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Old Jan 19, 2012, 04:40 PM
jbb
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mSRx Manual Servo Link Adjustment Methods, MMM vs JBB

I just wanted to clear some things up with the ‘manual trimming’ scheme called “MMM” on these mSRx threads, formalize my own JBB Method, and make sure folks are getting accurate information, and also have a centralized location for folks to search (alot of posts ask 'where is the method') and since it's so critical for everyone to do something to get their servo links set to the correct length, here is it's very own thread:

Adjusting the links was originally posted by Spainman back on 1/2/12

Quote:
Originally Posted by spainman View Post
Tuning the links so that the swashplate is tilted with the servos on their zero position when the heli holds a still hover, helps eliminating the problem. When touching the ruder stick, the servos will try to move to zero (because of the bug) but won't move that much, because they are already zeroed. The result is that the heli will behave more neutral during yaw.
And ‘a’ method was first proposed by Martyn McKinney to adjust the links on 1/10/12 10:53 am
Quote:
Originally Posted by Martyn McKinney View Post
Could you try this and report back.

Fly the heli and adjust the trims on the transmitter so that the heli hovers with no stick input.

Land the heli and while holding the heli horizontally in your hand after initialization, apply a bit of throttle. The swash may move slightly from its zero throttle position. Make a note of this new position. This is the hover position.
And then the name “MMM” was coined by Toys2Cars2Toys later that same evening
Quote:
Originally Posted by toys2cars2toys View Post
I tried the Martyn McKinney Mod and it works well
http://www.rcgroups.com/forums/showp...3&postcount=12

Henceforth referred to as the MMM
I wanted to put this comment in the main msrx thread as more people may see it
And then Martyn formalized his method into 6 easy to follow steps on 1/12/12 at 1:43pm est
Quote:
Originally Posted by Martyn McKinney View Post
Did you do this? Is your swash moving when you apply throttle or rudder? It shouldn't be.

1. Hover the heli and set the trims on the transmitter so that it will hover hands off.

2. Land the heli. Don't turn off the transmitter.

3. Hold the heli in your hand reasonably level and steady.

4. Increase the throttle. The swash shouldn't move, but if it does move remember where it moved to. Call this the hover position.

5. Move the transmitter stick to zero throttle (this is the neutral position). If the swash had moved in 4. above, adjust the swash links so that at zero throttle the swash attains the hover position in 4. above.

6. Refly the heli. Readjust the transmitter trims so that the heli hovers and again check to see that the swash doesn't move when throttle is applied.

A couple days later I, JBB, was actually the one who added the ‘3 clicks of rudder’ (disable Heading Hold) step to this process and proposed “MMMv.JBB” verson on 1/12/12 7:23pm

Quote:
Originally Posted by jbb View Post
I submit to you MMM version JBB, or more simply MMM v.JBB

1. 3 clicks of rudder trim to disable "Heading Hold"
2. Get into hover and go hands off, note which way it drifts
3. Land, adjust the offending servo link, rinse and repeat.
To which Martyn had a couple of ‘rhetorical’ questions, apparently to imply the ‘3 clicks of rudder’ should be done while already in a hover...and apparently rejected the idea of a vJBB...

Quote:
Originally Posted by Martyn McKinney View Post
What would happen if you reversed steps 1 and 2?

1. Fly heli. Adjust trims for stable hands off hover.
2. 3 clicks of rudder trim to disable "Heading Hold"
3. Note which way it drifts
4. Land, adjust the offending servo link, rinse and repeat.
Quote:
Originally Posted by Martyn McKinney View Post
When I asked my question about interchanging steps 1 and 2, I had intended it to be a rhetorical question.

By flying the heli into a hands off hover using trim and then adding 3 clicks of rudder to disable the "heading Hold", the heli will immediately veer off if the neutral and hover positions are not identical. It is then easy to determine in which direction the links must be changed.

What would happen if you reversed steps 1 and 2 results in the sequence below.

