Contact points

[gryshnak]

Questions, always more questions!  This time it's about contact points.

I read the Aircraft Container SDK, used the ruler function in FSDS to measure where my wheels touch the ground, and typed them carefully into aircraft.cfg.

When I start up FS9 the plane jumps up and down a few times, and launches itself down the runway at 30KIAS with the throttle still closed.  If I get up to flying speed and make a landing approach, I can touch the wheels gently to the runway and even get a puff of dust and a little screech at the appropriate time - which suggests the contact points are in the right place.  But the plane continues to descend, with a bit of careful piloting I can fly straight and level down the runway with the wheels underground!

The contact point is where the wheels (or skids or whatever) actually touch the ground, right?  So if they've been measured correctly, how can they go underground?

Before anybody asks:

[contact_points]
point.0= 1, 1, 1.4, -5.6, 1500, 0, 0.85, 0, 0, 0, 0, 0, 0, 0
point.1= 1, 1, -1.4, -5.6, 1500, 0, 0.85, 0, 0, 0, 0, 0, 0, 0
point.2= 1, -4.5, 0, -5.5, 1500, 0, 0.6, 0, 0, 0, 0, 0, 0

Gryshnak

[Firestriker]

Since you have a tail dragger, have a look at the SopCamel and Jenny config files. I think you have too many 0 values.

Lou

[Falcon500]

point.0=1, -4.5,  0.00, -5.5, 1700, 0, 0.40,45.0, 0.30, 2.5, 0.90, 3.0, 3.0, 0, 0, 235
point.1=1,   1.0, -1.4, -5.6, 2200, 1, 1.13,  0.0, 0.45, 2.5, 0.83, 6.0, 7.0, 2, 0, 235
point.2=1,   -1.00,  -1.4, -5.6, 2200, 2, 1.13,  0.0, 0.45, 2.5, 0.83, 6.0, 7.0, 3, 0, 235

try that that is from the Stock CFS2 F4F wildcat, but i modified it to fit your touch points


and this configuration would make the plane land like a tricycle going backwards with the body of the aircraft almost level?

[Felix/FFDS]

used the ruler function in FSDS to measure where my wheels touch the ground, and typed them carefully into aircraft.cfg.

If FSDS can do one thiing right, is set the basic contact points.

All you have to do is create small reference parts called gear.left, gear.right, gear.center (as well as for the scrape points), and set them where you want.

When compiling, FSDS will take the values of these reference points and modify the aircraft.cfg with these position values.

Having said that, FSDS does not alter the damping ratio, gear retraction/extension values, spring values, etc.

Check out the airprams.fsc file for the basic reference parts.

You can also tag the correct reference part name from the part properties dialog box, using the drop down list for "reference parts".
[reference parts]
pilot.view            ; view point in aircraft virtual cockpit view
gear.right            ; aircraft right landing gear ground contact position
gear.left            ; aircraft left landing gear ground contact position
gear.center      ; aircraft center landing gear ground contact position
scrape.front      ; aircraft ground contact point if tipped forward on nose
scrape.rear      ; aircraft ground contact point if tipped backward on tail
scrape.side      ; aircraft ground contact point if tipped to side
aircraft.radius      ; aircraft over-ride of aircraft radius for FS preview display
panel_light      ; aircraft position of panel light source
scenery_icon      ; API macro display shape in scenery design programs

[gryshnak]

Thanks for the help so far everyone, I didn't know about that Reference Parts bit!  And it works even better when you finally spot the checkbox marked "Process Reference Parts"  ::)

So, I now have the contact points set.  I've copied a set of lights to the same locations so I can see what I'm dealing with.  The plane is Santos-Dumont's 14 bis which flew in Paris 100 years ago, in 1906.

My next problem is the CG, which is obviously too far forward and makes the plane tip onto its nose as soon as it loads.  I added another red light (you can see it between the main wheels) which is directly below the reference point.  In FSDS the origin (0,0,0) is more rearward so I don't know how the reference point got to where it is.  I currently have the CG set behind this point but the plane still tips over forwards, which is very frustrating!

Right now my brain is too tired to work out what to do next, so I'm going to bed.  Suggestions on a postcard to the usual address please.  I made that plane in one day, so all the messing around with the contact points etc has actually taken longer than the creation of the model!

Gryshnak

[Felix/FFDS]

*IDeally* you want to take all measurements from the reference point, which does NOT have to be the model's 0,0,0 point.  When first compiling in FSDS, your data reference point and model center are usually one and the same.

I would suggest that you recompile a new model setting your model center at the FSDS 0,0,0 point.  (Select All parts, then move the assembly until you have your data/reference point at 0,0,0).   (NOte that if you have a VC and other models, you must also do the SAME translation)

Recompile into FS, process reference parts, etc.

If you have messed around in the aircraft.cfg file with the COG location, then manually set the COG point to 0,0,0.

Good luck

[gryshnak]

I have the contact points in the right place, I can see where they are by copying lights to the same locations.  So why, when I drop out of slew mode, do my wheels go straight through the floor as if they weren't there?  The plane ends up sitting on its skids (one under the nose, one under each wing) and then merrily bounces down the runway at 70KIAS.

I'm just about ready to take up stamp collecting, it's gotta be easier on the stress levels!

Gryshnak