Design Question - Skids, no wheels

[pstrany]

Two questions for aircraft design. I have an aircraft that uses a center skid and two outriggers. I have created contact points for my skids (c_gear, l_gear, r_gear) but for some reason, CFS2 doesn't want to recognize these contact points so my aircraft sits embedded in the runway. Its not recognizing scrap points either, which is weird.

Second, this aircraft sat on a wheeled cart for take-off, then dropped the cart, and landed on skids. Is there a way to set this up for either CFS2 or FS9 so that I can get a reasonable facsimile of prototype operation?

Thanks!

Paul

[crossram]

Hiya, Paul.

163 ??

It's been a long time since I've fooled with any CFS2 stuff, but I think the basics are the same for CFS3, as far as the contacts info.

Don't know if it would work without trying it. But since the drop-able dolly that contains the 'wheels', isn't a fixed part of the a/c, perhaps setting the dolly as a load? That load could be placed as an a/c, needing it's own FM, aircraft.cfg, etc. That way the separate contact points (for the wheels) might work, and be drop-able.

Not sure on the skid contacts, except making sure the 'class type' is right. They should work.

Off hand, without trying things, that's as far as my thoughts go.
(I still have CFS2 installed, if I can be any help, and try things for you.)

Good luck with it!!

[tobob]

I may be totally wrong but, could you name the skid parts as wheels in gmax or fsds?

ie... r_wheel, l_wheel, c_wheel...

That way the sim thinks they are wheels.

[pstrany]

Hi;

thanks for the tips. I'm actually thinking of an Arado 234 A - the Antons had a center skid and two outriggers. They lifted the whole thing up onto a massive three-wheeled trolley, which was jettisoned upon take-off (the aircraft landed on skids alone.) The skids were retractable in flight.

It was one of these (the V7) that made the first jet reconnaissance flight, over Normandy. Up until that flight (august '44) Allied air superiority had prevented the Germans from getting any accurate intel on what was going on in the beachhead. With that single flight, the Germans were finally able to get a complete and accurate picture of just what they were facing. Of course, it was too late by then, as the Allies had 1.5 million men ashore, and so the Germans could do little more than record the tools of their own destruction, but it was nonetheless quite an accomplishment.

Anyway, I'm just exploring the possibility, and not having a lot of luck at this moment. I must be getting something wrong in the contact points, because for some reason, my airplane wants to sit on the runway like this:

http://www.virtualwings.org/8-234.JPG

The first job is to get it to sit right, the next to stick a trolley under it and get it to sit right. I can cut and paste contacts from other aircraft, and it will sit up a bit, but these contact points (which should be right for this aircraft) won't work. This is the relevant section of the aircraft.cfg file:

[contact_points]
max_number_of_points = 7
; location max have wheel max static max to damp time to time to assoc exten damage
; type, xx, yy, zz damage brake radius rotation comp static ratio extend retract sound speed speed
point.0 = 1, 11, 0, 0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
;point.1 = 1, 11, 0, -0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
point.1 = 1, -1.75, -3.25, 0.08, 1800, 0, 0.01, 0, 0.4, 2.5, 0.85, 3, 3, 2, 0, 0
point.2 = 1, -1.75, 3.25, 0.08, 1800, 0, 0.01, 0, 0.4, 2.5, 0.85, 3, 3, 3, 0, 0
point.3 = 2, -3.58, -20.66, 5.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0
point.4 = 2, -3.58, 20.66, 5.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0
point.5 = 2, -22.75, 0, 2.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.6 = 2, 16.67, 0, 1.50, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0

static_pitch=0
static_cg_height=0

I've broken it down this way to try and get a handle on the problem. so far, this has got me flummoxed.....

Paul

[hairyspin]

I may be totally wrong but, could you name the skid parts as wheels in gmax or fsds?

ie... r_wheel, l_wheel, c_wheel...

That way the sim thinks they are wheels.

And rotates them as you roll? Perhaps not. :redface: But I think you may have fore/aft, lateral and up/down muddled.

[hairyspin]

[contact_points]
max_number_of_points = 7
; location max have wheel max static max to damp time to time to assoc exten damage
; type, xx, yy, zz damage brake radius rotation comp static ratio extend retract sound speed speed
point.0 = 1, 11, 0, 0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
;point.1 = 1, 11, 0, -0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
point.1 = 1, -1.75, -3.25, 0.08, 1800, 0, 0.01, 0, 0.4, 2.5, 0.85, 3, 3, 2, 0, 0
point.2 = 1, -1.75, 3.25, 0.08, 1800, 0, 0.01, 0, 0.4, 2.5, 0.85, 3, 3, 3, 0, 0
point.3 = 2, -3.58, -20.66, 5.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0
point.4 = 2, -3.58, 20.66, 5.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0
point.5 = 2, -22.75, 0, 2.75, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0
point.6 = 2, 16.67, 0, 1.50, 1400, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0

static_pitch=0
static_cg_height=0

I've broken it down this way to try and get a handle on the problem. so far, this has got me flummoxed.....

Paul

If I've got this wrong (CFS3 is my area of experience), my apologies and I hope someone more practised can sort you out, but here goes...



The first four figures in each line are
contact point class (wheel, scrape, skid etc)
longtitudinal position (fore/aft)
lateral position (left/right)
vertical position (up/down)
and all of your contact points have positive vertical positions and are therefore above the model reference centre. The static height is zero, therefore the model is 'dropped' on the runway at the height of the model reference centre, after which it will sink until enough contact points make contact with the runway. So it's going to 'mole' as your picture shows.

HTH (and you have PM)

[thicko]

Paul,
The last time I tried it I had to use wheel entry's. I just set the brake to 0. For me it would not take-off. I do see an extra Contact point 1 in you entry.

point.0 = 1, 11, 0, 0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
;point.1 = 1, 11, 0, -0.5, 3200, 0, 0.01, 0, 0.5, 2.5, 0.85, 4, 4, 0, 0, 0
point.1 = 1, -1.75, -3.25, 0.08, 1800, 0, 0.01, 0, 0.4, 2.5, 0.85, 3, 3, 2, 0, 0

Perhaps it is this?
Cheers Thicko

[hairyspin]

The extra point 1 is commented out, surely?

[aeromed202]

I don't have cfs3 but if the cfg and contact points work like fs9 I can help. Does this aircraft work in fs9? If not, one thing that would help is visualizing the points. I assume you can add lights to this thing, so you create lights, I use green, with the contact points as locations. This often allows some quick understanding about problems as well as where the CoG or focal point is for the whole model. Just assign one red light at 0,0,0. The easiest way is to copy and paste a few existing light lines, number them sequentially, replace the location data and choose what light fx you want for each.

[hairyspin]

A good article on aeromed's tip is here at SOH:-

http://www.sim-outhouse.com/index.php?loc=articles&page=cp (http://www.sim-outhouse.com/index.php?loc=articles&page=cp)