[Stock Helicopters & Turboprops] Non DLC Will Always Be More Fun!

[OffsetIsMyName]

Continuing work on the cyclic swashplate + collective tail. Got something that you could say is a proof of concept working for the tail rotor part. The cyclic swashplate needs redoing and perhaps replacing the "swashplate" with a decoupler too to get it more compact, though I guess it has more friction to it. At least the tail rotor proto is tough to get turning, and then it explodes  Craft in KerbalX in case someone's interested.

Album a/XVkwo2x will appear when post is submitted

 

Edit: How can I get the imgur album visible? It just shows me the blue link to it.

Edited July 15, 2018 by OffsetIsMyName

[qzgy]

4 hours ago, OffsetIsMyName said:

Edit: How can I get the imgur album visible? It just shows me the blue link to it.

You can't..... Sorry. You can imbed single images using the bbcode but there's no good way to imbed the whole album. 

 

At least to my knowledge

Edited July 15, 2018 by qzgy

[OffsetIsMyName]

I've never tried to make a great flying prop plane, but now trying to tune a design to fly straighter with both throttle on and off. With throttle on everything is just fine in pretty much all speeds, but throttle down enough and the thing pitches down quite bad. I have the main wing angled 5deg, tail is horizontal, like are the engines (except for what they flex).

I am looking at Aero arrows with F12 and I see this:

 

That seems to be the case in all orientations except when going vertical, then the yellow lift vectors are quite even. I've noticed this plenty of times, but never thought anything of it.

In the above image the plane is close to horizontal and so are the engines and it does a decent job of going straight without elevator trim, but only when given power.

I understand the receding blades producing less lift, but when everything (except the wing) is horizontal that shouldn't be the case in my mind.

If I enable the Aero info on parts and select a blade I see constant lift & drag values that don't change during a rotation of the prop. I tried to pause the game to get the selected blade to be without that yellow vector and sure it still read the very same figures.

Is this just an UI issue with KSP or am I not understanding something? The pitch down tendency when power off would be understandable with uneven thrust from the props, but not sure if that's the case.

 

Thanks in advance for any help!

The plane at KerbalX. Main wings are a little too far back in the craft file though flies ok anyway.

[OHara]

2 hours ago, OffsetIsMyName said:

but throttle down enough and the thing pitches down quite bad.

I tried it just now and liked it. Turn off that silly SAS.  With throttle down, the airflow keeps the engine turning, creating a lot of drag, airspeed falls, lift falls, aircraft descends, so the nose drops.  The craft tracks the trimmed angle relative to prograde, as it should.  You can feather the props (extend 150%) before cutting power to reduce their drag.

[Edit: also the drag model seems to be confused by the fairings; alt-F12:aero-data in action menus shows the fairings and parts ahead of them as if they were disconnected,  where they should show near-zero entries in YP and YN.  When we enable "clip parts in editors" the final part attached to a node seems to determine what is attached there for airflow purposes, so maybe a re-assembly of fairings with that in mind can cut 20% from the drag.]

The aero-forces overlay sometimes drops a couple arrows on props.  If you switch to a prop and set camera to 'locked' you generally see the true arrows, though you might get dizzy.

Edited July 22, 2018 by OHara

[OffsetIsMyName]

2 hours ago, OHara said:

I tried it just now and liked it. Turn off that silly SAS.  With throttle down, the airflow keeps the engine turning, creating a lot of drag, airspeed falls, lift falls, aircraft descends, so the nose drops.  The craft tracks the trimmed angle relative to prograde, as it should.  You can feather the props (extend 150%) before cutting power to reduce their drag.

[Edit: also the drag model seems to be confused by the fairings; alt-F12:aero-data in action menus shows the fairings and parts ahead of them as if they were disconnected,  where they should show near-zero entries in YP and YN.  When we enable "clip parts in editors" the final part attached to a node seems to determine what is attached there for airflow purposes, so maybe a re-assembly of fairings with that in mind can cut 20% from the drag.]

The aero-forces overlay sometimes drops a couple arrows on props.  If you switch to a prop and set camera to 'locked' you generally see the true arrows, though you might get dizzy.

 

Thank you!

