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Modefo's RC Helicopters . XHELI.COM . Autography FlightPower

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Miniature Aircraft Nitro/Gas Helicopters > Digital Servos & CCPM
 
 
Ray Fernandez
Elite Veteran
Location: Guam (U.S.A.)

Hi All,

I don't know if this subject ever came up but I started pricing those High Tech Digital Servos and began thinking.............Is is really necessary to HAVE digital servos to run a CCPM system? Most especially, on a XCell Fury?????

Thanks for any assistance.

Ray Fernandez - GUAM
05-03-2002 Over year old.
 
 
crash-
Veteran
Location: Ca

I am running futaba 9202 on my Fury
But I want to upgrade
BURN MORE FUEL
05-03-2002 Over year old.
HOMEPAGE  
 
 
dwarness
Heliman
Location: Sunnyvale, CA

The short answer to your question is: no you don't need digital servos. Todd Bennett uses a Fury with Futaba 9202 Servos on it for his flight school. The problem you'll run into the fact that since all three servos have to move together you'll want servos that are matched both in centering and in speed. When I origionally setup my Fury, I had 3 9204 servos lying around that I used. Unfortunately, one of the servos wasn't matched perfectly, and when I'd pull back on collective to decend, the heli would want to pitch over. It was a big pain trying to fly it. After that, I put 3 9252 servos in, and all my problems went away.

Hope this helps.
05-03-2002 Over year old.
 
 
BIGRCR
Veteran
Location: Easley, South Carolina

No, you do not have to use digital servos for CCPM mixing or in the Fury for that matter. What you do need, as previously stated, are good quality MATCHING servos that are precise and are free of slop. Coreless non digital servos work very well for the Fury.
IMO the metal geared digitals are not very good for CCPM for these servos seem to have more "float" as I call it. This is because using metal gearing tends to leave more space between gears and induces wear more quickly making the "float" even worse. The first metal geared servos did not work well at all and several attempts were made to remedy the slop and even by using helical gears. The metal gear trains of today use dissimilar metals to make each gear ( brass, anodized hardened aluminum, steel, etc.) so that these gears can be run closer together (similar metals don't get along well together). I feel that the best of them use wide gears that places the stresses over a larger area and also use at least one plastic gear (usually Nylon-66). The nylon geared digitals using wide gears are the best in my opinion. JR has just put out nylon geared versions of their metal ones to remedy the slop, wear and extreme cost of the replacement gears!

I am running JR 4131 coreless servos in MOST of my Furys and other X-Cells. I believe a good strong coreless such as the JR 4131(I would quote some Futaba units also but do not have the experience with them) has less slop than the metal geared digitals and are more precise!
Buy your servos for CCPM all at one time and don't use one old one from this drawer, a rebuilt one from another bird and a new one off the shelf. Servos are funny and almost seem to build a "memory" of what they were last used for!
I do own digitals and use them exclusively on the tails of my birds and love them for that application!

Hope this helps!!

Later,

BIGRCR- John Garst
05-04-2002 Over year old.
 
 
av8er
Senior Heliman
Location: NH, USA

bigrcr (or anyone that has exp in 4131 servo in ccpm), I was wondering what kind of flying u did? aerobatics? 3d? just hovering? And how the birds behaved/held up with the 4131? A friend of mine just bought a fury 60 and has 3 new 4131 that he could use or go buy new servos......He is just getting into forward flight btw.
05-05-2002 Over year old.
 
 
BIGRCR
Veteran
Location: Easley, South Carolina

Av8er,
Although I throw my Fury around quite a bit, I do not consider myself a 3D pilot (this term is far too loose nowdays), so I will say that I fly sport aerobatics. I also fly scale and really enjoy "pattern" type flying.
The 4131s can take anything that you can put to them as long as you don't abuse them ( binding set ups). A feature of CCPM is that the servos work together to make a pitch change so there is almost always a surplus of power to work the swash with any GOOD servo. The 4131's have 90.4 oz/in. at 4.8 volts. That means that the swash plate will see UP TO 271 oz/in. of torque.

