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hidding control linkage? tips and techniques.

Old 11-14-2006, 09:29 AM
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transatlanticflight
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Default hidding control linkage? tips and techniques.

I'm working on my first scale project - a 1/6 scale spitfire by KMP. I want to hide the control linkage to duplicate scale looks but I don't want to compromise performance. I'm Looking for any information about the various techniques employed by all you master builders out there.

Specifically, I'm looking for a break down of techniques applicable to a given control surface and the vendors that might supply the parts. ie. I'm familiar with torque rods and have heard they are well suited to aileron and flap control -Am i right? But I still need a list of part sources.

Also searching for the best techniques for rudder and elevator control without visible control horns.

Would especially entertain methods of replacing mechanical advantage lost by giving up the leverage of control horns.

Any help would be greatly appreciated!

Rick
Old 11-14-2006, 10:18 AM
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Default RE: hidding control linkage? tips and techniques.

I'm getting ready to start a 1/7 scale P-51B in which I too will be trying to conceal the control linkages. For the elevator, the horn is mounted at the center of the elevator torque rod, which hides it inside the fuse. For the flaps, I plan on using torque rods that will also be hidden inside the fuse. For the ailerons, I'll be using a rotary drive system with two separate servos mounted in the wing.
Here's a link for the parts: http://www.irfmachineworks.com/rds/
Finally, there's the tailwheel and rudder. I have not yet come up with a final solution, but will probably use a pull-pull setup with the smallest horns I can get away with.

Scott
Old 11-14-2006, 10:34 AM
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Default RE: hidding control linkage? tips and techniques.

Somewhere, either in this forum or the Warbird forum I've seen an EXTENSIVE thread discussing all the differernt techniques. Lots of photos. Try the search with "hidden linkage."
Old 11-18-2006, 11:37 PM
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Default RE: hidding control linkage? tips and techniques.

It all depends on how "scale" you want to be with your spit. First off, the Spitfire used Frise ailerons; where the hing point is near the bottom surface of the aileron, which would allow you to attach your push rod near the top surface of the aileron without making it visible. If you are on the other hand going with conventional ailerons, then the irfmachineworks units would work there. The elevators are easy, just use a horn concealed in the fuse that is attached to a "U" shaped wire with then ends embedded in the elevator halves. For the rudder, you are in luck; the Spit had an external push rod that exited the fuse under the port tail plane and attached to the rudder's external horn.
Old 11-20-2006, 09:59 AM
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jeff naul
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Default RE: hidding control linkage? tips and techniques.

finally a post about concealing linkages! i absolutely cannot stand seeing linkages hanging out of a beautiful airplane. don't get me started on servo's sticking out. the guy's were passing aroung a picture of a ziroli mustang the other day, when it got to me i blew up when i saw not only the linkages but the whole top of the servo sticking out. how can you but that much time into an airplane, with that much scale detail and then just cut a hole and screw a servo in?
i built a d&r mustang with everything concealed, the rudder is easy, just exit the tail straight out the back. you have to cut a square out of the rudder leaving enough room to work and epoxy a small wooden horn in the rudder. remember no wider than the rudder. i looped the cable twice in the horn and then crimped the wire in brass. then using 1/16 balsa i sheeted over the horn sanded and filled. all you see is the cables where they exit the fuse and go into the rudder. now naturally you have alot of throw because of being that close to the hinge point but you just take that out using your a.t.v. in the radio. as far as leverage goes you don't have any so use a hi-torque servo and use the last hole in the horn. i don't know how important that is because how much pressure is on a rudder? i'll post some pic's when i can. i have a cub on the bench i'm building for a friend that i can use to show how to do an elevator. also another friend is on me to do a top flite arf mustang for him. that may be a good one to do and document for everyone to see. i'll call him now and see if we can get that going.
Old 11-22-2006, 03:47 PM
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Default RE: hidding control linkage? tips and techniques.

Thanks for all the ideas guys! Sorry I had to post and run...just getting back to the discussion. It would be great to keep this thread going and build a comprehensive file of tips and techniques. I am not surprised that this topic resurfaces...after all it seems to be an essential part of the scale building process. Yet, beyond the rds link, there seem to be few commercial solutions. Am I the only one that is stunned at the lack of solidly engineered, high-performance, concealable hardware for this hobby? I share the sentiments of the last post. A lot of precious time and money, high-tech hardware and detailing in these models...depending on a pin hinge, a bent piece of music wire, a plastic control horn bolted on and applying force on a ca hinge. $30 fast response, high-torque servos operating sloppy 2 cent hardware to the control surface. Am I just obsessive to think that a plane should be designed with precision control mechanisms. Is it just not possible to overcome the loss of mechanical advantage to hide control horns?

I like the idea of rds...but it still looks dicey. Seems like performance would depend a lot on achieving proper mounting locations, angles and it would still be up to the modeler to lock down the main pivot point which would still be placing a lot of stress on the plane structure (say a fragile wing former or trailing edge balsa bit).

