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erospawn
01-22-2011, 09:05 PM
Hello,

I was wondering if any one had or knew of any settings for the Walkera 1#A with a WK-2801 TX? Is it any different that for the Novus 125CP settings?

john aeras
01-23-2011, 01:28 PM
Hello,

I was wondering if any one had or knew of any settings for the Walkera 1#A with a WK-2801 TX? Is it any different that for the Novus 125CP settings?
Here you go:

http://www.walkera.com/cn/upload/explain/Z11-A2601_expe.pdf

Pay attention to the first sentence under the title.

erospawn
01-23-2011, 06:18 PM
Thanks! You know, I did find that and set it up accordingly, but it didn't work. After noting what you said about reading the 1st sentence, I realized I never saw that. That's what I get for looking at the pictures! I finally switched channels 2 and 6 and low and behold she flies! Took her out for her maiden flight and she flies beautifully!

Dave S
04-18-2011, 03:10 AM
John, Had a fascinating experience with the 2801 settings for the 1#A. Initially, I set it up mostly per the reference you gave me, but didn't change the swash or gyro settings, and it flew fine, if a bit touchy for my inexperienced thumbs. Then 60something gave me some suggestions about setting D/R for ST1 to tame it down, and that worked very nicely. Then I noticed the rudder was drifting with the nose going left. So, I fiddled with the linkage, tried moving the servo horn (after I'd run out of trim), and while flyable, I had to keep some rightward pressure on the rudder stick to keep it straight. So, I decided to go into the Tx and set the swash and gyro per the sheets you referred me to. That's when the fun started.

I think I've narrowed it down to having reset the aileron % on the swash setting from 60 to the -70 that's called for in the 2801 setting sheets. After that I could either have proper elevator and aileron movements but not proper pitch movements, or vice versa, and with some settings (mostly changing Reverse settings) I'd have either aileron or elevator on the pitch (moving the left stick with the motor unplugged), and odd either aileron or elevator reversed or acting like pitch. Sooooo, I decided to start over, which meant carefully reading the first line of the 2801 settings sheet, which I have, of course, skimmed over before... got lucky I think. And after switching channels 2 and 6 as it instructs, everything works fine! No surprise to you, I'm sure, but interesting, at the least, to noobie me! At least I can give myself credit for going slowly and methodically, trying all the combinations and having the motor unplugged, and most importantly not trying to fly the bird! So, no harm done, the settings are correct now, and I've learned another couple lessons! Actually, as things started to get weird, I did actually have the thought that the aileron and pitch servos were acting reversed, but I couldn't explain why it sometimes seemed to also involve the elevator. Still not sure about that, but it is clear how different settings can and need to be depending on the Tx and Rx, including that the 1#A works with the 2801 swash setting at 3 servos, vs. 1 servo as is the case with the 4F200.

I'm guessing you'll read this and go, "Yeah, and what else is new?!" But it did turn out to be a good exercise for me. BTW, while you probably know this already, setting the elevator and aileron to 75% and EXP to +5 as 60something suggested, and then flying with switches set to ST1 has made a very nice difference for my inexperienced hands. The bird is much more tame, and I can see how I'll gradually be able to tighten the settings as I get more capable. I've said before I decided to get into this hobby for the challenge/s, and it's definitely fulfilling that need! I never imagined it could be as complex as it is, but it is fascinating, consuming and entirely addictive! Hope I haven't bored you, but I wanted to let you and others know if my little adventure into Tx settings. Maybe someone else will save some time for knowing this stuff, or at least pay better attention when someone advises carefully attending to the first line, or whatever else needs attention. In one's eagerness to be flying, it's so easy to move way too fast and not attend to and learn important stuff! I'm sure I'll be a more careful, observant and, hopefully, better pilot for the sake of paying attention to what's always turned out to be good advice from you and others here. Thanks, John! :)

john aeras
04-18-2011, 07:38 PM
No problem Dave! You are absolutly right, the complexity of this hobby is what keeps me interested as well! There are so many things to learn, it never gets boring.

I've also mentioned this, in another post; one very important aspect of this hobby, are the people involved and willing to give advice to others, that are starting out! That for me, is just as entertaining as building and flying helis. Just as others, have helped me, it's my pleasure to help others, when I can!

