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Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Tue Feb 13, 2018 9:46
by lonestarbuckeye
Hi -- I just took my first VKB stick out of the box this evening. It's a Mk.II Gunfighter. I'm trying to follow the Quick Operations Guide in regard to adjusting the dry clutches. The guide says that turning the two screws adjusts the damper force of the x and y axes, respectively, and I can feel the deflection force change as I adjust the clutch screws. The problem is that if I adjust for any tension other than the minimal amount (clutch screws all the way counter-clockwise), the stick won't return to center. This isn't the leaning-slightly-left-or-right-by-design phenomenon; the stick won't return to any center. If I deflect the stick right, let go of it, and let the oscillations die out, it will come to rest right of center. The same short-return happens when I deflect it left, up, or down. The centering error is so large that it's easy to see just by looking, but it's very clear from the vkb_joystester program (I've flashed the firmware and calibrated the stick, following the directions in the guide). The offsets are not small--they're far too significant to be compensated by a reasonable deadzone.

Am I supposed to completely loosen the clutch screws? (That's not what the manual seems to say, but perhaps I'm misreading it.) If so, what's the point of the screws, or of the clutches for that matter? Is it possible to adjust the stick's deflection force without changing the springs or cams?

I'd really appreciate any guidance you can offer. Thanks in advance!

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Tue Feb 13, 2018 17:26
by Ace
It is a characteristic of the cam gimbal and completely normal. If you want a clear-center return, then you might as well change your cams to #30 hard center cams.

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Tue Feb 13, 2018 17:51
by lonestarbuckeye
I'm not doubting what you say, but that doesn't make sense to me. Under what circumstances would one want to use a stick that doesn't return to center?

Thanks for your feedback.

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Tue Feb 13, 2018 22:58
by PhoenixCNE
For flight sims the soft center is nice, there is no bump to cross when you are aiming and pull the axis across center. If your plane is a touch out of trim being able to nudge it a bit one direction to level it out is nice as well. I would imagine on the space sims like elite and star citizen more of a center would be nice maybe? Other than that I've always wondered if you could remove the gimbal springs and use the dry clutches to hold the stick in place wherever you leave it, closer to how a helicopter is. In the end they are there for options, these sticks are built to be tuned to suit what you are using it for. You may not see a purpose in it but someone will.

**just as a note, I loosened my dry clutches completely because I felt they added a slight sticktion that would jump around as you tried to do fine aiming. I'm not worried about my stick oscillating back and forth, who just lets go of it like that? :P

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Tue Feb 13, 2018 23:26
by lonestarbuckeye
Thanks. You make a fair point. After I submitted my last post, I thought about it some more and came up with the same scenario you suggest: one might like a stick that has no centering force and just remains in whatever position you leave it when you release it. But I still don't see the use for a stick that sort-of-but-doesn't-quite return to center.

I use my stick primarily for flight sims. I played with it a bit last night after removing all (or at least most) of the tension on the dry clutches, and I do like the lack of a strong bump in the middle. Adjusted like that (using the original springs and cams), the throw is extremely light (lighter than I'd like), but, as you say, it allows for more precise fine adjustments (particularly mixed x-y adjustments) around the center. Perhaps the unavoidable price to pay for that is that the center will just be somewhat imprecise. Perhaps I should try the heavier springs with no tension on the clutches to get similar center performance with a heavier throw?

I'm still wondering what the purpose of the dry clutches is. They seem to cause centering errors and stiction (I also noticed this), but they must be intended to have some positive effect. Is it just to damp oscillations?

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Sat Feb 17, 2018 2:04
by aaron886
Yes, the dry clutches exist to dampen oscillations. (Think free-stick motion.) It helps prevent minute over-corrections that your imperfect muscles will apply by nature.

To counter some of the original replies, I think there might be some misinformation in this thread. The stick may not always return to physical center, ie. it may appear to be very slightly tilted to one side. However, it should always return to logical center, in that the sensor value should be very consistent when you release the stick. In practice, this doesn't present itself as a problem at all... you might not ever notice the grip is canted slightly to one side, as long as the in-game axes center perfectly and the force gradient is consistent.

However, if you set up your stick with too much damper, you will find that the spring force near center with the soft cam is not sufficient to completely center the stick to logical zero. In this case, you'd better set some deadzone up in your games or consider backing off the damper. Unfortunately, the damper is not "sticktion" free as it was designed to be, so you will experience very slight sticktion if damper is used. I haven't found a way to involve the damper practically but also avoid some sticktion. It's a very fine tradeoff and depends on your intended use. It's a shame that as a Mk.1 owner, I can't quickly adjust damper on the fly to suit my use, but instead have to pull out the tool box and take it apart.

For flight sims and a lot of formation flying, I prefer the hard cam in pitch and soft cam in roll. I use an extension, so I have 50x2 springs on each axis. The hard center pitch cam is not uncomfortable when the airplane is trimmed properly for formation flying. The soft roll cam can require a slight deadzone at the center to avoid really small centering issues, but if I turned the damper off entirely I'm confident that those would go away. That said, I like the damper in concept and don't want to turn it off. Having built and used a very smooth stick that had spring-force only, I know it can be difficult to adapt to pure spring movement without continually over-controlling the simulator.

Re: Gunfighter Mk.II dry clutches, damper force, and centering

Posted: Sun Feb 18, 2018 1:08
by lonestarbuckeye
Thanks, Aaron -- that was extremely helpful! (And just to be clear, my references to "center," were to the post-calibration logical center, not the physical center.)