1. Fly heli. Adjust trims for stable hands off hover.
2. 3 clicks of rudder trim to disable "Heading Hold"
3. Note which way it drifts
4. Land, adjust the offending servo link, rinse and repeat.
And then Martyn came up with his “4 step” second version (MMMv2), which was a mashup of his original and my own ‘JBB’ method on 1/14/12

Quote:
Originally Posted by Martyn McKinney View Post
I found it difficult to eyeball the swash position.

I don't think a photo will help, but tilted a bit to the right and level fore and aft.

I would suggest the following. I found it the easiest way to set up the heli.

1. Fly heli. Adjust trims for stable hands off hover.
2. 3 clicks of rudder trim to disable "Heading Hold"
3. Note which way it drifts
4. Gyros will turn back on by applying rudder. Land, adjust the offending servo link and repeat.
Which was revised again the following day with an extra 5th step 1/15/12

Quote:
Originally Posted by Martyn McKinney View Post
1. Fly heli. Adjust TRANSMITTER trims for stable hands off hover. The heli will move around, but it should be possible to remove your hands from the transmitter for a few seconds.
2. Apply 3 clicks of rudder trim to disable "Heading Hold" The heli may rotate a bit.
3. Ignore the small rotation and note which way it drifts
4. Heli will now be unstable. Applying rudder will re-enable the AS3X system and allow you to land.
5. Land, adjust the offending servo link and repeat by hovering and readjusting TRANSMITTER trims.
And repeated in the following days 1/17/11
Quote:
Originally Posted by Martyn McKinney View Post
1. Fly heli. Adjust TRANSMITTER trims for stable hands off hover. The heli will move around, but it should be possible to remove your hands from the transmitter for a few seconds.
2. Apply 3 clicks of rudder trim to disable "Heading Hold" The heli may rotate a bit.
3. Ignore the small rotation and note which way it drifts
4. Heli will now be unstable. Applying rudder will re-enable the AS3X system and allow you to land.
5. Land, adjust the offending servo link and repeat by hovering and readjusting TRANSMITTER trims.
And now some questions are coming in concerned that the 3 rudder clicks should not be done while in flight, but should be done while the heli is at zero throttle 1/18/12
Quote:
Originally Posted by spainman View Post
Btw: When tuning the links, land and enter the tree clicks of rudder trim while the motor is not running. When restarting the motor the out of trim rudder will be considered the zero position and the links can be tuned without constant slow yawing. Everytime I read how to tune the links the description says to enter the trim in flight. Not the best way for beginners that may even have problems to enter a still hover without the bird constantly trying to turn around.

Cheers,
Ruben
So first I’d like to give my opinion on MMM
Quote:
Originally Posted by Martyn McKinney View Post
1. Fly heli. Adjust TRANSMITTER trims for stable hands off hover. The heli will move around, but it should be possible to remove your hands from the transmitter for a few seconds.
2. Apply 3 clicks of rudder trim to disable "Heading Hold" The heli may rotate a bit.
3. Ignore the small rotation and note which way it drifts
4. Heli will now be unstable. Applying rudder will re-enable the AS3X system and allow you to land.
5. Land, adjust the offending servo link and repeat by hovering and readjusting TRANSMITTER trims.
step 1: IMO Should not fly heli before disabling Heading Hold, and I see no point to adjusting trims (right stick?) to get a stable hover…what's the point in doing this? IDK.
step 2-3: Why would you do the 3 rudder clicks while the heli is in flight, only to then have to ‘ignore’ the resulting yaw...when you trim the rudder while flying, the heli will start to yaw in that direction.
step 4: While the heli has, for example, ‘3 left clicks’ then the only way a rudder application will then ‘re-enable the AS3X’ is if you push the stick to the *Right, just enough* to get the Tx signal back into ‘rudder center’ range (which is within 2 clicks either side), so seems one would need to be very precise to accomplish this, and it is completely unnecessary.
step 5: again, I just don’t understand the concept of ‘adjusting Tx trims’ to get it into stable hover

