Lubricating flex cable
 

I am scratch building a Grumman XF5F for .074 Norvels. I am using Sullivan 1/2a flex cables for the throttles, retracts, and rudders. I am trying to lube them for easier movement and less slop. They are not too bad as there are, but I would like them to be better. I have tried spray lock graphite lube. That worked ok but left the cables stiff and "notchy" after a few weeks. I am thinking that the petrolium in the spray has affected the plastic outer sheath.
Does anybody know of anything that works?

Heres a link to the build: http://www.rcuniverse.com/forum/m_39..._1/key_/tm.htm
Thanks,
Ben

RE: Lubricating flex cable
 

Something silicon based won't hurt the plastic. I use silicon grease a lot for lubing axles, o-rings, etc. I don't know if adding grease would help the flex cables. If it is thick, it may not make it any easier to slide.

RE: Lubricating flex cable
 

I think that instead of trying to fix a situation with a lubricant (and I retired after 40+ years in the fuels and lubricants industry!) I would go to either the next size outer tube or the next size smaller inner cable. This is what I did when I wanted to improve the movement on the rear nacelle-mounted engine throttle using a Sullivan throttle cable.

RE: Lubricating flex cable
 

The lubricant might solve the first problem, but will only appear to solve the slop. The forces that take advantage of a sloppy connection will not even notice the thickest grease. And if the grease has to be thin to keep movement forces down, absolutely nothing will be working against the slop.

Flex cables have to be a snug fit in their tubes to not have slop. If they are snug then tight bends will make them hard to move. About the only solution is to route them with wider bends. Friction in the bends will give the appearance of no slop, but they won't perform like that for long.

It takes a special talent to build with flex cables. Or it takes experience using them to get them right.

After first believing they were the greatest things since sliced bread, I've come to use them only if nothing else could be used. I came to that conclusion after replacing some in old airplanes that'd started flying badly. The braided wire can wear through the plastic tubing. That is just one of the problems.

RE: Lubricating flex cable
 

Try some lithium grease. You will need to remove the cable, grease the cable, then put the cable back in. Lithium is compatible with most things so it should not cause any problems.

Opening up the bends will solve the problem, unfortunately that is not always possible.

RE: Lubricating flex cable
 

The only reason that I am using the flex cables is because nothing else will work. I have used them before for flight controls and always ended up replacing them with something else after a season or so. When l installed the throttle cables, I lubed them with spray lock lubricant and that helped the friction noticably. They worked well and without slop. I left the plane alone for a month or so and that is when they became stiff. There aren't any really tight bends to constrict the cable, so I am left trying to fix the problem. I thought that lithium grease was the answer, but it is a little too thick for the application. I havn't tried silicone spray yet, but I think that it will be the trick.
Increasing the sleave ID or decreasing the cable OD would help the friction problem, but would introduce a lot of slop. Also, when I got the cables to work properly, I glued them in, making replacement of the sheath difficult.

Ben

RE: Lubricating flex cable
 

My comments were related to plastic inner sections, not braided wire.

Not sure that you have exhausted the options available since this has worked very well for me and a bunch of other folks. The 'slop' you mention would not be problem with a small difference in outer diameter of the inner tube.

If you still want to try/use a lubricant, I suggest the "3-in-1 Professional Lubricant wirh Teflon".

RE: Lubricating flex cable
 

I'm not sure if nyrod's inner plastic rods would fit into the outer tubes you have, but plastic to plastic often does work better than the braided metal in plastic.

I've had a problem like you're having. I pulled the cable and used some silicone lube in a spray can to blow into the tube. I had to RubeGoldberg a setup to capture the spray out the other end so as not to soak the balsa around that end.

There are a couple of magic potion lubes that're sold to the gun guys. One is a grease that's got teflon and lord knows what else in it that works very good in plastic. I've used that recently to rejuvinate an elevator cable in a 2m glider that had gotten sticky. It was built in the 80s so had a good excuse. I blew the tube clean with silicone lube and then rubbed the cable with the grease.

The grease is Tetra Gun Grease. They also have a liquid in a squeeze bottle.

