Yoke Centering Revisited... #2

[tigert]

Okay, some fun testing.. I was (like I wrote in the last thread) looking for something heavy to attach in the end of the lever for centering force, and figured a hammer with wooden shaft worked.. There's some additional junk strapped to it for testing purposes, since it needs more weight :))Here's a small animation:http://tigert.gimp.org/aviation/vatsim/coc...ff/yokeanim.gifThe stuff you dont see is a small washing machine suspension under the sim "floor" that stops the pendulum swinging pretty nicely. It's attached to the yoke pole underside.Still some rough edges, and lots of work to ponder (the aileron axis for example is not done yet at all) - but I can definitely say this idea does have some serious potential. Smooth as silk, very precise and no creaking springs :) And VERY heavy if you want, depends on the lever attach point positions and the size of the weight ballast..//Tuomas

[Guest MikePowell]

Very nice, Tuomas.Mikewww.mikesflightdeck.com

[Guest nauwa]

This is the way it's done in a real airplane. There is a hydraulic jack that moves the center point when pilot trim aircraft, the electro magnet add force to control when autopilot is engaged.Johanhttp://forums.avsim.net/user_files/102357.jpg

[jmig]

Now, THIS is interesting! I would be interested in seeing more real world solutions. Unless, you are a Airframe/Powerplant or aircraft maintenance person on military or commercial planes, it is hard to find out how it is done in real aircraft.Thanks for the input.John

[Guest nauwa]

The original design is way to large and complex to use in my sim, but I have started to make my own device using the sketch as template. I will post pictures of the design when ready.

[Guest Chris B.]

Hello,I will try to explain how the flight control surfaces are centered on the CRJ 100/700 because I know this system very well and it is relatively simple and a common solution on aircrafts with hydraulic operated flight controls.There is a so called feel and centering cam mounted on one cable quadrant in the cable circuit. The cam is shaped like you can see in the attached picture. On the cam is a roller which is connected with a link to the A/C structure. A spring pulls the roller against the cam. If you delflect the flight controls the cam rotates around its pivot. Due to the shape of the cam you have progressive feel on the control yoke. Centering is achived by the spring tension. If you put your hands off the yoke it will return to its neutral position. All three primary flight controls surfaces (aileron, elevator and rudder) are centered this way.It is a very simple system and should work on your simulator, too.Sorry for my bad english. Nevertheless I hope that this short explanation will help. If you have further questions let me know.

[Guest Project777]

Hi Chris!Thanx a million for this helpful description and drawings!Is there more available (pics etc.??)Best from ViennaHans G. SchuetzProject777---------------------------------------http://www.project777.com[email protected](LOWW - Vienna)

[Guest fullington99]

Ok, now taking this one step further, is the following correct? When the control surfaces are trimmed, the force on the yoke is replaced by the aerodynamic forces of the trim tabs, which in turn is counteracted by the spring. Hence the yoke stays in its position once trimmed (i.e. not always in the 'valley' of the cam). In our simulators, couldn't this trimming action be replaced by changing the length of the roller link (say with a worm driven mechanism)? Also we should be able to replicate feel by attaching hydraulic / pneumatic dampers on one side of the cam. Thoughts? Thanks for the info!

[rickalty]

Does that mean that the centering force is not affected by the airspeed?Richard

[tigert]

>Hello,>>I will try to explain how the flight control surfaces are>centered on the CRJ 100/700 because I know this system very>well and it is relatively simple and a common solution on>aircrafts with hydraulic operated flight controls.>>There is a so called feel and centering cam mounted on one>cable quadrant in the cable circuit. The cam is shaped like>you can see in the attached picture. On the cam is a roller>which is connected with a link to the A/C structure. A spring>pulls the roller against the cam. If you delflect the flight>controls the cam rotates around its pivot. Due to the shape of>the cam you have progressive feel on the control yoke.>Centering is achived by the spring tension. If you put your>hands off the yoke it will return to its neutral position. All>three primary flight controls surfaces (aileron, elevator and>rudder) are centered this way.>>It is a very simple system and should work on your simulator,>too.>>Sorry for my bad english. Nevertheless I hope that this short>explanation will help. If you have further questions let me>know.>Yep, this looks a lot like the mechanism I am going to try to use for aileron (and what we use in the MIK Cessna sim for ailerons) - it is originally from the arcade game "Turbo Outrun" - the mechanism is very simple and it works great:http://tigert.gimp.org/aviation/vatsim/coc...ng/p1010009.jpgBasically just what you have on the pic.The problem with stuff like this is the tools: It needs to be ball-bearing (skateboard/inline skate bearings work for this though, they are small "wheels" - the Outrun wheel uses exactly those in the roller) - but the other problem is making the "off-center" block shaped correctly and smoothly so it is both symmetric and also with a smooth edge. Plus you need bearings for the main shaft too, since the spring needs to be *strong* and thus puts quite a bit of a load on the shaft. It should be all-metal (or at least all joints should be with metal bearings or bushings) to make it durable.Sigh, I can see myself rebuilding a lot of the stuff from metal in the future, fortunately a friend has a workshop..The problem is, with stronger centering forces you get a LOT more strain on the parts and everything wears out a lot faster if you have "bolt through a hole" -stuff - things need to have at least two metal tubes as bearings or something.//Tuomas

[Guest Chris B.]

Hello,the trimming of the control surfaces depends on the aircraft type.The CRJ has hydraulically powered flight controls and does not have any tabs.When the aileron and the rudder are trimmed the yoke or pedals respectively are also moved by the amount the surface is trimmed out of center position.That's done the following way:The lower end of the spring and the roller/link assy is actually not attached to the structure. I explained it that way because I think it is easier to understand. Actually the spring and roller/link assy is attached to another cam which can pivot around its attachment point. And this cam is really attached to the structure. The cam can be moved by an electrical trim actuator (linear). When the actuator rod extends or retrects the cam will rotate. The roller will remain in the neutral position of the centering cam because the cable quadrant and centering cam will also rotate. The quadrant is connected with the yoke with control cables. That means that a movement of the quadrant moves the yoke, too. Because the lenght of the spring does not change when the cam is moved their is no feelable springforce on the yoke (yoke deflected to left or right due to trim but roller in centering cam still centered). During pitch trim their is no movement of the control column. But that is another story.I am also licensed on BAE 146 and this aircraft has servo and trim tabs for aileron and elevator and this surfaces are trimmed aerodynamically. But I think that the CRJ style is easier to simulate.I hope this clarifies some of your questions.Sincerlly,Chris

[Guest Chris B.]

>Does that mean that the centering force is not affected by>the airspeed?>>RichardYes, not at this aircraft.Chris

[tigert]

>During pitch trim their is no movement of the control column.>But that is another story.>>I am also licensed on BAE 146 and this aircraft has servo and>trim tabs for aileron and elevator and this surfaces are>trimmed aerodynamically. But I think that the CRJ style is>easier to simulate.Yeah, sounds like the "CRJ" style can be done by just not doing anything with elevator trim, and just using the FS's trim function.But what I am trying to achieve is precisely the "trim off control forces" effect of aerodynamic elevator trim tab - I dont care that much about aileron trim myself - does for example inbalanced fuel need aileron trim in FS? Rudder trim then again IS needed for a twin - but I am not going to try to construct some aerodynamic trim feel in the pedals - my personal goal is set to elevator trim that moves the yoke with trim position, that will be enough for now.However, thanks for the descriptions, those have been very interesting to read! The mechanisms are pretty clever and inspirational! :)//Tuomas