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

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Synergy R/C Synergy N9 > Synergy bellcrank geometry?
 
 
ChristianM
Veteran
Location: Oslo, Norway

The loads transmitted to the servos will be the same provided that the loads produced by the blades and the total motion of the swash plate is the same.

Christian

Burn fuel, be happy
02-08-2006 Over year old.
 
 
rdalcanto
Key Veteran
Location: Salt Lake City, UT

I don't like the fact that the servo is having to move that long lever arm to the swash without the benefit of a push-pull setup. I can't imagine it will be as tight a head as you would get with an Avant (CCPM setup) or EVO (mechanical setup), both of which use push-pull on everything. I guess we'll see....

Rick

Team MRC & Magnum Fuels
02-09-2006 Over year old.
HOMEPAGE  
 
 
damaen
Senior Heliman
Location: Umeå, Sweden

The servos are placed with their length in the direction of the forces which should make the mounting ridgid. Add to this the fact that they use braces over the servos to further reduce any movement.
Push-pull wouldn't make any difference at all in that regard IMHO.

Henrik
02-09-2006 Over year old.
HOMEPAGE  
 
 
tym2fly1
Senior Heliman
Location: Troy, Ohio

The intent of push pull control is to take the load off the servo output shaft by using a force balance. The Synergy has the same effect by using the servo horn supports. In other words, comparing the two setups, they are the same with the only added benefit of the two opposing control rods is to provide redundancy in case one control rod would happen to fail.

Tim
02-10-2006 Over year old.
 
 
blade3d
Elite Veteran
Location: New Jersey

Think every one got it by now ??




Blade3d
02-10-2006 Over year old.
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
sp1nm0nkey is right on the money. If the length of the servo horn is the same as the length on the bellcrank, then the ratio is the same and the load on the servo is the same. However, the load in the pushrod is higher with the shorter servo horn and bellcrank, thus it is important with a heavy duty pushrod and no slop.

Christian


If I may ... The torque load on the servo is the same but as you said the tension and compression load brought on by the pushrod has increased. So what you say? Servos are mounted in rubber bushings and as you put a load on a link the rubber gives a little. This is lost motion that occurs in the real world whether you realize it or not. A higher load will squeeze and move the servo in its mount even more. You can understand that if you shorten the links some more this problem gets worse, two fold. One, because you have more lost motion and two, you have less motion to begin with so the lost motion is a larger percentage.

Again, in the real world, there is no such thing as no slop. There must be some clearance in every bearing or link in order to rotate. The more you have in a system the more slop you will have. Granted, this should be kept to a minimum but it is lost motion. The shorter you make the driving link the more this lost motion will have an affect.

It is always better to gear down rather than gear up.

Ace

Ace
What could be more fun?
02-23-2006 Over year old.
 
 
ChristianM
Veteran
Location: Oslo, Norway

Ace

Your statement is true but the servo shaft is supported on the Synergy so the direct reaction forces are handled through the support and not the rubber grommets. Having said that, the servo will try to rotate about its shaft but the reaction moments / forces on the grommets are a lot smaller than what is takes up by the support. These are the same reaction forces that a push/pull system will see.

Christian

Burn fuel, be happy
02-24-2006 Over year old.
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
Ace

Your statement is true but the servo shaft is supported on the Synergy so the direct reaction forces are handled through the support and not the rubber grommets. Having said that, the servo will try to rotate about its shaft but the reaction moments / forces on the grommets are a lot smaller than what is takes up by the support. These are the same reaction forces that a push/pull system will see.

Christian


Christian, I have since gone to the website and noticed the added support bearing on top of the servo. I am not in favor of outrigger bearings because they give you a false sense of security. It solves the problem of lost motion in the linear direction but only directs the loss motion in the rotary direction. Remember, as long as the servo in mounted in rubber mounts in will compress in any direction that the force is transmitted. The only real way of eliminating lost motion because of rubber mounts it to eliminate them altogether and make the mount solid. I don't know what the ramifications are for mounting the servo solid. So as a general rule, I always try to use the longest servo arm I can so any lost motion that I do have will be a smaller percentage. If this yields too much motion at the output end then you bellcrank (first class lever) down to get what you need.

