XF-3D

Kha'Zix

Active member
On another note I'm still trying to find something to model and started looking at a Piper J-3 Cub. I was never really a Cub person but I finally came around to thinking it's a cool plane, so one more added to my list.

View attachment 121794
How about a clipped wing cub? The one that can be downloaded flies weird. I haven't gotten it to perform quite like mine20200814_192932 (1).jpg20201016_173034 (1).jpg
 

technoid

Well-known member
I may have fixed the gear dancing problem but I need to test it more to be sure. I made a change to the pivot points and haven't been able to make it dance since I made the change. When you look at the gear dancing in a 3d field and zoom in on it what's really happening is the tires on both sides of the main gear jump back and fourth from right to left but the nose gear never does it. So a while back I had an idea but forgot about it and never tried it. What I did was align the pivot point x-axis for the tire and the tire collision mesh the same as the gear strut, so all those pivot points align vertically. I tried for quite a while to make the gear dance and couldn't but that's the way it works, sometimes I can't make it dance for a long time and then it comes back. So I'll keep playing with it and see if I can make it dance after the fix. Hopefully this will fix the problem because I really want to use the springy gear. Even though it makes the tire stick into the wheel well when it retracts. You'd think they'd disable the springy gear extension when the gear starts retracting. Anyway I hope I fixed the dancing problem.
 

legoman

Well-known member
I may have fixed the gear dancing problem but I need to test it more to be sure. I made a change to the pivot points and haven't been able to make it dance since I made the change. When you look at the gear dancing in a 3d field and zoom in on it what's really happening is the tires on both sides of the main gear jump back and fourth from right to left but the nose gear never does it. So a while back I had an idea but forgot about it and never tried it. What I did was align the pivot point x-axis for the tire and the tire collision mesh the same as the gear strut, so all those pivot points align vertically. I tried for quite a while to make the gear dance and couldn't but that's the way it works, sometimes I can't make it dance for a long time and then it comes back. So I'll keep playing with it and see if I can make it dance after the fix. Hopefully this will fix the problem because I really want to use the springy gear. Even though it makes the tire stick into the wheel well when it retracts. You'd think they'd disable the springy gear extension when the gear starts retracting. Anyway I hope I fixed the dancing problem.
tech I read your post and it might be because its almost 3am here, but I could tell it it was bouncing currently or not. mine is not. I could send you my AV which is not bouncing.

the scale springy gear moves the tire/wheel along the axis drawn between the pivot of the tire/wheels visual frame (~CS_RW, LW, SW) and the pivot landing gear's visual frame (~CS_RG,lg, etc). the amount of travel is determined the distance between the pivots and Stiffness. I dont think the weight of the gear effects the spring rate (pounds per inch). angling the pivot should not do much if anything I am 99 percent sure its angle does not effect the handling of the compression but it location most certainly does affect it.
 

technoid

Well-known member
tech I read your post and it might be because its almost 3am here, but I could tell it it was bouncing currently or not. mine is not. I could send you my AV which is not bouncing.

the scale springy gear moves the tire/wheel along the axis drawn between the pivot of the tire/wheels visual frame (~CS_RW, LW, SW) and the pivot landing gear's visual frame (~CS_RG,lg, etc). the amount of travel is determined the distance between the pivots and Stiffness. I dont think the weight of the gear effects the spring rate (pounds per inch). angling the pivot should not do much if anything I am 99 percent sure its angle does not effect the handling of the compression but it location most certainly does affect it.
First your question about is it still doing it. Last night when I wrote that post I could NOT make the gear dance after modifying the pivot points. But I should have waited till this morning to write that post because this morning I got the gear to dance after quite a few tries. So NO modifying the pivot points didn't fix it.

And yes I agree I didn't think the "angle of a line drawn" from the Tire Pivot (LW) to the Gear Pivot (LG) would cause a problem because I've used springy gear many times and never had a problem like this until "this plane". But since the nose gear never jumps back and fourth I thought it was worth a try to see what happened. But I should have tested it a couple days before writing anything about the modification I tried. So YES send me your AV and I'll try it. But you saw the video I did showing the gear dance it jumps back and fourth a lot and when you look at it close the jump seems to be the distance between the y-axis of the Gear (LG) and Tire (LW).
 
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technoid

Well-known member
legoman.

I've been playing with your AV a lot and so far the gear haven't danced but I need to play with it for a couple of days because sometimes I can't get it to happen for a day or two. So I'll let you know after I play with it more.

I noticed you did lots of stuff to the physics would you care to say what you think you did that would have fixed the gear dancing problem? Thanks for your help.

Also I noticed the aileron rolls don't wobble in your AV what did you do to fix that. I was thinking it was the pivot placement for the fuselage but I haven't played with it to see.
 

doug schluter

Well-known member
Thanks Doug I tried one thing that came to mind so if you have any suggestions let me know.
im trying to find where we had discusions about the gear i think it was G4 but haven't come across it yet

i found some of the discusions here , scroll down read what jeffpn and others were talking about " If the pivot is not set properly, springy gear will bounce uncontrollably. There is nothing a user can do to fix that, except not to use springy gear". with this comment so i take it back then the modeler had to set the pivots in the right place

 
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doug schluter

Well-known member
here is another link to the gear bounce fix dhk79 fixed his issue with gear bounce with better alignment of the pivots and gear. scroll down through the info

 
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