I took a quick flight without SAS and indeed it is quite logical. Just needs some flaps to be able to land easier I guess. Wouldn't want to give more control authority to the elevator as I fly with a keyboard and it's nice and slow now, but will need something to point the nose up at slow speeds.

It really does seem the lift & drag arrows are just not drawn. I flew away from KSC, toward west, and they all show as supposed. Turn to east and they get messy.

I will take a look on that fairing thing. If you mean the axle & bearing parts that are inside the fairing generating drag then I'm not actually sure what it should or shouldn't do. As the axle separates, the parts are still kind of inside the fairing, but some time ago when doing a "re-entry box" with a door & "claw" made from elevons I noticed that at least heat effects pass through everything if the parts are not the same craft / docked. Same for aero?

The middle fuselage fairing is probably useless, it was to allow me to attach the Wheesley plus a nocelle in front and in the hopes the fairing would take away any drag the Wheesley would generate. But it seems it doesn't.

Also thanks for explaining what the part clipping actually means  I haven't enabled it as surface attaching with EEX has done the job (plus that I didn't know obviously, but didn't need to look for ways to attach things like that). I get it now and how you explain it sounds it can be very useful in some contraptions to reduce drag.

Edited July 22, 2018 by OffsetIsMyName

[OHara]

8 hours ago, OffsetIsMyName said:

I noticed that at least heat effects pass through everything if the parts are not the same craft / docked. Same for aero?

I was about to say "yes" but just checked what the alt-F12:aero-data says, and am happily surprised to see the parts of the prop that are inside the fairing have no drag. [Edit: if the fairing is closed on the nose-cone at the front] 
Maybe the game remembers they were shielded at launch, and 'forgot' to un-shield them because the fairing never opened before they un-docked.  (Off topic, it would be nice if ships 'rescued' for contracts, when we bring them back to KSC loose in cargo bays, were also sheilded.)

But I was noticing a bigger problem, where the static nose-cones that are part of the main craft had big drag on their flat surfaces, which should have been joined up to the fairing walls. [Edit: Now I see. Those nose-cones were not intended to be static, but were meant to rotate with the prop, separated from the fairing.  In that case they would have a flat surface unprotected by the fairing.]  When I picked up the nose-cones, dropped them on inter-stage nodes, and closed the fairing on those cones, that extra drag went away.  

8 hours ago, OffsetIsMyName said:

The middle fuselage fairing is probably useless, it was to allow me to attach the Wheesley plus a nacelle in front and in the hopes the fairing would take away any drag the Wheesley would generate. But it seems it doesn't.

You can stack the Wheesley in front of the cylindrical pre-cooler air-intake, and then offset it, and stock KSP's rules assume no net change in drag from the offset; the Wheesley still counts as protecting the flat face of the pre-cooler.  This gives  a reasonable result, with no fairings needed.

The fairing where you had it could be extended to enclose the pre-cooler, removing its skin-friction drag, but also preventing it from taking in air (which is only fair).

Before: drag was 20.3kN at 82m/s and 800m;  After: drag is 17.8kN at 91m/s and 800

Edited July 23, 2018 by OHara
A little off topic, it looks like closed fairings and cargo bays *do* shield other craft that lie inside them, in KSP 1.3.1 and 1.4.4

[OffsetIsMyName]

7 hours ago, OHara said:

I was about to say "yes" but just checked what the alt-F12:aero-data says, and am happily surprised to see the parts of the prop that are inside the fairing have no drag. [Edit: if the fairing is closed on the nose-cone at the front] 
Maybe the game remembers they were shielded at launch, and 'forgot' to un-shield them because the fairing never opened before they un-docked.  (Off topic, it would be nice if ships 'rescued' for contracts, when we bring them back to KSC loose in cargo bays, were also sheilded.)

But I was noticing a bigger problem, where the static nose-cones that are part of the main craft had big drag on their flat surfaces, which should have been joined up to the fairing walls. [Edit: Now I see. Those nose-cones were not intended to be static, but were meant to rotate with the prop, separated from the fairing.  In that case they would have a flat surface unprotected by the fairing.]  When I picked up the nose-cones, dropped them on inter-stage nodes, and closed the fairing on those cones, that extra drag went away.  

