Acceleration comparisons

[horseback]

Originally Posted by MaxGunz

From 2002 discussions on trim with Oleg I got some answers.

Question was why holding the stick steady off center doesn't get the same speed/acceleration as stick centered by trim. After all, trim will move a hands-off stick or column.

Answer worked out to that we think the stick is held steady but it is not. This is mainly due to hardware, short gaming sticks and small involuntary muscle tremors.

This is partly borne out by the reported results from those who made and use full size sticks to play IL-2.

And since 2002 the impact of needing to be trimmed has been less.

For my part, and you can easily check this yourself, there are two things that help.

1) use a light touch on your joystick. Try flying holding the stick with just 2 fingers and thumb just for while.
When you catch yourself resting your arm weight on the stick or elbow on the table, get your arm up so it's not weighing the stick down. If you find yourself clenching the stick, loosen up. Besides the weight and ham-handing those are great ways to transmit tiny muscle tremors to the stick.

2) go into stick sensitivity and add FILTER to the pitch/elevator axis. Try about 50% at first. Maybe you need more or less but you should see results in minutes of testing. FILTER will flatten out the small and fast shakes even at less than 50% while yes, slowing your jerk-speed by a fraction of a second that you can see by watching the red and green blocks in the stick test area of the same stick sensitivity screen.

It's not perfect but you should gain something if you're not already light-handed and using FILTER.

I long ago came to the conclusion that I needed to ensure that my stick position was consistent and properly anchored, in order to limit things like resting forearms on the desk and the like; to that end, I bought a 5/8” (approx. 16mm) thick seasoned hardwood plank about 28” long and 13” wide. My flight sim computer’s desk has a keyboard tray about 24” wide, so I cut out 2”x 2”sections out of the corners (which keeps the tray from sliding in & out on me) and then cut out holes that closely match the outlines of my CH Combatstick and Pro Throttle, with the Combatstick almost in the center of the tray (3” offset to the right). The stick fits in the hole rather snugly, and the stick will stay where it is while I thrash it about. I recommend the idea to anyone who has trouble keeping his stick from running away from him.

So for the last six or seven years, my stick, pedals and throttle have been in exactly the same spot, which cut down on a lot of problems that plague other simmers, especially the ones who use sticks that feature heavy springs and no way to anchor the darn things.

I haven't played with filtering very much, though; that's a worthwhile suggestion. Thanks.

The addition of a smaller pot in series with the larger one is also a good idea; one of my nephews managed to break the case of my CH Yoke several years back so I took it apart and used the electronics as a base for a trim and button box; trouble is, the pots will only use about (the most linear) 60 degrees of rotation, so just breathing on them can be excessive when I try to use them for trim in Il-2 (not so much with FSX or the DCS Mustang, but you still have to be careful).

cheers

horseback

[MaxGunz]

60 degrees turn? You can get better ones.

What matters is how many ohms range you get from stop to stop and how many ohms your hardware uses. Ohms is resistance. I would start with the pot you currently use and put a meter across one of the outside legs of the pot to the center leg to find out what you got.

The standard plug into the gameport stick runs from 0 to 100k ohms. 1/100th of a turn covers 1k ohms. If I put that in series with a 10k pot then that pot will be 1/10th as sensitive as the 100k. The digitizer measures how much voltage gets through with 0 ohms meaning full and increasing ohms going towards none, 110k total as opposed to 100k is not a big deal and should only affect calibration.

That's why I tell that you can have one pot/slider for coarse adjustment and the other for fine adjustment. If you want 20x fine then for a 100k coarse you would add a 5k fine that would change the total resistance 1/20th as much for the same turn as the coarse knob.
Maybe the better setup would be a coarse long slider and turn pot for fine adjustment.

What your stick uses for values, you will have to find out for yourself. If you're up for it there are hobby controller electronics in the $60 and under range like the BUO-series at leobodnar.com (has 12-bit A/D) and less-accurate (10-bit) but far cheaper DIY MCU's like the Teensy's and Leonardo's (that can use external ADC chips to get more bits resolution but that's 'cheating', hehe) and make your own stick which is not for the faint of heart or mind.

The hard part could be making acceptable knobs, grips, and bases, ie the mechanical bits. Plaster molds and bondo then hours of sanding, filling, etc?

I can code the latter and breadboard them but have no shop space and am lousy at soldering and fine work due to shaky hands. The newer controllers and software (since 200 make it easier than ever but I say that already knowing C since the 80's. Your mileage may vary, learning to code from zip may not be worth what you get. There's a lot of help available from Leo for his products (already coded) and on the Arduino forum for those.

