What is the best way to lube control cables e.g. the ones for the heater, throttle, mixture, alternate air, etc?
On the TB, one of the four heater control levers has no less than three cables coming off it.
Many say these should simply be replaced. But it isn’t just the cost; it is also the huge time it can take to route the new ones, especially as they are held with P-clips in various almost inaccessible places.
One would think there would be a device which clips onto the end, which allows the internal wire to pass through, and which a grease gun would be attached to. Then you could pump grease in until it comes out of the other end…
Some cables have a teflon liner and those should never go stiff, but they do.
These are often used on motorcycle cables.
How do these work for a cable which is either in situ (usually, disconnecting the end is really difficult) or the inner wire cannot be extracted.
What most people do is they lift up one end as much as they can (the higher end) and pour oil in there.
For example, this is the prop rpm cable. All one can do is pour oil where shown. It is a very slow job because the orifice is tiny.
In the days of my youth when My transport was ancient and unreliable motorcycles we lubricated control cables by putting a small hole in a plastic bag, pushing the end of the cable into the hole and using insulating tape wrapped around the cable and bag to make a seal. Oil was then put in the bag and the bag suspended at the high end of the cable, leaving this arrangement overnight resulted in the oil finding its way down the length of the cable. It was a messy but effective method of lubrication that was rendered obsolete by nylon lined cables.
Most aircraft cables are lined with nylon of some similar self lubricating substance and when they become stiff it is usually time to replace the whole assembly.
when they become stiff it is usually time to replace the whole assembly
That’s my feeling, too. If it has become stiff, it probably means the reciprocating motion of the inner cable has dragged enough dirt from the ends inside the sheath. Short of replacing the whole thing, one will need to remove the inner cable and rinse the hole thoroughly.
My cable experience is mainly marine orientated.
I posted the tools above in a hurry, but agree with the guys about the fact it may be time to replace.
It’s a common conversation where a huge effort to lubricate a cable does sometimes provide relief but is short lived. It’s a boating winter job and usually ends up on cable replacement, maybe the following winter.
During the lubrication times it’s either ineffective or slightly effective with lubricant constantly weeping from the cable ends.
To some extent this depends. You can get semi-seized cables because some dirt got in at one end. Or you can have a cable with a solid rod portion at one end and this rod started to corrode; this is not unusual on throttle and mixture cables. Lubrication is a good way to deal with this and get another say 10 years out of it.
After almost 2 months undergoing paint strip and repaint, the throttle cable had very little movement. It was removed, cleaned, greased, and refitted. No problems so far. A short cable on an O200 in a Bolkow Junior.
Never had a problem with cables going under the cowling, but our trim cable’s orifices are quite exposed at the rear of the aircraft, and and moisture can have a tendency to get in leading to the trim getting excessively stiff. Since I’ve owned the plane I’ve been squirting it with LPS-2 on every 6 monthly check, and the problem has never recurred. LPS-2 seems to wick down the cable pretty well.