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Fast Lad Performance . Ace Hobby . Esprit Model

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Main Discussion > CCPM: P-mixes or ATVs
 
 
Britflyer
Veteran
Location: Derby, England

OK guys

I am ready to setup my first CCPM model (Fury Extreme), I have all the tools I need, swash plate level, spirit level bubbles etc

I have set the swash to level, bellcranks @ 90 degs at midstick.

Now for Full Positive and Negative pitch I need to level the swahplate abit.

But, should I use ATVs or P-mixes for this ???

I have seen that both methods are used, but not seen an argument as to why one method is better than another.

I guess this has more to do with how the Tx processes the signal/command/P-mix etc

I am using a JR 3810.

Thanks in advance

Paul
12-03-2003 Over year old.
HOMEPAGE  
 
 
Mujenpwr
Senior Heliman
Location: Mickleton, NJ

I would use a Pitch to Elevator mix as needed but not too much maybe 1 to 3% worth. But you should not need much at all. I use a Futaba radio and Futaba 9252s. And I only needed a bit on one of my Furys. I used the Miniature Aircraft swash level tool for the Fury to ck at pull positive and full negative pitch. My .02 cents
12-03-2003 Over year old.
 
 
rckrzy1
Elite Veteran
Location: Hurst Texas

Quote 
....but seriously....

if the multiplex tx isn't an option


Or get a predator where you can adjust the swash timing and not have to fuss with any radio mix.



Wildcat Fuels
12-03-2003 Over year old.
 
 
alwallash
Senior Heliman
Location: Morgan Hill, CA (near San Jose)

How do you adjust the swash timing on the Predator?
I am setting mine up now.
al
12-03-2003 Over year old.
HOMEPAGE  
 
 
rckrzy1
Elite Veteran
Location: Hurst Texas

SORRY FOR THE POST HIJACK[/B]


Quote 
How do you adjust the swash timing on the Predator?


Rotate the pin assy that holds the washout assy, you adjust in small amount either direction as needed, I was getting a slight right ail with ele and needed about .5 mm into the direction of rotation and now I have no more mixing, flips are good as is gets same with big loops.



Wildcat Fuels
12-03-2003 Over year old.
 
 
choppertime
Senior Heliman
Location: Virginia Beach

Yea, how do you adjust the swash timing on the predator?
OK, looks like we posted at the same time.
12-03-2003 Over year old.
 
 
Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

What Dave said....................

.......and my 2 cents:

Assuming all the servos arms are squared up and true at exactly half stick, throw the collective to full and CLOSELY look for which, if any servo is throwing farther than the other. Use that servo as the baseline, then open up the ATV's on the other two to level out the swash perfectly. Repeat for the other side of the collective range. This process matches the total throws of the servos.

Next "track" the swash in the intermediate positions, at least at 1/4 and 3/4 stick. You can use a multipoint pmix to correct any deviations in those stick positions.

PLEASE do NOT mess with the subtrim. That's where you'll cause more problems than you could imagine.

You need to go back a retrack the swash from time to time. Servos change, especially over the first case or few of fuel. You'll be surprised what you'll find when you do the periodic fine retuning. It's the price you pay for the mechanical simplicity of CCPM.


Ben Minor
12-03-2003 Over year old.
 
 
choppengruven
Key Veteran
Location: Flagler County, FL USA

Yep, not subtrim at all. I don't know what servos you are using, but even my 9202s on my Pred are level all the way through. If you are having an issue, you may want to double check your subtrim menu.
12-04-2003 Over year old.
 
 
ipluu
Heliman
Location: San Jose, CA

Please explain

Please explain why not using subtrim which is what designed for. It is recomended in the JR 10X manual to use subtrim for CCPM setup. I also measure the servo throw on both side when subtrim being used and they are perfectly equal unless excessive subtrim is used.

JR 10X instruction manual page 47:

"...

3. With all of the swashplate servos in their neutral positions, use the Sub-Trim function, Code 15, to bring each servo's control arm to 90 degrees to the control linkages. the swashplate muste be level at this time.
4. When making pitch changes, it is important that all servos move an equal amount in order to keep the swashplate level throughout the entire pitch range. you must compensate for any difference in the unequal throw of the servos by using Code 12, Travel Adjust, and making precise adjustments to the end points of the servo's travel.

..."

I am very interested to know the reason why.

Thanks
Dinh
12-04-2003 Over year old.
 
 
choppertime
Senior Heliman
Location: Virginia Beach

I guess I need clarification on the use of subtrim. Why is subtrim undesireable to use in a eCCPM setup?
12-04-2003 Over year old.
 
 
Britflyer
Veteran
Location: Derby, England

I have setup the swash using P-mixes.

The maximum mix value I required was 4%.

I figured using the P-mixes I could then use the 5-point curve and level the swashplate at 0,25,50,75 and 100 %.

But looking at CY website and replys from WIngtip and Dr Ben, it seems ATVs is the way to go.

