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Old Sep 29, 2012, 07:10 AM
teamwork, do it my way!
Dubai, UAE
Joined Jun 2007
731 Posts
Aero, I have a basic understanding of mixing, but the 18 has a different manner of doing things that requires a little paradigm shift.

In my experience, I have mixed before but just the basics like adding ele to flaps, ele to throttle and rudd to ail, that sort of thing. This plane is set up very basically and doesn't require any mixes really, I only have some dual rates and expo, and some differential. I don't use any flight modes, it more or less stays in one mode from take off to landing...so, no major mixing required...
To answer your question, I just want a switch to change from HH to Rate....I had this functionality with the way I had it setup, I just could not adjust the gain...so for now, that's what I need to do.

I bought the 18 for the model memory, and the desire to learn mixing techniques as well as the telemetry and other functions. I would probably benefit a lot from the additional functionality, but it is rather daunting....
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Old Sep 29, 2012, 10:01 AM
AndyKunz's Avatar
Illinois
Joined Sep 2001
24,711 Posts
What you are asking for is a flat line for each switch position.

In Acro Gyro screen, select the switch to be what ever one you want (D I think you said). For each position of D, set the curve to be a flat line at the desired position.

Note that Heli gyros are different than Acro gyros. Since you are using a Heli gyro, 0 gain will be with the line in the center of the graph, heading hold mode will be with the line above the center, and rate will be below the center. The amount of gain you have will depend on how far above/below the center you make that line.

The purpose of the Acro Gyro function is to give you the ability to have the gain change based on stick position. You aren't wanting to use that, it seems, so you just use a flat line. If you come back later and want to change the gains, you are already set up by having a (flat) curve there.

Andy
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Old Sep 29, 2012, 01:25 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,679 Posts
The way the linkage is set up on my elevator causes the need to set D/R at 50% to bring the correct amount of travel down to where it should be.

Does that cause a limitation to the expo curve programming ability?

I have three more holes in the elevator control horn that I could use to move the clevis away from the elevator.

Could I get a better expo curve that gives softer control around center yet does not rise as sharply beyond say 50% stick movement?
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Old Sep 29, 2012, 01:40 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,679 Posts
Quote:
Originally Posted by davidmc36 View Post
I have had a great time flying my Twin Otter with the DX18.

Yet I still occasionally stuff the nose and bounce the landing.

With the down elevator mix with flaps out it tends to dive as I dial the throttle off. If I forget to keep some up pressure near the ground I get the stuffed nose landing.

So I was thinking of the throttle to up elevator mix. I have tried it on the sim and liked it in part. If you drop the throttle very quickly just as you touch down the added elevator can make it balloon back up.

So what I thought about was two mixes. One starts dialing in the up elevator as throttle goes below 50%, the other one starts counteracting below say 15% so no more up elevator is added after that point.

Is this the easiest/most sensible way to do something like this?
Just a tad off topic, but I ended up working out this problem by changing the COG to nearly the aft end of the range. Now when I have the not so great landings it does not bounce up and immediately nose back into the ground, it just hangs in the air basically level and I can continue feathering it in for landing. Also it does not dive down excessively if I release back pressure on the elevator a bit too much.

Something I never thought of before, that one of the great guys who is a regular at our field and is always ready with helpful advice, was to put a fair bit of expo (use throttle curve) into the throttle stick. It makes it much eaiser to tweak just the right amount of power for landing.

By the time I discover how to use all the abilities of this radio they will probably be coming out with mind control of RC models.
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Old Sep 29, 2012, 01:59 PM
teamwork, do it my way!
Dubai, UAE
Joined Jun 2007
731 Posts
Andy, thanks for that, I think I know what you mean now, so I will try that in the morning.

With regards to the heli gain, I think I have that setup incorrect as well. Again, referring to my old DX6i setup, a negative value was Rate, and positive was HH (or vice versa, can't recall). If I a, correct, the 18 requires that both the values be positive? I looked at a thread in heli freak, http://helifreak.com/showthread.php?p=4262011 and that's what I understood. And that servo reversing could play a part in its functionality. Aerocal was a contributor in that thread so between him and Andy I will hopefully get some answers to my questions...
Thanks to both of you for your contributions, without your interest, some of us would be very lost.
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Old Sep 29, 2012, 03:25 PM
Registered User
Central California
Joined Dec 2006
2,580 Posts
Quote:
Originally Posted by davidmc36 View Post
The way the linkage is set up on my elevator causes the need to set D/R at 50% to bring the correct amount of travel down to where it should be.

