Hello. What would be the best setup for a patter plane as far as control linkages are concerned. I have a Showtime 50 Thats been sitting around and I would like to improve the linkages over the bent push rod/servo conection it currently has. Could you guys point me towards a good post or article? I was thinking ball links on the control surface end would be best but not sure if it is, or how to go about doing it. I would like to try and stay away from soldering as Im not very good at it. Any help would be appreciated.

Ball links are for sure the way to go, on both ends of the pushrodto the control horn, and to the servo arm/wheel. No soldering involved.

If you want to use the Showtime as a pattern-dedicated model (as opposed to a switch-hitter pattern on low rates and 3D on high rates), you should use servo wheels on your aileron and elevator servos, not the longer arms. For pattern style precision aerobatics you'll do much better with your mechanical linkage set for 15 degrees up & down on ailerons, 12 degrees up & down on elevator. Even that may be too much on the elevator. You do this by setting your transmitter ATV on ailerons & elevators to the maximum (125% or 140%, whatever your system allows), so that full stick on your TX produces full rotation (60 degrees either direction) on your servo. BUT by connecting the pushrod to the servo wheel instead of the long arm, your full-stick movement will produce only a short push or pull on the pushrod. Then connect the other end of the pushrod to the longest setting on the control horn, and see what you get for degrees of deflection on the control surface with full-stick at the transmitter.

If you're at the shortest distance possible from hub to connection on the servo wheel, and longest distance possible from hingeline to connection on control horn, then you have maximum resolution from your servomeaning a little bit of stick movement will produce even a smaller angle of deflection on the control surface. Now you have precise control. If your CG is set anywhere close to where it should be, you'll have all the control you need, and more. You'll also be using your servo torque to maximum advantage, for good control authority.

If the control surface is still moving too much, one possibility is to substitute a longer control arm. Short of that, you can reduce your ATV setting on your TX. If the control surface is not moving enough, move the connection on the control horn in a bit. To go back to a 3D set-up, take off the servo wheels and replace them with longer arms.

Bravo majortom-RCU!!! I have been advising people to set up their linkages for resolution and proportional travel for a long time. Not only do you take better advantage of the servos' torque, the plane will fly more smoothly than ever before. I've seen planes at the field that were so squirrelly that the pilots could hardly get them down in one piece. Simply reversing the connection points of the pushrods as you explain turned them into solid, precise, smooth flying models; a complete night and day difference. It's possible that 3D flying has conditioned some pilots to hook up their pushrods backwards in an effort to get maximum throws, while only using a small portion of the servos' full travel and torque.

David

Question 2 - If no soldering is required...what would I use to replace the existing pushrods? THe rods I am using now are threaded on one side and bent at 90 degrees on the control surface side. I know they sell pushrods threaded on both ends in various lengths...but do these lengths usually fit all planes? Ive been told it is NOT a good idea to use the rods that are threaded the entire length of the rod.

Question 3 - This setup would only be advantageous to pattern flying? Would I not be able to get as much out of 3D as well with this? Is this where I kind of have to make a choice for this particular plane?


Thank you for the detailed response! Bravo is right~

To make custom length pushrods use 2mm carbon rod and glue good quality helicopter rod ends on with slow setting epoxy. The heli guys use these for their tail rotor push rods and they can get a hammering.

I agree on not using all-thread rods, since they don't stand up to stress & vibration all that wellthe longer they are the worse they are for durability and rigidity. I like the Darrol Cady rods (http://www.darrolcady.com/Carbon_Fiber/carbon_fiber.htm). You need thecarbon fiber tubes plus the threaded steel ends. The website says (or used to sayI haven't read it lately) you can use rubberized CA to glue in the steel ends into the tube, but I find the JB Weld holds stronger. Central Hobbies also has sets for making up your own CF pushrods, and they are pretty good with technical support if you need a little guidance.

I cut the carbon fiber tube to length with a dremel cutting wheel. I do the cutting with tube end and cutting wheel inside a plastic bag. I can see where I'm cutting, but the carbon fiber dust (nasty in the lungs) gets captured inside the bag. I also wash my hands when I'm done cutting.

The first end goes in with the JB Weld on it, no problem. When you go to glue in the other end, you'll have air pressure resisting the second end with the epoxy globbed all over it, and it tends to push out when you let go of it. You need to clamp the ends in place while the epoxy cures; otherwise one or both ends will slide out while the epoxy is setting up.

I have the Showtime 90, but not the 50, so I'm not sure what the servo mounting set-up is. If the servos are tail-mounted, you can use the Hangar 9 titanium pro-links, which I like very well and use a lot. These are threaded right-hand thread on one end and left-hand thread on the other, so you can turn them with the small wrench they sell as an accessory to adjust like a turnbuckle. They aren't cheap, but they save a lot of time setting up neutral, no disconnecting, turning, reconnecting, checking deflection, disconnecting all over again, many repetitions before you get it right. With the pro-links you're set dead-on in seconds. With a little luck, you will find pro-links of suitable length for both the ailerons and elevators.

Somewhere I've seen ball links with left-hand threads, specifically intended for use with the pro-links. I didn't pay too much attention when I saw them, because I got myself a left-hand tap to re-thread the standard Dubro ball links. Retapping them is a lot easier than trying to force a left-hand thread into a right-hand tapped barrel. I put a little band of red nail polish on my left-hand tapped ball links to distinguish them from the standard right-hand pieces.

I will grant you that all this is a bit more time consuming and a little more expensive than sport model pushrods, but if you want to fly precision aerobatics, I consider it a small price to pay. Also as you go up in model size, this becomes totally standard practice.

For 3D or any other kind of model, this is how I link everything I build. Linkages are tight but smooth, slop-free. Also, don't neglect to seal your hinge gaps for better control surface effectiveness. A lot of little things go into setting up a well-behaved model.

I don't fly helicopters, but I will say the guys I know who do are generally a lot more particular about setting up a model compared to the sport flying crowd.

Major Tom....You have just told me EVERYTHING I wanted to know about upgrading my linkage setup. THANKS A TON> I havent been able to find a simple answer to this anywhere. Much appreciated. I will start this with my showtime....then probably take it on to my Aeroworks Edge.... thanks again!

For the pretty good sport flyer who wants to step up to precision aerobatics, I've found that this business of high resolution servo set-up with low slop linkage is an absolutely essential step toward improving the model's good behavior. With this kind of set-up, plus a decent powerplant, judicious trimming & mixing, all you need is time on the sticks. If you haven't already done so, check out nsrca.org for links to some great pattern websites.