Now I’d like to explain what will now be called the “JBB Method” of Manually Trimming the mSRx Servo Links:


1: Initialize heli as normal, and enter 3 clicks of rudder while the motor is off (or as many as it takes to disable your Heading Lock)…..or I suppose you could alternately give the rudder 3 clicks of rudder even before initializing the heli.
2: Fly the heli into a stable hover, (it will NOT yaw left, because you entered the Left Rudder trim while the motor was off….when you then turned the motor ON to takeoff, the system baselined the yaw, so in effect your rudder trim is not affecting the heli to yaw, it’s only turned off the Heading Lock.)
3: While the heli is in hover, release the right stick for a brief moment and note which way the heli drifts.
4: Land the heli and adjust the links, based on your observations in step #3, and repeat to step #2


So, do NOT fly the heli before disabling the Heading Hold
Do NOT adjust trims for stable hovering

Just shut off the Heading Hold before flight, get it into stable hover using only the sticks, (shouldn't even need rudder for stable hover this method), let go of the right stick (see which way it drifts), and land.
Adjust.
Repeat.

So, there's 2 methods, choose the one most comfortable for you, or suggest your own version. Since I'm a fairly new 'heli' pilot, I choose the method without the 'yaw'. MMM v1.0 was too difficult for me to do, and MMMv2.0 just didn't make sense to me and seems too difficult due to the resulting yaw.

And just for fun, after you've adjusted your swash as close to perfect as you can....have a romp around the gym with the Heading Hold turned OFF....see how skittish it flies? That's what is going on in 'Normal' mode, when you have the rudder applied. It's hard for me to believe that this was an intentional design, esp. in light of the earlier mCPx not doing it, and it being the better flyer.
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Old Jan 19, 2012, 07:26 PM
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Actually I don't see the point of discussing what "method" makes more sense - it's pretty obvious that it makes sense to just disable the attitude hold mode before taking off and to adjust the linkages then for a stable hover like we have done for decades on mechanical flybared helis.

Of course it doesn't make sense to enter yaw trim in flight and try to trim mechanically a constantly yawing heli. It's difficult and it's not accurate!

Actually the knwoledge that the servos go to zero on rudder input and JBBs discovery (thanks for that again) that rudder trim position on takeoff is considered zero rudder in flight while still having disabled the "attitude hold mode" (no, it's not heading hold what we are talking about) are THE intresting things to know.

From there it's just adjusting linkages - does anybody really need step by step instructions to do that?!

Hey... we are talking about adjusting linkages... this is no vodoo, rocket science or patent pending operation.

Cheers,
Ruben
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Old Jan 19, 2012, 08:11 PM
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Thanks jbb, for turning this into a separate thread and summarizing the history so it will be easier to find by others.

Quote:
Originally Posted by jbb View Post
1: Initialize heli as normal, and enter 3 clicks of rudder while the motor is off (or as many as it takes to disable your Heading Lock)…..or I suppose you could alternately give the rudder 3 clicks of rudder even before initializing the heli.
2: Fly the heli into a stable hover, (it will NOT yaw left, because you entered the Left Rudder trim while the motor was off….when you then turned the motor ON to takeoff, the system baselined the yaw, so in effect your rudder trim is not affecting the heli to yaw, it’s only turned off the Heading Lock.)
I have to disagree slightly here. My mSRx yaws with 3 clicks (actually 2 clicks will do it for me). I've tested clicking rudder trim with the motor off and I've tested clicking rudder trim with the battery un-plugged (initialize with 3 clicks). Under every possible condition, my mSRx will yaw as a result of the trim on the rudder. There's no way around it for me.

If you can enter rudder trim with the motor off and not get yaw, then that's what you should do. It's hard enough to hover without correcting for a small rotation. But for me, rudder trim is going to induce yaw no matter what.

