trim and AP hold cont'd (and other issues)

[Guest]

Hi all,This weekend i took some time (..) to build my new home cockpit extension. Nothing very special, at least not compared with all those great looking cockpits i watch in this forum. But for me this was a first and i like it. I haven't got any photo's (yet) so will describe its functions briefly:It's build around a gamepad (Thrustmaster USB) and a joystick (MS Sidewinder USB) and features 3 axis and 20 buttons. I'm always short of buttons to push, you know....One axis is used as a flaps lever (through FSUIPC's excellent feature to work around this FS2k2 flaw) one other as elevator trim. That's done by using a wheel (for the mechanics i used some old meccano, kids construction toys i had lying around for some twenty years)with some gearing. The third axis is still available, awaiting FS2k4's new axis-functions (i hope).The buttons are connected to pushbuttons (10) and switches (also 10), the last ones to operate from the button section in FSUIPC (i.e. gear up on "button press" and gear down on "button release").All is mounted in a case i bought for this (no spectalulair homebrew panels i'm afraid) which sits nicely next to my CH Yoke.Everything finally worked as it should, and a had some time left (late last night) to test it in FS. The most important feature to me is the trim wheel, as using a switch on the yoke doesn't do it for me. I always fly VC with an extra monitor with radio's etc and there is not always a trim indicator visible. Last week i had a nice discussion with my fellow dutchman Rob about using trim on an axis together with the AP Alt Hold function. So i tested that first. As Rob already suggested the two work together nice as long as there is a deadzone to put the wheel in. Whenever the AP receives input from the axis (and it does, even when it's USB and FSUIPC doesn't show changing values)the A/C makes really spectaluar, yet unwanted moves...Another thing is that i rapidly discovered a problem using the trimwheel. The gearing made it possible to transfer the 270 degree potmeter-turn into an (almost) 720 degree wheelturn. Great, that should give me enough precision to trim to perfection. It would have if the USB logic of the sidewinder didn't have it's own resolution. Easy to see in any A/C with a trim display, and otherwise in FSUIPC. Turning the wheel results in valuechanges in steps (from -16xxx to +16xxx) of about 100someting. That was very disappointing, it took away some of the charm of the whole project. So much for my choice for USB as input device, the gameport hasn't got this resolution thing (at least i believe). But i didn't opt for that because of jitterproblems and my wish to be "future-proof". Anyone with experience on precision controls on a gameport ? Resolution ? How does it work through a USB-adapter ? Anyway, the trim works OK for now, but i'd sure like a smaller resolution on the pot.Now i'm even more curious how the Goflight module with elevator trim works and whether the resolution problem exists.For the rest, the controls worked just fine. Took some time to set functions to the switches through FSUIPC (the list of available functions is looooong and not very logically build up) but it works fine. I had to recalibrate the pots once after shutdown but that seems to have gone now. So far. Thanx for your patient reading !Cas.

[rcbarend 37]

Hi Cas,"Turning the wheel results in valuechanges in steps (from -16xxx to +16xxx) of about 100someting" .Does that means you have some 150 - 200 discrete steps now over the whole range ?If so: You won't improve that with a gameport axis, because of the jitter and (more important for a trimwheel in combination with AP) spontaneous 'spikes'.And it's certainly much better that the seperate gameport-USB convertors: the best I know (Rockfire RM) has only 64 steps.So I guess you have to live with it.There are probably better USB sticks you could use, but they will cost much more.Anyone else have any ideas ?Cheers, Rob

[Guest]

Rob, hi again. I just counted thos steps (well half of them, from 16392 to 0) and came to 81 steps. Double that for mu total range and it gives 160+ steps. Difficult to count precisely, but that's about it.And i understand that's not a bad result. OK, it's just how you say: I will live with it.Even if there's a better USB stick around, how can i be sure which one to get ? I've never seen the resolution listed in the specs ;-)Thanx for your help again. Still waiting for someone to answer about the goflight issue though. Just curious.Cheers,Cas

[Guest]

Cas, Thanks for posting in the FS forum and inviting me over here to see what you found. I think your set up sounds really cool. As far as the trim wheel and the steps you describe it sounds like you have done all you can to get a smooth trim set up. I really believe that from here Individual aircraft files can be tweaked to achieve a very smooth trim from your wheel, although I know not how to do this. I say this from experience with the vast number of planes I have flown and how they all differ with trim inputs from the same controller. What plane are you testing with? I know from experience that FSD has done wonders with the trim on the Cheyenne and Seneca to the point where they don't need near the attention that most other aircraft do to achieve stable trim. The draw back to this is if you load the plane from a default plane with the trim set way to one side of the scale it takes a very long time to get the trim centered. What I see they have achieved is the trim seems to move much slower and in doing such allows you much finer control of trim placement. Just how that will work with your wheel I am not sure but I think it will work well. Do you have either of these planes? If so try and load it up and check the trim inflight for "feel".To watch the indicator won't tell you much because it will barely move but the actual input to the control surface is there. As far a finding the null zone for autopilot engagment do you have a mark on the wheel itself? Ken

[Guest]

Hi Ken,thanx for the reply. Interesting points you come up with. I'm at work now, so don't have time to do the testing on different ac's. But tonight i'll give it a go. Testing sofar has been done on FSD's commander primarily as it's my favorite (untill now..). And a bit on the default cessna 172 too, that one seemed to handle trim input's better than the commander. I'm planning to buy the seneca also, but haven't found time for that yet.Also i found a way to center the trim through FSUIPC's buttons section. That way it's possible to trigger the ALT HOLD function AND centre the trim in a dead zone at with one "flip of a switch" at least i think so. Simply by assigning ALT HOLD in FS and the center function in FSIUPC to the same switch. Tonight i will also try that and see what effect this has. Right now i don't have a marking on the trim wheel yet, but it's a good tip. When my tests are done i will follow up on this off course.Cheers,Cas

[Guest]

Ken,i just tried the above mentioned things. The marking on the trim wheel is working great, a real help to center it. Also the combined "center trim" and Alt Hold switch is doing what i want it to do. Whenever i flip that switch to "on" (and if the AP is enabled) the trim centers and alt hold does it's job. I can easily operate the altitude from the AP. When i turn the trim wheel it still goes crazy, but that's not unrealistic. The FSUIPC function is called "elevator trim set". The function listing in that buttons section still confuses me, but i also find nice functions for my 20 switches and buttons though....Furthermore i tested a few ac to find out how the trimwheel works. I tested the default C182 and Baron (with steve small's airfile), the beech G-18 and the DC-3 from the NATS guys (the DDA version, i'm Dutch y'know) the FSD Commander and the Dassault Falcon.Overall my opinion is that the faster the AC the more difficult it gets to trim it with my wheel. But that's the same (in my experience) for trimming it with a switch (as on my Ch Yoke). I tried some different alt's and speeds on every AC and finally i got it to fly at a constant altitude. But it took some power adjustments too, especially on the faster AC. The falcon is the most difficult one, but i hardly ever fly it seriously. The cessna however trim's a lot easier, so if that's your thing i guess you're OK. Let me know if there are other AC that you like, i can give them a go if i have them.That's it for now, i can definitely reccomend building an outfit with a trimwheel, but a higher resolution Joystick would be even better.Cheers,Cas