Elevator control horn
06-25-2006, 08:36 PM
#1
Thread Starter
Elevator control horn
Project: Radio Craft Extra
Question,
I understand that with a pull/pull rudder system
it is important to get the hole in the rudder control
horn lined up with the hing line....
Does the same hold true for the elevator?
Thanks for the help.
Question,
I understand that with a pull/pull rudder system
it is important to get the hole in the rudder control
horn lined up with the hing line....
Does the same hold true for the elevator?
Thanks for the help.
06-25-2006, 09:27 PM
#2
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RE: Elevator control horn
Yes, it is generally easier to get the pull-pull system set up this way. otherwise the lines tend to get tighter or looser when the servo moves.
06-25-2006, 09:43 PM
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RE: Elevator control horn
Kelly,
Get the pivot point as close to the hingeline as you can.
I remember on my RadioCraft it was a little off but not bad.
You can mix out the throw differential with your radio though.
Get the pivot point as close to the hingeline as you can.
I remember on my RadioCraft it was a little off but not bad.
You can mix out the throw differential with your radio though.
06-26-2006, 05:56 AM
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RE: Elevator control horn
I just use the standard Rocket City horns on teh elevators on my RadioWAVE (close...).
You can use the radio to mix out differential, but you can also get rid of it by adjusting the push-rod length.
Set your ATVs to approx 130% up and down (130% is for JR... may need to use slightly less on Futaba or Multiplex) to allow room for subtrim. Then I roughly center the surface with subtrim. Measure up and down throw. If you have more up than down, then shorten the pushrod (and vise versa). Now, re-center the surface with subtrim, but do not touch the ATVs... leave them alone at 130ish%!!! Re-measure up and down throw and repeat the above proccess until the surface moves the same amount up and down. Your servo arms will likely be tipped slightly toward the rear when done, but it depends on your geometry. If you end up using excessive subtrim you may need to rotate the servo arm 1 spline one way or the other. Look at your servo monitor page to make sure you aren't over-driving a servo (i.e. a servo stops before the stick reaches full travel).
The result is a setup where both halves will travel at exactly the same speed and they'll track together perfectly throughout the range of motion.... very linear. Mixing out the differential in the radio CAN give you a setup where the surface might match at the ends, but they are off at in-between throws. Been there.
Cheers
You can use the radio to mix out differential, but you can also get rid of it by adjusting the push-rod length.
Set your ATVs to approx 130% up and down (130% is for JR... may need to use slightly less on Futaba or Multiplex) to allow room for subtrim. Then I roughly center the surface with subtrim. Measure up and down throw. If you have more up than down, then shorten the pushrod (and vise versa). Now, re-center the surface with subtrim, but do not touch the ATVs... leave them alone at 130ish%!!! Re-measure up and down throw and repeat the above proccess until the surface moves the same amount up and down. Your servo arms will likely be tipped slightly toward the rear when done, but it depends on your geometry. If you end up using excessive subtrim you may need to rotate the servo arm 1 spline one way or the other. Look at your servo monitor page to make sure you aren't over-driving a servo (i.e. a servo stops before the stick reaches full travel).
The result is a setup where both halves will travel at exactly the same speed and they'll track together perfectly throughout the range of motion.... very linear. Mixing out the differential in the radio CAN give you a setup where the surface might match at the ends, but they are off at in-between throws. Been there.
Cheers
06-26-2006, 10:55 AM
#6
RE: Elevator control horn
I've done this the same way and it works great. It tracks perfectly up to 50 degrees (both speed and position). It's the best way to do it IMO. The subtrim will limit your travel if you are max'd and need more. Using the next spline position is a good idea to solve that though.
ORIGINAL: sillyness
I just use the standard Rocket City horns on teh elevators on my RadioWAVE (close...).
You can use the radio to mix out differential, but you can also get rid of it by adjusting the push-rod length.
Set your ATVs to approx 130% up and down (130% is for JR... may need to use slightly less on Futaba or Multiplex) to allow room for subtrim. Then I roughly center the surface with subtrim. Measure up and down throw. If you have more up than down, then shorten the pushrod (and vise versa). Now, re-center the surface with subtrim, but do not touch the ATVs... leave them alone at 130ish%!!! Re-measure up and down throw and repeat the above proccess until the surface moves the same amount up and down. Your servo arms will likely be tipped slightly toward the rear when done, but it depends on your geometry. If you end up using excessive subtrim you may need to rotate the servo arm 1 spline one way or the other. Look at your servo monitor page to make sure you aren't over-driving a servo (i.e. a servo stops before the stick reaches full travel).