I'm glad you got everything sorted out and, yes, it's very easy to get distracted from exitement, but, that's human.
Have fun with the new heli!:thumbup:
John

60something
04-18-2011, 09:53 PM
Ok, just to clarify for Dave, in case we have a reference problem -- the discussion on D/Rs the other day did NOT include ST1 (or any of the idle-up positions - ST-1 and ST-2). I was speaking about setting up two different rates to be switched using the D/R swtiches on the tx when in flight mode NORM, for aileron and elevator. Up position is position "0", down is position "1" for each of the corner D/R switches. When the tx is in Flight mode ST1 (or ST-2), you can set completely different D/R rates in each Flight Mode. That is, for the 3 flight modes NORM, ST-1 and ST-2, there each have their own independent settings, for 12 in total (6 aileron, 6 elevator)! Put another way, for each flight mode, you can set the D/R rate switches for aileron and elevator completely independently of the other flight modes. Its not necessary to be in ST-1 to use dual rates, although you can set up ST-1 to be identical to NORM and play with D/R rates in that mode, rather than in the NORM mode. Not sure why you would want to, but you can. Everybody confused yet? :)

60something
04-18-2011, 10:08 PM
Still not sure about that, but it is clear how different settings can and need to be depending on the Tx and Rx, including that the 1#A works with the 2801 swash setting at 3 servos, vs. 1 servo as is the case with the 4F200

Its not just about the tx and rx, its also about the servo mounting geometry, and in the case of FB helis, there is also a 90 degree phase angle to contend with. The normal situation is the 3-servo setup used in the 2801 for the1#A. The 1-servo position is actually a special case of channel mixing built into the tx and specialty rxs (like in the 4F200), which is also dependent on the location of the servos,

john aeras
04-19-2011, 01:30 AM
Ok, just to clarify for Dave, in case we have a reference problem -- the discussion on D/Rs the other day did NOT include ST1 (or any of the idle-up positions - ST-1 and ST-2). I was speaking about setting up two different rates to be switched using the D/R swtiches on the tx when in flight mode NORM, for aileron and elevator. Up position is position "0", down is position "1" for each of the corner D/R switches. When the tx is in Flight mode ST1 (or ST-2), you can set completely different D/R rates in each Flight Mode. That is, for the 3 flight modes NORM, ST-1 and ST-2, there each have their own independent settings, for 12 in total (6 aileron, 6 elevator)! Put another way, for each flight mode, you can set the D/R rate switches for aileron and elevator completely independently of the other flight modes. Its not necessary to be in ST-1 to use dual rates, although you can set up ST-1 to be identical to NORM and play with D/R rates in that mode, rather than in the NORM mode. Not sure why you would want to, but you can. Everybody confused yet? :)
I was sort of wondering, you telling him to set up DR in ST1!:thinking
Your post explains everything, I hope Dave understood it right! (maybe just described it wrong)
Cheers!:cheers

Dave S
04-19-2011, 03:01 PM
Hey 60something and John, Delightfully, and with a touch of surprise, I did understand, and had somehow deduced at some point that there could be independent ST-1 and ST-2 relating to each of the three flight modes. Needless to say, I doubt I'll be using anything but NORMAL mode for some time to come :lol: but it's good to know about the others.

While I'm here, I'm so pleased with the change in flying comfort with the 70%, EXP +5 settings for the 1#A that I wonder if the same would be true for taming the 4F200? Makes sense in my little mind, but I thought I'd ask.

Thank you both for all the help. You guys make this site's motto true! :noteworthy:noteworthy

john aeras
04-19-2011, 05:03 PM
Not quite sure how the FBL works, maybe someone else can pitch in?

60something
04-19-2011, 07:06 PM
Hey 60something and John, Delightfully, and with a touch of surprise, I did understand, and had somehow deduced at some point that there could be independent ST-1 and ST-2 relating to each of the three flight modes. Needless to say, I doubt I'll be using anything but NORMAL mode for some time to come :lol: but it's good to know about the others.

While I'm here, I'm so pleased with the change in flying comfort with the 70%, EXP +5 settings for the 1#A that I wonder if the same would be true for taming the 4F200? Makes sense in my little mind, but I thought I'd ask.

Thank you both for all the help. You guy make this site's motto true! :noteworthy:noteworthy

The D/R ("dual rate") settings work on any servo plugged into the elevator and aileron sockets on the receiver. There is also a D/R function for rudder, but I'm not sure that its available in helicopter mode, due to the dual function on that switch - I think its available but the throttle hold function would have to be re-assigned. Haven't tried to do that. On helis, D/R rudder function is less important due to the relatively small servo movement for rudder control that you wind up setting up on the tail rotor.

