Tail Wheel steering and other hopes

[GAHorn]

Chris, I sure wish you and Bruce had been present at this very conversation I had with Steve Grimsley (TIC170A Historian) regarding this matter. I had noticed his slack chains and got into it with him, and he made the exact same claim you guys are making. I challenged him to prove it, so he slipped under his tail-cone and lifted his tailwheel off the ground and .... he found that the chain tension does NOT increase with the tailwheel off the ground. The geometry is not as you suppose.
Steve still owes me a beer on that one.

[4stripes]

I don't know what kind of springs he had but when I lift my tail, the chains definetly get tighter. My tail spring was replaced within the last 2 years so it's stiffness is up to par.
Cheers Eric

[GAHorn]

His was the standard set-up. So is mine and the "arc" of the steering chains match that of the tailwheel descent, so no appreciable change in tension occurs. We both have the standard Scott 3200 steering arms, as well. I do not know how the 3200A arms might change the "arc".
Those "upturned" arms were not originally intended for the 170, but were for heavier aircraft. Yet, I've seen several cases now where owners intending to "beef up" their steering adapted the "A" (upturned) arms to their tailwheels, and the new steering arm bent as well, just like the photos posted by Chris demonstrated. Some of those arms are reportedly made with inferior materials.

[Bruce Fenstermacher]

George I was there or at least became aware of the discussion but had forgotten till know. So I do not recall what my opinion of Steve's discovery of his spring geometry was.

I can tell you that last time I checked, which has been maybe 9 years ago, my chains got slightly tighter when the wheel is off the ground than with the wheel on the ground. It's not much but it's there.

And no I won't open the can of worms and tell you what springs I have. Lets just leave it at I'm pegging the GAHORN RENEGADE METER here. I do believe how ever that the overall length and shape of my spring stack is the same as stock. I could be wrong.

[GAHorn]

With the springs you have you shouldn't have any movement at all!

[Chris Christensen]

That's the problem George, we push on the rudder, and get no movement at all.

[n2582d]

Here's some reference material from Alaskan Bushwheel regarding chain tension-NOTE: don't use compression springs as shown in the video

http://www.youtube.com/watch?v=u3qFwzPNBgE

From http://www.akbushwheel.com/3200TailwheelAssembly.html

Removal & Installation Instructions of 3200/3224A assembly:
A) Following airframe manufacturers instructions, properly raise and support the tail of the aircraft off of the ground.
B) Disconnect & inspect the steering springs & chains from the tailwheel assembly.
C) Remove the old assembly from the tailspring, inspect the attach bolt and tail spring for correct arch. The center pivot spindle should angle back away from the airplane 5 to 7 degrees when un-loaded and be perpendicular to the ground at maximum gross weight. (Note: ABI recommends replacement of all attachment hardware.)
D) Re-install and adjust in reverse procedure, following the original airframe manufacturers installation instructions. (NOTE: Tension on connector spring is not required or advisable. Over tension will create binding of the steering arm causing it to bend and damage internal parts. Connector springs and connector chain should be just slack. ABI recommends connecting the connector springs to an eye-bolt, not to the rudder arm.
E) All ABI 3200 series assemblies are pre-lubed at the factory with Exxon-Mobile SCH-100 grease. Over greasing of the axle will force the wheel seals (PN: ABI-1863) out against the bearing pre-load spacer (PN: ABI-3227-00) causing premature wear on the seals.

[GAHorn]

That's a good video... if it weren't for the misleading commentary regarding the "short pawl" and the "unlocking" efforts commentary. The presenter is not "wrong".... it's just that the actual wording is misleading. The chain-tension has nothing to do with the efforts required to "unlock" the tailwheel.

To re-cap:

The compression-springs are not correct for a Cessna. They can damage your airplane! Use tension springs only.

The chains should be "just-taut" (no slack/no excessive tautness) at normal aircraft-weight with the aircraft sitting on the ground. Do not worry about what happens when the tailwheel comes off the ground.

Finally.... tailwheel "steering" is not actual steering at all. It's merely tailwheel-steering "encouragement". Do NOT expect your rudder imputs alone to steer your aircraft as you might expect a tri-cycle-gear airplane to do. Plan to use occasional braking. (And keep in mind that while tailwheel-equipped airplanes may not steer as precisely as tri-cycles.... they have a feature tri-cycles don't have: They can "pivot" by using brakes and unlocking that tailweel. Like everything else in aviation... these things are "compromises".... they have some good...some poor...features. (And if you have "shimmy" or poor "steering" ... you probably have a maintenance issue that involves poor geometry of that tailwheel spring.)

[wingnut]

We recently had a customer who remarked about poor steering response. I then searched these threads and found this a couple weeks ago. Great info on these forums!
With the tail in the air (tailwheel not touching ground), I observed that the tailwheel did not track with the rudder. It didn't even begin to move until maximum deflection of the rudder. I also noticed that there was a significant amount of tension on the chains/springs. What was happening, is that it took maximum deflextion just to "unload" one spring enough to allow the tailwheel to begin moving. We removed the chains, installed new ones (longer), just long enough to remove any "droop". Now, with near no tension on the springs/chains, the opposing spring does not have to "unload" before the other spring can do it's job. The tailwheel tracks perfectly with rudder now. Unfornately, the aircraft is still here and I can't give the results according to the pilot.
I also found no remarkable difference in chain tension whether the tailwheel had weight on it or not.

[KG]

Unfornately, the aircraft is still here and I can't give the results according to the pilot.

And if Del could control the weather as well as he performs maintenance, we could get that thing out of his hanger and try it out! It's been one line of thunderstorms after another.....
Keith

[jrenwick]

Here's some reference material from Alaskan Bushwheel regarding chain tension-NOTE: don't use compression springs as shown in the video

http://www.youtube.com/watch?v=u3qFwzPNBgE

From http://www.akbushwheel.com/3200TailwheelAssembly.html

That youtube video is precisely the problem I saw on Neil Otey's 170, as described here: http://www.cessna170.org/forums/viewtop ... f=2&t=6386. The problem was simply the compression springs, nothing else.