You can stack the Wheesley in front of the cylindrical pre-cooler air-intake, and then offset it, and stock KSP's rules assume no net change in drag from the offset; the Wheesley still counts as protecting the flat face of the pre-cooler.  This gives  a reasonable result, with no fairings needed.

The fairing where you had it could be extended to enclose the pre-cooler, removing its skin-friction drag, but also preventing it from taking in air (which is only fair).

Before: drag was 20.3kN at 82m/s and 800m;  After: drag is 17.8kN at 91m/s and 800

Would seem the axle parts are exposed to air if the nosecone is detached too so it seems the fairing is pretty much useless how I used it. Wanted to have the nosecone spinning so I could leave the blades partly inside of it, mostly for the looks of not needing to offset so much and was easier to keep the elevons from colliding the static parts. It would seem it doesn't matter much even if they do collide for some reason, at least with the fairing.

Ah yes, I see what you did with the middle fairing. Doesn't even look bad used like that.

The bearings are way smoother with the nosecone being static and look a lot more stable too. And less draggy.

Thank you again for your help! It's been really helpful understanding how KSP handles these things, and more importantly that the plane flew just fine hah

 

The spinning nosecone idea came from the electric fairing bearings people seem to use a lot, and they separate the nosecone too it would seem (or at least it wiggles in air a lot). I though it would provide support in high G as the cone collides with the fairing, but sure enough it is much more better having the cone just static. I see no vibrations going at high blade angle higher speed and high G.

Edit: forgot to mention that it's a lot more fun to fly now too as it would seem the engines like being without the nosecone and you can turn and turn without any problems. Put in some flaps and offset the propeller a bit outwards and it's great.

Edited July 23, 2018 by OffsetIsMyName

[OffsetIsMyName]

On 4/1/2018 at 7:24 PM, jfrouleau said:

@EpicSpaceTroll139  I retested the flexible shaft this morning and it looks like you're right. The thing was already flexing the same way before I changed the staging. I probably just forgot to free one klaw the first time I tested it like an idiot. Still it bends to about 60 degrees for 2 klaws which is what I expect it to do before problems occur. For 90 degrees you would need 3 klaws like my synchropter use on each side. I verified for the fuel crossfeed and indeed the klaw doesn't have fuel crossfeed which makes me sad  So yeah... back to the first idea unless you also put the fuel tank on that last part of the articulation with the engine. Sorry I couldn't help more.

 

On 4/1/2018 at 7:55 PM, EpicSpaceTroll139 said:

Yah you're right. It does look like it is bending a total of around 60 degrees or so. Maybe my brain is tricking me that one looks like it's bending less than the other.

Definitely going to try putting 3 claws to get 90 degrees.

The main reason I don't want to put tanks on the ends of the claws because it means one would have to regularly transfer fuel to them which could get annoying. Ah well

I was reading the topic for older posts when I bumped into your discussion about the claw. I am not sure if you figured it out as I have not read everything, but a fuel duct to the claw allows for one way transfer.

 

Before decoupling

 

After decouping, activating engine and throttle up

 

After freeing the pivot

[jfrouleau]

@OffsetIsMyName This is fantastic ! I didn't know that. I imagine by combining this with the klaw bug I found which allow it to flex more than 30 degrees (see an example here https://kerbalx.com/jfrouleau/Experimental-Spinning-Klaw-Copter) we could make an interesting F-35.

[OffsetIsMyName]

I think I found the reason why many of my test craft are getting major compounding feedback loops with aero parts (wings only, control surfaces seem to behave differently).

I was trying to make a lowest possible weight craft that can reach LKO and during that I fiddled with it's blade angles which were made from the smallest wing parts available. I found that turning the wing part upwards and reducing the actual angle of attack increased the thrust. Then I tried putting them completely vertical, with zero angle of attack, spun it up and shortly there was huge lift vectors going horizontally (no actual lift in this case then) and soon the rad/s went over 50rad/s and craft got spaghettied & exploded. The blue lift vectors before the explosion were as long as you can possibly see.

