Sign in to follow this  
Guest Milton

"springy" gear

Recommended Posts

Not sure what to actually call the effect, but with a lightweight(460 pound) craft sitting on tricycle gear, the plane wants topitch back and forth when power is applied or landing and applyingbrakes... to the point of the wheels dipping below ground.Is there a way to reduce the "springiness" of the gear other thanthe contact points? I've tried reducing compression ratios, staticcompression distance, and damping to no avail and if set too low,the plane will start wildly bucking and bouncing around, jumpingup off the ground, etc.In other words, is there a way to make the gear rock solid stiffso that it doesn't become a rodeo horse?

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

Setting the contact points exactly for the animated distance is key to great suspension.Divide total animated (frame 100-200) distance by the static compression (compression at rest on the ground (about 40% of total normally)) to get max to static ratio. Damping should be around .7 to 1.0, the higher number for critical damping/stiffness.If your engine thrust line is vertically distant from the CoG, you will get a sizeable pitching moment causing downward or upward nose movement. Ensure the thrustline is close to the vertical CoG position.Also ensure your CoG is near 25% MAC position, and main gear appropriately placed. If not, this will cause one gear to be very compressed and the other to be lightly compressed causing steering and handling issues along with the suspension problems.Hope this helps.

Share this post


Link to post
Share on other sites

> Setting the contact points exactly for the animated distance> is key to great suspension.This senario is... there is no suspension on this plane (anultralight), so there is no keyframed animation.> If your engine thrust line is vertically distant from the CoG,> you will get a sizeable pitching moment...Very slightly +, as in 0.23 ft above visual model center (0,0,0origin) and 4.18 ft foreward. CG = ref = 25% mac (that is, allare colocated). The model's "physical gear CPs are -1.2 ft long,+/- 2 ft lat., and -3.9 ft vert. but the config CPs need to be-4.1 ft vert to show them as not sunken below ground at rest.They all sink below ground when the plane pitches slightly forewardunder power or when the wing tips sway up and down.No steering issues except that the steering animation from keys0 to 100 (360 deg. on part "c_wheel" which is the nose wheel forkassembly) does not animate in FS. Does the 360 turn need to behappen between keyframes 100 to 200?

Share this post


Link to post
Share on other sites

Actually, the visual effect I see with this plane at rest islike it's teetering on a needle with its point somewhere around0, 0, -2 (the wheel contacts being at -4.1 per previous msg).It's a highly damped "teetering" that doesn't make the wheelslook firmly planted on the ground as they dip up and down inand out of it.

Share this post


Link to post
Share on other sites

Nose steering must be animated 100-200. It helps to use at least one position key at 150. Animate in a counter-clockwise direction (as in turning left).Not sure FS can handle well such a short wheelbase without suspension. It may help to take a look at other micro-lites. I would be curious how they resolved the issue (aside from exaggerated wheel base).

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this