tail wheel steering vs castering

[mbarkeralaska]

Hi folks
I am deciding on what type of tail wheel on this Alaska project I absorbed. Presently there is no landing gear or tail wheel. I think I am planning on doing the cabane vee type "cub style" gear up front. I love the look of the all wood, old school gear, but I think it might be better doing newer..... but for the tail wheel I am deciding on steerable or just letting it caster. Has anyone just let it caster? Or are they all hooked up for steerable?

I have looked at a lot of the pictures of various set ups and deciding what to do, so will probably have some questions, but thought I would throw out this idea of a simple castering set up........... and then just steering with brakes.
thanks
Mark

[KenBickers]

Mark,

I'm sure full swiveling has been done. It probably works fine if operating exclusively on turf runways.

It would give me heebie jeebies if on hard surface runways. I've flown tricylcle gear airplanes with castering nose wheels. On takeoff in cross winds, there's the awkward period of pecking at one brake to keep things lined up until there's sufficient rudder authority to keep things lined up. That extends the takeoff roll -- unnecessarily in my opinion. On landing it's worse, when slowing below rudder authority speeds, then it's time to get on the upwind brake. A little too much or too little and it's off to the edges of the runway. God forbid a brake fails at such a time. Then you get to find out how smooth the grass is along the edge of the runway. That's with a nose wheel airplanes, which mostly don't have any interest in ground loops.

Why risk it? You'll have cables running to the rudder horns. You can take advantage of those. On mine, I split off a second pair of cables from the the rudder cables just behind the pilot seat in the tail cone. This gave me cables to run to the tailwheel steering horn that were operated directly by the rudder pedals.

The one thing I had to experiment with was how to harmonize the control horns so that neither rudder inputs nor tailwheel inputs were overpowering or underpowering to the other. I found that making the tailwheel horn exactly the same width as the rudder horn made for precise, predictable steering.

If you want, I suspect I have some pictures I can post.

Enjoy your project, Ken

[mbarkeralaska]

Hi Ken
great comments........ thanks......
I think I have decided to go the "steering" route.
If you have pictures of your tail wheel and spring set up that would be great.
I see a number of folks that are using a single leaf spring, and then a typical small homebuilt steerable tail wheel. Like a Matco or something.
Would love to see your tail wheel and spring set up.

thanks
mark

[taildrags]

Mark; FWIW, here's my tailwheel setup. Very conventional, as you said, with a Matco tailwheel. This is an older photo... I now also have a tail tiedown release mounted back there, with a cockpit-operable release lever, for when I prop-start my plane unassisted. I patterned mine after the one Richard Roller built for his plane and it works great. Prior to this, I was using a wheel chock with a line on it so I could pull it into the cockpit with me and that was clumsy.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

[taildrags]

Ken; now you've got my curiousity going about the rudder horn and tailwheel horn having the same control arm lengths. The plans show the holes on the rudder horn to be 10-1/4" apart but I don't know what the tailwheel horn holes are spaced on my plane and will have to check. I do remember when I had the original little Scott 2000 tailwheel on it that Corky used, he had added some short extenders to each of the steering brackets on it so maybe that's why he had done that. I always just thought he did it to make the ground steering less twitchy.

-Oscar

[KenBickers]

Oscar,

A bit of background. My rudder horns are built to plans with the holes spaced approx. 10" apart, as you indicate in your message. I repurposed a standard Van's RV tailwheel for my Piet. The horns on those have the holes about six inches apart (I don't recall the precise distance, though I'm happy to measure it). As mentioned above, I have one cable running to each side of the rudder that Y's off aft of the pilot seat inside the tailcone. The second cable on each side runs to the tailwheel horn. This means that rudder pedal inputs are the same to both the tailwheel horn and to the rudder horn. The lever arm represented by the horn distances was what I needed to address. One more note. I have rudder pedals, not the rudder bar as called out in the plans. I am happy to chat about that, but I don't think that difference is relevant to the tailwheel/rudder issue.

When I was originally doing taxi testing, At slow taxi speeds, I found that I was having to use what seemed like excessive amounts of rudder pedal inputs even for relatively small turns. That was annoying but not dangerous. At higher taxi speeds, I found that when the rudder began to be effective, I was way overcontrolling the rudder inputs due to the amount of inputs needed to deflect the tailwheel. I added extensions to the tailwheel horns so that the holes would be at precisely the same distance apart as on the rudder horn. I don't know if they needed to be exactly the same. Once I made them that way the problem disappeared. So I largely forgot about it ... until this thread.