Thinking from where the vectors were pointing at it seemed logical to slightly tilt the blades, still no angle of attack, so that the vectors would point more upward. 15 deg tilt and the craft launched 150m/s in the air before exploding. Mass was around 400kg with one of the smallest reaction wheels doing the job. Works just the same with turboprops though.

So in a nutshell, you get lift while getting almost zero drag. Anything can spin zero angle of attack wing parts pretty easily.

My reasoning behind this is that KSP calculates the current physics frame lift values by using the current velocity of the part, but the orientation of said part from the previous frame. Or something in between assuming it tries to semi-properly integrate the movement that "happened" during two physics steps. But then, I think drag values are calculated with the current velocity and the current orientation so that while lift is calculated with incorrect angle of attack values, drag is calculated, perhaps incorrectly too, but at least closer to the thruth.

[jfrouleau]

@OffsetIsMyName : I once experienced too some weird propeller behavior that may related to what you described (or not). I was trying to build a really heavy lifter heli with 2 contra-rotating rotors. The blades were made with WINGS just like you. I tried a version with fixed blades and it lifted about 250t. Then I tried another version with flexing blades attached to klaws and this is when something unexplained happened. Using the same wings and the same angle of attack the thing could lift... Idk I was at 529t and it lifted without effort and was even accelerating upward before the force was too strong it it kaboomed. So I don't know how much this could have lifted if it wasn't exploding from too much vertical acceleration. The mysterious force manifested itself when the blades were lifted vertically at their maximum angle of about 30 degrees. This is what happens when you have 500t + holding on 8 blades. Perhaps there is a bug to be exploited here  Unfortunately I deleted the craft because it was a failure.

[OffsetIsMyName]

9 hours ago, jfrouleau said:

 I once experienced too some weird propeller behavior that may related to what you described (or not). I was trying to build a really heavy lifter heli with 2 contra-rotating rotors. The blades were made with WINGS just like you. I tried a version with fixed blades and it lifted about 250t. Then I tried another version with flexing blades attached to klaws and this is when something unexplained happened. Using the same wings and the same angle of attack the thing could lift... Idk I was at 529t and it lifted without effort and was even accelerating upward before the force was too strong it it kaboomed. So I don't know how much this could have lifted if it wasn't exploding from too much vertical acceleration. The mysterious force manifested itself when the blades were lifted vertically at their maximum angle of about 30 degrees. This is what happens when you have 500t + holding on 8 blades. Perhaps there is a bug to be exploited here  Unfortunately I deleted the craft because it was a failure.

That sounds very familiar! Not sure if you tried, but did the propellers work just as fine when spinning at the "wrong" direction?

Because if you arrange the wing parts on a prop, be it electric or jet propelled, pointing vertical and without any angle of attack, but tilt them slightly so that the tips point outward (like in the screenshots above), it doesn't matter which way you spin the prop it will generate exactly the same lift anyway. Certainly a bug, but for what I tested it was hard (or for me impossible so far) to get into control. With some designs I could go way up (20km) around 150-200m/s all the way, but at some altitude the spaghettification got so strong that after separating the rotor parts to leave behind a lightweight rocket for orbit the whole craft was mangled up so bad it was useless.

But no way a small reaction wheel could generate that lift with regularly angled parts.

I have a feeling this might have an effect on many prop designs as during load they flex and the angles are no longer what they were in the editor. They seem to move both laterally, vertically and rotate under load.

If I use rigid attachment then I feel the prop behaves more realistic due to no centrifugal expanding or any other that stuff. Making the blades offset more just slows it down and the total lift remains more or less the same. (Edit: oh wait, would that suggest that with expanding blades the drag is calculated with the original offset? props gain so much more power when they expand than when they don't) But.. Add more blades and suddenly the rad/s is still the same but lift increases linearly with blade count.. That's not very realistic.

The design that I got the most out of was the blades with almost zero angle of attack, but tips pointing upward, maybe 30deg from vertical. The small angle of attack prevented it exceeding the 50rad/s limit as much as it does without anything producing drag. It still did, but without any angle of attack and thus almost zero drag I noticed speeds of 700m/s when the physics engine got really mad. A split second later kaboom

Edit2: forgot to mention, that due to the direction of the lift vectors and almost zero drag, it means that after reaching a certain rotation speed you can no longer stop the rotation. The lift itself tries to accelerate the rotation even more. I guess a completely unpowered flying contraption is possible if something external just provides an initial kick to the rotor.