Even the "u-shaped" wire with bellcrank used for elevator control mentioned by scalebirdman , which seems like an excellent solution for joining split elevator control and hiding the linkage, should in my opinion be provided with a bearing and mount to prevent transferring torque to the hinges of the control surface. Without fixing the hinge point of the bell crank, what's the purpose in paying for expensive, light-weight, rigid carbon fiber pushrods?

Why not manufacture parts designed to work in a scale manner? Is there such hardware out there? Links?

Scalebirdman, many thanks, truly, for your post. I recently saw a photo showing the real life rudder control of a spitfire and I'm going to try to duplicate it in miniature even if only a mock actuator. Still been thinking that a pull-pull system concealed in the rudder would be more positive if I can devise something. Probably will resort to your idea for elevator control but will machine my own mounting system to lock the hinge point to the stabilizer instead of letting it push on the hinges of the elevator. As for aileron? I just don't know. The model I bought (KMP) is hinged in the top third so I've been tring to draw up some sort of working hinge system that has a built in pushrod linkage - a drop in mechanism (if you will) that joins what I'll call the "operating control hinge" via a mounting structure back to the servo itself. My hope is to limit unwanted travel and the additional torque generated by the loss of mechanical advantage inherent in concealed linkages while being mindful of weight. I will post back if I come up with something.

Meanwhile, I'm still looking for more ideas and info about solutions that others have tried. So feel free to share. Sort of thinking a web page should be devoted to the topic so that the threads don't have to rehash the same old stuff for every newbie like myself, but until then...

Thanks all.

Rick
Old 11-22-2006, 07:42 PM
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Default RE: hidding control linkage? tips and techniques.

I used a device sold by Hobby Lobby in my WW1 Albatros DIII. I don't have their catalog handy right now, but my last years catalog still showed this device. It is a hinge which uses the back-forth/in-out motion of a pushrod and converts this motion through an eccentric to an up-down motion of the control surface. To explain, imagine a push rod going out the wing, to one of the center hinges, which converts this motion to an up and down motion of the aileron/flap. To use on the elevator or rudder, you would need to use a bellcrank. How the device works is simple, however, to explain is difficult. Even to look at the device in the catalog won't really explain how it works. However, it simply uses an eccentric. There is some motion lost and my devices were fairly tight at first, so I had to work them a bunch to get them loosened up. I built the Albatros in the mid 1980s. I'm sorta surprised these things didn't catch on better. They do work! Once installed, the only adjustment will be at the servo.
Old 11-23-2006, 08:24 PM
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transatlanticflight
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Default RE: hidding control linkage? tips and techniques.

Mode One,

Thanks for your post. I have a recent hobby lobby catalog but have not identified the part you speak of. If it is not the "hidden control horn hinge" (which is a version of rds), it would be great if you could provide a picture or a web link for the device you describe. Perhaps it is the sort of thing I'm trying to design. As you admit it does seem difficult to describe and, therefore, difficult to imagine.

Thanks Rick
Old 12-20-2006, 02:01 AM
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Default RE: hidding control linkage? tips and techniques.

Well, this project has been on the back burner for far longer than I expected. I went through a lot of work on creating a useable drawing of the horizontal stabs from the factory drawings. The result: the outline of the Top Flite kit for the horizonal stab is dead on!
Another destraction was a very short flight and rough landing of my TF Spit as a result of to great of throw on the control surfaces. Ended up breaking the landing gear rails and punched through the skins above the retracts. Working on repacing the rails. Also was dragging on the building front and started another 4* for a quick build. I do hope to get to the p-51 soon.

Scott.
Old 12-20-2006, 02:01 PM
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Default RE: hidding control linkage? tips and techniques.

I could not agree more on making scale airplanes actually scale... But I would like to inject one idea here. Please in the name of saftey, good engineering practices and common sense make your airplane inspectable and repairable. Linkages come loose or just need replacing after wear or vibration or damage. Nothing is worse than a fine $3000 airplane that has to be hacked apart to replace a $2.00 part. Also, nothing is really worse than crashing your scale contest winner because you have not been able to actually see the elevator pushrod connector in 3 years and it fell off in flight.

It can be made scale and it can be safe if you put the extra effort into it.
Old 12-21-2006, 02:35 PM
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Default RE: hidding control linkage? tips and techniques.

If you go to the Hobby Lobby web site do a search for CH901, I believe that is what you are looking for.
Old 12-24-2006, 11:25 AM
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Default RE: hidding control linkage? tips and techniques.

ORIGINAL: transatlanticflight

Mode One,

Thanks for your post. I have a recent hobby lobby catalog but have not identified the part you speak of. If it is not the "hidden control horn hinge" (which is a version of rds), it would be great if you could provide a picture or a web link for the device you describe. Perhaps it is the sort of thing I'm trying to design. As you admit it does seem difficult to describe and, therefore, difficult to imagine.