The result is a setup where both halves will travel at exactly the same speed and they'll track together perfectly throughout the range of motion.... very linear. Mixing out the differential in the radio CAN give you a setup where the surface might match at the ends, but they are off at in-between throws. Been there.
Cheers
I just use the standard Rocket City horns on teh elevators on my RadioWAVE (close...).
You can use the radio to mix out differential, but you can also get rid of it by adjusting the push-rod length.
Set your ATVs to approx 130% up and down (130% is for JR... may need to use slightly less on Futaba or Multiplex) to allow room for subtrim. Then I roughly center the surface with subtrim. Measure up and down throw. If you have more up than down, then shorten the pushrod (and vise versa). Now, re-center the surface with subtrim, but do not touch the ATVs... leave them alone at 130ish%!!! Re-measure up and down throw and repeat the above proccess until the surface moves the same amount up and down. Your servo arms will likely be tipped slightly toward the rear when done, but it depends on your geometry. If you end up using excessive subtrim you may need to rotate the servo arm 1 spline one way or the other. Look at your servo monitor page to make sure you aren't over-driving a servo (i.e. a servo stops before the stick reaches full travel).
The result is a setup where both halves will travel at exactly the same speed and they'll track together perfectly throughout the range of motion.... very linear. Mixing out the differential in the radio CAN give you a setup where the surface might match at the ends, but they are off at in-between throws. Been there.
Cheers
06-26-2006, 06:42 PM
#7
Thread Starter
RE: Elevator control horn
Ok, thank's for the help...
I do have a Hitec programmer at my disposal and
always set up the servo's with it... I like to have
sub trim at 0 and atv's at 130 on both ends
for the highest rate.
Also I have relocated the elevator servo's from the
side of the fuse to the stabs. The servo push rod
will be exactly 90 degree's to the control horn at
neutral.
It would be no problem to get the horn drilled exactly
on the hing line with Rocket city horn's, but it looks like
they are being replaced with the Hanger9 type horns
that are pre-drilled.
Here is a sneak paek
I do have a Hitec programmer at my disposal and
always set up the servo's with it... I like to have
sub trim at 0 and atv's at 130 on both ends
for the highest rate.
Also I have relocated the elevator servo's from the
side of the fuse to the stabs. The servo push rod
will be exactly 90 degree's to the control horn at
neutral.
It would be no problem to get the horn drilled exactly
on the hing line with Rocket city horn's, but it looks like
they are being replaced with the Hanger9 type horns
that are pre-drilled.
Here is a sneak paek
06-26-2006, 07:25 PM
#8
My Feedback: (31)
RE: Elevator control horn
Looks great...
This is not likely a desirable setup... It will create lots more work for the servo in one direction and afford you non-linear travel arcs verse the desired scalar travel arc.
Original Rocket City stuff is the same as Nelson and or Hangar 9 current offerings. Dubro maybe the only company offering control arms you drill and center the pivot point over the hinge line.
ORIGINAL: Advent
Also I have relocated the elevator servo's from the side of the fuse to the stabs. The servo push rod will be exactly 90 degree's to the control horn at neutral.
Also I have relocated the elevator servo's from the side of the fuse to the stabs. The servo push rod will be exactly 90 degree's to the control horn at neutral.
It would be no problem to get the horn drilled exactly on the hing line with Rocket city horn's, but it looks like they are being replaced with the Hanger9 type horns that are pre-drilled.
06-27-2006, 09:21 AM
#9
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RE: Elevator control horn
I ran a couple scenarios on my servo force calculator just for giggles.... I never really used it before.
When you said you are mounting them in the stabs, I am assuming that you are mounting them sideways with the servo arm in the same plane as the control horn. I can't get accurate numbers if they are mounted like aileron servos upright in the stab bottoms. I wanted to see for myself what is the best setup since I'd never really used this program much.
