a/zVbUmua will appear when post is submitted

This plane is capable of flight on Duna, and can carry a maximum of 18 tons of cargo too! She's powered by two counter-rotating engines, each with 21 reaction wheels and 40 propeller blades. Maximum speed is 184m/s when empty. 

 

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Dude, why is there the HINDENBURG as your profile pic. Also, you copied that from stratenblitz.

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On 4/16/2018 at 5:13 AM, erasmusguy said:

Whats the record altitude for electric flight? 

I hit 11,xxx with @Squiddy's Javelin.  Might be capable of 12k.  You know it's got power if it can launch vertically.  :) 

SdiD9W1.jpg

 

Edited by klond

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21 hours ago, klond said:

I hit 11,xxx with @Squiddy's Javelin.  Might be capable of 12k.  You know it's got power if it can launch vertically.  :) 

SdiD9W1.jpg

 

I'm very pleased that you managed to squeeze that much altitude out of her, she was never designed for high altitude flight. :¬)

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