What D/R does is reduce the range of movement of the servo arm, then spreads that movement over the full stick range. Thats what makes it a "rate" change - the servo now takes more time to cover the same distance, because the stick movement causes less servo change relative to its movement., i.e., the rate of change of the servo position is reduced by an amount proportional to the percentage applied. The exponential function further and independently changes the rate change around the centre position in a non-linear fashion.

These control modifications are independent of the type and form of the heli, and will work on any machine using the elevator and aileron (and rudder in planes) functions.

Caution: the D/R function reduces the full motion of the servo, not the stick. For example, if you set the D/R function of the elevator to 50%, the servo will travel 50% of the distance it would travel at 100%, or in otherwords, if not set at all. The stick movement doesn't change. That's how, at 50%, "softer" control occurs, because the servo is moving half as much as it would at 100%.

Caution: Now, if you already have the mechanical linkage set to reduced motion, or have TRAVADJ set to pull in the endpoints, dialing in large D/R amount may reduce the movement of the servo below the amount needed to control the model.
Its always desirable in an r/c model to set the mechanical linkage to provide the full range of movement you might want for the control function. This is typically achieved by arranging the linkage position from servo or bellcrank centre so that at full srvo swing, the linkage moves the total amount you need and no more. That provides the maximum resolution of the stick assembly on the tx matched to the proportional response of the servo. Now, when you dial in D/R, you have a further, properly proportional, reduced movement. The caution is always true though - it is possible to reduce your servo action to an amount below what it takes to control model. A typical example of where this bites the modeler is in a loop. At 100% servo action on the elevator, the aircraft may complete a loop in, say, 60 feet of vertical height in the air. At a selected D/R position for tameness, there may not be enough elevator movement to allow the aircraft to complete the loop in the available airspace, due to the reduced elevator movement. Hence, the "dual rates" concept - one rate for relaxed flying, another rate for higher performance, but requiring more pilot attention. So, from a practical basis, you set the rates to match your abilities and/or the movement ranges you've designed into the control linkages.

For many 3D capable helis, these default control movement ranges are large, therefore in my case, I'll set lower than 100% movement on both positions, one lower than the other, because at 100%, unless I redo the mechanical linkage, I'm going to lose the bird...real quick.

Each bird will have, for you, its own optimum D/R rates that make it comfortable for you. Remember though, that if you spend a lot of time learning on low D/R rates, at some point you'll have to start pulling these rates up if you want to get to full aerobatic capability.

I fly the 4F200 at 75% ele/aileron usually - responsive but not wacky. You'll notice too, that as you lower the D/R percentage, the exponential will be less desirable - you've already reduced the movement rate, too much EXP will reduce if even more at the centre, causing you to fall behind the heli in motion. The saving grace is that if you also have a D/R percentage dialed in, the resulting overmovement won't be as severe. You'll get to watch yourself lose the heli in slow-mo. :D

60something
04-19-2011, 07:25 PM
Not quite sure how the FBL works, maybe someone else can pitch in?

Not sure what exactly you're asking, John ???

john aeras
04-20-2011, 01:21 AM
Not sure what exactly you're asking, John ???
I'm not quite sure if you can add EXP to a FBL heli, or how exactly the RX works since you have to setup the TX for one servo heli.

That's what Dave was asking; if he can add EXP to his 4F200.

Dave S
04-20-2011, 02:10 AM
Feeling totally free to be totally naive and stupid, I'd guess John is referring to not knowing how the FBL algorithms in the Tx and Rx might influence the effects of changes in D/R and EXP as compared to a system that isn't already compensating for the lack of a flybar. Just my guess.

Your explanations are great, 60, and I feel like I understand quite well, with the exception that I'm not entirely sure about EXP. What I think I understand is that while D/R changes the amount of servo arm movement relative to Tx stick movement, the EXP function relates to effectively causing less servo movement in the to either side of center, with a declining effect as the movement moves toward either end, thus "softening" the middle. Is that about right?