All numbers are based on what it would take to fully deflect one elevator surface on my 35% extra at 100 mph (extreme worse case... like doing a wall at 100mph). I based it on 37 degrees of surface deflection for 51 degrees of servo deflection. These all assume the best case of equal servo AND surface throw in BOTH directions, which does NOT mean the servo arm is perpendicular to the pushrod EXCEPT in the case where the servo is in the stab AND the control horn is on the hinge-line. More often than not, a servo arm tipped one way or the other is actually a better setup due to differential in the system... even if a servo arm is shorter than the control horn you induce differential. This example also assumes very good mechanical advantage (as is seen by the 51/37 ratio). There are more dimensional assumptions (pushrod length, servo loaction, etc) that I based on my Radiowave Extra.
Servos in Fuse, arm pointed up, with Rocket City Control Horns (behind hinge line):
Up: 153 oz-in @ 37 degrees, with a peak torque @ 27 degrees of 269 oz-in
Down: 290 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 12.4 pounds
Servo Arm-Pushrod Angle: 95.3 degrees
Servo Arm-Chord-line Angle: 85 degrees
Servos in Fuse, arm pointed up, with Control Horn on Hinge-Line :
Up: 294 oz-in @ 37 degrees, with a peak torque @ 34 degrees of 296 oz-in
Down: 409 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 16.3 pounds
Servo Arm-Pushrod Angle: 78.1 degrees
Servo Arm-Chord-line Angle: 75 degrees
Servos in Stab with Rocket City Control Horns (behind hinge line):
Up: 276 oz-in @ 37 degrees, with a peak torque @ 33 degrees of 290 oz-in
Down: 320 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 20.8 pounds
Servo Arm-Pushrod Angle: 110.7 degrees
Servo Arm-Chord-line Angle: 71.6 degrees
Servos in Stab with Control Horn on Hinge-Line:
Up: 298 oz-in @ 37 degrees
Down: 307 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 12.8 pounds
Servo Arm-Pushrod Angle: 91.3 degrees
Servo Arm-Chord-line Angle: 89 degrees
Convention:
The way the program works, it tells me that, for the case I laid out, I need 495 oz-in of torque to the control horn to deflect the surface 37 degrees at 100 mph, then it tells me how much SERVO torque I need make this possible (using a graphical and numerical outputs), along with other data. For the servo angles, a number below 90 degrees means the servo arm is tipped forward, while a number bigger than 90 degrees means the servo arm is tipped backward.
Conclusion:
Wow... I learned a lot!!!
Cases in order of good to bad:
1) Servo in fuse with Rocket City horns at 1.6 cm behind hinge-line (that's where they fell on my plane).
- Required the least torque, especially for up-elevator
- Put the least stress on the linkage
- Required small angles
2) Servos in Stabs with Control Horns ON THE HINGE-LINE
- Results very close to 1), but with slightly higher torques and forces
3) Servos in Stab with Rocket City Control Horns 1.6cm behind the hinge-line
- Required more torque yet, 10% more than best case
- 67% more stress on the linkage, servo bearings etc than best case
- Strange Servo angles required for equal throw on elevator and servo both
4) Servos in fuse with Control Horns ON THE HINGE-LINE
- 41% more torque (than best case) required for down elevator inputs!!!
- 31% more linkage stress (than best case)
- Strange servo angles
So… it seems that in some cases, putting the control horn on the hinge-line can be a very bad thing!!! In other cases (servos in stab) it seems to be a very good thing!
Anyway, take this for what it’s worth… it was very educational for me!!!!
When you said you are mounting them in the stabs, I am assuming that you are mounting them sideways with the servo arm in the same plane as the control horn. I can't get accurate numbers if they are mounted like aileron servos upright in the stab bottoms. I wanted to see for myself what is the best setup since I'd never really used this program much.
All numbers are based on what it would take to fully deflect one elevator surface on my 35% extra at 100 mph (extreme worse case... like doing a wall at 100mph). I based it on 37 degrees of surface deflection for 51 degrees of servo deflection. These all assume the best case of equal servo AND surface throw in BOTH directions, which does NOT mean the servo arm is perpendicular to the pushrod EXCEPT in the case where the servo is in the stab AND the control horn is on the hinge-line. More often than not, a servo arm tipped one way or the other is actually a better setup due to differential in the system... even if a servo arm is shorter than the control horn you induce differential. This example also assumes very good mechanical advantage (as is seen by the 51/37 ratio). There are more dimensional assumptions (pushrod length, servo loaction, etc) that I based on my Radiowave Extra.
