How do you make robust time warp proof propellers?

[xendelaar]

Is there a way to attach propeller to a motor in a way that the propellers don't fly off the vessel when you initiate a 2x time warp while the blades are spinning? In my case, the craft gets very unstable and the whole vessel eventually disassembles.

I read somewhere that lowering the RPM to 300 could help? Any other tips would be great!  

I’m planning on circumventing a planet with a propeller plane.. so it would be helpful if I could speed some stuff up.

[AHHans]

1 minute ago, xendelaar said:

Is there a way to attach propeller to a motor in a way that the propellers don't fly off the vessel when you initiate a 2x time warp while the blades are spinning?

Well, I haven't found one.

To make matters worse: when I save while a plane is flying with spinning propellers then there is a chance that the propellers are messed up in the save-file and the plane is unflyable after loading the save.

[xendelaar]

21 minutes ago, AHHans said:

Well, I haven't found one.

To make matters worse: when I save while a plane is flying with spinning propellers then there is a chance that the propellers are messed up in the save-file and the plane is unflyable after loading the save.

didn't even think about reloading problems! thanks for the heads up. so prior to saving, I should brake the propeller and save after they come to a stop? 

did you experiment with a maximum rpm of 300?  I haven't tried it yet. 

Or maybe there is a way of "welding" the parts together? 

Edited July 26, 2019 by xendelaar
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[AHHans]

3 hours ago, xendelaar said:

so prior to saving, I should brake the propeller and save after they come to a stop? 

I haven't explicitly tried that, but that is my plan for when (if?) I need it. (After loading a savefile all the motors are off, so I need to get the plane into a situation to survive without power anyhow.)

3 hours ago, xendelaar said:

did you experiment with a maximum rpm of 300?  I

Nope.

I did notice that the deformation that you can see in a "healthy" propeller (no time-warping, no saving or so, just looking at the propeller spinning) gets better when I lower the RPM from 460 to 440. But not better enough to survive time-warping.

[Loskene]

I think this is just a physics engine thing squad have had a hard time getting around, since the best they could say when releasing the props is that they should pull away from the point of rotation "a bit less". No idea what causes it, I'm not a programmer, but it's an issue that's been with us a long time and so smacks of a Unity problem that's out of squad's hands.

[AHHans]

@Loskene The root of the problem is not really something Unity specific. Whenever you (try to) simulate rotating physical objects in cartesian coordinates you'll run into these kinds of problems. In cartesian coordinates the forces on rotating parts change all the time, so if you only compute the forces at the beginning (or end) of a time-step, then you'll never get them 100% correct. If the rotation is slow compared to the time-steps of the simulation then the effects are small (or negligible), but at higher RPMs you'll get these simulation artifacts.

You could get around that by doing the simulation of the rotating parts in a co-rotating reference frame. But implementing this is a teeny, tiny bit of work. (I'd estimate about one master thesis worth of work.)

P.S. What Mister Bond has to say about this issue.

[Gargamel]

Moved to BG discussion. 

[xendelaar]

On 7/26/2019 at 1:59 PM, AHHans said:

I haven't explicitly tried that, but that is my plan for when (if?) I need it. (After loading a savefile all the motors are off, so I need to get the plane into a situation to survive without power anyhow.)

Nope.

I did notice that the deformation that you can see in a "healthy" propeller (no time-warping, no saving or so, just looking at the propeller spinning) gets better when I lower the RPM from 460 to 440. But not better enough to survive time-warping.

lowering the rpm to 300 does make the craft more stable in time warp.. but due to deformation, the blades get oriented in a weird way.. which causes the velocity drop almost tenfold!   

[Cannoneer_Mae]

Try offsetting the propeller blades into the rotor itself (so they get pushed out to their normal position in time warp). This will likely significantly lower performance at 1x speed / any speed below the time warp that the blades were designed for.

Perhaps pistons could be used for variable offset if you want functionality at different time warps, probably using the largest rotor head.

Alternatively, you might just need to look into creating a faster propeller craft. See contra-rotating propellers and experiment with variable pitch propellers and the perfect pitch for your top speed.