In the last two years I have recovered/relearned a lot of my old "skillz" playing with Arduino. I have even made leds that self-adjust with changes to ambient light (LOL Fehler, how much resistor? MINE changes itself!).

[horseback]

Originally Posted by MaxGunz

60 degrees turn? You can get better ones.

What matters is how many ohms range you get from stop to stop and how many ohms your hardware uses. Ohms is resistance. I would start with the pot you currently use and put a meter across one of the outside legs of the pot to the center leg to find out what you got.

The standard plug into the gameport stick runs from 0 to 100k ohms. 1/100th of a turn covers 1k ohms. If I put that in series with a 10k pot then that pot will be 1/10th as sensitive as the 100k. The digitizer measures how much voltage gets through with 0 ohms meaning full and increasing ohms going towards none, 110k total as opposed to 100k is not a big deal and should only affect calibration.

That's why I tell that you can have one pot/slider for coarse adjustment and the other for fine adjustment. If you want 20x fine then for a 100k coarse you would add a 5k fine that would change the total resistance 1/20th as much for the same turn as the coarse knob.
Maybe the better setup would be a coarse long slider and turn pot for fine adjustment.

What your stick uses for values, you will have to find out for yourself. If you're up for it there are hobby controller electronics in the $60 and under range like the BUO-series at leobodnar.com (has 12-bit A/D) and less-accurate (10-bit) but far cheaper DIY MCU's like the Teensy's and Leonardo's (that can use external ADC chips to get more bits resolution but that's 'cheating', hehe) and make your own stick which is not for the faint of heart or mind.

The hard part could be making acceptable knobs, grips, and bases, ie the mechanical bits. Plaster molds and bondo then hours of sanding, filling, etc?

I can code the latter and breadboard them but have no shop space and am lousy at soldering and fine work due to shaky hands. The newer controllers and software (since 200 make it easier than ever but I say that already knowing C since the 80's. Your mileage may vary, learning to code from zip may not be worth what you get. There's a lot of help available from Leo for his products (already coded) and on the Arduino forum for those.

In the last two years I have recovered/relearned a lot of my old "skillz" playing with Arduino. I have even made leds that self-adjust with changes to ambient light (LOL Fehler, how much resistor? MINE changes itself!).

I'm fairly aware of ohms and resistance; they covered it pretty thoroughly while I was attending the USN's Electronics Technician 'A' School at Great Lakes over the winter of '75-'76 (August to April, which was the full Magilla back then), and I have applied that knowledge & training fairly regularly as a field & test engineer over the last 30+ years.

The pots that CH used for my old yoke are all 270 ohms, but they use only the 'middle range' of the pots because that is where the change in resistance is most consistent; the resistance between the 10th and 11th degrees is almost exactly the same as the resistance between degrees 45 and 46. This allows them to use less expensive pots and still give you pretty good precision across the range of movement that their mechanical setup allows.

Since little Joey only cracked the plastic case and one of the Yoke handles (it was only a drop of about six feet!), I was able to recover the CH control circuit card as well as the five axes and the 12 buttons plus POV hat; this means that when I plug the USB into my computer it sees a CH Yoke and automatically puts me into the CH Control Manager software, which allows me to combine it with my other CH controllers into one or two (rather than four or five) controllers for Il-2, which I'd rather not lose.

I was able to cut out the throttle/prop pitch/mixture levers' mounts so those three axes are intact, while the X-Y axes are now mounted in the box as twist knobs, with that short range of movement I was complaining about; I'm wondering if rather than putting another potentiometer in series, it might be better to put one in parallel to get that fine control. I'm also still looking at those gear kits that Tamiya makes for robots and RF controlled vehicles with an eye to adapting one of those to my needs with something along the lines of 20:1 ratios.

I'm not very familiar with programming (one course in Basic back in college 25 years ago), so tossing the little CH CCA is something I hesitate to do.

cheers

horseback

[horseback]

Two more charts and data tables; USN/USMC fighters at 100m/330ft, and Mid-War Soviet Fighters @100m/330ft.

A few notes:

1. The Soviet fighters really shine at this altitude (this means that I said "Holy *&^%*&%$%!!!!" a lot when I reviewed the data and had to slow the track down to half or quarter speed to catch the speed changes in time); compared to the 3000m data, they are far more impressive. The La-5FN is indisputably 'king of the hill' at this level, although I have yet to do the Seafire LF III.

