I'm about done building my OMP Edge (small one) and am beginning to set up the radio and gear. Everyone says for 3D, you need all the throw you can get. Is there any other way to get lots of throw other than using an outer hole on the servo and an inner hole on the horn? It seems to me this method reduces the torque available at the servo, the further you go out from the shaft.

I'm using Hitec 225mgs all around. What type of arms and horns do you guys use to get max throws?

if you have a computer radio...set all servos for 150% movement for 3d rates

You can double bevel the edges of the control surfaces... if they aren't already. Just try to get 45 degrees and you'll be set.

Mike

If you run pull-pull to your controls you can set your horns behind the centerline about 3/8 to 1/2 inch and this will increase your overall throw and your torque compared to running the horns on the centerline. But remember as you said the longer the arm and shorter the horn....the more torque you need to make the system work.

I may be wrong but I think that moving the horns back from the centerline of the hinge causes increased tension of the pull pull cables when a surface is deflected. How much and whether it could be a problem, I don't know. It's called Ackerman and a good link for an explanation is: http://members.cox.net/bdfelice/Ackerman/ackerman.htm .

Just saying- if it works for you, more power to you and forget I said anything.

JESTER

All good advice. Will set the radio to 150%. Just got a brand new 9C, and didn't remember the throws could be set that much. My old 7UAFS would only go to 120%, 110% on chan 6&7. Servo setup prevents me from using pull pull, so I'll have to save that idea for a later time.
The OMP Edge has double beveled surfaces, so deflection isn't a problem. I've just always had trouble getting enough movement from the servo. But, now that I have the new radio, it may be a lot easier.


Thanks for the info!

Ahhh, now I understand a little better. If you can't get enough movement with your servos and standard arms, go to a bell crank (tiller bar I think?) or longer servo arms.

Mike

The Futaba 9CAP only allows 140%, not 150

Get the strongest servo you can afford, go as far out on the servo horn as possible, even if you have to buy longer servo horns (I use the Futaba 45mm wheel and cut servo "arms" from it..it is thicker than the other Futaba horns or the 35mm wheel). Then you don't have to go to the closest hole on the control horn.

But this only works if you have strong servos, weak servos will not enjoy this set-up, nor will your plane.

Lots of throw, no flutter.

to get extra servo movment go to end point adjust to max eg elavator then go to dual rates set elavator to max then check for maxed out servo problems adjust to suit setup for 9 cap radio set exp at minus 20% to start with then back of to suit model total travel 140%

This might work.. I haven't tried it, but in theory...
Probably need LOTS of exponential to make the system flyable when you aren't "insane".
I have seen some planes with this much throw... but why?????????

It is generally better to use very long servo arms and long (or at least average sized) control horns. This, plus increasing servo throw to 140-150% will generally get you what you need. The advantage of long arms/horns is that any slop in the setup results in less control surface movement.

Tight linkages are a must: ball links, short control rods, 4-40/titanium pushrods, etc.

Leonard

Don't go shorter on the control horn at the surface, it's better to go longer on the servo horn. Dubro makes some extra long servo horns that work well.

D

Tall paul:

Are you actually building that kind of system for one of your planes?
Can you give any specifics? Do you think the the pulley might slip under tenssion? I see what you are trying to do there i'm no expert in the mechanics subjet but it looks quite promising! Post details when you try it out!

Dan

There are commercially available pulley driven pull-pull systems. I'll have to dig for links, but if that's what you want, they are out there.

i've found that anything above 40deg throw (each way,80, total) is a waste and jldecarlo is right, to minimize slop in the controls don't go with short anything, use longer servo horns like the dubro one's.
the servo will move over 90 deg total so you realy should not need longer control surface horns than servo horns, about equal is a good start with the atv (travel volume) maxed out.
my plofiles now have the about 40deg each way travel and i have to hold back on the deflection for flat spins (almost climbing) and the waterfalls are very tight.
good luck
don't forget to use about 30 to 45% expo (start with more and then back off till you like the feel)

No, I haven't built one of those... If I did, the wheel at the surface would be pinned to the hinge axle.
I can't imagine needing that much throw for anything, but there are kits which do use it, so I doodled up that sketch to see how I would do it.
Anything more than 45 degrees adds only drag. At 90 degrees the stabilizing influence of a stabilizer, for a full-flying surface for example, would go away. And which way the plane would then depart to..............

1

Ok well back to the question, I use max deflection on my elevator and rudder, 50% expo on the elevator, 40% expo on the rudder, aileron throw is around 50% throw with 50% expo. How you hook up to your control horns is up to you. And i'm using standard servos.

For the OMP Edge or any other high performance plane, 45 degrees of throw (sometimes a little more is ok) is all you need as long as you have a well designed plane. Any more can cause too much turbelance and thus instability. So if you use a control horn on your servo with a 3/4" distance between the screw and the pushrod hole, and then a 3/4" control horn on the surface (distance between the hinge point and the pushrod) then you will achieve exactly 45 degrees of throw assuming your servo travel is 45 degrees either side of neutral. Do use your computer radio to fine tune this and lots of expo as well.

Mike Pilkenton
Ohio Model Planes