Maintain those tailwheels

[JonJay]

Super easy to check your tailwheel during preflight. A light push side to side and observe it is locked. It will also tell you if it is sticking, or sticky, and needs service.
I know some folks here are not mechanics and rely on others for maintenance. However, you should be familiar with all the critical control items, how they work, and what their purpose is, so you can evaluate your machine is in a safe condition to fly.
Flying for months with a critical component not working shouldn?t happen. That?s why we preflight. A preflight check list would be a must for the non-mechanically inclined.

[RV7Guy]

Hi Everyone,

First, thanks Dan for the kind words on my JD Air tailwheel assembly. A lot of thought and testing went into the development. Still, without proper maintenance they can all fail.

I have conversed with Vic on this issue and Blake and I have talked. We all agree that regular maintenance is needed on the tailwheel assemblies. The tailwheel takes an absolute beating back there but is probably one of the most over looked pieces on our planes.

Over the years I have talked with dozens of owners that have had steering issues even it isn't our product. Those having problems generally have one thing in common, lack of maintenance on the tailwheel and in some cases lack of knowledge. I see this more often in owners that bought their planes than those who built them.

My recommendation is very simple. Do a complete removal, cleaning, regreasing and reassembly every 25 hours when you change your oil or no more than 6 months if you don't get the 25 hours. The logic is simple, you've got to wait for the oil to drain anyway. Why not do the tail wheel?

I have a saw horse that I cut the legs down on, probably 14" high. I lift the tail and put the saw horse under the rear bulkhead, with foam padding. I get the oil draining and then get ready to service the tail wheel.

Before you start, one of the hardest things in getting the tail wheel set up is determining just how tight to get the nut so it operates as intended. Once this is set up you hate the thought of losing it. I used a jewelers file with a sharp edge and made a mark on nut and on the housing of the yoke as an alignment point. Look and how many threads are showing and take a picture of it. Now you have a baseline.

Remove all the parts and clean them with brake cleaner. Try to get all the grease out. Inspect the pin for any signs of nicks or burrs. File out as necessary. Same with the receptacle in the arm. Put fresh grease in and reassemble.

It took longer to write this than to do it!! Follow these guidelines and you'll have a happy tail wheel and eliminate flying surprises.

Feel free to call if you have any questions!!

[DanH]

Originally Posted by RV7Guy

My recommendation is very simple. Do a complete removal, cleaning, regreasing and reassembly every 25 hours when you change your oil or no more than 6 months if you don't get the 25 hours.

Absolutely. I lift the tail for oil drain anyway. It's 50 hours for me, but a tailwheel interval really depends on operating conditions. Offhand I don't recall ever seeing one with shaft seals, so it's all about the local dirt/grit.

Before you start, one of the hardest things in getting the tail wheel set up is determining just how tight to get the nut so it operates as intended.

That's odd. The washer sits on top of the shaft, and is clamped firmly to the shaft with the nut. The washer sandwiches the control arm between the top of the housing and the underside of the washer with a small clearance set by the relative lengths of the housing and shaft. Put another way, the sum of A+B is slightly less than C, ballpark 0.020". The control arm will have a little wiggle room with the nut fully torqued.

[Sam Buchanan]

Originally Posted by DanH

That's odd. The washer sits on top of the shaft, and is clamped firmly to the shaft with the nut. The washer sandwiches the control arm between the top of the housing and the underside of the washer with a small clearance set by the relative lengths of the housing and shaft. Put another way, the sum of A+B is slightly less than C, ballpark 0.020". The control arm will have a little wiggle room with the nut fully torqued.

I'm sure that is the way the tailwheel yoke is designed, but both tailwheel yokes I've used on my RV-6 have required a bit of finesse when it comes to tightening the nut. It is possible to get the nut tight enough to bind the yoke, but it isn't difficult to adjust for smooth operation (sorta like tightening/loosening an axle nut). Perhaps there was some manufacturing variation in the housing.

[DanH]

So you guys are operating with the washer not firmly clamped to the top of the shaft? That ain't right.

BTW, I understand the axle nut analogy, but if the washer is free to rotate, the nut needs to be keyed, just like that axle.

[Sam Buchanan]

Originally Posted by DanH

So you guys are operating with the washer not firmly clamped to the top of the shaft? That ain't right.

BTW, I understand the axle nut analogy, but if the washer is free to rotate, the nut needs to be keyed, just like that axle.

Dan, I don't know how much the washer is rotating, but the nut hasn't loosened in twenty years between many relubes/servicing. It only takes a tiny bit of rotation of the nut to take it from too tight to just right. I've considered filing the housing a few thousandths but since there have been no service issues and the tailwheel works flawlessly I've left well enough alone all these years.

[andrewtac]

Evidently A+B was to excessive on mine, and someone put a washer underneath the collar. I had been flying that way since I bought the plane. There were several signs that should have told this was wrong.

