Tailwheel rebuild

[james_layman]

Is anyone aware of a shop where I can send my Scott 3200 for rebuild? Those resources are not available in my area.

[Brad Brady]

Is anyone aware of a shop where I can send my Scott 3200 for rebuild? Those resources are not available in my area.

James, You should be able to do it your self......with the parts and pictures from spruce......If you don't want to do it, send it to me.......Brad

[james_layman]

Thanks. Seems like a job I could do. What we are lacking here is an A&P to inspect my work and make the log book endorsement. The independent guys have been run off because of new (over the top) insurance requirements from the airport.

[Showboatsix]

I buy from these guys, they own the manufacturing rights to the Scott 3200, buy direct from the source, they are great with questions too!

Alaskan Bushwheel Inc.
PO Box 2380, 83496 E. Russell Ln.
Joseph, OR 97846
USA
Phone Numbers: Phone: 800-442-8473 or 541-432-8473
Fax: 541-432-0649

[Brad Brady]

Thanks. Seems like a job I could do. What we are lacking here is an A&P to inspect my work and make the log book endorsement. The independent guys have been run off because of new (over the top) insurance requirements from the airport.

Yea James
Looks like your stuck between a rock and a hard place.......still I can only offer.....send it to me It'll probably cost you more in shipping than I will charge you to fix it But that's the way things are going ....Brad

[james_layman]

Brad. That would be great, after the first of the year. Plan to order the parts kit from the guys in OR next week.

[james_layman]

Spoke with the guys in OR, they are very nice by the way. They suggested when my Scott 3200 TW is rebuilt I upgrade it to the 3224A. Understand it is a direct replacement for the 3200 with better seals and a beefier steering arm. Any thoughts?

They also felt a lot of tailwheel shimmy is caused by worn tail springs. They would not put a service life on them but felt the pressure over time just sitting tends to induce wear and results in shimmy.

[GAHorn]

My thoughts are: I wonder if the 3224A parts are the only ones they mfr and therefore are the ones they recommend?
The tailwheel steering springs do not contribute to shimmy, nor do they wear out unless stretched beyond their elastic limit. Shimmy can be caused by worn parts within the assembly and/or by improper mounting angles (sometimes due to leaf-spring worn out or sagging/bent/damage...perhaps that is the spring to which they were referring?)

Think about the relationship between the steering-springs/chains and the interior make-up of the tailwheel friction-plates and how that relationship is unlikely to contribute to shimmy. The springs/chains only provide input to the steering arm to pull it to the right or left. This input is transmitted to the wheel-yoke via a stack of friction-plates whose friction is regulated by compression-springs. The wheel-yoke is allowed to disregard the steering input should side-pressures overcome an angled flat-spring (shaped thusly: \_/) mounted within detents. (The side-force is usually caused by braking, but could exist by some side-load on the fuselage such as wind, momentum or, if being manhandled on the ramp, a person.)
The tailwheel itself is too small to be of any consequential input to shimmy due to imbalance, but if it is mounted with too much trailing-rake it will be compelled to vibrate at a natural frequency upon it's outer tiretreads/sidewalls. (Notice how the tire "leans" heavily in tight turns. This is normal, but if the wheel assy is mounted with excessive trailing-rake it is exacerbated to the point of shimmy.)
Be certain that the forward edge of the turntable is higher than the aft edge. Not level... buth higher. The angle and condition of the main leafspring controls this angle on a 170, and some owners have taken it upon themselves to re-bend (incorrect action) that spring from it's original-mfr'd condition. I believe that cold re-bending that spring weakens it by causing permanent distress to the molecular structure of that steel. I also believe that spring should be regularly replaced at 500-hour intervals to avoid rudder damage from flailing tailwheels when that spring breaks (due to ordinary wear and hastened by owner-bending.) Only the main-spring needs replacement, as the rest of the leafspring stack does not appreciably flex. (In fact, that is the contributing factor they make to the breakage of the mainspring. The spring immediately above the mainspring rests with it's aft edge placed directly upon the mainspring at a point just forward of the final downward bend of the mainspring. This edge abrades against the top of the mainspring causing a stress-riser to be created on that mainspring. Eventually that mainspring will break at that exact location. The tailwheel, now restrained by the steering chains, begins to flail against the runway and the rudder, severely damaging the rudder lower-skins. (Notice how many 170's and other taildraggers have rudders that are either damaged or repaired in this area.)

