John Perry:
What’s the story with greasing the gear knee pins? Not to sound like I have no idea what everyone is talking about, but what is this “grease needle” everyone keeps mentioning?
Editor: While we’re working on the gear, how can we tell whether our gear cushions, or donuts, are still good?
Search strings: Needle Fittings, needle adapter, needle fitting adapter, zerk adapter, Alemite adapter, flush fitting, flush grease fittings, flush fitting adapter, NAPA adapter, Plews adapter
Carl Foster:
The landing gear knee pins and donut attach pins are hollow, and are used to grease the joints. To do this properly, you need a grease gun and a Lincoln Engineering 5803 utility needle nozzle. I had a full hard drive meltdown or I would suggest a supplier. Search on “Lincoln Engineering” and you should find a source. It is important to keep these joints lubricated every 25 hours, or more often if you are doing touch-and-goes.
Bill Howard:
When you are attempting to grease the gear (every 25 hrs, or daily if used for training – yeah, shure!), lie down on your back; with a flashlight, you can look right up into the bore of the gear housing. The appearance of the donuts should be pretty obvious. The grey, cracked, and wrinkled (kinda like my face) donuts just look BAD – and as wide as the bore (kinda like my BUTT…).
On mine, the hinge point for the mount base that is at the bottom of the donuts was actually UP INSIDE the bore, where I could hardly reach it with the grease needle. The specs in the Maintenance Manual show that joint as being over 1″ BELOW the housing. So, if you can’t see the joint below the gear leg, you got ‘flattening of the donuts disease…’
I can see that the major effect of time, UV, and just plane (pun) weight pressing down, is the deformation of the shape. The bore of the gear leg is nearly the OD size of the metal washers that are bonded onto the donut. I’m guessing that they are designed that way to allow the donuts to compress without the drag of rubber on metal; just the washers sliding up and down in the bore. The washers also provide a measure of fore-and-aft and side-to-side resistance – centering the rod they are on. As the donut rubber squashes and breaks down over the years, it deforms out to the diameter of the bore and the washer. Now you have rubber rubbing on the bore – LOTS more resistance to the movement of the swingarm.
Also, the swingarm hinge pins had built up corrosion and rust, even as much as I tried to grease them with that stupid needle. So with the pins out and some cleaning up of the hinge joints, shafts, and holes, plus nice fresh grease – those 40PSI tires ought to just float over the ramp expansion joints, and that Priest Lake runway should feel smooth as a baby’s bottom. You just have to wonder how I could have made so many greaser landings (at least that’s how I describe them to my wife) when the pins were pretty much seized, and the donuts were expanded so much that they were jammed in their bores.
One of the first things I found out two years ago when I found MM, was the info about greasing the gear pins (Hinges.) After I ordered the Maintenance Manual from RAPID – about $70, I found the section about greasing & oiling everything & schedule, including the ‘right grease.’
The landing gear is done by pumping grease into the hinges thru tiny holes in the end of the pins (each end of two pins.) To get grease into the holes, you need a tip for your grease gun that looks like a needle, and you have to press real hard to get the grease to go in, while you are pumping. Unscrew the regular Zerk end. The first needle I bought was from an on-line store suggested by a MM member – and was $15 plus freight. About the 2nd time I tried to use it, I broke it off. I tried to grind it down, but the tip was the only part that was tiny – after I ground it down, the hole was too big. SO, in desperation, I went to the local Farm & Home store, and found the exact same part for about $2.99 – bought several – have yet to break one. Sure wish the pins had Zerk fittings, though.
As to the ‘right grease’ for the landing gear, there is a spec in the maintenance manual that mentions a specific grease. I could only find it as a 12 oz tube for $15 or a 5 gal bucket for $80 or more. VERY messy to put in a gun, and HOW much am I ever gonna use. There have been LOTS of new greases developed in the last 50 years.
I looked up all I could and figured out a substitute – a red lithium low-temp grease at NAPA for $2.99 a tube. You need to decide what to use. I figure I saved enough by buying the red stuff at NAPA, I could afford a nice folding foam pad to lay on, while I’m under there cussing at those tiny holes. BUT, getting the right grease seems less important to me than greasing more often. I know Bob has specific info about compatibility for the different metals of the pins, and the magnesium legs, and the grease, so buyer beware.
Get the book, read the book. You really don’t know about your plane without that manual, and also the parts book.
Carl Foster:
Here is a source for the needle. It is about the ninth listing down. It is $6.70. I use Lubriplate 630-AA grease.
http://www.toolparadise.com/pricelist/databasenp_31.html
Bob Steward:
Its a FLUSH Zerk. (Ed. note: The flush type looks like a small button with a depressed center, as opposed to the standard Zerk fitting that most people are accustomed to seeing). The “Needle” is the style of grease gun fitting to fill the FLUSH ZERKS. I think this has really been blown way out of proportion. You buy the “Needle” style fitting and you buy the recommended grease, and you periodically lube all the fittings in less than 5 minutes.