Servos in Fuse, arm pointed up, with Rocket City Control Horns (behind hinge line):
Up: 153 oz-in @ 37 degrees, with a peak torque @ 27 degrees of 269 oz-in
Down: 290 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 12.4 pounds
Servo Arm-Pushrod Angle: 95.3 degrees
Servo Arm-Chord-line Angle: 85 degrees
Servos in Fuse, arm pointed up, with Control Horn on Hinge-Line :
Up: 294 oz-in @ 37 degrees, with a peak torque @ 34 degrees of 296 oz-in
Down: 409 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 16.3 pounds
Servo Arm-Pushrod Angle: 78.1 degrees
Servo Arm-Chord-line Angle: 75 degrees
Servos in Stab with Rocket City Control Horns (behind hinge line):
Up: 276 oz-in @ 37 degrees, with a peak torque @ 33 degrees of 290 oz-in
Down: 320 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 20.8 pounds
Servo Arm-Pushrod Angle: 110.7 degrees
Servo Arm-Chord-line Angle: 71.6 degrees
Servos in Stab with Control Horn on Hinge-Line:
Up: 298 oz-in @ 37 degrees
Down: 307 oz-in @ 37 degrees
Max torque on control horn: 495 oz-in
Max force on Push-Rod and linkage: 12.8 pounds
Servo Arm-Pushrod Angle: 91.3 degrees
Servo Arm-Chord-line Angle: 89 degrees
Convention:
The way the program works, it tells me that, for the case I laid out, I need 495 oz-in of torque to the control horn to deflect the surface 37 degrees at 100 mph, then it tells me how much SERVO torque I need make this possible (using a graphical and numerical outputs), along with other data. For the servo angles, a number below 90 degrees means the servo arm is tipped forward, while a number bigger than 90 degrees means the servo arm is tipped backward.
Conclusion:
Wow... I learned a lot!!!
Cases in order of good to bad:
1) Servo in fuse with Rocket City horns at 1.6 cm behind hinge-line (that's where they fell on my plane).
- Required the least torque, especially for up-elevator
- Put the least stress on the linkage
- Required small angles
2) Servos in Stabs with Control Horns ON THE HINGE-LINE
- Results very close to 1), but with slightly higher torques and forces
3) Servos in Stab with Rocket City Control Horns 1.6cm behind the hinge-line
- Required more torque yet, 10% more than best case
- 67% more stress on the linkage, servo bearings etc than best case
- Strange Servo angles required for equal throw on elevator and servo both
4) Servos in fuse with Control Horns ON THE HINGE-LINE
- 41% more torque (than best case) required for down elevator inputs!!!
- 31% more linkage stress (than best case)
- Strange servo angles
So… it seems that in some cases, putting the control horn on the hinge-line can be a very bad thing!!! In other cases (servos in stab) it seems to be a very good thing!
Anyway, take this for what it’s worth… it was very educational for me!!!!
06-27-2006, 08:06 PM
#11
Thread Starter
RE: Elevator control horn
Wow! You guys lost me!!! 
I will be mounting the elevator servo's like
the aileron servos. This will make it easier
to remove the stabs for transport.
Where did you get the calculator, or did you
make it yourself?
I will be mounting the elevator servo's like
the aileron servos. This will make it easier
to remove the stabs for transport.
Where did you get the calculator, or did you
make it yourself?
06-27-2006, 11:04 PM
#12
My Feedback: (31)
RE: Elevator control horn
Silly
Did you try moving the control arm location around span-wise? This horizontal offset is a key factor. I'd guess your not realizing the optimal setup do the the actual physical location for the control arm verses the best plausible location... Bag that comment I re-read your notes and noted you used a rotary short axis setup demo, my comment only applies for perpendicular axis setups.
The best linkage set-up number wise is rotary short axis, both the hinge line and the servo axis are in the same rotational plane... Atypical aileron setups are known as the perpendicular axis setup.
I ran some numbers in my program and found disparaging differences in required values (232/222oz-in) compared to your findings based on a 110sq-in elevator halve. How big is your elevator halve (surface area)? I provided for 51*/37* with the servo on its side and the arms in-line @ 100mph. The control arm on pivot point was best with nearly identical torque requirements with push-rod compression/tension numbers reasonably close too (418/311).
