Frank,
Ball links have been used for a while now in the CL airplanes.  I think that they are using primarily the Rocket City ones that are now made by Nelson Products.  CLC or Tom Morris should have some in stock if you can't find any at the LHS.  Perhaps others can chime in with their experience with other suppliers.  As far as I know, the balls are not lubed as it only tends to pick up dirt/dust and restrict movement.  You do need to be careful that you do not screw the pushrods too far in as some binding has been known to occur.
John

I'm no expert flyer, but when I want an airplane to fly well I use ball links EVERYWHERE, bellcrank, flaps and elevator, though I have had to resort to bushings for some elevators because there just wasn't enough space for the ball link.

As a previous poster said, no lube, it's 'cause the ball link to pick up dirt.

ANother big advantage from where I stand is tha ability to bolt the ball link to the horn, makes assembly (or disassembly for 2 piece take apart models) so much easier.

I haven't tested them at all but the Dubro Heavy Duty Ball Links look pretty much the same as the Rocket City links that I bought from Tom Morris. I don't know about any other differences.

I am using the standard duty Dubro ball links in models smaller that .25 power when I need to.

I don't know that I would use the Dubro units with the screw in the socket and I would not use any sort of lubricant.

Cheers, Geoff

Now that I am back into building C/L again, I am tempted to use some of the R/C hardware that I have laying around. The most likely candidates are the ball link ends for 4-40 pushrods. Since these have Delrin fittings with brass spheres, should they be run dry or lubricated? I have some Du-Bro units that have a small tension screw at the ball end - are these trustworthy on a bellcrank?

    Just about everybody uses ball links on both ends of the bellcrank-flap pushrod, and at least at the head end of the elevator pusrod. I use a bent wire with a keeper at the elevator end - just easier to fit in the space available. Just turn the whole pushrod in or out to adjust.

   A short history of the ball link in stunt...

      The first person I know of to use ball links, and show them on plans, was Ted Fancher in the Imitation article (built in 78, published in 1979). He use the closed-side DuBro clear nylon jobbies, 2-56. They worked well and last I heard, were still functional on the original airplane. A bunch of people started trying it in the early 80's, the most extreme example being Gid Adkisson's "take-apart" Bud Light Laser, where he routinely popped them on and off the ball with no apparent issues. In about 1986, I was building a new airplane, and was going to try ball links, after the soldered-washer system had resulted in a corroded pushrod (from the flux) that eventually rasped it's way through the nylon making a slot instead of a hole.  I was always a little suspicious of 2-56 hardware on stunt planes, so I went to the local hobby shop and got the biggest they had - Rocket City #87. There was no other reason to choose those over anything else aside from that's what they happened to have at San Antonio Hobbies (in Mountain View CA) the day I went there. Those worked fine (and are still in the same airplane 23 years later and exhibit no slop, wear, or any degeneration that is detectable). Dave and Ted started using them, too, and the first place they were on published plans that I am aware of was the Trivial Pursuit plans. Since then everybody has given up their mistaken notion that ball links and adjustable hardware are not durable. Kwik-links, no way, no matter what kind or what size, but ball links seem fine even in the relatively small sizes. Of course it makes a frictionless and slop-free system almost trivial.

    Now, maybe 20-30000 flights later (around 10,000 or so between the three of us) and one apparent failure later, people are differentially seeking out Rocket City #87 links. 1/30,000 is about the same as your chances of getting hit by a meteorite at some point in your life, and about 2 orders of magnitude more reliable than soldered washers, so I contend they are just fine and will use those I have until they are gone.  But there's nothing special about those particular links. Anything that can take an application like tie-rod ends on an R/C car for more than an afternoon is tough enough for stunt. And there are plenty of those. I think David is using the DuBro "adjustable tension" type, but I could be wrong. You can even get metal versions, although I can't see why.

    The only ball-links that I have seen fail on a moderately regular basis are the clear nylon types. The plastic is very soft and I have seen two of those fail in the last year, in both cases where the threaded part ends and the flat part that goes around the ball begins. But you can pretty much look at those and see that it's not going to work. Otherwise, anything with 4-40 thread and about a 1/4" ball seems to be good enough.

     Brett