dhk79
06-03-2006, 11:23 PM
opjose asked me to post a message about how I resolved an over-long takeoff problem with an airplane I had just modeled, as this problem seems to plague many planes.
I was building the Velocity XL and the pre-release version Velocity XL, dtd 5/31/06 (http://www.knifeedge.com/forums/showthread.php?t=12923) needed pretty much the whole runway to get airborne. I had originally thought this might be a factor of the canard's design, which does require more airspeed to lift off due to a negative incedence of the main wings, but other forum members disagreed thinking collision meshes may have something to do with it too.
So, I taxied the plane up real close to the pilot viewpoint to get a good look and found that the steering wheel was bobbing up & down. On the down bounce it also seemed to penetrate the runway surface slightly. Going back to the model in 3DSMAX and zooming in so that the wheel and its collision mesh filled the whole viewport, you could see that the collision mesh was not round. It seems that when I added the collision mesh to go around the wheel and scaled it to fit, I missed the "scale uniformily" handle and pulled it out of shape. It wasn't by much, but it was now an oval shape rather than round.
To fix the problem, I didn't bother with trying to true the collision mesh. I just deleted it and made a new one. The new mesh used a cylinder as a base shape to give it a nice smooth, round rolling surface. Being sure to scale uniformly, I put the mesh around the wheel being careful to keep it centered on the wheel. I linked the mesh to the wheel and the wheel to the steering gear.
Checking the pivot points, I made sure they were first centered on both the mesh and the wheel; and then confirmed the Y axis was pointing towards the front of the aircraft.
As you can see in the Final Release (http://www.knifeedge.com/forums/showthread.php?t=12967) , the problem has been resolved.
Doug
I was building the Velocity XL and the pre-release version Velocity XL, dtd 5/31/06 (http://www.knifeedge.com/forums/showthread.php?t=12923) needed pretty much the whole runway to get airborne. I had originally thought this might be a factor of the canard's design, which does require more airspeed to lift off due to a negative incedence of the main wings, but other forum members disagreed thinking collision meshes may have something to do with it too.
So, I taxied the plane up real close to the pilot viewpoint to get a good look and found that the steering wheel was bobbing up & down. On the down bounce it also seemed to penetrate the runway surface slightly. Going back to the model in 3DSMAX and zooming in so that the wheel and its collision mesh filled the whole viewport, you could see that the collision mesh was not round. It seems that when I added the collision mesh to go around the wheel and scaled it to fit, I missed the "scale uniformily" handle and pulled it out of shape. It wasn't by much, but it was now an oval shape rather than round.
To fix the problem, I didn't bother with trying to true the collision mesh. I just deleted it and made a new one. The new mesh used a cylinder as a base shape to give it a nice smooth, round rolling surface. Being sure to scale uniformly, I put the mesh around the wheel being careful to keep it centered on the wheel. I linked the mesh to the wheel and the wheel to the steering gear.
Checking the pivot points, I made sure they were first centered on both the mesh and the wheel; and then confirmed the Y axis was pointing towards the front of the aircraft.
As you can see in the Final Release (http://www.knifeedge.com/forums/showthread.php?t=12967) , the problem has been resolved.
Doug