DLC Rotor Blues-exploding copter and slow plane

[Klapaucius]

I'm a little frustrated at the moment. I certainly did not expect to immediately create a wonderful flying machines, but I also did not expect to have my first helicopter attempt simply explode as soon as I launched it.  I was hoping to muck around for the next few hours trying to see if I could make a viable copter.  But the exploding thing is just annoying.  Any thoughts?

 

 

Also, what am I doing wrong that twin four-bladed props on the highest power and rpm settings only push this plane along at 26 mps?  I've tried varying my blade pitch angle, but so far no luck.  Suggestions on this one? I have no experience with stock props, so I assume I am missing something fundamental here.

Any suggestions? 

 

 

[bewing]

I haven't messed with 'copters, so I don't know the answer to that.

As far as the plane goes -- props depend on lift. Which depends on the size of the lifting surface. Those blades are very small, and they are not lifting surfaces -- they are control surfaces. So their lifting area is only half the size of an equal-sized modular wing part.

Also, props in general are weak. That plane there would need two afterburning jet engines to fly at a decent speed. You built a massive spaceplane, and gave it the engines of a cessna. You might be able to get it to go a little faster by putting a second rotor on each engine. I don't know whether inline or parallel would work best.

 

[Klapaucius]

1 hour ago, bewing said:

I haven't messed with 'copters, so I don't know the answer to that.

As far as the plane goes -- props depend on lift. Which depends on the size of the lifting surface. Those blades are very small, and they are not lifting surfaces -- they are control surfaces. So their lifting area is only half the size of an equal-sized modular wing part.

Also, props in general are weak. That plane there would need two afterburning jet engines to fly at a decent speed. You built a massive spaceplane, and gave it the engines of a cessna. You might be able to get it to go a little faster by putting a second rotor on each engine. I don't know whether inline or parallel would work best.

 

To be honest, that is a pretty stuffed up system then. Considering the physical size of the rotor, it ought to be able to do better than power a Cessna.  On a real plane, those would be huge props.  So that what the heck are we supposed to use for blades?  Many stock props I have seen posted use those.

 

That is not a huge plane--it is a 16 passenger aircraft, half the capacity of a DC-3.  And for kicks, pulled off the props and put two Wheesleys on it. They push it along at a respectable 230 m/s.  

 

PS. I tried stacking the rotors. It got me 3 additional m/s.

[bewing]

They aren't intended to be used for propellers. Maybe props will come along later. This stuff is intended to be used for robots.

 

[Klapaucius]

2 minutes ago, bewing said:

They aren't intended to be used for propellers. Maybe props will come along later. This stuff is intended to be used for robots.

 

Yes, but this:

https://kerbalx.com/Brikoleur/BAK-50-x2

 

I just tried it out. It is brilliant.

 

[FleshJeb]

7 hours ago, Klapaucius said:

That is not a huge plane

KSP parts are denser than real life, and the lifting surfaces are less powerful. What seem like reasonable real-world proportions, aren't.

[Klapaucius]

2 minutes ago, FleshJeb said:

KSP parts are denser than real life, and the lifting surfaces are less powerful. What seem like reasonable real-world proportions, aren't.

Either way, it seems that my dreams of building easy stock prop planes have yet to be realized.  I've built an awful lot of planes (of which the above is a pretty lame example--just a test bed), so perhaps this is another hint that it is time for me to go back to space.

[Foxster]

A desire to have or to be able to build easy stock electric prop engines has been a wish for many players for a long time. It does feel as though out of all the loveliness of Breaking Ground this was an unfortunate miss.  

[KerikBalm]

Well, I don't know what the cause of that helicopter explosion is, but I was able to get a working helicopter very quickly. I of course used contra rotating blades for the torque problem.

I only use 1 standard size rotor for power. I had blades on the top, and blades on the bottom/a part attached to the bottom. The torque makes them spin in opposite directions. I used a tiny unpowered rotor to prvent torque from being transmitted to the main body of the craft:

I couldn't get it to fly much over 20 m/s in level flight though.

I have a feeling these things will be very finniky, but as you've seen from Brik's craft file, they are useable... but harder to make than an SSTO (at least for me). The one above I tested on Duna, and it worked there.

I tried to make a practical one that I could use to explore duna, one that could fit in a mk3 bay and be flown over larger distances, carrying a full science loadout (including cargo bay for the surface experiments):

It flies, but worse than my first helo, even using 2 motors instead of 1.

