Airplane PhysX Wheels

[DSabre 2325]

I just restarted work on some of my old mods and did a few more tests. Not really managed to resolve the tail drag issue (rolling away when standing idle) but confirmed some suspisions. Is anyone else working on tail drag airplanes and has some insights to share?

[NightIntruder 710]

At the very beginning, I would check the following things:
- is the CoG centered between all the wheels (I suppose there are 3 of them) ?
- are the sprungMass equal in those wheels (ie. do they have the same values) ?
- are the MOIs value the same for all wheels ?
- do the springStrenght and springDamperRate values relevant (properly calculated, not artificially weakened) to the sprungMass values ?
Later you can tweak the plane's behavior on dampers by moving CoG towards the main landing gear while removing part of the strength of the tail damper. From my experience, after getting the correct plane's behavior any further (dynamic) mass manipulation - for example through adding cargo or weapon mass to a plane - may result in wrong dampers behavior again, ie. a plane rolling away, etc. You may look at my YT channel, just unlocked some footage to show you it may be doable, but getting such a feature in multiple addons might be really tedious. 
Do you mind sharing what your suspicions were?

PS. I forgot to add one crucial thing - CoG also affects the plane behaviour in air, which means that after tweaking, the plane might become "tail heavy". You should do as much as possible to locate CoG within the aerodynamic centre of a plane. In that case, most of PhysX burden while taxing is intended to rest on the main landing gear (as IRL). It will also allow you to tinker with springDamperRate to create a plane that rather bumps on a runway surface than "glue" to it after touchdown.

[DSabre 2325]

Thanks for the reply. To be more precise, I did resolve it for most of my planes most of the time,  but only by trial and error instead of really understanding what is going on.

Last week I redid some of my old addons and nothing seemed to work so that was very frustrating. Now I got them half working again.

 

So I am wondering if there is a reliable non trial and error way to resolve this issue. Of course I also used copy/pasting successful setups a lot too (having the drawback that mass has to be equal). Tricycle setups are so much easier too do.

 

Yes agree with all your points. I always use 3 physx wheels no matter how many wheels the aircraft really has. I have summarised all findings in the first post which I update every now and then.

I think most of my recent problems setting up new planes and redoing old aircraft were in fact damper settings as you describe. In one case it was also droop and compression values. If they are too high the plane will roll off too.

[NightIntruder 710]

6 hours ago, DSabre said:

 In one case it was also droop and compression values. If they are too high the plane will roll off too.

 

I understand 🙂I must admit, I have used some 4- and 5-wheel settings too. The last one was for C130 and Tu124 and both planes worked really great, whenever loaded with 50-100% cargo, otherwise not really well. We just don't have proper tools at hand, ie. PhysX doesn't have a complex suspension simulation or it was not fully implemented into ARMA3. This is how I see things dampers-wise - apparently the forces are computed linearly and we need some coefficient to compute them more like IRL: the higher the load on damper is, the more resistant it becomes. I'm not sure springStrenght does it properly.
Regarding the drop/compression issue, I don't know if it's true but I found a similar thing - if the mass applied on a plane is too high, and dampers will hit the 100% (animPhase=1) then the force behind it hits the fuselage, and the plane will react by moving (ie. rolling away or oscillating on its dampers). Especially true for too "bumpy" dampers settings. While it is intended and desired (to bump a plane into air after hard landing or crash its gear), sometimes it simply creates an issue tho.
Going back to the main concern - no, I don't know any magic or systematic approach for creating PhysX suspension other than the one presented by BI on BIKI and trial and error way. Sure, there are some tricks like the fourth wheel on the tail for a taildragger, etc... But, basically, general aviation knowledge, skills in solving problems a bit, and literally doing exactly what is on BIKI is my way to solve a problem in addon making when aviation is concerned. Whenever I want to create problems for myself to solve later - I am tinkering with values and literally go crazy 😉 Which is not actually a healthy way of spending one's free time.
Oh, by the way - I have also been using proved PhysX set in different planes, just adjusting the settings if needed. But I do understand that in a large volume of addons, it may become PITA. I believe, that having one proven template for every kind of addon you build a new addon upon, is a good practice in such case.