Edited August 7, 2018 by OffsetIsMyName

[jfrouleau]

I didn't try to spin the propeller in the wrong direction but my rotor had a very similar configuration as yours. My angle of attack was not zero because I wanted to produce lift so it was between 2 and 4 degrees. Under heavy load the blades pointed upward to 30 degrees. It produced way more lift than it should have and once airborne the thing was unstoppable even if I reduced the throttle. It exploded 2 or 3 seconds later. Thats all I know, I did not investigated further but it's certainly interesting if you can put 0 angle of attack and produce great lift. Further tests would be needed before we can RELEASE THE KRAKEN !!! :-) (I love to say that).

I also tried at some point to make a Flettner rotor making a rotating cylinder out of control surfaces. The thing didn't work as expected. It turns out the lift vectors were completely in the wrong direction for an unknown reason. In this case the control surfaces were pointed parallel to the rotation axis, so 90 degrees instead of 30.

Edited August 9, 2018 by jfrouleau
Another example

[jfrouleau]

@OffsetIsMyName : I successfully replicated the bug you described. I confirm that there really is a force that come out of nowhere. Here is an example craft : https://kerbalx.com/jfrouleau/The-Magic-Rotor .

[OffsetIsMyName]

10 minutes ago, jfrouleau said:

@OffsetIsMyName : I successfully replicated the bug you described. I confirm that there really is a force that come out of nowhere. Here is an example craft : https://kerbalx.com/jfrouleau/The-Magic-Rotor .

Wow, great job! And it's unpowered when in flight haha so that indeed is possible! Seems then from your experiments it happens with control surfaces just aswell. For some reason I had differing results, though I spent a whole of 16 seconds trying that out and then went back to checking how the wing parts behave.

[seiryu]

Well,I aleady  made some"eternal engine" crafts year ago.

https://mobile.twitter.com/seiryu_ksp/status/923428492141723648/photo/1

[OHara]

On 8/6/2018 at 2:48 AM, OffsetIsMyName said:

My reasoning behind this is that KSP calculates the current physics frame lift values by using the current velocity of the part, but the orientation of said part from the previous frame.

I came to a similar conclusion, except that it seems to be the velocity that is dated.  

The physics time-step is 0.02 seconds.  I spun one of these eternal engine propellers with blades spaced by 45° at 2250°/s, so that the position and orientation of a blade at previous time steps is illustrated by the successive blades. 
The velocity defined by the change in position between time t−0.02s and t  
is applied to the blade as it oriented at time t
to compute a force applied to the blade in its position at time t,
but the overlay draws that force on the blade in its position at time t+0.02s.

I find it difficult to use this to make a craft like @seiryu's because the effect makes the rotor speed tend to run away. Greater rotational rate gives more lift until the rotor self-destructs.

Edited September 17, 2018 by OHara
corrected my thinking and conclusions

[seiryu]

This is the"eternal engine Mk1 prototype"

I found this  whole "eternal" events

when I was makeing this bucket wing craft.

 

And I think it isn't so hard to make stable effect

Edited September 18, 2018 by seiryu

[NoobTool]

I recently started playing KSP again after a long break. I was pretty bummed when 1.4 released and killed my favorite helicopters. I finally got around to fixing some of them. I also revived an old project that I had back-burnered. 

https://kerbalx.com/NoobTool/BumbleBug

 

Sporting the new UberNoob turboprop engine, the BumbleBug may be a bit smaller than my other helicopters, but she's pretty spunky.

 

She produces a bit over 800kN of static lift, and sports the same retractable grapple arm as the Wyvern. I built her originally just for something fun to putz about in, but it turns out she might be more useful for moving small payloads than the Wyvern. She's definitely more fun to fly. The Wyvern has her beat for top speed, but the BumbleBug is much more nimble. 

 

[qzgy]

28 minutes ago, NoobTool said:

I recently started playing KSP again after a long break. I was pretty bummed when 1.4 released and killed my favorite helicopters. I finally got around to fixing some of them. I also revived an old project that I had back-burnered. 

