Questions and Answers If you have general RC questions or answers discuss it here.

aileron servo idea

Reply

Old 10-14-2006, 10:11 AM
  #1  
GoNavy
Thread Starter
My Feedback: (15)
 
Join Date: Jan 2002
Location: Rib Lake, WI
Posts: 535
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default aileron servo idea

I like to mount aileron servos on their sides within the wing with only the servo arm protruding. The difficulty is the length of most servo arms; Most are too short. Near neutral they are long enough, but they disappear below the wing surface with deflection. This means the pushrod must be bent, and the slot in the wing must be wider - enough to accomodate the pushrod keeper.

Longer servos arms on standard throw servos require much longer horns on the ailerons.

One solution would be special aileron servos geared for, let's say, one half the normal throw, combined with the longer servo arm. This would allow for easier servo installation, a better appearance, shorter aileron horns, and push rods without bends.

I wondered how others address the in-wing aileron servo, and if the above idea had merit.

I use non-computer transmitters.
GoNavy is offline  
Reply With Quote
Old 10-14-2006, 10:50 AM
  #2  
exeter_acres
Senior Member
My Feedback: (2)
 
exeter_acres's Avatar
 
Join Date: Sep 2004
Location: Johns Creek, GA
Posts: 7,457
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

switch to a computer radio and adjust end points...

get Hitec digital servos and the programmer and program the end points into the servos

use either an MSA-10 or JR Matchbox and use that to adjust the end points
exeter_acres is offline  
Reply With Quote
Old 10-16-2006, 02:13 PM
  #3  
skeeter_ca
Senior Member
 
skeeter_ca's Avatar
 
Join Date: Nov 2005
Location: Yucaipa, CA
Posts: 973
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

I was thinking about that same problem for my Supersportster 60 i am going to build soon. The only idea i could come up with was mount the servo deep in the wing so the arm does not stick out. Attach the control rod to the servo and lead out through a small slit in the wing. The only draw back seems to be you need a bigger access hatch to get to the servo when needed.

skeeter
skeeter_ca is offline  
Reply With Quote
Old 10-16-2006, 06:20 PM
  #4  
daveopam
My Feedback: (9)
 
daveopam's Avatar
 
Join Date: Oct 2002
Location: ELK CITY, OK
Posts: 7,464
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

I have several servos mounted the way you described. I have not noticed the arms being to short. I do however use the longest 4 sided arm that comes with the servo. Maybe your mounting the servo to low. I do mine as follows. I make the servo cover out of ply. Then use two hardwood blocks to mount the servo on the hatch. I have the side of the servo case right up against the hatch. Then I mount the hatch to the wing again using hardwood blocks and servo screws.

David
daveopam is offline  
Reply With Quote
Old 10-16-2006, 07:29 PM
  #5  
GoNavy
Thread Starter
My Feedback: (15)
 
Join Date: Jan 2002
Location: Rib Lake, WI
Posts: 535
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

I also use a plywood hatch cover, with wooded blocks to accept the servo mounting screws. I use 1/16 inch ply for the hatch. I maintain a 1/32" clearance between the servo and the hatch. I have purchased longer arms from Dubro but then you need a really tall horn also.

The 1/16th thick hatch is okay, but not quite as ridgid as I would prefer.

I suspect that the mechanics of such a servo would not present any problems for the manufacturer - we have retract servos with almost twice the standard throw. I would suppose it's a question of marketability.

Limiting the throw via a computer radio means you will need more powerful servos for the same force and throw of the aileron.
GoNavy is offline  
Reply With Quote
Old 10-16-2006, 08:04 PM
  #6  
flapper
Senior Member
 
Join Date: Sep 2004
Location: Green Point NSW, AUSTRALIA
Posts: 189
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Gday,
Have fitted servos side mounted without any great problem. As previously mentioned, if it mounted too low you may have trouble with horn arm length. Pics below are for my Top Flite spitfre wing. Servos mounted on side using hardwood rails and aluminium servo bracket in an 'L' shape. Servo is screwed to bracket and bracket to rails. Top side of servo just (hair width) under the 1/16th ply hatch cover. The servo is a Futaba S3010 and using an aftermarket heavy duty horn which is slightly longer that the ones supplied with servo.

