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Vario Sky Fox - Benzin - Evolution - Xtreme > 3 or 4 servoes on swash?
 
 
Paalk
Senior Heliman
Location: Oslo, Norway

What do you guys think? I have a big Jet Ranger and the 1:4.5 scale MD 500(both petrol)with 3 servoes for the swash plate. Should I put in the 4th servo or is it ok with 3?
09-25-2007 10:30 AM
 
 
Disciple4123
Veteran
Location: Waynesboro, VA USA

It is my belief that 4 will always bind ever so slightly at the extremes of travel. So I run 3. Difficult to explain the physics, but think it through. A four legged chair will never be happily level unless the floor and chair are perfectly flat, a three legged chair always finds it's level.

Eric
09-25-2007 09:24 PM
HOMEPAGE  
 
 
Paalk
Senior Heliman
Location: Oslo, Norway

Thanks Eric, that sounds pretty logical. The reason I asked is because I had the elevator pushrod snap right of on my maiden flight with my 1:4.5 scale Hughes here the other day. Thougt maybe I should have used 4 servoes to avoid it.
09-25-2007 10:47 PM
 
 
tkn0spdr
Heliman
Location: Indian Harbour Beach, FL USA

I don't know. As god of your helicopter's universe, you should make sure that it's 'floor' is perfectly flat.

I'm just saying that if set up correctly you don't have to worry about that particular issue.

More servos is more redundancy = better in my book.

Thanks,
David
06-16-2008 07:50 PM
 
 
dazzaster
Veteran
Location: right next door to hell

im with the above poster . any binding is minial and the worst that could go wrong with 4 servos binding is one fail in which case you have the other three as back up. ive always used 4 servos and have no issues to date

I have a load of spots... two of which are white heads
06-16-2008 08:07 PM
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bcook01
Senior Heliman
Location: central ontario

IMO four servos work fine especially providing redundancy.

Suggest using analogue servos rather than digital as their deadband is larger than the digitals and they tend not to fight with one another. They seem to work better and are more reliable.

Monitor current on one of the servos and tweek for least interaction. A small 1.5 flashlight bulb in series with the servo works as well for setup.

If one servo fails the other will bring you home including loss of a ball link. The overall current drain tends to be less based on my experience.

Some radios do not support 4x90 such as the dx7.

fyi

Bob

You cannot afford to learn by your own mistakes.
06-16-2008 08:12 PM
 
 
Disciple4123
Veteran
Location: Waynesboro, VA USA

Quote 
I don't know. As god of your helicopter's universe, you should make sure that it's 'floor' is perfectly flat.

Hmm. can't help you with that, I am human, not divine

The servo arms move non-linearly with respect to the linear commands, when they are out of an orthogonal angle. Despite any efforts to perfect geometry, pitches near the top and bottom of travel will see binding if the cyclic control also being used, the very effect of cyclic inputs varies depending on where you are on the collective. Linear screw servos would be inpractical, but would not have this effect, think it through a bit.

Because of this issue I run 3. Additionally some servos fail due to pot failure, then it will be a tug of war between two bogging servos if you run 4. You will lose control and voltage simulteneously if that happens, and you will lose control with 3 also. In the end failures can happen, but I don't consider the 4th servo to help things. Has anyone looked at how fullscale swashes hook up?

Eric
06-16-2008 09:40 PM
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doorman
Elite Veteran
Location: E.Berne, NY

Four For Me Too!!!!

I agree 100% with bcook01 on this one.... I started with 3 until I tried a Benzin with the forth and now all three of mine are set up with 4 servos.... and I do use analog servos....9202 or 9206 futaba.

I would agree that you might have a problem with 4 using the digitals IF you were using the "extremes" but flying scale heli's. you will very rarely ever use a max throw unless you are on your way in anyway!!!!

I am in my fifth season with the Vario Benzins and have not had any problem with the 4 servo set up... and it does have a more "solid" feel then it did with the original set up....