Your example of what could happen with a loop and too much change in D/R, it makes me think of the turning radius of a car. In other words, if I were to decrease the amount the steering wheel would have to turn to produce a certain amount of change in the angle of the wheels, at some point it would be possible to turn the steering wheel around many times while changing the direction of the car very little... translation, the turning radius would be hugely increased, the car would only turn very gradually at best, and I'd probably never make it around a corner before jumping the curb on the far side of the street I was trying to turn onto. In the case of a heli trying to make a loop, a sixty foot diameter loop might become 75 or 80 or 100 feet. So, on the way around I'd literally run out of air before smacking into the ground. Is that about right? The same physics and geometries could also be described in terms of turning too slowly to compensate for the movement of the heli, and increased EXP would only worsen the situation by making the center area of servo movement increasingly ineffective as the EXP went up. Translation: mushy and slow. Yes?

So, if I've pretty much got it, I need to be mindful of continuously making the bird more sensitive as my skills improve, thus allowing for more precise control and tighter maneuvers. Am I on the right track or at least pointed in the right direction?

Right now, 70%-75% with +5 feels OK, and I think I'd be very likely to be getting into that over correcting loop and quickly losing the heli if the values were tighter right now. I'm thinking I'll try, once I'm more comfortable, moving the % up maybe by increments of 5 at a time, and alternately moving the EXP down by increments of -1 at each change point. Sound reasonable? And I'm glad to know the same principles apply to the 4F200, which is still too sensitive for me at the factory settings. I can manage it, but I come awfully close to causing wider and wilder gyrations that would certainly end in crashes if I didn't stay pretty low and set it down as soon as it (uh, that's me getting increasingly out of control, of course!) starts to get wild. So, I'm eager to try dialing down the elev and aile %s and possibly also increasing the EXP, maybe +1-+2 to start and seeing how it feels. The 4F200 reminds me of the difference between flying a Cessna 182 and my friends Mooney... no I'm not a pilot, but have friends who have been foolish enough to turn the yoke over to me sometimes! Of course the real planes are far easier since the orientation never changes, but that's a whole 'nuther story.

I gotta tell you I'm having a blast learning about all this, frustrations, crashes, repairs and all. It's fascinating the more sense of depth and complexity I start to be introduced to. Which reminds me, is there any other reading material, either more Schleuter or later that gets into what we're discussing now? I'm very curious, too, about swash timing and related factors, and on the larger scale, things like sliding, stalls, turns and other movements of the heli and how they relate to control functions, pitch, head speed and like that. Yeah, I know some or much of this is beyond what I need to know about at this point, and there's much more to learn at the level we've been talking about. As you can tell, I get increasingly curious and have more and more questions the more I get exposed to, so I do have to take some care not to get too far ahead of myself. But I'm sure you'll just not address stuff you know I don't need to know about yet.http://www.helifreak.com/images/smilies/icon_%20peace.gif

At the moment, I'm writing this while I'm watching weather radar as a huge squall line is moving through our area... not that I'd be out trying to fly at this hour anyway. We're having winds up to 70mph! Come to think of it, right now I'm sure I could fly without a heli :wow2: Hope your weather is rather more tame right now!

john aeras
04-20-2011, 03:43 PM
Feeling totally free to be totally naive and stupid, I'd guess John is referring to not knowing how the FBL algorithms in the Tx and Rx might influence the effects of changes in D/R and EXP as compared to a system that isn't already compensating for the lack of a flybar. Just my guess.
As I don't own a FBL, I haven't tried adding EXP to AIL & ELE travel.
(Wow Dave, your diplomatic approach and engineer's description of my lack of knowledge in the particular field, leads me to believe that you started your career in legal / political science and ended up in astrophysics! LOL! Well done!)

Your explanations are great, 60, and I feel like I understand quite well, with the exception that I'm not entirely sure about EXP. What I think I understand is that while D/R changes the amount of servo arm movement relative to Tx stick movement, the EXP function relates to effectively causing less servo movement in the to either side of center, with a declining effect as the movement moves toward either end, thus "softening" the middle. Is that about right?

My understanding of EXP, is reducing the amount of servo travel at mid-stick. The more expotential you add the less servo tavel along the length of stick travel on the TX.
DR (as per my understanding and I may be wrong) is having a switch set up on the TX where you can have access to normal settings and settings that you have added EXP to.
As I mentioned, these are my understandings and may be wrong as I am new to ccp setup, myself.
However when you find spare time you may want to go here (http://www.helifreak.com/showthread.php?t=41692) and watch the two videos under EXP 101 and DR 101.
Hey 60's, I enjoy your explanations and your knowledge contributed to this forum!
Keep up the good work as I also have a lot to learn (and thank you for it!)
Cheers!
John

60something
04-20-2011, 08:59 PM
Your explanations are great, 60, and I feel like I understand quite well, with the exception that I'm not entirely sure about EXP. What I think I understand is that while D/R changes the amount of servo arm movement relative to Tx stick movement, the EXP function relates to effectively causing less servo movement in the to either side of center, with a declining effect as the movement moves toward either end, thus "softening" the middle. Is that about right?

