Using a flex cable for throttle control...
 

I'm looking at a Dubro flex cable. Can someone give me the rundown about how these connect. I see it has 3 or four different connectors, both plastic and metal. Does it matter which ones you use?

RE: Using a flex cable for throttle control...
 

More info would be helpful... However I think I know what you're looking for. I've flown a 4 Star 60 with an OS 61 FX for over a year, I keep a log book on my aircraft and I have 104 flights on her. She uses a flex cable otherwise know as a throttle cable. It connects to both ends with a connector that lets the cable pass through a hole and secured with a set screw. the connector itself pass through the servo arm and throttle horn and is secrured with a plastic snap ring. It has never caused me any problems, never came loose. I've seen this set up come loose on 1 other aircraft 1 time.
There is a draw back though if you shut down your aircraft with the throttle open you can't push it closed with your finger like you can using a push rod.
Just make sure that the plastic tube that the cable passes through is cut just so. If its too short the cable will flex and you won't get a good throw if its too long the tube will interfer with the throw itself.
Hope this helps Good Luck

RE: Using a flex cable for throttle control...
 

I usually connect a flex cable this way. I use an EZ Connector at the servo arm end, and solder the provided threaded end on the carb end. Use a mini nylon clevis on this end.

Dr.1

RE: Using a flex cable for throttle control...
 

Hi xray, there have been cases of RF interference caused by all metel rods connected to the engine throttle. The vibration of the engine on the metel can set up an RF signal which has been known to cause problems. To prevent this its best to solder a threaded coupler onto the end of the flex cable and then use a nylon clevice threaded onto the coupler to connect to the throttle on the engine. At the servo end you can use a screw lock type of connter. The cable just pushed through the hole in the connector and then you tighten down the screw when the cable is whwere you want it. Hope this helps, Fast![8D]

RE: Using a flex cable for throttle control...
 

So does the tube end at the firewall or do I extend it all the way to the coupler?

RE: Using a flex cable for throttle control...
 

Don't cut it off at the firewall.

If you do run it all the way to the coupler, you'll soon see that the coupler won't move in or out. ;) I'm guessing you really meant, is it run as far out as possible without restricting the throttle movement. Yes, but with just a little extra room.

The outer tube helps the inner tube or flex cable to stay straight and keep from flexing. When the cable/tube that's supposed to do the work flexes, the flex robs the movement that's supposed to go to the throttle. So you run the outer tube as close to the servo and as close to the throttle arm as you can. You also glue the outer tube in lots of places along it's path to keep it from moving. If the whole thing flexes, it robs the throttle movement as well.

Getting the outer tube close to the servo and throttle is an art. You want to be as close as possible, but you don't want the outer tube to fight the natural flex that's going to be required by the circular path the servo arm and the throttle arms must follow. Some outer tubes are really flexible and they need to be supported every inch of the way. That is, glue them to something about every inch.

Some people actually glue a brace to the firewall that extends out to hold the outer tube so it won't flex too much. And when using flex cable, some people run hard solder into the last inch or so of cable that's unsupported by outer tube at both ends. All that could be considered overkill, but it's not wasted effort if you have the time and inclination to do it.

RE: Using a flex cable for throttle control...
 

Re: "when using flex cable, some people run hard solder into the last inch or so of cable that's unsupported by outer tube at both ends." < I have done instead of extending the support much further than the firewall and it works well. Reason being, the linkage cable has to run just below the muffler to connect to the carb on 2 stroke engines and if you extend the support for the cable it could interfere with the muffler. [8D]

RE: Using a flex cable for throttle control...
 

I only use flex cable for the engine throttle pushrod and steerible nose gear. It's benefits are it is very flexible allowing passage through and around tight areas in the nose (always a busy place). I use a ball connectors at the carb's throttle crank or nose gear crank and solder a threaded connector to the flex cable. The threaded connector is screwed into the ball connectors. The plastic sleeve is cut short so as to not interfer with throw and I may flow solder into the cable, if it needs to be stronger and less flexible (nose gear). From my point of view flex cable is the correct product to use in this application.

RE: Using a flex cable for throttle control...
 

I'm not familiar with using a ball connector. Is this it?

http://www2.towerhobbies.com/cgi-bin...?&I=LXD908&P=7

What the advantage here? How do I use this? Does the screw go through the throttle arm?

RE: Using a flex cable for throttle control...
 

You could use the one you showed but I prefer this one.
http://www2.towerhobbies.com/cgi-bin...&I=LXK090&P=ML
Alignment less critical.

Mount the ball on the throttle arm. Solder the threaded adapter on the end of the cable. Let the solder wick up the cable a little bit but do not allow it to increase the cable diameter. Only looking for slight stiffening. Cut outer tube to a length where it does not interfere with threaded adapter movement. Easy to do. Pops on and off easily when needed.

RE: Using a flex cable for throttle control...
 

What solder do I use? Its not the same as the stuff for the electrical connections is it?

RE: Using a flex cable for throttle control...
 

That's what I use. Use flux paste or liquid too if you have it. Helps a lot. Clean well when done. Should be nice and shiny like a good solder connection. OK if you can still see orig cable color when done "Tinning" the cable. That is basically what you are doing. If you have ever "tinned" wire for an electrical project, you know what to do. Easiest to control heat application with a small iron and not a torch. Obviously keep heat away from outer tubing.
I use one of these at the servo end:
http://www2.towerhobbies.com/cgi-bin...4&I=LXE114&P=K
Tin the cable end before making final cut and it will slip in and not try to unravel. Many don't like these for flight controls but fine for throttles IMO.

RE: Using a flex cable for throttle control...
 

JUst to add one more tiny detail. After I solder the ends, I will take the Dremel and a grinder wheel and taper the ends slightly. And I will just clean up the soldered areas in general.

RE: Using a flex cable for throttle control...
 

Ball connector, Ball link, probably one and the same. However, the type I was refuring to is shown on page 82 of the Tower catalog. They are Great Planes P/N GPM03840. Goldberg used to make them and possibly DuBro, also. They arn't the bolt-on type; but, the snap-on type. The reason for using them is they allow for an amount of "un-fair lead" (they allow for an amount poor alignment). They also have very low friction.

Other folks have nicely jumped in here and given further ideas on their use and set-up, thanks!

Mark DeSchane
AMA59157

RE: Using a flex cable for throttle control...
 

Mark,
that's the same one I listed in post #10 except you have a typo in the P/N. It should be GPMQ3840.:D