So for me its:

1. Fly the heli into a stable hover, Give it 3 clicks of rudder to turn off heading hold
2. Adjust the linkages until it will fly a stable hands free hover (or as close to it as possible)
3. Return the rudder to zero trim.

But Like Spainman says. It doesn't really matter how you do it, as long as you do it.

The important points for a well behaved mSRx are:

- you must adjust the servo linkages, not the stick trims.
- you must disable the AS3X 'heading hold' in order to observe and adjust the trim.
- 3 clicks of rudder trim will disable the AS3X 'heading hold'
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Old Jan 19, 2012, 08:28 PM
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Quote:
Originally Posted by ruzam View Post
I have to disagree slightly here. My mSRx yaws with 3 clicks (actually 2 clicks will do it for me). I've tested clicking rudder trim with the motor off and I've tested clicking rudder trim with the battery un-plugged (initialize with 3 clicks). Under every possible condition, my mSRx will yaw as a result of the trim on the rudder. There's no way around it for me.

I wonder where the difference is

- what transmitter are you using? I've tried it with the stock transmitter and it works. Maybe your trim clicks are more coarse if you are using another tx and you move out of the range that the rx tolerates as "zeroable".

- does the swashplate counteract movements while the motor is off? Maybe your throttle trim is high enough to enable the algorithms but low enough that the motor is still not turning...

- have you tried triming left and right without success? Now that I think about it I always give three clicks of left rudder before takeoff when I want some "extra fun" ;-) Maybe it depends on the direction.

Considering that this is software and most likely we have all the same firmware there should be no variations in the behaviour.

Cheers,
Ruben
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Old Jan 19, 2012, 08:49 PM
jbb
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Either way it gets done...jes git'er done!

If the swash didn't do what it does, then it wouldn't be so critical...but that's what we've got, it is what it is.

Btw I usually need some rudder action to get into hover but once there it is set pretty well. And that's in either mode.
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Old Jan 19, 2012, 10:00 PM
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Quote:
Originally Posted by spainman View Post
- what transmitter are you using?
DX6i. 2 clicks either direction will reset the AS3X. No dual rates, no expo.

Quote:
Originally Posted by spainman View Post
- does the swashplate counteract movements while the motor is off?
No, nothing moves while the motor is off. zero trim on the throttle.

Quote:
Originally Posted by spainman View Post
- have you tried triming left and right without success?
Yep. Left or right, same result. Now 2 clicks doesn't result in very much yaw, but it's there. Hmm... I am using the longer mCPX tail boom. That may have something to do with it.

Quote:
Originally Posted by spainman View Post
Considering that this is software and most likely we have all the same firmware there should be no variations in the behaviour.
Yes, I agree they should all be the same. You're convinced the yaw isn't there? Not even a little? If not then the longer tail boom is probably the source.

It's not worth worrying about anyway.
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Old Jan 20, 2012, 11:22 AM
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Quote:
Originally Posted by ruzam View Post

Yes, I agree they should all be the same. You're convinced the yaw isn't there? Not even a little? If not then the longer tail boom is probably the source.

It's not worth worrying about anyway.
A longer tail boom shouldn't matter at all. The rudder controls the amount of yaw degrees over time and the gyro adjusts the power output to conform.

I just had a flight and rechecked it - it doesn't yaw (really not a bit) as long as the trim change is small enough. Doing the same with a "serious" tx (module based transmitter with trim slider) needed some fiddling to find the point where the mode changes and the rx still re-zeros the input on motor start.

Cheers,
Ruben
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Old Jan 20, 2012, 12:16 PM
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Quote:
Originally Posted by spainman View Post
A longer tail boom shouldn't matter at all. The rudder controls the amount of yaw degrees over time and the gyro adjusts the power output to conform.

I just had a flight and rechecked it - it doesn't yaw (really not a bit) as long as the trim change is small enough. Doing the same with a "serious" tx (module based transmitter with trim slider) needed some fiddling to find the point where the mode changes and the rx still re-zeros the input on motor start.
I'll see if I can fine tune my trims and find a 'sweet spot'. If the rudder trim really is that sensitive, other people are going to find that 3 clicks affects yaw as I have.
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Old Jan 20, 2012, 12:26 PM
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I have to go 4 ..but 3 will get it sometimes..people have reported 2 clicks being enough.