First, (and most important); the airplane had horrible ground handling characteristics. I had flown a couple tail wheels years back doing evaluations; then got an endorsement in a cub quickly followed by transition training in an 8. The 8 I received training in had a van's setup with chains. It had some caster, which does add to positive stability, the chains allow for a little more rudder prior to tailwheel action than mine is setup. My tailwheel is aftermarket, sits vertical relative to the ground, neutral stability; and has wires and springs. I had convinced myself that little positive stability and chain setup on the other airplane were significantly enhancing to ground handling. What was happening was the pin would disengage occasionally in my tailwheel (not to my knowledge); and this was very unpredictable. I had to use the brakes way more than I should. It would be holding center line with my inputs then just randomly dart off. I went off roading once (my runway is 23') when I was about 40 knots decelerating on what I thought was a low wind day. I had let my guard down a little, then I am pretty sure a gust of wind hit, now I know the pin came out, and I swerved. Luckily no damage, and got back on the runway. There were numerous other times this swerve happened on much larger runways and I saved it with a combination of rudder and brakes. At my home field I stayed on it like it was a boat landing and flew it until the engine was off and I was stopped (which is how a tailwheel should be handled anyways, but I gave way more attention than normal), and I always dreaded coming home. Anyways, I was compensating for an abnormal, unpredictable, negative behavior during ground handling.

Second, the pin and the notch in the control arm where the pin sits had a couple burs in them. I even broke one pin. The burs were towards the bottom of control arm. So I took the plate out, filed out the burs and flipped it.

Third, (after seeing some people talk about nut tightness, I figured I should post this). On a recent landing at my home field, I had used so much brake to stay on the runway the tail came off the ground. Scared the **** out of me. Post flight, the nut was loose! I would tighten it, if too much the tail wheel wouldn't spin, not enough and it would get loose (found this out the hard way).

So I after almost running off the runway again (probably 70ish hours now since I bought the plane); I decided to inspect the tail wheel again ( I probably inspect it at about 25 hour intervals, but do it now about every three flights). I pulled it all apart, cleaned, greased, and put it together. I tightened the nut, and the tailwheel locked up. For some reason, I decided to look at the assembly this time, thinking it should not lock up regardless of how tight I torque the nut. When I pulled the nut off and looked at the pin, the light bulb (and a very bright one) was finally on! I looked at the mechanism, and the pin was riding in the lower maybe 30% of the control arm (just a guess could have been less. Someone had added a washer below the collar {A in Dan's picture} and when I put everything back together I put the washer in too (every time). Well I removed the washer, put everything back together. Now the pin was all the way in the notch of the control arm, I could tighten the nut as tight as I wanted, and everything worked! What was happening, was the engagement surface of the pin was not enough to hold the tailwheel, due to the excessive height of the washer. This led to my first problem, random unlocking. Also, problem two, because pour engagement it led to burs. Problem three compounded one and two. Because I could not torque the nut properly or it would lock the tail wheel, it was always a little loose; cycling the tailwheel/rudder back and forth on the ground would cause the nut to loosen further resulting in less engagement surface and so on. pin inspection with the washer out I think I know why someone added a washer. The 0.020 that Dan describes as C - (A + B) was more like 0.20. The control arm wobbled very badly. Rather than put a washer in that was 0.18ish, a washer of something like 0.40 was used (just guessing at the numbers). So I made a shim that would result in a spacing out 0.020, reassembled; everything functioned properly and the control arm had minimal play.

[Greg Arehart]

So, what kind of grease are you all using on the pin mechanism?

[skylor]

Originally Posted by DanH

That's odd. The washer sits on top of the shaft, and is clamped firmly to the shaft with the nut. The washer sandwiches the control arm between the top of the housing and the underside of the washer with a small clearance set by the relative lengths of the housing and shaft. Put another way, the sum of A+B is slightly less than C, ballpark 0.020". The control arm will have a little wiggle room with the nut fully torqued.

This has also been my experience with stock Van's hardware as well. One note though: I found that the washer was bottoming out against the radius of the transition to the threaded portion of the steering shaft instead of on the face of the "step". I added a chamfer to the ID of the bottom side of the washer so that it sits flat on the step face. This reduced what I felt was excessive end-play of the steering arm but still allows everything to swivel freely.

Secondly, I have not had a stuck pin in 900 hours of airframe time. I clean and re-lube everything 2-3 times per year, which is about every 40-50 hours or so. I use grease on the steering shaft, but keep it below the locking pin area. I use LPS-1 "greaseless lubricant' on the locking pin parts and the steering arm. I also slightly knocked-down the edges a little of the locking pin and the broached bore of the steering yoke with a scotch-bright wheel because these are the areas where burrs begin to form that can cause to pin to stick.

Skylor

Skylor

[RV74ME]

I, too cannot fully tighten the nut without it binding. So I tighten ?just enough? to where it doesn?t bind.