Think I will have a play with the ATV method.

Cheers

Paul
12-04-2003 Over year old.
HOMEPAGE  
 
 
ipluu
Heliman
Location: San Jose, CA

Britflyer

Britflyer

You need to use both ATV and pmixes to make it perfectly level.

In my case, I used pmixes 1% at the intermediate positions in addition to changing the ATV.

Dinh
12-04-2003 Over year old.
 
 
Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Dinh,

Will you please post the PM I sent you about the subtrim issue here for Choppertime?

I didn't save a copy, and I don't have the time right now to retype it.

Thanks,

Ben
12-04-2003 Over year old.
 
 
ipluu
Heliman
Location: San Jose, CA

PM reply by Dr. Ben

"Re: Please explain
Assume a servo has 120 d or so of total throw with 60 d on either side of neutral. If you use the subtrim to shift the neutral of the servo off to one side, you've GUARANTEED that the servo is going to move farther in one direction/side that the other. In doing so, you instantly create mismatching of the servo not only at full high collective, but at full low as well. Then you'll need to go back and further adjust the ATV's to help the problem. That'll work sorta OK for extremes of throw, but the swash tracking in the intermediate collective will be off in some points and back in track in others. You'll have no good way of eliminating that problem.

Honestly, subtrim should all but be eliminated from radio software. There are precious few, if any, cases except for some detailed HH gyro stuff where the menu is not (mis)used to make up for a less than optimum mechanical set up. In the case of JR with CCPM, esp with a Fury, you often just can't get those straight, heavy duty arms to go on the servos exactly square and true. In those cases, the Airtronics wheels will fit and allow you to drill the hooe for the ball link in the correct.

There are many who will use JR's instructions WRT subtrim use and get along just fine. But it will never be as interaction free as one based on a rock solid mechanical foundation.

Ben Minor"

We appreciate your expert support.
12-04-2003 Over year old.
 
 
King Cobra
Veteran
Location: Virginia. USA.

I am against subtrim at all time . It 's a time bomb !

C.T
12-04-2003 Over year old.
HOMEPAGE  
 
 
Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Dinh,

The Futaba subtrim menu works exactly the same way. When you mention 10 points of subtrim and the way it adds 10 to one side for 110 toal and subtracts 10 on the other for 90 total, that's exactly the problem with using it that I described; the servo in question now has asymetrical throw, and it will show up at extremes unless something is layered in on top to correct it.

As you saw, you can get away with using small amounts of subtrim. I just haven't been able to bring myself to use it when I can get the arms on there dead squarely by drilling a servo wheels.

Best regards,


Ben Minor
12-04-2003 Over year old.
 
 
choppertime
Senior Heliman
Location: Virginia Beach

That's what I thought. But are you aware of the true centering capability of the Airtronics Stylus radio? It actually allows you move the center and offset each end in the same direction! Now that's a cool feature. Not sure about any other radio but the Stylus kicks butt.

Chris, I'm surprised at you since you have the Stylus and don't even know about this capability. Don't be affraid to use subtrim with that radio. The only exception would be a large amount of offset that causes the end values to go outside of the throw of the servo. Of course you need to get it as close as possible mechanically first.
12-04-2003 Over year old.
 
 
Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

That Airtronics software is nice.


You know what I look forward to?

Position the servo where you want it for center. Press a button and that position is memorized. Move to either extreme of throw and repeat and match for each servo. Effectively, a servo which has no endpoints or center until you tell it where they are supposed to be.

One can dream........


Ben Minor
12-04-2003 Over year old.
 
 
Optech
Key Veteran
Location: Vista/Oceanside, CA.

Choppertime,
Like you said.... try for a correct mechanical set-up first. Yes the Stylus has some neat features but they still don't make up for a bad set-up. Its simply too easy to slap on a wheel and drill your own hole.


Ben,
Hitec took one step in the direction your dreaming about. Their digital servos allow to reset the center and the endpoints. Of course, you have to buy a seperate programmer to do it but you could fine tune all the servos in your heli. So, you could probably start holding your breath as I imagine this feature is one we'll see soon coming from other radio brands.

Back to the topic, I'm a little surprised to to see your views on ATV use. You were one of the people that were anti-ATV when I first started asking questions. I'm using c-mixes now but never considered dual ATV/C-Mix use.... Hmmmm interesting, looks like I've got something new to try over the next couple days.

Mike

Viva La Airtronics!
12-05-2003 Over year old.
 
 
King Cobra
Veteran
Location: Virginia. USA.

Mike

I have used subtrim in my Stylus and CP-EPA in my early day with this radio. Anything subtrim, CP-EPA or swash mixing around 5% is acceptable other than that I don't care for it.
I have at least 5 ECCPM models and as always I end up with no subtrim, cp-epa , and little mixing if any. That how I like it ! Some time it take me hours but I like thing as SIMPLE AP.

C.T
12-05-2003 Over year old.
HOMEPAGE  
 
 
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