Does that cause a limitation to the expo curve programming ability?

I have three more holes in the elevator control horn that I could use to move the clevis away from the elevator.

Could I get a better expo curve that gives softer control around center yet does not rise as sharply beyond say 50% stick movement?
If you are mechanically setup to get more throw than you are actually using and you dial the rate down to reduce the throw you dont affect the actual expo operation.Expo acts on the entire range of the set rate.What it does do though is reduce the amount of resolution you have in the surface.The servo will be traveling less and giving more throw for a given amount of servo travel.If you take this idea to the extreme what you will see is the control surface will not move smoothly.It will jump from point to point.In other words the steps of the servo will become more pronounced and there can be dead spots where the surface simple cant go because it would be in between steps.If you are mechanically setup to provide more throw than you would ever use it would be a big advantage to move the clevis farther out on the horn or the connection closer to the center of the servo arm allowing the servo to work more in its entire range.
The movement at the surface will be smoother.This is apparent on the elevator during a landing flare.With a big loss of resolution you will find it difficult to get that "sweet spot" to flare.It will kind of jump from too much to too little without being able to find the right spot.Expo will only help so much.
If you are mechanically losing alot of resolution Expo can make the fight to get the surface in just the right spot even tougher.Especially past half stick where the curve gets steeper.
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Old Sep 29, 2012, 03:45 PM
Registered User
Central California
Joined Dec 2006
2,580 Posts
Quote:
Originally Posted by Cathurga View Post
Andy, thanks for that, I think I know what you mean now, so I will try that in the morning.

With regards to the heli gain, I think I have that setup incorrect as well. Again, referring to my old DX6i setup, a negative value was Rate, and positive was HH (or vice versa, can't recall). If I a, correct, the 18 requires that both the values be positive? I looked at a thread in heli freak, http://helifreak.com/showthread.php?p=4262011 and that's what I understood. And that servo reversing could play a part in its functionality. Aerocal was a contributor in that thread so between him and Andy I will hopefully get some answers to my questions...
Thanks to both of you for your contributions, without your interest, some of us would be very lost.
I think you may have confused the gain scheme.It is kind of a definitions/scaling thing.
Heli gyros(for the most part) use center(zero) as the gain off position.Adding travel to the plus side gives HH gain and travel to the minus side gives Rate gain.The confusion arose when changing from the DX7(original) to the newer radios.The DX7(original) used 0-100 for the gain menu.0 was -100,50 was center(zero) and 100 was +100.So all the gains were positive in the menu.Less than 50=Rate and more than 50=HH.There were only 100 total steps so every step resulted in 2% of gain change.With what we are using now we control the gains with the standard channel scheme of -100/0/+100.The gain menus reflect this.
The confusion arose when guys going from a gain of 70 in the DX7(original) tried to put 70% in using the different scaling.Since 70 was 20 above 50 and each step was 2% this translated to a true gain of 40%.70% was way too high and they got severe wag/hunting and couldnt figure out why.
It was a simple scaling issue.
The DX6i also uses the 0-100 scaling for gyro gain in the gyro menu.The DX18 is different and uses -100/0/+100.So with the DX18 you will use positive values for HH and negative values for Rate.
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Last edited by aerocal; Sep 29, 2012 at 03:55 PM.
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Old Sep 29, 2012, 03:53 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,679 Posts
Quote:
Originally Posted by aerocal View Post
If you are mechanically setup to get more throw than you are actually using and you dial the rate down to reduce the throw you dont affect the actual expo operation.Expo acts on the entire range of the set rate.What it does do though is reduce the amount of resolution you have in the surface.The servo will be traveling less and giving more throw for a given amount of servo travel.If you take this idea to the extreme what you will see is the control surface will not move smoothly.It will jump from point to point.In other words the steps of the servo will become more pronounced and there can be dead spots where the surface simple cant go because it would be in between steps.If you are mechanically setup to provide more throw than you would ever use it would be a big advantage to move the clevis farther out on the horn or the connection closer to the center of the servo arm allowing the servo to work more in its entire range.
The movement at the surface will be smoother.This is apparent on the elevator during a landing flare.With a big loss of resolution you will find it difficult to get that "sweet spot" to flare.It will kind of jump from too much to too little without being able to find the right spot.Expo will only help so much.
If you are mechanically losing alot of resolution Expo can make the fight to get the surface in just the right spot even tougher.Especially past half stick where the curve gets steeper.
Thanks for the insight there. I had a feeling by looking at the curve in the expo screen I was experiencing what you described. Going to slide the clevis out to the end and re-set the D/R and expo for my next flight.
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Old Sep 29, 2012, 04:02 PM
Registered User
Central California
Joined Dec 2006
2,580 Posts
Quote:
Originally Posted by Cathurga View Post
Aero, I have a basic understanding of mixing, but the 18 has a different manner of doing things that requires a little paradigm shift.