2. The Soviet fighters also tended to drop their noses as speed increased, generally around the 360 to 400 kph range, but it was only about half the radius of the gunsight circle in WW view. I started taking screenshots at certain intervals to confirm this, so I am certain that it is happening.

3. The USN/USMC fighters are mostly 4.11.1 versions that I had already completed before the patch was released; after three comparisons to 4.12 runs, it became obvious that there were no changes.

4. I haven't had a chance to do the same sort of screen shot comparisons with the Corsair and Hellcat that I did with the Soviet fighters because the idea didn't come to me until I was doing the Russian runs; I have started a folder labeled 'nose drops' and will use it for fodder on another thread, I think.

5. Using Max' suggestion of applying 50% filter to my ailerons, elevator and rudder axes made some difference; still, very tiny movements in elevator or rudder when I attention wandered from the climb or alt indicator or artificial horizon (and when these instruments are obscured or widely separated, I had some real issues) resulted in big swoops and climbs in a matter of two or three seconds, often well out of proportion to the indicated displays (as mentioned in an earlier post)

Enjoy, discuss, debate.

cheers

horseback

[majorfailure]

Originally Posted by horseback

2. The Soviet fighters also tended to drop their noses as speed increased, generally around the 360 to 400 kph range, but it was only about half the radius of the gunsight circle in WW view. I started taking screenshots at certain intervals to confirm this, so I am certain that it is happening.

I'll ask again, how else do you think the wing can generate the same lift at a higher speed (e. g. plane stays level), else than decreasing AoA?

[horseback]

Originally Posted by majorfailure

I'll ask again, how else do you think the wing can generate the same lift at a higher speed (e. g. plane stays level), else than decreasing AoA?

First of all, I meant it as a matter of degree; there has to be a reasonable limit of movement down as a result of the direction of thrust and limiting action of the elevator. I don't buy into the notion of an aircraft like the Thunderbolt wallowing with its nose up in the air at the speeds it travels when it enters the landing circuit or in economy cruise. It is simply exaggerated, and again, appears to be limited to that same group of fighters that there is the greatest amount of data and modern pilot reports about. We are talking about relatively straight, high lift wings across a fairly limited (by modern standards) range of speeds. We aren't talking about swept-wing jets here.

The Soviet aircraft all have a 'drop' of around a quarter of the WW gunsight circle's diameter, and it generally takes place between 370 to 400 kph ias, varying somewhat from Yak to LaGG to La. It also appears that the drop is not as great when the aircraft is in a constant speed compared to when it accelerates and that some aircraft have little or no 'drop' with acceleration or greater speed in general.

My impression so far is that aircraft like the Lightning, Corsair, Hellcat and P-47 have much greater 'drops' and that at certain speeds the nose will suddenly rise again somewhat at higher speeds. I haven't fully quantified it yet (as I have said, it takes about 45 minutes to actually make a 4 run track and at least the same amount of time to replay it and transcribe the raw data) but I think that these aircraft's noses raise and lower (and sometimes raise again) by nearly the full diameter of the WW gunsight circle, possibly more. At 100m, that puts the 'pipper' well below the horizon, while the Soviet fighters' gunsight center is just a bit above it (and at considerably higher speeds in many cases).

I contend that it is way too much variation, and plan to create a separate thread about it, but only once I have my ducks in a row. Right now I'm struggling to maintain level flight and have noticed that my key visual references are either unreliable in the case of my cockpit instrument displays or are changing on me in the case of the view of the horizon, which I could normally 'set' at a certain point in my cockpit framing to keep level. I need to (a) fly a reasonably level course while accelerating through the speed range and (b) take a series of screen shots from the track after doing so to confirm what are so far just impressions.

If I'm wrong I will say so; it won't be the first time.

cheers

horseback

[MaxGunz]

Series resistance will give you linear changes.
Rtotal = R1 + R2

Parallel resistance will give you curves and the total will be less than the smallest resistance (pot adjustment) and relative to it.
(1/Rtotal) = (1/R1) + (1/R2)

A microcontroller can use a lookup table to correct non-linearity of the sensor. There's room in a Teensy 2.0 to adjust _every_ step of all 12 10-bit analog inputs and still have room for useful code.

The most accurate stick I ever had used optical encoding. That wasn't analog at all. When the new hardware came out something changed and it wouldn't work so I sent it off to Rookie from the old Delphi FSF.