Yes..sometimes I do get a very slow rotation{very slow}..but not enough to interfere with checking for drift.
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Old Jan 20, 2012, 01:05 PM
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I just wanted to point out there is still another way to set the heli up if you have a transmitter with visible trim position indicators (DX6i).

1. Fly the heli. Adjust for a hands-off hover using the transmitter trims.
2. Land the heli. Note the position of the transmitter trims and adjust the corresponding swash links so that they move the swash in the same direction as indicated by the trim position on the transmitter.
3. Fly the heli again and repeat until the transmitter trims are in their neutral position when hovering.

The heli swash will now be in the same position in hover mode and neutral mode.

I believe that this works because it is likely that the software sets the servo neutral position to be servo center (1.5 ms. pulses). This is the same timing that most transmitters put out when their trims are centered.

If you are able to hover the mSRX in a hands-off hover with the transmitter trims centered, that means that in the hover position the swash is in the same neutral position that it goes to when rudder is applied or the motor is off.

This also means that if you are unable to attain close to a hands-off hover with the transmitter trims centered, it is likely that your heli is not properly set up.
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Old Jan 20, 2012, 03:02 PM
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Quote:
Originally Posted by Martyn McKinney View Post
I just wanted to point out there is still another way to set the heli up if you have a transmitter with visible trim position indicators (DX6i).

1. Fly the heli. Adjust for a hands off hover using the transmitter trims.
2. Land the heli. Note the position of the transmitter trims and adjust the corresponding swash links so that they move the swash in the same direction as indicated by the trim position on the transmitter.
3. Fly the heli again and repeat until the transmitter trims are in their neutral position when hovering.
I see what you're saying about using the visible trim positions indicators. That's a good suggestion. Funny story, when I got the transmitter I wasn't using trim for anything and the indicators just looked like an odd choice of graphic embellishment It wasn't until I started wondering about how I would remember the trim clicks that it finally hit me.

I think I finally understand now why you keep suggesting to use the trims to adjust for a hands free hover, then adjust the linkage arms based on the trims. It always sounded more complicated then it needed to be.

My style is to observe the corrections needed to hold the hover, then adjust the links accordingly without touching the trim buttons. It's quick and easy, but admittedly, the closer you get to 'true' pitch, the harder it is to decide what corrections to make and it becomes a game of 'maybe needs more right then left'. The longer you hold the hover, the more instinctively you adjust the stick and the harder it is to realize what direction you're correcting. It gets the job done, even if that final adjustment is closer to splitting hairs.

But I see now that if you use trim buttons to find that sweet spot, then you can yank it around a bit and play with it a little (loosen the brain and the thumb) to see if center stick really is just right. It's like a fine adjustment to my course adjustment. I think I'll play around with half turns on the servo arms (flipping the arm hook on the servo) to get it down to that last fraction of an adjustment.

Besides, the concentrated hovering practice never hurts
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Old Jan 20, 2012, 08:04 PM
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I'm trying real hard to get this but when I get my hands off over, lasts a few seconds, the heli never start drifting in the same direction, witch makes it hard to adjust the servo links.

Also what does heading off do? Yeah I know I'm a real noob, I have probably 50 flights on this, but I'm really enjoying this 1st heli of mine.

Never was able to make the MMM work.
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Old Jan 20, 2012, 08:13 PM
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Where are your transmitter trims when you are hovering hands off?

If they are near center, your heli is close to being OK.

If not, it is not.
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Old Jan 20, 2012, 08:31 PM
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No trim, but when I use left rudder wow flies back fas
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Old Jan 20, 2012, 08:33 PM
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But can you hover hands off with the transmitter trims centered?

If you cannot then your heli isn't set up correctly.
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