ATV on radio set at 100% and throw of servo adjusted with dual rate settings at 50% and 70%. Arm moves front and rear without catching on hatch cover.

Regards
Mark
Attached Thumbnails Click image for larger version

Name:	Ca81670.jpg
Views:	17
Size:	55.3 KB
ID:	542345   Click image for larger version

Name:	Gb90690.jpg
Views:	15
Size:	54.0 KB
ID:	542346  
flapper is offline  
Reply With Quote
Old 10-16-2006, 09:21 PM
  #7  
GoNavy
Thread Starter
My Feedback: (15)
 
Join Date: Jan 2002
Location: Rib Lake, WI
Posts: 535
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Flappers' installation means the hatch does not have to support the servo. You just have to the near perfect alignment on the mounting rails.
GoNavy is offline  
Reply With Quote
Old 10-16-2006, 09:35 PM
  #8  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Couple of ideas............

-- There is little value to spacing the servo away from the hatch cover. Actually, is there any? I've never done that and never seen any problems associated with the servo being flat against the plywood.

-- With the very short reach required to connect the servo arm to the horn, a bend in the pushrod won't compromise the strength enough to matter on any rod that's sufficient for the size airplane.

-- The idea that the connection at the servo arm should be as close to the servo as possible is more a suggested starting point. Moving out the arm reduces the servo's leverage, but won't come close to defeating the sucker as long as it's adequate for the size airplane. I've found that with all my models built in the last year, the connections have usually been in the 2nd hole out from the servo. I've had a couple that needed the last hole out, and those airplanes have yet to show anything close to blowback.... and they have had every opportunity to experience it!

-- I usually do not center the servo output shaft front-to-back in the slot. If there is room under the hatch, I usually position the servo away from the hingeline, toward the LE of the wing. That gives the arm more room in the slot when it's pushing the connecting rod. It is less apt to experience interference with the hatch that way. It doesn't need as much opening in the pull direction since the hatch is usually slanted up in that direction and the servo arm is moving "down into" the slot.
da Rock is offline  
Reply With Quote
Old 10-17-2006, 05:46 AM
  #9  
flapper
Senior Member
 
Join Date: Sep 2004
Location: Green Point NSW, AUSTRALIA
Posts: 189
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Hi,
Re GoNavy's reply re the hatch cover. Maybe I am being a bit over protective but for some reason I don't really trust the 1cm square surface area which is all that retains a servo to a hatch cover when using the two small hardwood blocks as supplied in most kits and ARF's. I see many build threads where a lot of strengthening is carried out to flying surfaces, fuselages and the like but when I see the aileron and flap servos here are the servos screwed onto two small pieces of hardwood with a dab of epoxy holding them on.
flapper is offline  
Reply With Quote
Old 10-17-2006, 06:02 AM
  #10  
flapper
Senior Member
 
Join Date: Sep 2004
Location: Green Point NSW, AUSTRALIA
Posts: 189
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

In addition to my previous post, I just wanted to add it is my preference not to use the hardwood blocks despite that technique may be adequate in a lot of situations.

You are right about making sure the alignment of the servo rails is spot on. If they are out of alignment you will have an uneven throw of the servo arm. Just needs a bit of elbow grease and patience and it comes out good in the end.

A friend and fellow flyier has recently received his Hanger 9 P47 and has stripped it fully and is modifying it. He showed me his wing and hardware and I saw the ailerons and flap servos involve the hardwood blocks glued to the bottom of the hatch covers. He is fitting a Zeus 220 and I was wondering if anyone can comment whether or not the block on hatch technique is really suitable in this situation.

Anyway, like most people I am here to learn from others and would appreciate any advice or criticism so that I may enjoy the hobby more.

Regards,
Mark.
flapper is offline  
Reply With Quote
Old 10-17-2006, 08:55 AM
  #11  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Mounting the servo on blocks that're glued to the servo hatch is almost always an adequately strong design.