I've found blade pitch to be very important:

and using variable props can really help give adequate power over a wider range of flight speeds (although I guess you can use a fixed pitch blade optimized for the high end). The RPM is so low that shallow blade angles will simply reach zero angle of attack at a moderate speed, and thus thrust from them drops off rapidly as you approach that speed. To go faster, the blades have to be closer to perpendicular to the direction of travel.

I'm a bit disappointed that I could get better performance out of the old stock props:

Reaction wheels and not being part of the same craft meant that torque could be ignored, and varying prop pitch was as simple as moving a slider. I've found that contra rotating props don't allow for thise control, so I'm experimenting with action grouping to "deploy" (and inverse deploy on the one rotating the other direction) to at least give me the ability to select between 2 blade pitches.

Here you can see my old prop with the blades looking nearly parallel to the direction of travel:

I think the RPM limit needs to be raised, and the torque needs to be raised, they shouldn't be beat by the old reaction wheel based designs. IMO.

 

[swjr-swis]

On 5/31/2019 at 9:14 AM, Klapaucius said:

Also, what am I doing wrong that twin four-bladed props on the highest power and rpm settings only push this plane along at 26 mps?  I've tried varying my blade pitch angle, but so far no luck.  Suggestions on this one? I have no experience with stock props, so I assume I am missing something fundamental here.

The BG rotors can't do enough RPM to produce significant prop power. Apparently it can still be done by using the rotors as free bearings, adding one or more regular reaction wheels, and using the RW torque to power the prop. I've seen some people post about putting rotors in series on each other, effectively adding their individual max RPM to each other - not sure if that has been successful yet.

High-RPM rotors and single/minimal part-count stock props will remain on the wish list for now.

[Klapaucius]

1 hour ago, swjr-swis said:

The BG rotors can't do enough RPM to produce significant prop power. Apparently it can still be done by using the rotors as free bearings, adding one or more regular reaction wheels, and using the RW torque to power the prop. I've seen some people post about putting rotors in series on each other, effectively adding their individual max RPM to each other - not sure if that has been successful yet.

High-RPM rotors and single/minimal part-count stock props will remain on the wish list for now.

I tried doing in series, but there is an RPM limit. Stacking them got me an addition 3 m/s.

[cerberusti]

It depends what you mean by working.  I have a test craft that can take off vertically under rotor power:

https://steamuserimages-a.akamaihd.net/ugc/800991879186028145/BD40FDBDC1A784563C2D9FD8988B574538A9A3EF/

https://steamuserimages-a.akamaihd.net/ugc/800991879186028579/F4508A401CF7B7D1CDE01FAFF18E81EC0298B7E6/

transition to forward flight:

https://steamuserimages-a.akamaihd.net/ugc/800991879186028936/C1192EA32ABF8204E3803CBB6A638540A516A9BB/

get up to about 70 m/s still on rotor power only:

https://steamuserimages-a.akamaihd.net/ugc/800991879186029237/A2A44813643BE5CA245C8028D79431B7D07E835C/

and fly on jet engines with the blades feathered and off:

https://steamuserimages-a.akamaihd.net/ugc/800991879186029531/380493D634BFC8741FA4D937D4DFB9554C769A4F/

Hotkey groups set the rotor angle between 0, 15, and 60 degrees, switch hinge orientation, and power the engines.

It has more than enough RTGs in those bays to fly forever, and even to add extra rotors (this is a test bed).  It is very stable and difficult to destroy, unless you feather the blades fully with the motor power on.

 

I also have a plane which can lift a mammoth and a couple of suitably sized tanks into the air by the end off the runway on propeller power.  I have not managed to get it to fly long without disassembling itself, and even taking off is a 10% of the time affair.  That does make use of multiple stacked rotors from both directions, but you cannot get much above 500 rpm.  If you stack 2 on top of each other on some batteries, it sums to just over 500, but that is also true if you stack 5, or if you stack 4 with two rotating from the other side.  It very briefly exceeds 600 total, then seems to limit itself to around 500 for the entire stack no matter how large.  Once you hit the limit one of the rotors will also start wobbling quite a bit.

You can stack rotors (either opposed with opposite motor rotation or on top of one another) to increase speed so long as it is still under the limit.  You can exceed the power the motors used to set rotor pitch can handle with a stack and large blades, in which case you need bigger ones. 

I decided it needed to be smaller for stability.

 

Edited June 3, 2019 by cerberusti

[Snark]

Moving to Breaking Ground Discussion.