There are always exceptions to the rule in the real world. The amount of losses could be so small that it doesn't make a difference to the average pilot. But if I were manufacturing this heli I would take actual measurements with dial indicators of different linkage designs to know what the losses really are. You might find huge variations from different servo suppliers in the test so you could also recommend the best performers.

Ace

Ace
What could be more fun?
02-24-2006 Over year old.
 
 
ChristianM
Veteran
Location: Oslo, Norway

Ace

The loss of motion in the rotary direction is something we have to live with regardless of the linkage system unless like you say the servos are mounted rigidly to the frame, which will significantly reduce the life of the servo. However, like I mentioned in my previous post these forces are not that large and do not in my experience make much difference in the real world.

Christian

Burn fuel, be happy
02-24-2006 Over year old.
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

maybe you are right because the torque that the servo sees is the same in either case.

This new Synergy is not a gas version is it?

Pretty sleik.

Ace

Ace
What could be more fun?
02-24-2006 Over year old.
 
 
DOKEY
rrProfessor
Location: Northampton UK

Check it out for yourself:

http://www.synergyhelicopters.com/

Check the gallery!
02-24-2006 Over year old.
HOMEPAGE  
 
 
AceBird
Elite Veteran
Location: Utica, NY USA

Quote 
Check it out for yourself:


I did. it still looks to be glow not gas.

Ace

Ace
What could be more fun?
02-26-2006 Over year old.
 
 
DOKEY
rrProfessor
Location: Northampton UK

correct, glow.

Check the gallery!
02-26-2006 Over year old.
HOMEPAGE  
 
 
helimanSenior Heliman - Location: Fullerton, CA -
It's more widespread than you think......

Here are pictures of 4 mechanics and they all have the same basic bell crank geometry that everyone is making a big deal about in the Synergy. RappyTappy has started something again. He's a big jack.

Jason has changed the geometry of the bell cranks in the meanwhile.

Hell, the Vigors geometry is more extreme than the Synergy and no one is harping about that.

Synergy
Vigor
Avant
LM Mechanics

It's no big deal. Fly your heli!!!
02-26-2006 Over year old.
 
 
sp1nm0nkey
Senior Heliman
Location: Redwood City, CA

All the helicopters in those pictures have push-pull, except for the synergy. That means the forces are distributed evenly along the links and the rods.
02-26-2006 Over year old.
 
 
RappyTappy
Elite Veteran
Location: Las Vegas, NV

As you see in the top pic from heliman, Jason Krause actually machined a new bellcrank with revised geometry and had it on his heli at the Las Vegas fun fly. He increased the distance from the pivot point to the input ball. Don't know if I started him to do that, maybe just a coinceidence though. I'm no big jack! LOL

Chris
Xero G

Forever Brothers
Mickey Tylo
02-26-2006 Over year old.
HOMEPAGE  
 
 
bigblock
Senior Heliman
Location: sweden

It would be interesting to know why JK/ TB did choose to
not use push/pull setup?
02-26-2006 Over year old.
 
 
heliman
Senior Heliman
Location: Fullerton, CA

Some people are changing the point of discussion.

RappyTappy said
Quote 

I was just checking out the Synergy pictures. If you look at the aileron bellcranks, note the distances from the pivot point:
-ball link that goes to the servo
-ball link that goes to the swashplate.

I would think that the servo would be working harder than it has to because of the mechanical disadvantage. Maybe it may not be that big of a deal, but a good discussion would be nice.


The concern at the beginning of the post was about the stress put on the servo due to the leverage, not the push-pull issue. Also, the Synergy has servo braces to help limit the side loads. The example at the beginning of this post was the Fury/Stratus which used balls equidistant from the pivot point, but does not use push-pull.

Now that it has been shown that many manufacturers use the same system, please don't change the discussion point.
02-26-2006 Over year old.
 
 
bigblock
Senior Heliman
Location: sweden

sorry!!
02-26-2006 Over year old.
 
 
blade3d
Elite Veteran
Location: New Jersey

Push pull = servo brace does it not, and servo brace is much simplier



Blade3d
02-26-2006 Over year old.
 
 
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Synergy R/C Synergy N9 > Synergy bellcrank geometry?
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