About 1972, I once landed a 140 at Lufkin, TX just ahead of a Texas International Convair and the tailwheel mounting bolt sheared at the point of attachment to the leafsprings. I was slowed almost to the point of turning off the runway and was spared rudder damage from a bouncing tailwheel, but the Convair had to execute a go-around and subsequently landed on the crossing runway, as I had the favored runway blocked by the disabled 140.
We removed the 140 from the runway with helping hands, and examined the tailwheel assy. The bolt. It had the appearance of having been cut, as if by a chisel. Since the tailwheel casting was aluminum I do not believe it was the offending edge. I believe it was cut by the substitution of two mainsprings being sandwiched together in lieu of the original stack of springs which are "stair-stepped". In other words, apparently in an effort to decrease the likelihood of a single mainspring breaking and causing rudder-damage, someone had substituted two mainsprings and thru-bolted them with a longer mount-bolt for the tailwheel itself. That bolt demonstrated a cut as if the two mainsprings, sliding against each other, had cut the bolt. (More likely had cut a stress-riser on the bolt which subsequently gave away.)
I was given a ride to the local hardware store ( a dusty old place in almost-deserted downtown Lufkin, a lumber-town.) I found a coarse-threaded black-iron bolt amongst the dusty wooden boxes that made up the hardware section, and re-mounted that tailwheel and flew on down the pipeline. My boss thought that iron bolt was probably better than the AN bolt it replaced and as far as I know it never broke again.
That was a long time ago and I've slept many times since then but that's the way I remember it. But the image of those two mainsprings flexing and their bolt-holes sliding back and forth with every hard landing made by patrol-pilots contributing to cutting that bolt makes me think of a discussion I once had with former members of the "Classic Cessna 170 Club" (which ultimately became the basis for these forums) ...., and how we discussed the idea of installing two mainsprings in order to avoid mainspring breakage and the resultant rudder damage. My position is to use the original set-up to avoid cutting that bolt. One of the member's had already installed two mainsprings and decided to keep it that way. I worry about his mount bolt being cut. (The opposite ends of that spring-stack has a bushing within the spring-stack to avoid damaging the single bolt that holds them together.)
I also do not expect that particular member to ever win an originality award with his unique set-up.

[Bruce Fenstermacher]

George I remember that thread from the "Classic Cessna 170 Club" vividly. OK maybe I don't remember the actual typed words but I do fondly remember your position. I remember because it was the first time that I recall you being so adamant and stead fast with your view point. Of course 10 years and an estimated 10000 posts of yours I've gotten use to it. In fact your positions have become somewhat predictable as of course I'm sure you think my posts are as well. Great times friend.

As for that member I can attest that the setup they had, though it has not been mentioned since, is still being put to the test.

Annually if not sooner I get to inspect that bolt as I have a special interest in its life. I'd want to report back to the brain trust immediately on the first indication of a change of it's airworthy state. So far the bolt which I assume is actually the L-19 equivalent with the ring weld on the top, is showing no indication of failure. I say assume because there is no way of knowing where this, so far super bolt, came from.

Besides being illegal it is no wonder no one with a superior Cessna would want two main springs JUST LIKE PIPER DID on their taildraggers of equal size and weight.

[GAHorn]

Doubtless Bruce, your alightings so sweetly kiss the ground (as depicted in the Petit Jean video) that I doubt you are properly testing that bolt. You should begin a proper testing procedure by slamming the tail into the concrete with ample up-elevator after making wheel-landings.

(In any case, I can't help but wonder if it truly is a PN 0642105 eyebolt anyway, since with the proper nut and washer it would likely be too short if it were required to pass thru a 3200 AND two leafsprings? Does the self-locking nut have ample bolt-threads showing thru the nut?)


This is a good group.

[Joe Moilanen]

I've read all the tailwheel steering woes forever it seems like, lots of ideas, opinions, problems, etc., etc. My 3200 has been trouble free for 20 years, I've replaced the main leaf religiously every 500 hrs., wheel bearings once, wheel seals twice, and tire and tube as needed. I keep about 1/8" to 1/4" slack in both chains when on the ground empty. Never need brakes to steer except to rotate on a dime or initiate a turn from a stop. Taxis as effortless as a trike.

Must be living right...

Joe
4518C

[Bruce Fenstermacher]

Doubtless Bruce, your alightings so sweetly kiss the ground (as depicted in the Petit Jean video) that I doubt you are properly testing that bolt. You should begin a proper testing procedure by slamming the tail into the concrete with ample up-elevator after making wheel-landings.

Thanks for noticing but who said it was me doing the testing?

(In any case, I can't help but wonder if it truly is a PN 0642105 eyebolt anyway, since with the proper nut and washer it would likely be too short if it were required to pass thru a 3200 AND two leafsprings? Does the self-locking nut have ample bolt-threads showing thru the nut?)

What washer? Ok there might be a thin washer and there is a trace of thread thru the nut. It is close probably to close for some. I think the bolt is an authentic part....for something.