Argh,
I'm finally getting down to the nitty-gritty of installing servos and setting throws but I cannot get enough throw no matter how I slice it on my elevators. I've got a 5925 with a 1.25" airwild arm placed in the side of the fuse where they have a hole slit for it and a Nelson's Offset swivel link on the elevator about 1.5" from the hingeline. No matter how I place the servo (so the rotation is further or closer from the swivel) or if I set the axis of rotation closer to the elevator or further away, nothing gives me a '3D' throw, is there some secret, some rule I didn't follow? Can anybody point me to a picture of how it should set it, I'll try and post some pictures of what I'm doing now.

The connecting point at the elevator control horn should be right on the
hinge line not 1.5 inches from it.

tommy s

But how could I do that? Its top-hinged at 30-deg on each surface,

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So if that is the elevator half, with the hing on the left, and the rod down as such, it has to be away from the hingeline. I have offset swivel's that say "can be .5" off from hingeline", but to get the connection to be on the hingeline I'd have to put the rod in at an angle so that the tip of the rod would be under the hinge line, is this how you do it?

Thanks,
Sam

hope this picture helps. I ended up moving that elevator servo hole down so that i could fit the arm pointing up like it is. I get at least 50 degrees of throw, and the planes flies great. Hope this helps.

Yes, _thank you_, that helps much. I also lowered my hole but didn't know if it would help, it would appear that I need to move my hinge forward too. Thanks Zak!

Sam

_Awesome_, I moved the linkage forward to the edge and now I have much more throw but my airwild 1.25" arms are .25" too long now, geeze now I gotta buy another pair of $10 servo arms :P Anybody interested in some 1.25's Also, when you say 50 deg you mean total right? Thats about what I'm getting now and having seen your plane fly at the field I think 50 is all that I'll need.

Sam

Seems like you can move the control arm side of your linkage further out to compensate?!

Control arm further out, what do you mean by that? Also, I went back to putting the servo in the 'upper' position with the 1.25" arm and have 80deg of total throw now, so I guess I'll stick with that though I really wish I could get 50 or 60 in each dir (100-120 deg total).

I'm confused... What is the specific hardware you’re using?

Moving the servo will have little to no effect on the actual throw realized by the elevator surface. Changing the control link length will have no effect either.

No matter your doing, aileron, rudder or elevator the control arm pivot point should be located over the hinge center line (this is where the linkage attaches to the control arm pivot) or as close as possible. Otherwise you'll get uneven non linear travel.

The things that do affect the throw are;

Servo arm length
Control arm pivot point length, from hinge line to pivot point
Servo travel arc or rotation from center to end-point
ATV, AFR or travel volume of the TX

Many large scale planes use top hinging, similar to what a real airplane uses, which makes putting the control horn on the hinge line impossible. This drawing demonstrates...

DP

Exactly, thank you, that picture demonstrates the probem. I've moved the bolt-horn on the elevator as close to the hingeline as possible and its now 1" away, since I have a Nelson's offset swivel linkage it's moved it about another .75" closer so I'm about .25" away from the hingeline. I still only get about 40deg in either direction so I've ordered a SWB 1.5" servo arm (currently using 1.25") and I bet that'll give me the extra 5-10 deg that I'm looking for.

True, but you can use an offset adapter or horn such as the Nelson hardware which is limited to 3/8" or so and then there is the Dubro control arm which is much longer...

3dbatix, it looks like your rudder cable rubs your servo slightly, is that working out ok for you? I ask because I can lower my servo enough to fit a 1.25" arm in there and get good throw but the cable rubs the servo slightly, about the same amount as yours does.

Thanks,
Sam

Sizam.to prevent the rudder cable touching the elevator servo,move the cable exit to lowest part of the fuse.For rudder control horn you can make it out of epoxy board or buy it and bolted to the bottom of the rudder.Beside if double bevel you get over 50 degrees.

Yah,
I wish I had tried this out a while ago, as I already have a horn installed in the rudder with the assumption that the servo would be higher and its all covered. I guess I can uncover just that part and rip the horn out to install just a bolt, slightly lower but what a pita...

The pivot point of your control horn needs to be at the hinge line when the servo is in the neutral position. Move the control surface side as close to the covering as possible, and move the servo side as far from the servo as possible. When you do these three things, you should have the maximum throw on your control surface.

I ripped out the rudder horn as it was worth it to use the 1.25" arms on the elevator servos, now I get around 50deg each way which was the goal.

My cables do touch just a slight amount, but it has not really been a problem. I have the cables there because i already had the control horn in.