RE: Lubricating flex cable
 

How about cable lubricant they sell at motorcycle shop for throttle cables? Just a thought.

RE: Lubricating flex cable
 

Get a teflon spray lubricant, spray down the cable, allow the solovent to flash off and install as usual.

RE: Lubricating flex cable
 

I appriciate all of the suggestions that have been brough forth. As I was spraying the silicone lube into the tube, I noticed that a rust colored liquid was coming out of the other end. So I flushed the tube with alcohol and ran a few bits of cotton through to clean and dry it out. I also cleaned the cable well and lubed it with castor oil. I had some lying around and figured it wouldn't hurt anything. A light coating of castor and reassembled the cable. The friction and notchyness is gone and it works quite will. It seems that the spray lock lubricant left some kind of residue that didn't work well on the plastic to cable friction. On the rest of the cables for this airplane, I am just going to leave them alone, that seems to work well.
Ben

RE: Lubricating flex cable
 

I'd get the castor oil out and use something else, since the castor may get gummey and sticky with age.

RE: Lubricating flex cable
 

That is a good point that I didn't think about, it does have a tendancy to do that. I will have to clean the tubes out and just go at it dry.
Ben

RE: Lubricating flex cable
 

Hi!
Castor oil is the worst oil you could use as it oxidizes and stiffens with time.
I agree that fixing twin rudders is a challenge but using miniature servos and bellcranks is a better way of doing it than flexing cables.
I do recommend Sullivan thinnest cables for throttle control though.

Regards!
Jan K

RE: Lubricating flex cable
 

Hi beenie,

I used a graphite oil on the throttle cables on my Bonneville, it didn't last,Molyslip grease was better. The only way I solved the problem on the bike was to crimp cable lubricator nozzles over the position nearest to the middle of the cable that was accessible without removing the tank. I then used frequent lubrication.

I seem to understand you have no access to the cables/snakes. Graphite alone without an oil to carry it may work. I used graphite on wood to wood in sliding conditions. It was a drawer, the lubrication worked but the clothes were marked so for a drawer I now use candlewax. I understand Graphite was used in the space program, oils & greases evaporated in vacuum. I don't know how it was used but I suggest that a very soft pencil lead rubbed over the inner cable should last for a long time.

The prototype you've chosen really looks really evil, I look forward to see the finished pics.

Best of luck.


old git - - - - -aka John L.

RE: Lubricating flex cable
 

I would use the silicon and Teflon spray first over the greas or oil based lubricants. I personally have used the Silicon spray lubricant with good results.

RE: Lubricating flex cable
 

similar, i have used teflon gun lube. goes in wet, carrier evaporates quickly, leaves whitish slippery powder type teflon lube, lasts a long time. comes in a spray can with a flex tube.

RE: Lubricating flex cable
 

From out of left feild (or at least the sail boat circles, model and full size), try Team McLube Sail Kote. http://www.888teammclube.com/frames/sailkote/index.html
It is a dry lubricant using PTFE (Dupont Krytox®), and is said to out last teflon type lubricants by many times. I have used it on my sailboat blocks (pulley's), fairleads, small motors, window tracks and yes, throttle cables on my aircraft. Spray it on and let it dryto an almost clear white powder that does not collect dirt. It comes in a 6 oz spray can, but is a little pricey ($8). Keep the throttle cables clean from oil and fuel and bends large and you should have no problems. Good Luck.

RE: Lubricating flex cable
 

I have found that Tri-flow to be a fantastic lube for metal, nylon and plastic parts.

http://www.deeteeenterprises.com/NS....-Flow.Lube.php

Main thing though, is to have the moving parts with no binding to start with.

Mando.......

RE: Lubricating flex cable
 

skylarkmk1: Where did you buy the SailKote? I notice you are from Missouri, but the site does not call out a Missouri dealer. Do most marinas have it on the shelf? Not a sailor:D, Dzl

RE: Lubricating flex cable
 

Try West Marine, both store here in the St louis area have it as well as the catalog. Also the St.Louis Sailing Center in Bridgeton has it. Haven't really looked for it in other Marine stores.

RE: Lubricating flex cable
 

Thanx. Dzl