I've attached a photo where you can see the extensions.

Cheers, Ken

[taildrags]

Ken; those tailwheel control arm extensions that you have are pretty much identical to what Corky added to the Scott tailwheel that used to be on the plane. Now you've got me started on this and I'm going to have to go measure the spacing on the Matco arms that I'm now using, and the Scott arms with extenders that are still lying around the hangar somewhere. Parts for that tailwheel got astronomical so that's why I swapped.

-Oscar

[KenBickers]

Oscar, as an FYI, I had a conversation about this issue at the time with Douwe Blumberg. He had had a similar experience and had also added extensions to his tailwheel horn. I suspect his are more artfully installed. I've seen his Piet in person several times, but have been so wowed that I didn't notice the tailwheel. Cheers, Ken

[mbarkeralaska]

great conversation........... I think I will check some other planes and see if the hole spacing from rudder horn, and from tail wheel is similar. Although some planes have the tail wheel steering come directly off the rudder horn. So of course a bit different geometry.

Other similar question........... is there opinions up or down.... on the plans "Y bar" tail wheel spring or going with a single leaf spring like I see from some folks?
thanks
mark

[KenBickers]

Mark,

Oh boy, now you're about to open a huge can of worms. More electrons have gone to electron-heaven over this debate than almost any other than whether a Grega should be allowed to be considered a Piet.

I haven't searched the Old Forum Archive for this question. You might want to see what's there. You might see what turns up using key workds like "leaf spring", "coil spring", "tailskid", "ladder style." If that doesn't turn up some good information, post something. I'll be happy to discuss why I ended up with the tailwheel assembly that I currently have. It wasn't my first assembly. But it seems to work just fine.

Cheers, Ken

[taildrags]

Every now and then something comes along here that really gets me excited and today the tailwheel steering is it! Talk about little light bulbs lighting up. Remember I said that when I got 41CC it had a Scott 2000 tailwheel on it and that Corky had added extension arms to the stock arms on it? I could never understand why he would have done that but the pieces of the puzzle are coming together.

The first time I "soloed" 41CC wasn't a flight at all; it was about 0.5 of ground operation, getting a feel for how it handled on the ground, how it responded to throttle and brakes, and just getting an idea of the general view out the front and sides of the plane as I taxied it around the apron, ramp, and taxiway at Zapata County airport in Texas. It handled like a dream. Very responsive, crisp, predictable ground handling in taxi at all speeds that I tried. I flew it with the Scott until the guts of the free-castoring mechanism gave up the ghost and I didn't want to spend the $557 that Spruce wants for the "arm assembly" for that tailwheel (when it's available). I bought a very lightly used Matco from a friend and it seemed to work fine on my Piet except for one annoying thing and one puzzling thing. The annoying thing was that it doesn't return to steerable mode without some help, as in a firm kick of the rudder to the opposite side to get it to lock back into steerable. The Scott just seemed to naturally lock back in without any effort on my part, and I almost learned about the Matco the hard way when I was kicking out of a tight turnaround and the Piet just kept on turning till I really put my opposite foot into it. I'm used to it now, but still don't like it.

The puzzling part is that I haven't seemed to be able to make the landings that I used to make when flying with the Scott. I know, I know... "a poor workman blames his tools", and I'm sure my skills are mostly to blame but now I'm wondering. Today I measured the spacing between the holes in the extension arms that Corky added to the Scott tailwheel and guess what? Yep... almost exactly the same spacing as those on the rudder horn. I then measured the spacing between the holes in the cable connections on the Matco and each arm is a good 2" shorter than the arms on the rudder horn. Instead of being in the neighborhood of 10" spacing as on the rudder horn, the holes are spaced about 6" apart on the arms of the Matco tailwheel. You can insert the music from a TV movie when someone has a real eye-opening "AH-HAH!" moment right here, because I'm wondering if this is why my landings and ground handling with the Matco haven't been as pleasing as when the Scott was on the plane. I'm going to fabricate a pair of 2" longer control arms for the Matco and find out! A big thank-you to Ken Bickers!!!!!!!!! First the front cockpit cover for more comfortable cold weather operations, and now this improvement too!

