Ball Joint control surface horns?

[Matt Carlton]

Does anyone make a longer version of the ball joint connectors that go on servo horns? 

 

It occurs to me that they would make an ideal elevator control horn to avoid having to put a bend in a pushrod. 

 

There are many control horns with ball joints to accomodate up/down movement, but I can't find any to accomodate lateral movement. 

 

 

 

[J D 8]

  Thing is if the shank of the ball was long it would itself impose a twisting load on the control horn, you would have to make sure the horn is strong enough.

[EarlyBird]

These work Matt and no bends in the pushrods.

 

 

Steve

[Andy Stephenson]

This type has a little more stand off...

[Nick Cripps]

Dubro used to make a control horn that had a captive ball to which you attached a normal clevis and was available in various lengths. It appears to be discontinued now but they still offer this heavy duty version for large models:

Heavy Duty Dual Control Horn

[Matt Carlton]

2 hours ago, J D 8 said:

  Thing is if the shank of the ball was long it would itself impose a twisting load on the control horn, you would have to make sure the horn is strong enough.

 

I don't mean mounting the ball to the horn, I mean using the ball as the horn, so essentially a long shanked ball, through the control surface near to the hinge line. Then a cup type ball joint on the end of the pushrod. Makes absolutely perfect sense for a control surface connection but nobody seems to do it. The only downside I can see is the security of the cup and ball under load. 

Edited March 5, 2022 by Matt Carlton

[Martin Harris - Moderator]

I was wondering what the problem with a ball joint was - I've used them for several elevator connections...

 

However, I would definitely advise against using an open cup type.  I know of the loss of a beautiful Hurricane on its maiden caused by one of these detaching.  Even a small amount of aerodynamic flutter will exert a tremendous force on the connector and easily pop it off.

[Keith Berriman]

You could use the ball joint as shown by Early Birds option with a long M3 screw to catch the ball joint then the extended thread with nuts and washers each side of the rudder 

[John Lee]

You may want to look at helicopter linkages, eg https://www.modelhelicopters.co.uk/avant-extended-length-ball.html

[PatMc]

 

 

I made several pairs of these years ago from piano wire for models with strip ailerons etc, the balls are soldered in place. 

 

 

This pair didn't get used as I forgot to slip the plastic tube bearing in place before the final bend. If I was making them today to use as elevator or rudder horns I'd use bike spoke wire instead of piano wire as it's easier to bend & adequately strong.

 

Edited March 5, 2022 by PatMc

[Matt Carlton]

Those look absolutely ideal actually Pat, and for what I have in mind, I wouldn't need a bearing tube.

If I could solder worth a damn I'd give that a go. Unless of course, those ones are, you know, looking for a new home

 

?

 

Edited March 6, 2022 by Matt Carlton

[Paul De Tourtoulon]

8 hours ago, PatMc said:

 

 

I made several pairs of these years ago from piano wire for models with strip ailerons etc, the balls are soldered in place. 

 

 

This pair didn't get used as I forgot to slip the plastic tube bearing in place before the final bend. If I was making them today to use as elevator or rudder horns I'd use bike spoke wire instead of piano wire as it's easier to bend & adequately strong.

 

I also use them but I do bend the end 90° where I solder the ball links to and only use Schluter ball links,

[EarlyBird]

1 hour ago, Matt Carlton said:

Those look absolutely ideal actually Pat, and for what I have in mind, I wouldn't need a bearing tube.

If I could solder worth a damn I'd give that a go. Unless of course, those ones are, you know, looking for a new home

A 2mm push rod with a threaded end means the ball can be bolted between two nuts rather than solder, adjustable as well.

[Ron Gray]

As EB says, use a couple of nuts either side of the ball but also include washers to prevent the ball housing coming adrift (as per MH’s post).

[Frank Skilbeck]

You can get the threaded ball clevis's here https://www.rcworld.co.uk/acatalog/Maxi-Ball-Link-with-Ball-M3-Pk2-RCW1404.html#SID=105

[Paul De Tourtoulon]

8 hours ago, Ron Gray said:

As EB says, use a couple of nuts either side of the ball but also include washers to prevent the ball housing coming adrift (as per MH’s post).

If they come off then they aren't installed properly or they are rubbish,, just look at a helicopter ball link does when 3 D flying !.

[Martin Harris - Moderator]

These are similar to the type I was warning about:

 

[Nigel R]

Those are great for throttles, as they're compact. Can't say I'd touch them for control surfaces though.

[John Lee]

 

I've used them often on control surfaces for smaller models without any problems. They are great when you have awkward geometry as in my Tony Nihaus BAe Hawk. In this case the ball ends have been drilled & piano wire soldered in with the cups bolted to a plastic insert on the elevator. Been flying like this for two years.

[Martin Harris - Moderator]

I’m in agreement with Nigel and  yes, they are ideal for throttle use - I often use them for the purpose. Would I use them on a primary control surface?  Not on anything of any size/weight/speed. 
 

They may be ok on a lightweight model and I’m glad yours have worked well but having witnessed a fuel tube ring retained clevis detaching from an elevator servo arm as a result of flutter on a normal 40 engined sports model (luckily I was able to fly it on the throttle round a large gentle circuit and put it on the ground ok and confirm what happened) I know the loads it can exert so I really wouldn’t advise their use. 
 

As I mentioned before, some years ago, one failed on a fairly large scale Hurricane at my club and caused its total loss. 
 

 

 

 

[Matt Carlton]

Interesting thoughts chaps, thankyou. I'm slightly dubious about using them for a single elevator horn. On the Hawk posted, there is at least a level of redundancy should one fail. 

 

I suspect that a slight bend in tbe pushrod is probably an ultimately simpler solution, but I'll have a bit of a fiddle and a think! 

 

[Martin McIntosh]

MH, I now use those SLEC ones almost exclusively and with a little attention from a heat gun can be made a perfect bind and slop free connection. The ones from SMC above are also very good. In a high stress situation such as a central elevator horn or mechanical retracts I use M3 bolt on ones. They can be spaced away with washers if need be.