The case of the bouncing jet.

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The case of the bouncing jet.

Postby Pyrat » Sun Oct 03, 2004 6:10 pm

I downloaded the Eclipse 500 from avsim.

When I switch from the VC to the Tower view I can see the jet bouce up and down three time and then crash.

lololol :o

Any ideas what could cause this?
Last edited by Pyrat on Sun Oct 03, 2004 6:10 pm, edited 1 time in total.
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Re: The case of the bouncing jet.

Postby andyjohnston.net » Sun Oct 03, 2004 10:23 pm

That's nothin'.  I have a jet I'm building where it works great while the tanks are full, but If I let the fuel get really low it bouces like a kangaroo!

It's caused by the contact points, check the damping ratio.

Good luck and report on your results.
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Re: The case of the bouncing jet.

Postby Pyrat » Mon Oct 04, 2004 6:01 am

I have no idea what the contact points do. ???

The Damping Ratio isn't used in any files that I have looked at.  Do you have a sample Damping Ratio entry?

Thanks
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Re: The case of the bouncing jet.

Postby Milton » Mon Oct 04, 2004 7:22 am

In the aircraft.cfg file, the Contact Points section describes and defines your gear relative to the rest of the aircraft.  It also defines the crash or "touch" points like the wing tips, the nose and tail extremities.

Part of the gear contact points describe your suspension, movement, compression, and 'shocks"  or stiffness.

The combination of the static compression, max-to-static ration and damping defines the "spring load" and stiffness.  Parameters 8 and 9 define the total suspension travel.  Parameter 8 indicates how much of the available suspension travel is used when sitting on the tarmac.  Parameter 9 defines how much of the total suspension is left as a ratio.  Ideally, these numbers will exactly match the animation in the model.

Below are the first 3 contact points for the Lear 45.  The // entries define the positional parameters in each contact point.  Contact points 1 and 2 are the main gear, and 0 is the nose gear.  Parameter 10 is the damping suggested above.

       //0  Class
       //1  Longitudinal Position        (feet)
       //2  Lateral Position             (feet)
       //3  Vertical Position            (feet)
       //4  Impact Damage Threshold      (Feet Per Minute)
       //5  Brake Map                   (0=None, 1=Left, 2=Right)
       //6  Wheel Radius                (feet)
       //7  Steer Angle                         (degrees)
       //8  Static Compression           (feet)  (0 if rigid)
       //9  Max/Static Compression Ratio
       //10 Damping Ratio               (0=Undamped, 1=Critically Damped)
       //11 Extension Time              (seconds)
       //12 Retraction Time             (seconds)
       //13 Sound Type
[contact_points]
point.0=1, -10.00,   0.00, -4.35, 1181.1, 0, 0.6349, 46.8, 0.3000, 2.5, 0.9100, 10.0, 10.0, 0, 260.0, 260.0
point.1=1, -37.25,  -4.75, -4.87, 1574.8, 1, 0.6349,  0.0, 0.4798, 2.5, 0.5456,  9.0,  9.0, 2, 260.0, 260.0
point.2=1, -37.25,   4.75, -4.87, 1574.8, 2, 0.6349,  0.0, 0.4798, 2.5, 0.5456,  9.0,  9.0, 3, 260.0, 260.0

The aircraft.cfg can be edited with Notepad.
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Re: The case of the bouncing jet.

Postby Pyrat » Mon Oct 04, 2004 2:29 pm

Thanks for the info!
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Re: The case of the bouncing jet.

Postby gregbrown » Tue Oct 05, 2004 6:01 am

hi milton! ive a small problem with a jet as well , hoping you may be able to help. ive dealt with contact points before although without always having proper definitions of what setting does excactly what - not too user friendly please see topic 777 300 engine vibration .cheers  8)
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Re: The case of the bouncing jet.

Postby Pyrat » Thu Oct 07, 2004 5:12 pm

Well I made a little progress. My aircraft still bouces some but at least it doesn't crash. lol
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Re: The case of the bouncing jet.

Postby Woodylepic » Mon Oct 11, 2004 4:04 pm

Milton are right if its bounce again just lower the damping again !

i have experience same thing on a projet i have made last years !  hope this help !
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