IMO the big differences between the analog coreless servos and the digitals is that the digitals make their power peak almost as soon as they start moving and have a super "holding" torque boosted by their electronics , where the coreless analogs make their torque as the servo arm moves away from center and builds to maximum torque at some point away from center (usually rated @ 60 degrees).

Later,

BIGRCR- John Garst
05-05-2002 Over year old.
 
 
ZZ3Astro
Senior Heliman
Location: Panama City, Fl

Why would anyone consider Hitec digital servos when you can get Futaba 9252 digital servos for $65 each from http://www.heli-kraft.com . I just ordered a set for my Fury from them.

As for non-digitals, I know of a couple of Fury's running 9202's, and even helped set one up with standard Airtronics servos that come with the RD6000 Super. They all fly - but in the case of digital 9252's you have three advantages.. they have tremendous torque, a fast transit speed and tend to be closer match to each other.

steve
05-05-2002 Over year old.
HOMEPAGE  
 
 
BladeStrike
Senior Heliman
Location: Shelby Twp, MI

kraft

Where are these guys heli-kraft based??
05-06-2002 Over year old.
 
 
Buzzin Brian
Elite Veteran
Location: College Station, Texas

Looks like my post got deleted. Interesting!

Thanks alot.

Build it, fly it, crash it. Repeat as often as needed.
05-07-2002 Over year old.
 
 
ZZ3Astro
Senior Heliman
Location: Panama City, Fl

Heli-kraft is located in Taiwan. They ship through EMS so it arrives in several days.

Steve
05-07-2002 Over year old.
HOMEPAGE  
 
 
JEFF_SE
Heliman
Location: Pittsburgh PA

4131 Servos

Didn't JR update the 4131 with dual BB support in the 8101 (at the same price)? I switched to Futaba about a year ago, but still use a few 8101's and 8231's.

JEFF_SE
05-07-2002 Over year old.
HOMEPAGE  
 
 
ed vega
Key Veteran
Location: nyc, queens

started with the gyro/ tail servo sets...

I agree you can fly with the non digital ones .
05-07-2002 Over year old.
 
 
jrice45516
Heliman
Location: SoCal

Does ccpm REALLY mean less work?

Does ccpm Really mean less work for all or any of the servos involved? I have not seen the claim justified. I don't see any big reduction in average or peak work load for any servo.

Compare a 3-servo non-ccpm setup with ccpm. In the non- case, each of the elevator, aileron, & collective servos has its own job to do with no shared responsibilities. In ccpm, the collective gets shared amongst the 3 BUT the collective servo gets stuck with part of the cyclic load. Sharing 3 jobs does not necessarily mean less work for anyone.

Now again most are going to claim the collective servo has the bigger job of the 3. This again would be hard to prove. A servo whose pushrod is 90º at neutral is most vulnerable at neutral because its leverage is least there. Yeah? so big deal. Neutral is where the collective servo has the least work to do anyway since blade pitch is zero. As blade pitch departs from zero, yes, the load on the servo goes up BUT the moment arm length (the perpendicular distance From servohorn center of rotation To pushrod) shrinks giving the servo the leverage it needs to feel no pain.

I still say we need the electronics propeller heads to make us a black box which will record inflight peak & average servo current draw for all channels of interest. Such a tool would answer these questions.

Dances With Woofs
05-07-2002 Over year old.
 
 
basmntdweller
Senior Heliman
Location: Indianapolis IN

Why was my reply to this post removed. Is there a law banning the mention of Tower Hobbies or the servos I suggested?
later,,,basmntdweller


Stupid people have no idea how stupid they are!!!
05-08-2002 Over year old.
 
 
kenman
Senior Heliman
Location: Columbia, Maryland, USA

I still wish we would have 4-servo 90 degree CCPM setups. This way, control is not lost if a cyclic servo fails. It would be a simple matter to check all four servos before each flight to be sure of proper operation. Or I'm sure some EE could design a circuit that would warn of a bad servo. I don't think the penalty of the weight of an additional servo would be too much to ask considering increased safety factor.

