What’s the story on replacing the pivot bushings and pin on my landing gear? I’m talking about the knee, where the lower fork attaches to the upper housing; as well as the compressor plate on which the gear cushions (donuts) are stacked. These joints seem to have a pin that is retained by a long, small-diameter clevis pin. It looks like there is a bushing on each end of the pivot pin. (Search strings: knee pins, knee pivot, knuckle joint, pivot pins)
These are the perfect parts for using your Owner-Produced Parts option.
You do not want to order these parts from Beech, almost regardless of price. Their knee bushings all come with an undersized ID, and must be machined to fit anyway. Half of the pins that come, and which appear to be drilled for grease fittings, have not been properly drilled. They look OK to the naked eye, but the drillings do not intersect inside the pin (!). When you try to pump grease in, it can’t go anywhere, and will pop out the grease fitting instead. I have returned three of them to Beech for this reason. Fortunately, I caught all three of them pre-installation.
It is very uncommon for these parts to freeze in place. This is usually one of the higher wear points in the nose gear, due to inadequate lube and constant motion during taxi. If you have an A&P friend, and a safe place to work, where you can leave the plane with the tail tied down (and a safety cradle under the firewall bulkhead), I would get this apart yourself. Soak it with Corrosion X or ACF 50, and let it sit for a week or more. Then try to remove the small Clevis pin. I know you are smart enough to make sure that the cotter pin has been removed. You have to be careful when you tap upward on the bottom of it, to avoid peening it oversize, or it won’t go through the hole to come out. If that happens, or it keeps bending, try locking Vise-Grips on it and turning it. If it snaps off at the surface or inside, switch to a short-necked pin drift of the same diameter. Once that drift bottoms out, so that the hole will support a long-nose drift, switch to the longer drift, and keep tapping out the pin. The key to this is soaking everything with the Corrosion X or ACF 50, and then letting it sit long enough to work. The stuff will creep in by just one molecule at a time, and it takes a while. Nothing else I know of has the same degree of “creep” capability; not even the venerable Liquid Wrench, which I seldom use anymore. If worst comes to worst and you are faced with drilling, it will be very difficult to keep a bit centered on the steel pin, and not off to the side in the softer casting. I have never had to drill one out yet.
With the capture pin removed, the knee pin can be tapped out, and then the bushings. If the bushings are the correct fit in the knee (snug OD), then the outer dimension is still correct. They should just be a light tap fit; no real pressure. Take the bushings and pin to a local small machine shop. Unless it is seriously damaged beyond the ability to polish it round, the pin is most likely salvageable. You want them to polish the pin, and make you two new Super Oilite (Iron-Copper Bronze) bushings with the correct OD for the knee, and the correct ID for the polished pin. Then you want them to drill the pin for you. There should be a small passage (1/8”) that goes straight in from each end, and another one that goes in from the middle of the bushing contact area on the side (this is repeated on both ends; the center hole should not go all the way through). The side drilling should be oriented so that when the pin is installed and the lock pin inserted, the grease exit hole points upward. This forces the grease into the bushing at the highest point of wear. The pin exit holes must be lightly chamfered, so they won’t wear the bushing (and the grease can spread out). If you take the weight off the nose gear when you grease it, the grease will enter right where it is needed.
Then the end of each entry hole is opened up large enough and just deep enough for a grease fitting. Most of the original fittings are press-in Alemite flush fittings, which take a needle (pointed) fitting on the gun. If you have flush fittings on your main gear, you might want to stick with that style. The most practical fittings, for both nose and main gear pivots, are screw-in Zerk nipple fittings. They are the easiest to grease, and they don’t get popped out if you use high grease pressure. You need to bring the desired fittings to the machine shop, so they can make the end holes the proper size and press (or thread and screw in) in the fittings. It would be best to use the MilSpec Cadmium-plated grease fittings, but they can be hard to find. Aircraft Spruce only sells the screw-in type. If you source your own, try to get the best quality ones you can find, in a name brand. Don’t use the junk imports from the discount auto parts places. NAPA often carries the name brand parts.
Bearing-Bushing data:
169-810016-3 Bronze pivot bearing, ID 3.5”, OD 3.640”, standard size
CO B73751-1 Bronze pivot bearing, ID 3.5”, OD 3.630”, .010 undersize
CO B73751-3 Bronze pivot bearing, ID 3.5”, OD 3.635”, .005 undersize
CO B73751-5 Bronze pivot bearing, ID 3.5”, OD 3.645”, .005 oversize
169-810016-5 Original .005 oversize bearing; superseded by the CO B73751-5
The -3 bearing is manufactured from cored bearing bronze, QQ-B-671 type 2 class 3
QPL Specs
Family ALUMINUM BRONZE
DIN CDA C95400
ASTM1 B505,,
ASARCON
SAE1 B505,,
AMS
FEDERAL1 QQC390 G5,QQ-B-671, CLASS 3
INGOT # 415
OTHER DESG. ALUMINUM BRONZE 9C
MILITARY1 MIL-B-16033, CLASS 3,
169-820016-29 Steel pivot bearing, mates with bronze
Above manufactured from 4130 condition N steel tube MIL-T-6736
MS9048-102 Roll pins for bronze and steel main pivot bearings, FG and RG
Superseding number is MS171528 (stainless steel)
NAS514P632-8P, -10P Cad-plate structural all-thread screws to replace roll pins.
50-820024 Laminated shim; ID= 3.50” , OD= 4.25”, .045” thick
NOTE: Typical fixed-gear nose gear steel mount cylinder bearing vertical clearance is 4.875”, top to bottom.
169-810011-11 Nose gear knee bushing, standard size; 169-810011-31 is .535” undersize bore.
NOTE: All bushings shipped under PN 169-810011-011 or -031 have had the .535” bore, since 1995
SPECS, NEW: .692 OD,.536 ID; 1.000 Flange OD, .067 thick; .651 Width
SPECS, WORN: .690 OD; .558 ID; 1.005 Flange OD, .066 thick; .650 Width
SPECS, PREF.: .690 OD; .550 ID; 1.000 Flange OD, .070 thick; .650 Wide; Shoulder radius.015; 45-deg chamfer
169-810000-139 Nose gear knee pin; diameter with slight wear and polishing is .553”
169-810000-79 Fixed nose gear knee pin; SS to -139
169-810000-25 Fixed nose gear knee pin; .010” smaller diameter, and undrilled (1962-63 only)
169-810000-109 Nose gear knee shim
169-810000-81 Nose gear compressor plate pin
169-810012-7 Nose gear comp. plate pin flanged bushing; same material/dimension as 11-11/11-31
MEASURED NEW DIMENSIONS 02/2007: Flange OD 1.000”, thickness .070”; body ID .545”, OD .688”,
O/A width .600”. Material specification is aluminum bronze bar stock, or Super Oilite bushing #SF805-1