Yup - EXP stands for "exponential", which is short for "exponential rate". Expo is independent of D/R, and can be programmed on any of the flight axis channels (rudder, elevator, aileron - "yaw", "pitch", "roll" axes), regardless whether or not you are setting a D/R rate.

Exponential rate means the servo response to the stick is not linear , but varies exponentially, meaning for each next stick movement, the servo moves increasingly more (positive expo). Therefore, with positive expo set, from centre, the servo moves a litlle, moves a little, begins to move more, begins to move a lot, in response to the stick. The amount of change of rate of movement depends on the percentage set. Large expo values make the centre mushy and the ends very reactive. Its easy to set expo up (too much) to the point where nothing happens, and then nearly everthing happens. The purpose of expo primarily is to reduce the centre "jitter" that comes from moving the stick with a little more force to overcome its resting inertia at centre, leading to an over-action which has to be immediately corrected. The expo function gives you some room to move without the model taking off in an unplanned action. The other point here is that some pilots have a tendency to lean of the sticks abit in the wrong axis - eg giving a little aileron at the same time as you're feeding in some elevator trying to do a loop and winding up with a corkscrew barrel roll. Expo can be used to dial out that tendency, especially if its something a pilot chronically does. He might then dial in 1 or 2% expo on elevator, but put 8-10% on aileron to prevent that unwanted interaction. Expo came about when pattern fliers started using what are known as "tightband" servos and receivers, to improve reaction times in manouevers. These receivers and servos had a very narrow neutral time pulse -it took very little stick movement to begin the servo action (you could actually sit there and listen to the servos buzz just by blowing on the sticks). Expo was introduced to allow them to fine tune the "deadband" area in the middle to their personal preference.

Take a servo sometime and plug it into a receiver and stick a long arm on it. Then play with the different rates and watch how the servo behaves - you'll start to figure what they do.

So, on the way around I'd literally run out of air before smacking into the ground. Is that about right?The same physics and geometries could also be described in terms of turning too slowly to compensate for the movement of the heli, and increased EXP would only worsen the situation by making the center area of servo movement increasingly ineffective as the EXP went up. Translation: mushy and slow. Yes?Yup!

So, if I've pretty much got it, I need to be mindful of continuously making the bird more sensitive as my skills improve, thus allowing for more precise control and tighter maneuvers. Am I on the right track or at least pointed in the right direction?Yup!

Right now, 70%-75% with +5 feels OK, and I think I'd be very likely to be getting into that over correcting loop and quickly losing the heli if the values were tighter right now. I'm thinking I'll try, once I'm more comfortable, moving the % up maybe by increments of 5 at a time, and alternately moving the EXP down by increments of -1 at each change point. Sound reasonable?Yup! You'll find likely that as your skills progress, you'll begin to see the centre as mushy if you have much expo in, and you'll lower that. That will work, because then you'll have learned to be quicker at reacting to the action of the heli, and be tending to do less overcorrecting.

And I'm glad to know the same principles apply to the 4F200, which is still too sensitive for me at the factory settings. I can manage it, but I come awfully close to causing wider and wilder gyrations that would certainly end in crashes if I didn't stay pretty low and set it down as soon as it (uh, that's me getting increasingly out of control, of course!) starts to get wild. That's "chasing" the heli - you've started to react by overcorrecting, then you begin to fall behind with the control needed.

Which reminds me, is there any other reading material, either more Schleuter or later that gets into what we're discussing now? I'm very curious, too, about swash timing and related factors, and on the larger scale, things like sliding, stalls, turns and other movements of the heli and how they relate to control functions, pitch, head speed and like that. There's not a lot of written material about swash timing that I've seen. With regard to slips, slides and stalls etc - best thing to do there is hit a good bookstore and look for beginner's pilot manuals for general aviation. The behavior of the model aircraft in the air is basically the same as a full sized plane, and good piloting skills are good piloting, regardless of the size of the plane. R/C helis have some compromises compared to their full sized cousins, but the piloting is not different.

