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General control line discussion => Open Forum => Topic started by: Avaiojet on December 31, 2012, 08:33:34 AM
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Certainly no grease fittings are available, yet, for bellcranks or pivot points on control horn wire HDWE.
I won't be able to get at them once the model is stiched up.
I'm thinking white grease for these pivot points.
What do you use?
Charles
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I use a clear silicon grease with Teflon, bought years ago for something I was doing at the time. I only use it on the bellcrank pivot, my understanding is not to lube ball joint rod ends like Tom Morris sells as it just attracts dust which will bind them up.
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Certainly no grease fittings are available, yet...
Charles
n~ HB~> This statement floors me!
...and I don't think the grease guns are available yet either. :-X
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I use nothing.
The control system needs to be ABSOLUTLY free with essentially no friction (can never achieve zero friction). The individual flying surfaces controls should fall under their own weight. I screen ball links and nylon hinges and reject (or fix) those with higher frictions. I take great care that there is no unintended slop anywhere. Some slop at the elevator horn is OK, but that is a completely different subject
A wet lube will attract dust and other debris into the moving joint over the life of the airplane. I believe a wet lube does more harm than good.
FWIW - the vibration associated w/ glow engines will tend to break up dry friction in the control system.
Jim Hoffman
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Best choice is the chain lube used on motorcycles and chain saws. Find it in local automotive supply
Tiny amount applied using the little plastic applicator tube is all you need on the flap and horn bearing surfaces and at the push rod ends (I don't use ball links)
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I use nothing.
The control system needs to be ABSOLUTLY free with essentially no friction (can never achieve zero friction). The individual flying surfaces controls should fall under their own weight. I screen ball links and nylon hinges and reject (or fix) those with higher frictions. I take great care that there is no unintended slop anywhere. Some slop at the elevator horn is OK, but that is a completely different subject
A wet lube will attract dust and other debris into the moving joint over the life of the airplane. I believe a wet lube does more harm than good.
FWIW - the vibration associated w/ glow engines will tend to break up dry friction in the control system.
Jim Hoffman
Listen to Jim...He's absolutely right. Any wet lube on the bellcrank pivot or ball ends will attract dirt and eventually cause high friction, Any grease, especially something like white grease or chain lube will thicken more with lower temperature and cause very sticky operation.
Chain lube for motorcycles has polymers in it that deliberatly thicken and get sticky so the lube stays on the chain and doesn't get thrown off. This works for a motorcycle chain but definitely not in a low friction bearing like the bellcrank pivot. As Jim says...vibration is our friend here. Electrics may actually have a disadvantage here %^@. Dry lube like graphite can be used but doesn't stay in the friction area very well and is of questionable value in an application like this.
Jim is an aerospace engineer with long experience in this area (as am I also).
Selection of components is key to free controls...if something is sticky or binding, fix it or chuck it, do not expect it to suddenly become better...it'll likely get worse.
Randy Cuberly
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A 6B drawing pencil or a bit of powdered graphite. works for me.
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Dry, free surfaces and the classic "no binding" throughout the travel. They will wear, but they will get looser. Any wet lubricant will collect dirt and both tend to bind as well as keep abrasive stuff held in place. Lubricated systems may actually wear out faster then dry ones.
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...if something is sticky or binding, fix it or chuck it, do not expect it to suddenly become better...it'll likely get worse.
An interesting difference between combat and stunt planes is that combat plane controls tend to loosen up after a flight or two, but stunt plane controls don't.
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An interesting difference between combat and stunt planes is that combat plane controls tend to loosen up after a flight or two, but stunt plane controls don't.
Agreed Howard...
But then Combat planes don't have 5 pivoting connections in the control system and 20 or more hinge pionts on the control surfaces. Mine usually squeaked a bit at the stabilator hinge when new...unfortunately most of mine never lasted long enough to wear very much... <=
Randy Cuberly
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An interesting difference between combat and stunt planes is that combat plane controls tend to loosen up after a flight or two, but stunt plane controls don't.
Mine got noticeably looser after the first thousand flights or so. Then it tightened up again after maybe 1500, until I figured out how to drip oil on the bellcrank pivot from the wingtip, after which is loosed up again. The latest airplane has a way of lubricating the bellcrank pivot directly.
Brett
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My last airplane had a way of lubricating the tailwheel directly, but not my latest one.
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My last airplane had a way of lubricating the tailwheel directly, but not my latest one.
Ahh yes...I forgot about my automatic tail wheel lubrication. I think that is referred to as a total loss oil system. <=
See how much you give up by using those electron thingys! ;)
Randy C.
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Leadout to bellcrank/bellcrank pivot: Permatex synthetic brake caliper grease.