In my experience, I have mixed before but just the basics like adding ele to flaps, ele to throttle and rudd to ail, that sort of thing. This plane is set up very basically and doesn't require any mixes really, I only have some dual rates and expo, and some differential. I don't use any flight modes, it more or less stays in one mode from take off to landing...so, no major mixing required...
To answer your question, I just want a switch to change from HH to Rate....I had this functionality with the way I had it setup, I just could not adjust the gain...so for now, that's what I need to do.

I bought the 18 for the model memory, and the desire to learn mixing techniques as well as the telemetry and other functions. I would probably benefit a lot from the additional functionality, but it is rather daunting....
Yes it can be alot to absorb at first.The one tool you can learn to use is the Monitor screen.Its very accurate and can show you exactly what difference changing a setting makes.
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Old Sep 30, 2012, 02:56 AM
teamwork, do it my way!
Dubai, UAE
Joined Jun 2007
731 Posts
Ok, thanks for the help. I was tooling around with the heli earlier, and I had the reverser setup on the gyro wrong....made for some interesting attempts at test flights!!

The monitor also pointed me to the fact that the servo reversing on the Tx will only affect the gyro going to HH or RM based on the + or - values, and does not affect the servo direction travel.

So, whilst holding the heli aloft, I did some testing (yeah I know, not very safe, but beats the thing beating itself to death on the floor) and it seems I am in the right ballpark now with direction and reaction of the gyro. I will do some flight testing later today.
Since we are talking about 'real' gain with the dx18 setup, I assume the further you go AWAY from zero, the larger the gain, regardless of value being + or -, i.e -30 on one position will be 30% gain in Rate, and 30 on the second swith position will be 30% gain in the HH mode.

That being the case, what would be a good start point for gain setting for setting up a heli with a std 2-blade, FB config?

I have turned the delay on the gyro to zero.

I think I have the ACRO gyro thing worked out now, and I can see how the ACRO gyro would want gains to change with throttle position, I would assume that i full forward flight you would want less gain than a slower speed.....or am I completely off the reservation?
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Old Sep 30, 2012, 04:04 AM
Registered User
Central California
Joined Dec 2006
2,580 Posts
Sounds like your getting somewhere.
Yes. The value you have set going one direction or the other from center will directly relate as gain%. On most FB helis 30% is a good place to start.

I honestly havent gained alot of experience with gyros in fixed wing.I have a couple gyros sitting around I need to try that with.I have a mustang that is a handful to keep straight on takeoff and landing in a crosswind.Ive been meaning to drag it down and do that.Im sure there are some threads here somewhere discussing it.Will have to do a search one of these days.
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Old Sep 30, 2012, 05:32 AM
teamwork, do it my way!
Dubai, UAE
Joined Jun 2007
731 Posts
Ok, 30% is working ok for me now, had the heli up and got her trimmed out, going to have to make some mechanical changes as there is too much sub trim and trim so will try even it out with adjustments.

I have certainly learned some interesting things with this TX, the monitor is a great way to help getting the mechanics set up. Just see which way requires compensation...
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Old Oct 02, 2012, 03:48 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,679 Posts
Quote:
Originally Posted by davidmc36 View Post
Thanks for the insight there. I had a feeling by looking at the curve in the expo screen I was experiencing what you described. Going to slide the clevis out to the end and re-set the D/R and expo for my next flight.
Got the TO out today with the control horn re-set. It made quite a difference to the controllability of elevator during the flare and touch-down. It has been a great summer of refining how I set up the radio and control surfaces.
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Old Oct 02, 2012, 04:26 PM
can't buy vaporware
7oneWo1f's Avatar
United States, MN, Minneapolis
Joined Nov 2011
8,479 Posts
Any cases work with this? Or a dual case for a DX18 and a DX8?
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Old Oct 02, 2012, 04:43 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
24,286 Posts
Cases as in transmitter cases?

I had a tool case lying around and so I ordered the Dual TX foam insert from HH and it fits perfectly.
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