Just a thought!

Ken
05-08-2002 Over year old.
 
 
BIGRCR
Veteran
Location: Easley, South Carolina

It was not stated that any of the servos did less ( or more) work in 120 CCPM than another servo. It was stated that there was more available power for a pitch change whether it be cyclic or collective-cyclic since three servos are working together and the load is being shared between the three. The servos are "named" aileron,elevator and collective in the 120 CCPM control system, but actually each servo is a collective servo as well as a part of the cyclic movement. Remember that the term "collective" pitch means that the cyclic pitch is being moved "collectively" (together) to increase or decrease the blades' pitch at any given point in it's 360 degree rotation.

Later,

BIGRCR- John Garst
05-08-2002 Over year old.
 
 
jrice45516
Heliman
Location: SoCal

<< It was not stated that any of the servos did less ( or more) work in 120 CCPM than another servo. It was stated that there was more available power for a pitch change whether it be cyclic or collective-cyclic since three servos are working together and the load is being shared between the three. >>

Actually your sentence reads:

<< A feature of CCPM is that the servos work together to make a pitch change so there is almost always a surplus of power to work the swash with any GOOD servo. >>

You imply, since the collective pitch is shared between 3 servos in ccpm, that the job of applying cyclic pitch is somehow made easier. This is an oversimplification, not just of the collective pitch work load in ccpm, but of the total situation & that is my interest. Yes, the collective servo no longer has full responsibility for applying collective pitch as it did in non-ccpm. Instead it has new duties. The hope that the new total might be less than the old total remains to be justified. Just saying it's true is not enough. Whether & how average or peak duty cycles have changed (e.g. improved?) due to ccpm remains to be shown, possibly by monitoring servo current draw.

<< The servos are "named" aileron,elevator and collective in the 120 CCPM control system, but actually each servo is a collective servo as well as a part of the cyclic movement. >>

We refer to servos in the 120º ccpm system as "aileron," "elevator," & "collective" because they are plugged into those Rx channels respectively, Not because they are doing those jobs exclusively any longer which they obviously aren't.

<< Remember that the term "collective" pitch means that the cyclic pitch is being moved "collectively" (together) to increase or decrease the blades' pitch at any given point in it's 360 degree rotation. >>

The term "collective" refers to both mainblades being simultaneously pitched an amount equal in magnitude & direction.

"Bad terminology is the enemy of good thinking." Warren Buffet

Dances With Woofs
05-08-2002 Over year old.
 
 
xcelllogo
Senior Heliman
Location: San Diego

I had the 9202's on my Fury to start and that worked fine but when I put the 9252's the feel got much better. They have a faster transit time and seem to move as I move the sticks not a mili second later I will always run 9252's now...

Adam
05-08-2002 Over year old.
HOMEPAGE  
 
 
Hooked
Senior Heliman
Location: Trenton OH

I've got 8411SA on mine for ccpm 4735 for throttle and 9253 on tail
05-08-2002 Over year old.
 
 
Buzzin Brian
Elite Veteran
Location: College Station, Texas

I agree. It would have been nice to be asked. I wold have changed it. All I did was inquire about Heli-Krafts location, and if anyone has used them before. It wasn't like I was cussing someone out, like I have seen all to many times here lately. And those posts got to stay. All I was attempting to do was to insure that a distributor is indeed legitimate. Which I thought would be in everyones best interest IMPO. Can't help to be to carefull in todays market place. But hey, I guess sometimes this place is not about everyones best interests. A true disapointment for sure.

Thanks though.

Build it, fly it, crash it. Repeat as often as needed.
05-09-2002 Over year old.
 
 
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