The blocks need to be better wood than balsa. They need to be adequately glued to the hatch cover. The hatch cover needs to be a decently strong wood or plywood. It needs to be screwed in place with at least 4 screws. The screws need to go into decently strong wood (balsa ain't) or plywood. The surrounding wood that supports the hatch and screw locations needs to be adequate to the task.

The small dimensions of most hatch designs keep the torques and forces from being amplified by leverage. Plywood and harder woods than balsa and woodscrews are certainly up to the task.

It's always sensible to strengthen anything on an ARF that you don't feel is strong enough, but don't add appreciable weight doing it. CA does wonders when soaked into anything.
da Rock is offline  
Reply With Quote
Old 10-17-2006, 09:04 AM
  #12  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

If you plan to replace any part that looks weak to you, make sure to look beyond that weak part.

I've seen aluminum stock glued into a structure to reinforce it. With the metal glued to balsa that has little or no strength itself. That situation needed a layer of glass cloth instead of the aluminum stock.

If you're suspicious of the strength of your aileron servo installation test it. When newbies show up with their trainer for flight instruction the first time, I usually work the sticks while holding each of the surfaces in turn. I've found aileron servos that weren't strong enough, aileron hatches that were screwed into balsa, aileron hatches that were stong and wrinkled the wing covering (because the hatch support wasn't supported worth spit by the wing structure), and on and on......
da Rock is offline  
Reply With Quote
Old 10-17-2006, 09:42 PM
  #13  
GoNavy
Thread Starter
My Feedback: (15)
 
Join Date: Jan 2002
Location: Rib Lake, WI
Posts: 535
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

ORIGINAL: darock

Couple of ideas............

-- There is little value to spacing the servo away from the hatch cover. Actually, is there any? I've never done that and never seen any problems associated with the servo being flat against the plywood.

GN: Servos are mounted using rubber isolators. I presume this is to minimize transmission of vibration from the airframe to the servo.
With the servo in contact with the hatch, vibration passes to the servo.

-- With the very short reach required to connect the servo arm to the horn, a bend in the pushrod won't compromise the strength enough to matter on any rod that's sufficient for the size airplane.

GN: I would agree.

-- The idea that the connection at the servo arm should be as close to the servo as possible is more a suggested starting point. Moving out the arm reduces the servo's leverage, but won't come close to defeating the sucker as long as it's adequate for the size airplane. I've found that with all my models built in the last year, the connections have usually been in the 2nd hole out from the servo. I've had a couple that needed the last hole out, and those airplanes have yet to show anything close to blowback.... and they have had every opportunity to experience it!

GN: Once upon a time I had a formula to determine the torque needs for so many square inches of control surface deflected so many degrees at a given speed. Now I use the Mark I eyeball method to determine servo power. But if I want to have the servo arm travel its full normal length, without the end going below the wing (hatch) surface, the arm has to be about twice the length of a normal arm. My airtronics standard arms are too short. They sell a longer arm which can be used. Some of my Hitec servos came with a longer alternative single arm.

-- I usually do not center the servo output shaft front-to-back in the slot. If there is room under the hatch, I usually position the servo away from the hingeline, toward the LE of the wing. That gives the arm more room in the slot when it's pushing the connecting rod. It is less apt to experience interference with the hatch that way. It doesn't need as much opening in the pull direction since the hatch is usually slanted up in that direction and the servo arm is moving "down into" the slot.

GN: For some reason I have always mounted the servos the other end around. Not really sure why, though.
Re secure mouting: You bet. I once crashed a 1.20 size Sukhoj when an aileron servo broke loose.
GoNavy is offline  
Reply With Quote
Old 10-18-2006, 04:06 PM
  #14  
scratchonly
Senior Member
 
Join Date: Jun 2006
Location: winnipeg, MB, CANADA
Posts: 950
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: aileron servo idea

Nothing wrong with a bent rod and a larger clearance hole; won't affect performance and your the only one to see it. I agree with Da... if you don't trust your block mounting, dummy one up and give it a test. Done properly it should pull the ply apart.
scratchonly is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service