Snap-On tools sells a great hand held grease gun for FLUSH ZERKS. Next time you see one of those tool trucks, stop and ask to see the grease gun they use to lubricate ratchets. You can buy the Lubriplate from Aircraft Spruce. Just a few bucks for a pint can which will be a lifetime supply for your Musketeer.
Editor’s notes:
The gun fitting for a standard Zerk fitting snaps into place on the fitting, and is self-locking by the grease pressure, if kept properly aligned. In fact, if the joint is tight and no grease can move, it can be very difficult to get the gun back off the fitting. You sometimes have to slightly unscrew the gun nozzle to relieve the hydraulic pressure… or you can just keep framming and yanking until it comes off or something breaks (like the fitting), because you don’t understand what is happening. The flush Zerk relies on the operator pushing the needle against the fitting, to seal the connection while pumping. This should give you a clue about how “free” the joints should be to accept grease. One more little tidbit. Some grease fittings DO NOT have the little spring-loaded check ball in the fitting. These are used in joints that are not designed to remain pressurized by grease following lubrication. They often involve expandable seals, sometimes made of thin metal. When the gun is removed, any pressurized grease will flow back out like a string of spaghetti. Unless you can see that the check ball exists but is corroded and not seating, you should not just replace a fitting that “squirts back grease” with a new one that has a check ball.
Some of the earlier planes had undrilled pins. Exacerbating this, Beech shipped many replacement pins that were undrilled, as replacement parts for the much later models that were SUPPOSED to have drilled pins. It was like a lottery, trying to get a pin that actually had the drillings in it. To make matters even worse, some of the pins were drilled at the ends, but the intersecting drillings that fed grease to the bushing area did not meet with the fitting bore drilling. You can imagine how tight those joints would feel, if installed. I have often wondered how many got installed that way anyway, because they were “official factory parts”. Since I was told by Tech Support that the later pins are superseding parts for the earlier pins, any of the planes should be eligible to use the drilled pins.
Now the fittings themselves. They are press-in fittings, installed in roughly a quarter-inch diameter enlargement in the grease passage bore. They can usually be turned out by careful use of drill bits. They can be replaced with press-in standard Zerk fittings. Places like Genuine Aircraft Hardware carry all the proper parts for this type of stuff. Now for the “buts”. If you do install press-in standard Zerks, because you have trouble getting grease in the joints, you will find that your next use of high pressure on the grease gun will conveniently pop the new fitting right back out for you. The lesson: The fittings are supposed to be flush fittings, because the joint is supposed to be free to take grease, so that you can’t develop enough pressure on the grease gun connection to pop out the grease fitting. Besides, do you really want all the extra drag from those standard fittings hanging out in the wind (grin!). At any rate, just another small example of why it can pay to understand what you are dealing with, or working on.
And finally, the pin-to-bushing fit. Even when you order supposedly compatible parts, you may well find that the new pin won’t go into the new bushings… by a wide margin. Unless you or your mechanic have a well-equipped machine shop, you will need to pay a machine shop to hone out the new bushings to fit the pins, before installing the new bushings and pins. The alternative option, if the pins you receive are not properly drilled, is to simply have a machine shop hone the new undersize bushings to fit your old pins instead. This assumes that they are not seriously worn or damaged. Of course, when you disassemble the joints and clean out all the gunk, you may discover that everything is still fine, and all you need to do is to properly lube, assemble, and re-lube the joints. Best of luck!
Addendum May 2006:
A link to an online ordering web page for Lubriplate has been added to the BAC Links section.
Addendum September 2007:
1. NAPA #715-1213 flush grease fitting adapter, long nose; $13.49 8/2007
2. NAPA #715-1215 grease gun screw-on flush fitting tip, $4.99 8/2007
3. NAPA #715-1200 flush grease fitting adapter, short nose; price not shown.
4. Plews or LubriMatic #05-045, SKU 0 28893 05045 2. May also be under the Plews/Edelmann name.
5. NAPA #720-1009 large-base, one-quart hand oiler; price not shown. If you buy about 18″ of approximately 1/8″ ID fuel-resistant tubing from an outdoor equipment supply store, you can attach it to the nozzle using safety wire as a clamp. Select something like a Cherry rivet to use as a plug for the open end. Unlike common clear tubing, the fuel-resistant tubing won’t harden up from exposure to the MIL-H-5606 hydraulic fluid used in our planes for brake fluid.
This makes a simple, inexpensive, stable, large-capacity bleeding tool to use on the wheel cylinders. It allows you to bleed from the bottom up, pushing out the air bubbles. The bleeding will go faster if you crack loose the top brake hose connection on the pilot’s side cylinders, until you quit hearing air escaping and start seeing solid fluid. I also recommend draining and disconnecting the reservoir, and running a small rubber tube from the reservoir line into a larger clear container. That allows you to complete bleeding without interruption, and without the mess of an overflow. The old fluid needs to be discarded anyway.