A book I haven't recommended to you yet, but am now going to is "Model Aircraft Aerodynamics", by Martin Simons. This is the bible of model aircraft as flying machines. I see its now in its 4th edition. Everything you ever wanted to know about how a model plane flies is covered -Everything. Professor Simons doesn't spare horses in this book, and if you're an r/c model devotee, this book will be a treasure on your shelves. Will also take a while to read it... about $25 new at the major outlets. Master about 25% of this book and you will be the expert on model flight. Master the whole book, and you'll be the expert designer, of model aircraft.

I have another book by Dave Day that goes into the radio usage and set up and chats about linkages, but I don't have it at my fingertips at the moment. Called "Setting up model r/c helicopters" I believe.

60something
04-20-2011, 09:14 PM
My understanding of EXP, is reducing the amount of servo travel at mid-stick. The more expotential you add the less servo tavel along the length of stick travel on the TX.

[edit] Ok, I just reread what you wrote above. Yes, partly - that's the outcome of setting expo rates - the higher the percentage set, the later the servo begins to complete its full movement. See my explanation to Dave just above about expo. With positive expo set the rate of servo action increases exponentially the further you move the stick, from very little at the middle, to a lot at the ends. Non-linear response of the servo to the stick. Negative expo, btw, reverses the expo action - lot in the middle, little at the ends. Unlike D/R, expo completes the full servo travel by the end of the stick movement.

DR (as per my understanding and I may be wrong) is having a switch set up on the TX where you can have access to normal settings and settings that you have added EXP to.Well, yes and no. They are two separate functions on the flight axes, but tied to the same switches. You can set up a D/R switch with only expo, or only D/R or some combination, in each switch position. D/R alters how much movement the servo makes per amount of stick movement, in a linear fashion. 50% D/R means the servo moves half as far for the same stick movement as it would at no D/R (100% function). The 50% setting would mean the servo would only travel half as far in total as it would with no D/R. Since the servo only has to move half as far at 50%, but the whole stick movement is available, then the servo will only move half as fast, in order to cover the half distance in the same amount of stick movement, hence the "rate" terminology. Try it - plug a servo into a flight axis (rudder, elevator, aileron) socket in a receiver, and play with the rates - stick a long arm on the servo and watch how it moves with the different settings.

Dave S
04-20-2011, 10:50 PM
(Wow Dave, your diplomatic approach and engineer's description of my lack of knowledge in the particular field, leads me to believe that you started your career in legal / political science and ended up in astrophysics! LOL! Well done!) John, you're gonna give me a great big head! Actually, glad you like the wording. It's really just how I think (and I am an admitted geek) and I've found if I can reasonably describe something in a way the other person agrees with, it helps confirm that I actually understood whatever it is. BTW, I'm not any of those things you've so kindly suggested, but I did stay at a Holiday Inn Express... :rotf

A book I haven't recommended to you yet, but am now going to is "Model Aircraft Aerodynamics", by Martin Simons. This is the bible of model aircraft as flying machines. I see its now in its 4th edition. Everything you ever wanted to know about how a model plane flies is covered -Everything. Professor Simons doesn't spare horses in this book, and if you're an r/c model devotee, this book will be a treasure on your shelves. Will also take a while to read it... about $25 new at the major outlets. Master about 25% of this book and you will be the expert on model flight. Master the whole book, and you'll be the expert designer, of model aircraft.

Thanks so much for all the great info, and the book references. I will get and try to understand at least as much as I can of the "Model Aircraft Aerodynamics" book. I do find I do better at things if I have some sort of cognitive handle on it. As you've described the book, it is obviously the true origin of "Simon(s) Says!" Sorry, I couldn't resist! :rotf Kidding aside, I do appreciate the reference and will get the book. BTW, since you also referenced Dave Day, I do happen to have one of his books (that I haven't started yet :oops: ) called, "Flying Model Helicopters." So, I'm glad you reminded me of him because I'd lost the book in one of my stacks and who knows when I'd have rediscovered it!

I like the idea of hooking up a Tx, Rx and a servo with a long arm. I'm sure that'll help reinforce my understanding. Visuals are almost always best. We'll I'm off to the basement for some repair and maintenance... and maybe, just maybe :lol: some hovering practice. Thanks, again, 60. I am so enjoying all this!

john aeras
04-21-2011, 12:12 AM
[edit] .