Good Luck, Stan

If there is a cure for this, please don't tell me about it!!!
06-16-2008 09:49 PM
 
 
MattJen
Elite Veteran
Location: UK,Gravesend, Kent

Agree also, on large models i always use the 4 servo setup, i have had one servo fail and managed to bring the machine back.

On my comp machine it is 3 servo, and i garuntee if the same situation had happend i would be looking at a hefty repair bill.

There is slight inter action, but with all the new radios now coming out with mixes and other electronics, intereaction is minimal and no where near as bad as it used to be. the 14mz and 12fg has little mixes for 4 servo's.

I have often found you only get resistance if you flying at extreme's, ie full pitch, full aleron etc, unless you are hard 3Ding you will NOT use the full limits, even less if you flying scale..

i prefer 4 x 9kilo 36kilo (9255)lifting the swash rather than just 24k.

Matt

I bought mymother in law a chair for xmas, but she would not plug it in.
06-17-2008 07:24 PM
 
 
bcook01
Senior Heliman
Location: central ontario

Dazzaster

Quote 
ive always used 4 servos and have no issues to date

On what machines?

Bob

You cannot afford to learn by your own mistakes.
06-17-2008 09:57 PM
 
 
Jack Martin
Senior Heliman
Location: AKA HeliJack, Washougal, WA

I have used both, had failures in both. The only servo failure you can survive is a total failure of power to/in the servo. Pots go hard over and even 4 servos will not hold it....makes a nice inverted nine.

I use 3 servo exclusively now. It is less problems, less expensive, more compatible with flybarless systems. I also use the digitals whenever possible, but I tailor the servo to the need.

Coincidentally, I find I have less servo failures on the 3 servo setup, and the above explanation by '4123 sure makes sense to me.
Jack

Remember our Veterans.
06-18-2008 03:15 AM
 
 
dazzaster
Veteran
Location: right next door to hell

Bob . in the vario acrobats and trainer airframes ive always used 4 servos useing futaba coreless analog servos they work very well and have been (touch wood) very reliable. why?
darren

I have a load of spots... two of which are white heads
06-18-2008 07:21 AM
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bcook01
Senior Heliman
Location: central ontario

DAZZASTER
Just Curious .... since you fly trex and raptor.

BTW I have been using 9202 and 9203 on Bergen and vario without and problems whatsoever.


Bob

You cannot afford to learn by your own mistakes.
06-18-2008 12:48 PM
 
 
Mark Spies
Senior Heliman
Location: LaPlace, La and Houston ,TX

I have switched over to 3 servo on all my ships even the turbine.No problems at all. Mark

Starwood Scale Models
06-18-2008 03:20 PM
 
 
dazzaster
Veteran
Location: right next door to hell

Quote 
DAZZASTER
Just Curious .... since you fly trex and raptor
i also fly hirobo,century, xcell and vario ?

I have a load of spots... two of which are white heads
06-18-2008 03:23 PM
HOMEPAGE  
 
 
Roger Oxe
Heliman
Location: Egelsbach, Germany

Hi Pilots,
i use in my Varios always 4 Servos.
This is the safety-related best solution you wear scalehelis...
I wear Standard and Digital Servos without any problems since years.

For the maximum servo arm move (like 3D or acrobtic use)
you need 3 Servos !!!
see the explanation from Eric

in my 222 i wear an rigid (elastomere) head there are no problems by 60% of the maximum way.

in my Huey i have 100% way and in the end positions the system of rods will brace(?) (in german: verspannen, klemmen)
so you must take a litle bit care on your fingers...

Greetings from germany
Roger



i wish my english were so good as i can fly Helicopters...
06-25-2008 09:05 AM
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heliman53
Senior Heliman
Location: Goose Creek,SC

I have been using four servo ccpm on both of my Vario Acrobats one is gas and one is turbine this is with 9252 servos. The turbine has nearly 70 hours on this setup with no problems the gasser has a little less time but also no problems. Craig B
06-25-2008 01:12 PM
 
 
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Vario Sky Fox - Benzin - Evolution - Xtreme > 3 or 4 servoes on swash?
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