Tailwheel cables slack

[daedaluscan]

Here are some photos.

[daedaluscan]

Some more

[daedaluscan]

And one of the bulkhead from the cockpit with a real camera.

[daedaluscan]

Tailwheel geometry is tomorrow.

My feeling is now that maybe my tailspring is starting to sag, and as it it "relaxes" that is allowing the chains to slacken? Or one of the tailwheel cables has slipped on the rudder cable, but both sides have two clamps ( I only see one in the parts book) The resolution of the borescope was not good enough to see tany signs of slipping.

I did find a crack in the bracket that has been stop drilled in the past.

[Bruce Fenstermacher]

The crack you found is common. You also have the thicker L-19 style main spring installed as do 80% or better I think of the 170s today.

[johneeb]

It maybe a optical "delusion" the cable in this picture does not appear to be tracking it pulley.

[blueldr]

Strangely enough, the tail wheel steering cabling on the '55 model C-170 looks like something added on in the field on some models. The attachment of the steering cables to the to the rudder cables often looks almost temporary with the use of "Kearney" bolts and I've seen a number of different inspection or access doors that look like field mods.
I have owned only one '55 model and it didn't steer any better than the earlier ones.

[canav8]

Charlie, reach in and turn the pulleys also to see if they are frozen.Since they are difficult to get to, they are often neglected by mechanics for lubrication.

[daedaluscan]

I wish I could reach in!

The only way I can even see in is through the elevator pushrod slot, and that is hard.

I think the pulley alignment is due to the extreme slackness of the cables, when they are snug everything lines up nicely.

If I can get to the plane today I will take photos of the spring/tailwheel pivot angle loaded and unloaded.

[daedaluscan]

I do have a bellcrank on the rudder with attachment points for tailwheel cables. I wonder if I should not just remove this entire system and got to the pre 55 (or whenever) system of direct of the rudder? Sure seems like a more simple solution, as Colin Chapman said "simplify, then add lightness".

[daedaluscan]

Tailwheel on the ground showing how slack the chains became

Here are some photos of the tailwheel/spring

[daedaluscan]

And some more.

I had to take out four links to get them snug off the ground, and they tightened significantly when they were back on the ground.

My parking spot is slightly sloped so the tailwheel is a little elevated.

The tailwheel seems to be locking and unlocking correctly, it was rebuilt by Alaska bushwheels about 50 hours ago.

I am still at a loss as to where all this slack is coming from, my best guess is that one of the tailwheel cables is slipping on the rudder cable.

Has anyone actually removed this system from their plane and gone to the pre 55 system?

[canav8]

Okay charlie, start chasing cables. Look at all the pulleys along the way for flat spots. Work your way forward. Hopefully you will get forward of the aft bulkhead.

[GAHorn]

Bruce, is that a subjective opinion (80%) or an observation of those you've seen?

The reason I ask is, the B-model 170 aluminum "alligator" bracket dispensed with the "pads, spacers, retainers" etc.. that the original steel "box" bracket used. (The Service Kit instructions for the conversion of earlier aircraft discards those parts.) The same spring-set is used in both versions.

The L-19A tailwheel bracket (referred to as the dash-3 bracket) closely follows the 170B bracket in design...but not exactly ...as it uses a different, rivetted-in pad to position the mainspring. This changes in the L-19D/O-1 BirdDog tailwheel bracket (the so-called dash-10 bracket). This -10 bracket uses a different "stiffener" which is that plate using multiple AN3 bolts to top the springset. The -10 bracket stiffener is shorter and does not have the "overhang" which fractures so commonly where the square U-bolt clamps the longer, 170B/L-19A stiffener.

Where I'm leading this is, I believe the late L-19E/O-1 BirdDog -10 tailwheel bracket uses the thicker mainspring, and that is why that -10 bracket and it's stiffener were changed from the -3 versions. IN ANY CASE, the owener who uses a thicker "L-19" mainspring should be aware that use of that spring in the original 170B hardware configuration may lead to cracks and failures of the bracket and stiffener.
If the thicker mainspring is installed then the installer must take into consideration those dimensional differences and make allowances. IMO.

I'll try to edit this msg post to include illustrations that might demonstrate the different profiles of the differing brackets.

L19Fig541.doc

170B bracket

(913.5 KiB) Downloaded 672 times

IPC B model pg 54 fig 29.doc

L19E/O-1BirdDog

(242.5 KiB) Downloaded 604 times

[Bruce Fenstermacher]

Bruce, is that a subjective opinion (80%) or an observation of those you've seen?

George, I don't know what others look at when they look at a 170, but there are certain things I always take note of on every 170 I look at. By now I have an above average knowledge of how these things came from the factory, what options where available, what changes where made through the production run, and popular changes that are made by owners. And these are the things I look at.

Probably because you and I had a very early disagreement in our friendship (over 12 years ago) with regard to the main tail spring it is almost always one of the first things I notice. Others might be ogling the polished finish but I'm inspecting the main tail spring and what parts are missing or installed correctly. So I've probably inspected every main spring on every 170 I've ever seen. And what I've noticed is it much more common to find the thicker l-19 spring than the correct original spring. If I felt it was more common to find the thick spring i might have said 60%. But since I fell it is much more common I assigned 80% to it. If it was most certainly to be found I'd likely have assigned 95%.

• BTW George in this time I have found at least two other renegade owner operators with two main springs installed and neither of them ever had a spring bolt shear. Not that i recommend that configuration.

Where I'm leading this is, I believe the late L-19E/O-1 BirdDog -10 tailwheel bracket uses the thicker mainspring, and that is why that -10 bracket and it's stiffener were changed from the -3 versions. IN ANY CASE, the owener who uses a thicker "L-19" mainspring should be aware that use of that spring in the original 170B hardware configuration may lead to cracks and failures of the bracket and stiffener.
If the thicker mainspring is installed then the installer must take into consideration those dimensional differences and make allowances. IMO.

I believe George is correct here. Even though the load seems to be placed on the part above the springs I'm beginning to think jamming the thicker spring in the pack and bracket, and that is what you have to do sometimes, is causing the cracks at the lower bottom. At least the thought it making me go hmmmmmm.