Acceleration comparisons

[RPS69]

There are commercial potentiometers, that allow you to turn around 10 times, and have a numerical track of your position.
They are very precise, and can move fast if well kept. Still, don't play unneadlessly with them, because they get noisy after so many changes. Still, they may work fine for around 10 years on an everyday use.

http://www.schukat.com/schukat/schuk...8&kb=DIAL15111

That was the first example I stumbled upon. Don't know how good they are though...

Horseback

Nice observations and I would agree with your assessment. You note the rudder boost tab reversal mod (from boost tab to anti-boost tab) on the P-51 and its effect on rudder use but you didn't note the same change was made to the long-tail P-40's rudder with the same result. Something else that I have difficulty with is all Mustangs seem to be able to snap the wings off in a dive with the same ease when there should be a very noticeable difference between elevator bob weight modded and un-modded aircraft. (Elevator bob weight mods were also installed on Spits starting with mid Vb.)

[MaxGunz]

Originally Posted by RPS69

There are commercial potentiometers, that allow you to turn around 10 times, and have a numerical track of your position.
They are very precise, and can move fast if well kept. Still, don't play unneadlessly with them, because they get noisy after so many changes. Still, they may work fine for around 10 years on an everyday use.

http://www.schukat.com/schukat/schuk...8&kb=DIAL15111

That was the first example I stumbled upon. Don't know how good they are though...

There's 20 turn pots too, made with high precision for test instruments. They're not cheap. Check Mouser, Digikey or some other electronics house for listings. Sometimes you can find the parts cheaper, just make sure of manufacturer and check the datasheet.

Here's the thing about multi-turn pots: how do you keep track of how many turns you have made? A single turn pot or linear slider is so much simpler.

[RPS69]

Originally Posted by MaxGunz

Here's the thing about multi-turn pots: how do you keep track of how many turns you have made?

They got numbers... and they allow you to reach the exact position, while sliders may lack precision.

[jameson]

Following this thread with some interest. I've always thought that regarding trim vs speed, the drag created by being slightly out of trim ingame was and is way overdone. Just a feeling on my part, but still...
Anyway I refer you to R&M 2361, The Royal Aircraft Establishment report regarding a Me109 E3 captured in France in 1940.
http://kurfurst.org/Tactical_trials/...ls/Morgan.html
You may read the whole thing, and it's quite long, but of most relevence here is Fig. 13 near the bottom of the page. This figure shows tailplane incidence vs speed (elevator trim achieved on 109 by moving the tailplane and not a tab on the elevator) in the lower graph of the figure. Suprisingly it shows that between 100 mph and 350 mph (160 kph and 560kph) with full throttle the tailplane only needs to be moved 1 degree to maintain level flight. (+ adjustment is nose down and - up). The tailplane is controlled in cockpit by a wheel 300mm in dia, and is geared at 2:1, i.e. one turn = 2 degrees of tailplane movement. Thus it appears that about a half turn is all that would be required between those speeds, so just slight tweaks on the wheel as speed increased/decreased.
I'd also like some trim indication being given onscreen, airstart being a case in point it, seems that trim is neutral? at the start of the mission and the plane out of control as a result. All this though does raise the question of how accurate drag is modelled ingame and it's level of sophistication, it seem fairly crude and overdone to me, and possibly a one size fits all kind of thing.

[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.

[horseback]

This is all very interesting, but it is still obvious that the elevators on all of these aircraft are far too sensitive and that trim displacement is disproportionately ineffective compared to other aircraft modeled on the basis of old data and reputation. “Easily trimmed” means easily trimmed no matter how you want to parse it. If an aircraft has “sensitive tabs” I would expect it to mean that the elevator and rudder require fairly minor displacement to wash out higher stick or pedal forces over a wide range of speeds. When one aircraft type is clearly identified by everyone who flew it as excessively demanding of trim and other aircraft types are specifically identified as needing very little or no trim adjustment by the same group of people I tend to think that I should need to adjust the one type fairly regularly and the others considerably less.

Let’s try to put ourselves in the 1930s-era high performance aircraft designer’s shoes. Aircraft are starting to exceed level speeds of 300mph (480kph), and if you didn’t place and design the control surfaces just right, control forces became greater than the average pilot could exert. The vast majority of trim tabs were on the rudders of monoplanes, usually big ones like the Martin B-10 until the mid-30s, at which point the technical issues appear to have been largely overcome and they start showing up on the rudders and elevators of an expanding variety of aircraft (and the ailerons of aircraft that had wing tanks).

The best pilots of the era tended to be drawn from the physical elites not least because you still had to exert fine control at a high force and because the buyers of high-performance military aircraft tended to be skeptical of depending upon new-fangled trim adjustment to keep the aircraft controllable. With good reason; changing trim was often clumsy and slow, unable to keep up with the higher speeds and acceleration of the modern monoplane fighters, so the designer/manufacturer was still expected to minimize the need (as opposed to the option) for trim for small speed variations. Trim was all mechanical, based on cables, pulleys, rods and screws motivated by human muscle and it was much slower than the digitally sensed and controlled systems we take for granted today, which were originally developed for high speed jets and found their way into civilian aviation, once they became cheap enough.

Simply put, trim adjustment in the late 1930s and early 1940s was considered a necessary evil to be avoided where possible and emphatically NOT a desirable convenience that obviates the need to exert even more (expensive) fineness in design and execution of the aircraft’s wings and control surfaces. It added weight and complexity to the aircraft, as well as cost.

So a wide range of speed change without requiring an adjustment in elevator or rudder was naturally going to be a primary design consideration. I would maintain that the Mustang was the most sophisticated high performance aircraft design around at the time of its introduction, and that the sophistication of its design would therefore be relatively sensitive to very minor changes.

How sensitive to change is the Mustang’s wing to minor changes? The wing was filler finished and hand polished. The upper and lower wings were covered with a surface to assure smoothness of the airfoil sections. The metal covered ailerons are statically, dynamically and aerodynamically balanced, and the wing’s efficiency is well known to be adversely affected by nicks, dents and scratches on the surface. Look at any shot of a Mustang in flight taken from above, and check out the wings—you will see nothing like the panel lines and obvious distinct panels of the fuselage on those wings (I think of all the Mustang models I built over the years and the care with which I ‘detailed’ those wing panels for the sake of ‘authenticity’…), even on aircraft that were in constant combat operations. I can picture the engineering officer responsible for maintaining those aircraft ordering 55 gallon drums of putty and reams of sandpaper to the bemusement of his buddies whose squadrons flew P-47s.

How adversely? It was found during factory tests that with a strip of wire 1/16 of an inch (roughly 1.6mm) taped along the leading edge of the wing, the aircraft would not leave the ground. America’s Hundred Thousand and every pilot I've ever read or talked to on the subject reports that the Mustang needed very little trim adjustment throughout its performance range and that tabs had to be applied with care; if the wings were that sensitive to minor changes, I would expect the elevators and rudder to be in very nearly the same class, that is, that very small adjustments would have great effect, and that they would not be necessary until a great deal of change in speed or power had taken place.

Is that consistent with what we see in the Il-2 Sturmovik ’46 Mustangs? Are the other aircraft I've mentioned treated in proportion?

cheers

horseback

[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!).

[JtD]

Originally Posted by horseback

...but it is still obvious that the elevators on all of these aircraft are far too sensitive...

Actually, if anything is obvious, it's that the control surfaces are far too insensitive. There's a whole bunch of fighter aircraft that could reach the stall angle of attack or designed load factor with as little as 10% control input from trimmed level flight. And as trim is linked to control sensitivity, obviously, trim is too insensitive as well.