Thanks Rick
Rick, Sorry, I forgot I had respoinded to this inquiry until just now. My Hobby Lobby Catalog is the Spring of 2005 issue. The item I described is located on page 129 of this catalog. The Item Number is HLBB001 and called a "Beckman Concealed Actuator". They cost $11.90 for a pair. I have visited Hobby Lobby's website to see if the item is shown, and it is not. If this means it has been discontinued, I don't know. However, to carry an Item for 20+ years and then drop it this past year would not seem likely. I suggest getting their catalog or calling them with the referance number I've given, to see if they still carry it
Old 12-24-2006, 11:58 AM
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jeff naul
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Default RE: hidding control linkage? tips and techniques.

they still have them, i just ordered some yesterday. i've used the rotary drives in the past with good luck but i want to see how these look. being mechanical i'm worried about how reliable they will be. are there any specs on how big of a surface they will handle? i bought four in case i need to put two on each surface. they part is ch901 as old scale guy listed.
Old 12-25-2006, 06:29 PM
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Default RE: hidding control linkage? tips and techniques.

being mechanical i'm worried about how reliable they will be.
I used a genuine 'swingee' (which was a similar concept to the CH 901) on the rudder of a pylon model years ago & it worked fine for a while but it coped a bump during a bad landing & developed heaps of slop. Because it was built into the fin it needed major surgery to remove it. [] Hopefully the CH 901 is more durable.

Close up pictures of full size aircraft often reveal that they do indeed use horns & rods in many cases but all but hidden & shorter than we use. These can be copied but are not very forgiving of slop in the linkages. - John.
Old 02-02-2007, 11:14 PM
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Default RE: hidding control linkage? tips and techniques.

Rick,
the best thing to do is to purchase a set of Brian Taylor SPitfire plans. http://www.bhplans.com/BTPlansPg1.html
This is the most scale available Spit winner of WOrld Scale contest.
It shows detailed information of how to build the control surfaces and scale hinges/pushrods.
Here are some samples
http://mywebpage.netscape.com/warbirdscale/SpitVII.htm
JG
Old 02-04-2007, 12:31 PM
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jeff naul
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Default RE: hidding control linkage? tips and techniques.

the hobby lobby ch 901 is not worth a hoot. although good in concept, i dont see it being usuable in anything but .30-.40 size planes or sailplanes. saw in ama magazine this month the durant drive. looks good but you have to have a trailing edge that is as thick as the servo laying on it's side. jeff
Old 02-04-2007, 10:26 PM
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Default RE: hidding control linkage? tips and techniques.

Here's a link to a "how-to" on the radial driver system (RDS):

http://www.rcgroups.com/forums/showthread.php?t=449106

Control surfaces are removable with the RDS (assuming your hinges are removable, of course).
Old 02-06-2007, 06:00 PM
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Default RE: hidding control linkage? tips and techniques.

Here is a picture of the method I developed to hide the horns on my Chinese AEW. It works great with no slop. The plane has over 90 flights on it. Of course the AEW is a slow flying "truck" but I'm sure this method could be expanded upon to fly just about any aicraft if you have the room in the wing.
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Old 02-06-2007, 07:02 PM
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Default RE: hidding control linkage? tips and techniques.

What materia did you use for the servo arm, and how was it attached to the servo?

Scott
Old 02-06-2007, 07:23 PM
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Default RE: hidding control linkage? tips and techniques.

We did the same thing as Ampbomber in our Barron-55 and it works great with NO slop..
Old 02-06-2007, 08:35 PM
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Default RE: hidding control linkage? tips and techniques.

Taking another look at the first photo, I now see how it is attached. Is it cut from G10?

Scott
Old 02-07-2007, 09:22 AM
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Default RE: hidding control linkage? tips and techniques.

I cut the slotted part from some "Delrin" I had laying around (Delrin® bridges the gap between metals and ordinary plastics with a unique combination of strength, stiffness, hardness, dimensional stability, toughness, fatigue resistance, solvent and fuel resistance, abrasion resistance, low wear and low friction.). I would think that nylon would be just as good. Just cut the slot acurately so there is no slop between the clevis pin. It's attached to a servo wheel with 2-56 machine screws.
Old 02-07-2007, 05:43 PM
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Default RE: hidding control linkage? tips and techniques.


ORIGINAL: jeff naul

the hobby lobby ch 901 is not worth a hoot. although good in concept, i dont see it being usuable in anything but .30-.40 size planes or sailplanes. saw in ama magazine this month the durant drive. looks good but you have to have a trailing edge that is as thick as the servo laying on it's side. jeff

Wow, talk about invalidating me and my opinion! All the hard work I did, writting about the device, researching where it could be found and telling you all about it! All summed in "It ain't worth a hoot!"

I used them and they worked for me, is all I can say.

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