Simviation Forums

need help to sort this out
haveing a problem with my landing gear sinking into the ground when you rotate the airframe it's ok when running along the ground contacts point's are ok gear compression seams correct but when you speed to try a take off or landing the main gear sink's into the ground
so need some advice on whats going on???





http://www.simviation.com/yabbuploads/l ... fear_1.jpg

http://www.simviation.com/yabbuploads/landin_gear_2.jpg

hope the screen shots came out tryed the preview but not showing at moment

any ideas of what is going on

sorry about mess up with earlier post my mistake for not checking the spelling

Do other aircraft have the same issue in the same spot?  Ground terrain is not "hardened" like runways and not "flattened".  Drive a land vehicle through the same terrain to see if there is an issue.

thanks for the reply milton as to the terrain it does not matter if it is on land or on the runway it still does the same thing on the runway as well wil post a screen shot for you so you can see
these are my setting for the landing gear

landing_ settings

point.0=1.0,52.459,0.0,-10.300,1181.102,0.000,2.100,60.0,0.500,1.00,0.920,5.000,8.0,0.0,0.0,0.0
point.1=1.0,-26.229,-11.475,-17.100,1850.805,1.000,2.700,0.000,0.500,1.00,0.920,7.900,7.9,2.0,0.0,0.0
point.2=1.0,-26.229, 11.475,-17.100,1850.805,2.000,2.700,0.000,0.500,1.00,0.920,8.500,8.5,3.0,0.00.0

What is your static gear height?

Lou

Here are the numbers that may be causing the issue.

0.500,

milton thanks for the reply thats helped a bit suspension system is working better now but still having that sinking problem
the model is made in gmax here's the gmax info i worked on for the config data




see if you can spot anything wrong with it
eddie

Looks fine to me ...  Do your cfg numbers match what you have animated in frames 100-200 for suspension?  

You show .5 meters in the diagram but .5 feet in the cfg for static compression???  Should be 1.6 feet in total.  Try using 1.0, 1.583, .92 for 12" static, and a reasonable amount left for shock absorption.

I still recommend reanimating the gear for more vertical suspension movement, at least 24" but this may work fine.

Generally, sinking happens because FS thinks the ground is exactly where you defined it.  :-)  Be sure you understand where the ground is (to FS) by using the light method to visually verify what is happening.

Another cause of sinking is the gear is defined longitudinally differently in the cfg than on the visual model.  That places the rotational pivot point forward or aft of the mains.

Lastly, with speed and lift, the sim raises the aircraft slightly and extends the suspension.  If the cfg static compression and max to static ratio is not properly reflecting animation, the suspension will extend more (or less) than the aircraft's vertical lift causing sinking of the tires.

So, recheck all your measurements but I suspect what I recommended above will work.

hi milton
thanks for that info gave it a try looks as if i have to go back and redesign the gear it's still doing the same thing.

those new figure's made the wheel's sink deeper this time .

from reading your infomation i have the inpression that i may have made a mistake on the animation i will check this tho over the weekend and let you know if thats what it is

eddie

The important thing is that the animation vertical distance agrees with the distance specified in the contact points.  Static compression plus (distance represented by) max to static ratio must equal animation distance.

BTW, If you increase max to static that in effect pushes the wheels down farther and you have to adjust vertical height to ground (parameter 4?) to raise the aircraft back to ground level.

Frame 100 = uncompressed (hanging gear), 200 = fully compressed.  Vertical distance moved is needed for contact point data.

hi milton

checked the animation at frames 100 and 200 frame 100 shows gear hanging and frame 200 show's it compressed

really now ahve no idea how to solve this one ??

eddie

Eddie,

Have a look at this:

http://www.oregon-coast.net/Tutorials/C ... /index.htm

Lou

cheers lou will have a look over the weekend from my info above the gear hanging at 5.7meters uncompressed and 5.2 compressed  thats the main by the way so there a diff os .500 of a meter (18") imperial
of movement and those value's are from the cg to bottom of the tire's so in effect the compressed value should be at .500 if i understand the contact point 's correctly i have adjusted the value's many times now thats why i need the experts to figures this out lol

borke my brain trying to figure it out  ???

but thanks for the link

eddie

Hi Eddie,

I don't know if this applies or not. I found "in CFS2 at least"  with the B24 that with the less weight the more the tires sank in the ground, more weight the less they sank. Just oppisite of what you would expect.

The same thing happens as the ac starts to get airborne the tires start sinking as the weight is taken up by the lift.

I wonder what would happen it you swaped the numbers for compressed and uncompressed?

B24Guy

i would like to thank milton and the rest

for the help.
in trying to solve my problem with sinking landing gear
and the time they have spent helping me as well

ok the good news its solved now but what a bigg mistake i
made

when i adjusting  the [WEIGHT_AND_BALANCE] section i
for got to reset the
reference_datum_position=0.000, 0.000, 0.000
to those setting as a result the first postion was set
at +12.000 which you will spot straight away moved the
datum forward so that would make the gear sink into the
ground if left set at that postion
i had assumed that i had reset the value back to it
normal postion but did not check it !!!

anyway thanks guys for your help

few thing left to do to it now then i will release it soon

eddie