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

[KenBickers]

This evening, I was at my hangar for a couple hours. I thought it might be interesting to measure the hole-to-hole distance on the repurposed Van's tailwheel in its stock configuration. It is six inches between the holes. I also measured the hole-to-hole distance on my rudder horn. Mine is 10 inches, so not exactly to plans (maybe the purist of the pure will insist that I not call mine a Piet). With my extensions, the hole-to-hole distance on the tailwheel horn is 9 7/8", so not quite precisely the same. Close enough to harmonize the deflections of the tailwheel and rudder.

[taildrags]

Ken; just think how much improved your landings and rollouts would be if you had just made those holes in your extensions another 1/16" farther out on the ends so as to precisely match the spacing on the rudder horn

-Oscar

[mbarkeralaska]

Fun, great conversation......... since I live in "aircraft meka" and in my DAR life I inspect a lot of experimental homebuilts.......... I think I am going to check out the rudder and tail wheel distance spacing on both certified and experimental. With all of us Super Cub guys arguing about stuff, I have never heard this discussion brought up. Might be an interesting one........ fun stuff.

I think I am going to do the Matco Tailwheel and the leaf spring.
I am looking for mounting info and pictures of how other folks did the leaf spring.
Probably tons of discussion on that also....... but after a while you just decide to do what you prefer.

When I built the Bearhawk, I put a Cessna 180 stinger style spring on it. But had to weld in all the necessary fittings.
Would love to see pictures or info on the mounting of leaf springs.

thanks
Mark

[taildrags]

Mark; I've got the leaf spring and Matco setup and will take some photos to post here, maybe add a sketch. You mention Super Cubs, I really enjoyed the time that I was able to spend in a Super Cub up here in Oregon. Flew it every chance I could. It was owned by one of the co-owners of a local FBO and he was pretty picky about who he let fly the plane, so I was one of the lucky ones. The attached photo was from shortly after we moved here from Texas, so that would be almost 30 years ago and I would have been 42. Good times...

-Oscar

Image_1.JPG (22.59 KiB) Viewed 1828 times

[KenBickers]

Mark,

My Piper Pacer at the moment is in California with my younger son. My recollection, though, is that the rudder horn and tailwheel horn are the same width, such that the cables/springs connecting them are pretty much parallel. If that memory is correct, the lever arms on both are the same. That's what I found I needed to correct on my Piet when using the repurposed Van's tailwheel.

Meanwhile, back to your question. I have the modified skid type tailwheel assembly that mimics what is shown on the plans. Lots of people have successfully installed the leaf spring and enjoyed trouble-free service with it. There have been a few problems reported through the years of the verical bolt that holds the leaf spring in place acting as a wedge to separate the two halves of the aft fuselage when placed under a severe side load.

The modified skid type assembly avoids that problem, but does need a cross member welded into near the pivot points to resist it from twisting when under a side load.

Cheers, Ken

[mbarkeralaska]

Ken
thanks.... good comment on the side loads with the leaf spring style.
This project came with a partially completed "plans style" skid. And I will keep looking at it.
I will soon have to choose my options. Just cause I am more familiar with it, I am leaning to the leaf spring, but understand the side load comment; and the bolt through wood mounting concern.
I hope to get some good pictures and info on the leaf spring style others have tried............ always experimenting......

thanks
mark

[taildrags]

Mark; see photos. First one is a side view of pretty much the whole setup and you can see that the front end of the tailspring shares a mounting point with the bracket where the lower tail brace wires attach on both sides of the underside of the tail. If I understand Ken correctly, that's the weak point of these setups when a side load is put on the tailwheel because then the tailspring creates a lever arm that is essentially prying open the V that the lower longerons form back there. The area can be strengthened, with some study, although I have not had any problems with mine.

The other shots are closeups of the two main mounting points for the spring. The bracket right where the top spring ends is really the key to the whole setup. I have solid rubber shock absorption pads on the top and bottom of the spring where it's clamped into that bracket because that's the way Corky built it. You will notice a red gadget sandwiched into that stack on the starboard side of the tail; that's my tail tiedown release and the bracket bolt on that side just happened to be a convenient spot for me to mount the release and it also provided a pretty much straight shot for the actuation cable to lead forward to the cockpit from the tail. Let me know if you want to see anymore detail, but it's a simple setup. The tailspring is, I believe, just the Aircraft Spruce "homebuilder" dual-leaf spring.

