Wing Actuation

[tf737sb]

I first posted this in the NACA 66 thread in regards to Carbiliner, but I figured I'd toss it up here, too.
In this expanse of uncertain downtime, we've been tinkering on our 'liner's aero package. It was always an intention to make the wings adjust angle at speed- much like the Carbiliner. I've got a system built in my mind (and on paper) to get the job done, but I was curious to see if anyone could shed some light on how Rob and the team manipulated their rear wing at speed. Of course if this info is proprietary skunk-works development, I'll kindly sit back down. If anyone else has details of their own successful system that their willing to share, I'm all ears.

[tallguy]

I don't know what was used on the Carbiliner, but would suggest something powered by ball screws rather than
hydraulics.  Pneumatics, as we know, are too "spongy".  Hydraulics is always subject to leaking or effects caused
by changing temperature.  A step motor can be used to activate the linkage to a wing. 

Of course, you might want to contact Carbinite (Rob Freyvogel) and ask for info.  I understand he was seriously
injured in a crash of the Carbiliner, so I don't know whether he's in any condition or mood to help.  Good luck.

[John Burk]

They used an air cylinder to keep the flap pitched up . The pressure in the cylinder or the reserve tank determined at what speed the flap laid down . The theory was lots of pitch at medium speed when drag wasn't very important and less pitch at high speed when down force was less important than drag .

[TD]

I _think_ (but am not 100% sure) that forum member Blue was involved with the aero design of the Carbiliner.  You might check with him.

I'm not on the Book of Face and it would be great to know how Rob F is coming along in his recovery.

Tim

[Rex Schimmer]

Being a "flange head" (mechanical engineer) I have always thought that you could have the wing rotate some where around the nose radius which puts the center of down force behind the point of rotation. Then attach a coil over shock some place to the rear of the center of down force for the selected wing section. You can calculate the amount of down force generated by the wing at different angles of attack then using this information and the placement of the spring/shock you could select a spring that would give you a variable angle of attack based upon speed. I would make the shock pretty stiff to prevent wing flutter and also to make the rate that the angle of attack changes be slow. Pretty crude but no wires and electrons!

Rex

[John Clutch]

I like the ball screw concept the best. Most likely the safest approach. They also can take a tremendous load without much deflection.

[Rex Schimmer]

If you use a ball screw then you need a brake on the shaft because ball screws are very efficient and will back drive. A better choice would be a standard lead screw, ACME threads and bronze nut material. Not very mechanically efficient but will self lock in position. Used on some airliners to move and lock in position trim tabs and horizontal stabilizers.

Rex

[tf737sb]

Glad to get some replies on this thread! Linear actuators or ball screw actuators are very cool thoughts. We are constrained to packaging in the rear due to the drive axle configuration (there's two in case you didn't know). We've designed a pivot arm that doesn't need much travel to make fairly large degree changes. I have all the engineering data for the wing downforce at various speeds as well as center of pressure location to make pivoting the wing easiest. Surprisingly it doesn't take that much force to manipulate the wing at 380mph+. Coming from top fuel racing background, we've been raised on air timers and delays for fuel and clutch controls. That's going to be the basis of the system- essentially a clutch controller. These controllers are made by Dave Lehey at Electrimotion. They're fairly simple, and an industry standard- so there's lots of support. Each air shift to the B&J will trigger air timers controlling hydraulic fluid bleed-off through adjustable needle valves. A pair of dual-action hydraulic cylinders will act as the wing actuator, and then as a fluid accumulator when the actuation cycle is completed after a run. This system is something we're comfortable with, and doesn't take any new proprietary controllers. The rams also have provisions for magnetic pickups on the piston so we can use the Racepak to monitor for any flutter or silliness, and verify they've achieved their travel. As far as leaks-my driver is a retired plumber, so I've got confidence in him... It should work... I think!

[manta22]

Just a reminder- flutter is DESTRUCTIVE! Make sure it won't happen.

[panic]

The wing's height vs. efficiency also varies with speed, how much depends in part on how the greenhouse masks the wing.

[Rex Schimmer]

I assume that when you say "dual action" hydraulic cylinders you mean cylinders that have a rod on each end of the cylinder and that the rod is the same diameter on both ends. Then the operation of the wing depends on an aero load on the wing which makes pressure on one side of the cylinder piston and you use a needle valve and several of the clutch controller valves that when they open the oil on the pressure side of the cylinder will be bleed, through the needle valve back to the opposite end of the cylinder which is at a lower pressure. So you will need as many control valves and needle valves as your B&J has speeds. Sounds good to me, a couple of things you want to consider are piston and rod seal friction, this can be as high as 10 to 50 psi depending on the bore of the cylinder and the type of seals. You also should make sure when you assemble the system that you really spend some time bleeding any air out of it as this can cause some instability. When you get the needle valves consider getting the type that are made with extra fine adjustment, they should give you better resolution. The fluid should be low viscosity, I would suggest something like the military's Mil 5606 which works with standard buna N seals.  Size the cylinder so that at your desired aero wing load the cylinder is at around 500 psi, this should keep the action tight and smooth.

Looking forward to seeing what you come up with.

Rex