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Perfecting Suspension Setup (Repost)

Milton Shupe

Milton Shupe

Staff Contributor
Staff member
I did not have a copy of this original thread but fortunately Felix had copied it over to the FFDS Tips forum. Thank you Felix.

Introduction

I struggled with suspension for a long time before I figured out the simplicity of it. I have been asked and have helped many others with suspension setup and thought maybe this would help here.

There are really only four aspects to this:

1. Provide an ample distance for suspension animation from frames 100 to 200 (tire height~)
2. Vertical distance to ground is the "hanging" (in the air) suspension measured at frame 100 (from Reference point to bottom of tire).
3. Static compression should be measured at max gross weight on the ground and be 75-80% of total animation.
4. Max to static ratio = total animation distance / static compression

Look at this A-26C with its hanging gear on approach:
http://www.sim-outhouse.net/downloads/SOHTeam/suspension_hanging.jpg

Aircraft have more total suspension movement than meets the eye on the ground. Just like with a car on a jack, suspension hanging is quite a distance relative to what you see when it's on the ground. Important: To setup aircraft suspension to improve visuals on takeoffs and landings and eliminate stiffness on the ground, ensure you animate suspension movement to at least 3/4 the height of the tires, more is usually better depending on the aircraft.

Setup in the contact points then becomes critical so that your animation is used fully and responds correctly. Check Tesco Offers and Lidl Offers. For a fully loaded aircraft (which is how I set my suspension visuals), I typically use 75-80% of total suspension movement for static compression. Think about it. Hanging gear plus full gross weight = most of the available suspension movement. Then divide the total distance by the 75-80% ... you get about 1.2 - 1.4 for max-static ratio. This allows all that suspension to be used at gross, allows the suspension to drop on takeoff and gives you a nice, softer landing. Carrier landings are greatly improved with lots of suspension travel.

For a really nice basic graphic explanation of hanging gear, static compression, and fully compressed gear, read this by Jerry Beckwith: http://www.mudpond.org/contact_points.pdf


Setup
Basic steps to suspension setup can easily be accomplished with the design tool and aircraft.cfg open.

Before you start, ensure you have the aircraft properly positioned in your design program so that CoG/FS Reference are where you need them. Example:
http://www.sim-outhouse.net/downloads/SOHTeam/s0.jpg


See Lou "Firestriker" Holland's tutorial for more examples: http://www.oregon-coast.net/Tutorials/CofG/index.htm

The suspension setup steps are:
1. Determine vertical distance from CoG/Ref point to fully extended (hanging) gear (keyframe 100)
http://www.sim-outhouse.net/downloads/SOHTeam/s1.jpg


This is also the distance to the ground when landing and is critical to proper suspension setup.

2. Determine suspension travel distance between frames 100 and 200 (total suspension travel)
http://www.sim-outhouse.net/downloads/SOHTeam/s2.jpg


3. Convert the vertical distance in meters to feet and update the aircraft.cfg contact point vertical distance to ground.
http://www.sim-outhouse.net/downloads/SOHTeam/s3.jpg


4. Calculate static and max-to-static ratio and update cfg.
http://www.sim-outhouse.net/downloads/SOHTeam/s4.jpg


Set the damping to your preference between .7 -1.0. I recommend at least .8 for these suspensions.
You may have to adjust vertical distance to ground by a tenth or so for proper tire-on-ground appearance.

Repeat the steps for the center gear but use around 40% of animated travel
When done, set static height and pitch so the aircraft tires are just a bit off the ground in slew mode, and drops gently when loaded.

If this is done correctly, your suspensions will be more realistic, wheels stay on the ground during rollout, and gear will drop when you depart the runway.

Hope this helps a bit.

I am attaching a .pdf of the above for off-line viewing and embedded pictures with the instructions.
 
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Aircraft have more total suspension movement than meets the eye on the ground. Just like with a car on a jack, suspension hanging is quite a distance relative to what you see when it's on the ground. Important: To setup aircraft suspension to improve visuals on takeoffs and landings and eliminate stiffness on the ground, ensure you animate suspension movement to at least 3/4 the height of the tires, more is usually better depending on the aircraft.
Click to expand...

This is the most often overlooked and/or misunderstood part of the modeling itself...

...because nearly everyone uses sideviews of actual a/c sitting on the ramp as a "comparison" when doing the gear...

...not remembering that those gear are compressed by some unknown weight. We have no way of knowing what the a/c's weight was when the picture was taken! :isadizzy:

More than once I've fallen into the same trap and wound up with suspension that was far too short in terms of overall travel. What I've had to do in such cases was to "drop the wheels more" and then add a slight recompression so that when retracted they'd still fit in the wheelwells... :ernae:
 
HI Bill,

I have done the same thing, the Dash 7 is an example.

It is typical to see contact point with < .3' static compression and 2.5 max to static ratio. That really is a stiff suspension.

The total distance is okay for a light aircraft (9") but I would rather see a ratio of 1.5 to 2.0 on the same distance.
 
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Milton,

By chance have you saved this tutorial anywhere as a webpage, to where it has the images included with the tutorial?
I would like to have full descriptive copy if possible.
 
I think I still have this. Let me dig out the pics and I will edit the posts here.

EDIT: Post above fixed and I attached a .pdf for downloading and off-line viewing. As Tom would say, I hope this helps. :)
 
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When I found this post, Milton, this sounded like something I needed to try. Even though the use is intended for aircraft, it may work for eliminating the symptoms I've been dealing with.
The PDF will work perfectly.

It's time to re-animate and test.

Thanks Milton. And thank you also Tom for responding.
 
OleBoy said:
When I found this post, Milton, this sounded like something I needed to try. Even though the use is intended for aircraft, it may work for eliminating the symptoms I've been dealing with.
The PDF will work perfectly.

It's time to re-animate and test.

Thanks Milton. And thank you also Tom for responding.
Click to expand...

OB,

If you are having a specific animation problem, give me the details and I will try to do a video to walk you through the general process of setting hierarchies, using Local Coordinate Pivots, and animating the parts. I know FS9 is a little different than FSX but the general concepts should be similar.
 
A few photos from a recent museum trip to demonstrate the variety of suspension conditions we might find.

0uViOH3.jpg



uUQW6BG.jpg



The Mossie is a particularly difficult case, the rubber-in-compression suspension is very tired but had a notably short travel and much of the shock of landing was taken by those big tyres, a notable portion also taken by grass runways!


lFz0O9q.jpg


This Messerschmitt is quite easy, but most suspension spacers are smaller than this.


xN88vGN.jpg



And just how much travel does the Beaufighter's suspension have? Decisions, decisions....
 
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Great shots HS. I like that more people are giving gear, wheels, brakes, etc more attention/thought today rather than just the old donuts they used to use. :)
 
Nice shots Tom.

Images and/or drawings, or the opportunity of placing a tape on things as reference help out a lot in modeling. Always one of the difficult opportunities unless the subject is close or someone else is willing to aid the need.
 
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