Which program do you have?
Did you try moving the control arm location around span-wise? This horizontal offset is a key factor. I'd guess your not realizing the optimal setup do the the actual physical location for the control arm verses the best plausible location... Bag that comment I re-read your notes and noted you used a rotary short axis setup demo, my comment only applies for perpendicular axis setups.
The best linkage set-up number wise is rotary short axis, both the hinge line and the servo axis are in the same rotational plane... Atypical aileron setups are known as the perpendicular axis setup.
I ran some numbers in my program and found disparaging differences in required values (232/222oz-in) compared to your findings based on a 110sq-in elevator halve. How big is your elevator halve (surface area)? I provided for 51*/37* with the servo on its side and the arms in-line @ 100mph. The control arm on pivot point was best with nearly identical torque requirements with push-rod compression/tension numbers reasonably close too (418/311).
Which program do you have?
06-28-2006, 11:18 AM
#13
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RE: Elevator control horn
Hey Mike,
I honestly estimated the size of the elevator half, but I wasn't really concerned about exact numbers for torque... I really take these values with a grain of salt because they also depend on altitude, temperature, surface shape, throttle setting, etc... I was really only concerned with geometry related issues, so I just accepted a number of 495 oz-in required to be delivered to the control horn... as long as that number stays the same for each example then fair comparisons can be made. I was really only interested in % increases, so I probably should have just listed that instead of all the data.
I did re-run a few scenarios and found that if I lengthed the elevator pushrod (moved servo forward) then the worst case got much much better, but it was still not as good as the servo in the fuse with RCL70 link... for some reason that works very well... geometry is strange. The initial data was run with a pretty short elevator pushrod, which is not a good thing when the control horn points down and the servo arm points up. The torque numbers for down elevator dropped to about 340 oz-in from 409 oz-in when I increased the pushrod length by about 2/3... I don't have the program here... I'm at work... can't get exact numbers now.
I can't run a scenario where the servo is set up like a typical aileron... the program can only do rotation in the same plane. Span-wise adjustments won't matter.
The program is a complex excel spreadsheet that was designed my some aero engineer... if you want a copy send me an e-mail.
Cheers
I honestly estimated the size of the elevator half, but I wasn't really concerned about exact numbers for torque... I really take these values with a grain of salt because they also depend on altitude, temperature, surface shape, throttle setting, etc... I was really only concerned with geometry related issues, so I just accepted a number of 495 oz-in required to be delivered to the control horn... as long as that number stays the same for each example then fair comparisons can be made. I was really only interested in % increases, so I probably should have just listed that instead of all the data.
I did re-run a few scenarios and found that if I lengthed the elevator pushrod (moved servo forward) then the worst case got much much better, but it was still not as good as the servo in the fuse with RCL70 link... for some reason that works very well... geometry is strange. The initial data was run with a pretty short elevator pushrod, which is not a good thing when the control horn points down and the servo arm points up. The torque numbers for down elevator dropped to about 340 oz-in from 409 oz-in when I increased the pushrod length by about 2/3... I don't have the program here... I'm at work... can't get exact numbers now.
I can't run a scenario where the servo is set up like a typical aileron... the program can only do rotation in the same plane. Span-wise adjustments won't matter.
The program is a complex excel spreadsheet that was designed my some aero engineer... if you want a copy send me an e-mail.
Cheers
06-28-2006, 11:21 AM
#14
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RE: Elevator control horn
Look here:
http://www.geistware.com/rcmodeling/calculators.htm
I think this may be it... my work computer has it firewalled.
http://www.geistware.com/rcmodeling/calculators.htm
I think this may be it... my work computer has it firewalled.
06-29-2006, 10:23 PM
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RE: Elevator control horn
Sillyness,
Just replaced my elevator servos and used your set-up tips. Took me about 30 minutes but was well worth it! Been coming here since the beginning and that was the first time I had seen it posted. Thank you for taking the time to put it in print.
Jon
Just replaced my elevator servos and used your set-up tips. Took me about 30 minutes but was well worth it! Been coming here since the beginning and that was the first time I had seen it posted. Thank you for taking the time to put it in print.
Jon