Looks nice. May I ask why not add another set of elevons to extend the blade and thus the static lift? Seems like it might be useful....

[NoobTool]

1 hour ago, qzgy said:

Looks nice. May I ask why not add another set of elevons to extend the blade and thus the static lift? Seems like it might be useful....

I tinkered with several rotor setups. Adding to the rotor diameter actually decreases the static lift. I've found that larger diameter rotors pair better with higher diameter blower plates (more torque). Since the engine needed to fit into a MK3 cargo bay, I was limited to 2.5m for the blower plates. I've tinkered a bit more with the rotors since I uploaded that craft (same parts, just played with the offsets/orientation). They're now pushing ~420kN of static lift a piece for around 840kN combined.

[klond]

 @NoobTool I got a chance to fly this last night and today.  Took her to the island at about 90m/s.  Landed successfully first time (took my time tho).

This thing is really packed with technology - the no-craft-switching arm action, rock-solid engine bearings, and easy docking of engine parts (the method-of-which kinda blew my mind).  It's got lots of fuel, but the mass is still dead center.  Low part count and I had no reliability problems.  The forward-motion jets are placed perfectly for a nice balance at speed so it's hand-free with SAS.

 There's a lot of impressive stuff going on here.  Wanted to let you know it didn't go unnoticed.

 Oh, I did hit the jet reverse button at speed.  Low altitude, didn't recover, but good for a few giggles.

[NoobTool]

5 hours ago, klond said:

 @NoobTool I got a chance to fly this last night and today.  Took her to the island at about 90m/s.  Landed successfully first time (took my time tho).

This thing is really packed with technology - the no-craft-switching arm action, rock-solid engine bearings, and easy docking of engine parts (the method-of-which kinda blew my mind).  It's got lots of fuel, but the mass is still dead center.  Low part count and I had no reliability problems.  The forward-motion jets are placed perfectly for a nice balance at speed so it's hand-free with SAS.

 There's a lot of impressive stuff going on here.  Wanted to let you know it didn't go unnoticed.

 

 Oh, I did hit the jet reverse button at speed.  Low altitude, didn't recover, but good for a few giggles.

Thanks for the feedback! It means a lot coming from you. My mind is routinely blown by your creations. 

I try to make my helicopters reliable and reusable. I have intentions of taking some to Laythe to help with construction and transport of surface modules for a large scale colonization project, but I keep running into snags. I was pretty disgusted when 1.4 broke my helicopters and I only recently got around to fixing them. The new bearings work great. The Kernuck Redux flies much better than the original ever did. 

In case you're interested in trying them:

https://kerbalx.com/NoobTool/Kernuck-Redux

https://kerbalx.com/NoobTool/Wyvern-Redux

Oh yeah, reverse thrust works best if you have enough altitude for a shallow(ish) dive. Still best to disengage before too long or she'll overflare and pendulum out of control.

Edited October 24, 2018 by NoobTool

[klond]

 Gotta keep this thread alive!

 Not a turboprop, but after many days of fiddling got a tiny leg-powered coaxial stuffed into a cargo bay.

 

 The tail decouples and folds out and redocks, then dumps all the heavy hardware.  We use the new context menu of the landing legs and set spring strength to adjust power.  Very exciting.

link

Edited December 1, 2018 by klond

[_Rade]

I've finally managed to build the helicopter rotor with the working swashplate and collective.

Rotor uses 2 decouplers to act as the swashplate, and then there is one rcs ball for each rotor blade captured between the decouplers. 4 elevons bellow the swashplate control its pitch and roll and this is then transferred to the rotor blades.

For the collective I've used 2 elevons to push up on the rcs ball that act as the bearing for the swashplate. You can toggle these by engaging the brakes, it's not perfect but it works.

Only problem is the rotor will only spin at about 7rad/s. I've tried adding more engines and using the reaction wheels but for some reason it doesn't want to spin faster. One thing that is interesting is that if you don't decouple the rotor blades the rotor will be able to spin faster, but then the swashplate and collective don't work.

Link to the craft file on KerbalX.