Tailwheel Details

This simple little Scott 2000 tail wheel which has followed me in several airplanes, Fly Baby, Taylorcraft, Champ, Cub, etc. has been quite a bundle of learning.  I started with 2 complete (?) assemblies and assumed I should end with at least one good one and one re-buildable one.  I have one good assembly now and a few parts.  This exploded assembly drawing does not show all the parts and several parts it shows I didn't have.

Let's start with the wheel.  The part at the left (12) is a felt grease seal.  It has a piece of felt about 1/8" thick trapped between a washer and a dish shaped piece which is rolled on the edge to trap the felt and washer.  The felt needs to be oiled.  I'll get to that later.  The ones I had were both so warn that there was no felt sticking out into the hole for the shaft.  As a result neither would provide any seal to keep the grease in, and keep out dirt or water.  They had probably been that way for a while since all the bearings were shot.  The rolling surfaces of the races were furrowed like a plowed field.  I'm shocked the wheels didn't shake to high heaven.

The part (11) to the right of the seal is just a short piece of tubing 1-3/8" O.D. x .050" wall and 5/32" tall.  It's a spacer to keep the grease retainer/seal in the right place on the step on the the fork shaft.  This spacer is pressed against the bearing outer race and the grease seal is pressed in against the spacer. Next are the bearing inner race and rollers and then the outer race.  Between the 4 bearing sets I had 3 Timken A4050 inner assemblies and 1 from Bower.  For the outer races I had 3 from Bower and one Timken A4138.  For what it's worth both of these part numbers, made by National, are available in from Advance Auto.  They can get them in 2 days, no shipping and a cheaper price.  The wheel half for this side has the grease fitting and hex shaped sockets for the nuts.  The tires tend to dry out and become lose in the wheel.  New ones are about $60, if the tire is lose get rid of it.  The outer half of the wheel has counter bores for the screw heads and threaded holes at the edge for the 4-40 screws which hold the hub cap on.  The drawing does not show the spacer on this wheel and it would serve no purpose but both my wheels have them, go figure.  The 3 screws, washer, nut, and cotter pin are all standard AN hardware. 

The next part has no call out but is a felt grease seal under the hub cap. I made mine with 3 layers of 1/16" felt glued together. I made it that thick because the boss on the wheel for holding the seal centered is that tall. I made the O.D. 2-1/2" to clear the screws for the hub cap.  To get it to seal out dirt and water I worked wheel bearing grease into it.  Just push it down over the boss and the hub cap squashes it down into a nice seal.  Speaking of wheel bearing grease.  The grease called out for the tail wheel is AN-G-15 which is a general purpose grease not wheel bearing grease.

For the seal on the other side of the wheel the part comes from Univair without any oil.  There is only about 1/16" of felt sticking out from the metal housing so working grease into it didn't seam a practical idea.  What I really wanted was for it to be well oiled.  After all grease is just a carrier with oil added.  It's the oil that does the work of lubricating.  I thought of just soaking it in oil but wasn't sure it would get further in than just the little bit of felt sticking out.  Instead I soaked it in 200 degree 5W30 motor oil like an Oilite bearing.  The coolest thing happened when I added the bearing to the hot oil.  The air trapped in the felt expanded and blew out so after soaking it about 15 minutes I just removed the heat and let it cool to room temperature to draw in as much oil as it could.
I didn't find and obvious wear or play in the Bracket (1) bushing (4) for the Fork (5) spindle so not much to say there.  I have no Idea what the acceptable limits for this are.
The next part at the top of the tailwheel is the magical Arm and Cam assembly (6).  It is riveted together so normally no one opens it.  One of mine had been opened and reassembled with screws by threading the lower plate.  The other assembly snagged when moving the arms so both were taken apart.  I'm glad I did because the screwed together one had the better parts but some were missing, never good.

The missing parts were the 2 little spacers I made in an earlier posting.  The first picture shows all the parts inside with the lower bushing installed as well as the 2 spacers. Inside the housing are 3 bronze bushings, 2 spacers and 2 arms.  The bushings are all identical and the arms are left and right based on the bend tipping the arm up slightly.  The stack-up of parts is: bushing, left arm, bushing, right arm, bushing.  The spacers which hold the covers solid also act as stops for the 2 arms.

When the arms are aft, straight out, the shaft hole is open and the tailwheel swivels freely.  Without the springs holding 25-30 pounds on the end of the arms there is no steering.

When the arms are held forward by the springs the hole becomes sort of triangular shaped which matches the angled slots cut in the spindle of the fork.  That little clamping force on the spindle is what allows the steering.  If you push the tail to the side the spring load on one side releases and the arm moves to open it's half of the hole and the tailwheel starts to swivel freely.

The arms in the assembly have to line up with the slots in the spindle so they made shims to put between the bushing in the bracket and the face on the fork as the bushing wears down.  I have one shim but it was not needed to line all this up correctly.  The last piece which I just figured out, and have none of, is a spacer which goes on top of the end of the spindle.  It allows the nut to be properly torqued while maintaining the needed clearance for everything to move.  It also provides a bearing surface for the top of the Arm and Cam assembly.  I'll see if I have one on the Fly Baby which I can copy or if I need to make 2 of them.
The tail wheel is back on but I still can't sign it off until I solve this last problem.