Rudder Pedal CAM help

[CosmicFloppyDisk]

This may have been a bigger project than I originally thought. I've made the decision to go with a CAM system for force feedback, much like the beautiful MFG crosswinds. Although I don't know where to even start when trying to figure out how my CAMs need to be shaped, if anyone has any insight it's much appreciated

[Sokol1]

CAM use in domestic joystick/rudder "born" in the (RiP) Sukhoi forum back in 2008~2009.

 

First, why use CAM?

 

 

 

Since rudder (and josyticks) need a center system (minus for helicopters, but these ideally need a retain position system), the used system for this are base on use of spring for force the controls back to center.

 

Happens that center system used in commercial pedals (or joysticks) have the inconvenient to cause a "hard" (clunk) return to center, as well in movements across the center position, e.g. from right to left (or vice versa), although they provide a good mechanical center position.

 

This center system are based - with variations - in a kind of "pincer", closed by one or two springs.

See the pincer in VKB RDRXXI-S pedal. Or in this Baloo Pedal DIY.

 

Use two opposite springs for center, although be seen in DIY pedals are not used in commercial pedals be know brands.

 

I think because they provide a poor mechanical center position, the effect of one spring tends cancel the opposite in center, making difficult have rudder centered with foots over pedal. Results in a "oscillating" center, requiring a big software deadzone in center. They provide a soft, noiseless, but less tactile center.

 

- In joysticks are used too a center system based on compressed spring, like in Saitek's, Warthog, T.16000M, old Suncom.

 

Notice: a system that provide a good mechanical center position is the one that make this center "hard", loud and tactile.

 

Conclusion: Is need a center system to deal with two conflicting characteristic: a soft and noiseless position, but tactile - you need know when pedals are in center.

 

 

 

CAM provide a good compromise for a soft, noiseless, but tactile center position.

 

Varying the CAM center profile you can achieve a more or less tactile center, a flat or increasing force in end of movement (what those people in their "Quest for Feel Simulator" want).

 

How design a CAM profile? I don't know,  but see some insights about. People what know make this a commercial secret.

- You can use a CAM with one lever (VKB, Slaw, MFG) or with two levers (Baur).

 

In one lever CAM you need a asymmetric profile, for compensate different leverage in both sides.

In dual lever CAM you use the same profile for both sides, what maybe make more easy design then.

 

Although the CAM profile can be worked for the "Feel Simulator" purpose, at first you need that the spring force over CAM lever be transmitted for pedal/joystick lever in uniform way, like describe  in this video:

 

 

I will send (PM) for you a "translated" document (by me), "Zagruzatelya calculations" posted in Avia-sim forum around 2010 for design a CAM profile based on this "Involute Curve". Is not a definitive way, but give you a start point. The more complicated is calculated the lever pivot placement, to achieve a low pressure angle, what are not in this document, but in another - at end of the above linked topic - complicated for translate, as involve "maths"... 

At end of document a link for a PDF available on Web "Cam Design Handbook" what is very technical but can help in understand the "pressure angle".

 

Sample of DIY CAM for pedal, posted in Reddit - don't know what was used as base for their drawing, maybe trial and error until have a good.... "feel". 

 

BTW - Mind that a Force Feedback pedal need support in games, most of then see only one Force Feedback device, or you use a FFB joystick or use pedal, and some maybe look for a X,Y axis ForceFeedback device.

Edited October 10, 2016 by Sokol1

[CosmicFloppyDisk]

@Sokol1 I can't thank you enough for such a wonderful response. The reason I want a CAM is for that sim feel, springs just never did it for me. I like the Baur rudder pedals system and feel I might go with a system similar instead of going through all the complicated maths with the one arm pedals(MFG), but it's still a nice learning experience, right. I will most definitely be reading through everything you've provided me with.

 

I also realize I may have been using force feedback in a wrong terminology...  I more meant the inconsistencies in real rudder pedals that can be modeled in CAMs over springs. 

Edited October 9, 2016 by CosmicFloppyDisk