Well, yes and no. They are two separate functions on the flight axes, but tied to the same switches. You can set up a D/R switch with only expo, or only D/R or some combination, in each switch position. D/R alters how much movement the servo makes per amount of stick movement, in a linear fashion. 50% D/R means the servo moves half as far for the same stick movement as it would at no D/R (100% function). The 50% setting would mean the servo would only travel half as far in total as it would with no D/R. Since the servo only has to move half as far at 50%, but the whole stick movement is available, then the servo will only move half as fast, in order to cover the half distance in the same amount of stick movement, hence the "rate" terminology. Try it - plug a servo into a flight axis (rudder, elevator, aileron) socket in a receiver, and play with the rates - stick a long arm on the servo and watch how it moves with the different settings.

Thanks for the clarification on that 60's! I now completely understand DR. I now have to get around the difference of DR and TRAV/ADJ! (when I find reading time)

Ok, this thread is starting to have so much info, it may be worth, making it a sticky!:thumbup:

60something
04-21-2011, 06:07 AM
I like the idea of hooking up a Tx, Rx and a servo with a long arm. I'm sure that'll help reinforce my understanding. Visuals are almost always best. One of the downsides of RTF helis for beginners is they don't get to play with the component pieces of the control and power systems before they go in the model. On of the very best exercises for a beginner wrt the radio is to lay out the radio, plug the servos into the various receiver ports, hook up a battery, and watch how the various settings, mixers and other tx doodads actual change or modify the behavior of the servos. Trying to work this out in the model can sometimes mean you have to fiddle with settings for things you don't yet understand the reasoning for in the first place. This makes way too much of your modeling experience, at the beginning, a trial and error process, with heavy emphasis on error. I'll tackle travel adjust later.

60something
04-21-2011, 06:24 AM
Another point about expo I just remembered, and another reason for its inception in the beginning (now that I recall, more important than the deadband issue). Rotary servo motion does not result in a linear motion rate of a pushrod.

If you visualize (or draw it out on paper) a servo arm as a wheel (like in some kits), with the ball out at the end and a rod attached at 90deg to the axis of the servo arm, as the servo arm moves from neutral, the pushrod moves a distance. At the beginning of the rotary movement of the servo, the distance traveled by the pushrod is almost the same as the distance the ball has moved with the arm (or disc).

But as the ball moves around the servo hub, the distance the ball moves away from the axis of rod travel increases(at 90deg to the axis of rod travel). This means that the rod, at the ends of the servo travel, moves less and less along the rod axis. This creates a movement on the control linkage that puts more action in the centre of servo travel and less at the ends - the reverse of positive expo. Setting positive expo compensates for this exponential travel issue at the servo, in order to return the rod movement to linear rate of travel action along the rod axis. Now that I think about it, this was the primary driver for pattern fliers in the development of expo - compensating for rate change due to rotary servo action, so that aerobatic manouevers would execute in a precise linear fashion without the exponential rate change imposed by the rotary servo action, through the manouever.

[Visual for Dave :) : piston, conn rod and crankshaft in an engine. Rapid rotation around the crank, slower compression and exhaust cycles at TDC, facilitating the setting of timing for valves...]

john aeras
04-21-2011, 11:31 AM
But as the ball moves around the servo hub, the distance the ball moves away from the axis of rod travel increases(at 90deg to the axis of rod travel). This means that the rod, at the ends of the servo travel, moves less and less along the rod axis. This creates a movement on the control linkage that puts more action in the centre of servo travel and less at the ends - the reverse of positive expo. Setting positive expo compensates for this exponential travel issue at the servo, in order to return the rod movement to linear rate of travel action along the rod axis. Now that I think about it, this was the primary driver for pattern fliers in the development of expo - compensating for rate change due to rotary servo action, so that aerobatic manouevers would execute in a precise linear fashion without the exponential rate change imposed by the rotary servo action, through the manouever.


Ok 60's, that is an incredible explanation and makes absolute sense of EXP implementation!
Thank you for that! You're a walking encyclopeadia!:noteworthy

Dave S
04-21-2011, 01:11 PM
A great explanation, indeed! And thanks for the visual. I was surprised for just a moment when I read "TDC", but quickly thought, "Of course 60 know's about that, too! John is right about you!!!

rzrfun111
02-19-2012, 12:44 PM
will this work if you have 2401 receiver? 2801 pro, I have a CB180Z and want to tame it down a bit?