By the way, there's a mix of hardware back there but everytime I work on something back there I replace nylock nuts with cotter pinned castellated nuts that I can readily inspect because back when I was flying with the Scott tailwheel I noticed a funny feel to the tail as I was taxiing one day and upon inspection I found that the nylock nut on the underside of the big bolt that mounts the tailwheel to the end of the spring had backed itself off enough to where the end of the bolt was already a few threads up into the nut. I had grown accustomed to just glancing back there on preflight and seeing a nut there, thinking all was well and moving on to other things. Not anymore.

-Oscar

[taildrags]

One more shot; this one looking into the spring bracket from behind. It is made up of several pieces and you can see that the two 'ears' that are bent up were going to be through-bolted but I guess Corky felt that the vertical bolt from underneath was plenty since there have never been fasteners in those holes. He also didn't exactly match the angle of those ears to the tapering profile of the lower longerons at the tail, but it doesn't really matter much.

-OZ

[Richard Roller]

Oscar. Are those homemade shackles on the brace wires to strap attach?

[taildrags]

Richard, I'm not sure what those are or where the builder got them from, but they're used in several places throughout the airplane. They are stainless steel. I've never had an inspector mention anything about them and I assume that the builder's FAA designee didn't either, but I have replaced them with conventional AN115 type shackles whenever I've worked on things and had a chance to replace them.

Looking through the Aircraft Spruce catalog, the shackles you're looking at on my airplane appear to be similar to the RANS tiedown shackles but smaller. See photo of the RANS shackles.

-Oscar

[mbarkeralaska]

Oscar.......... wow!!! thanks
Just what I needed. I think I will steal all those ideas and move forward.
Thanks so much.
I will let you know how it goes as I move forward.

also working on my rudder hinges.

Mark

[bob turner]

New to the Pietenpol. Ours has the “A” frame with coil spring and welded on kingpin section, and a “shopping cart” wheel.

I would have no problem with any of that except - unloaded the kingpin angle is about 15 degrees forward. I do know that either dead-vertical or a few degrees forward is good, but this extreme angle makes even pushing the airplane around difficult.

I can see maybe carefully bending the A frame to get a more reasonable caster angle - but at this point I am wide open to suggestions.

We now use the API tailwheel exclusively on the Cubs, but they are difficult to buy at the moment. I would convert in a heartbeat if I could buy more. The old Maules, Scotts, and Langs all languish in a box labeled “obsolete tailwheels.”

Should I expect that undamped coil spring to give me oscillations in a three point landing?

[KenBickers]

Bob,

The A frame design has been around a very long time. I'm not a fan of non-steerable grocery cart-style tailwheels, but I understand that they have been used on Piets in the past. I welded a Van's RV type steerable tailwheel assembly to my A frame.

My suggestion is to measure the rake angle with someone in the pilot seat whose weight is approximately your's. It might be that you need to shift to a softer spring (or perhaps even a stiffer one).

With the A frame on my Piet, I find the feel on three point landings to be just about right, with no tendency to bounce me back into the air. In fact, my best landings are when I touch down tailwheel first, followed shortly thereafter by the mains.

Maybe attach a picture. That would help us see what you have.

Cheers, Ken

[bob turner]

Pretty sure I can attach a photo. The tailwheel kingpin had a 20 degree(!) positive camber angle, unloaded. As you know, that does not change much when the A frame moves up and down, since the kingpin angle change is the same as the very small angle change of the A frame itself.

Photo is of the original. With a giant tubing bender, I changed that to a five degree positive angle, which is more in line with what we like to see on Cubs.

Also got the heel brakes all set up for testing. Remaining will be engine oil pressurization, runup, and taxi tests. We are going to repaint as well - dark green and silver is a prescription for getting run into.

[taildrags]

But... but... I LOVE green and silver paint schemes! Steve Eldredge's is a classic example.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

[KenBickers]

Bob, I see what you mean about the rake angle. That's pretty severe. I've attached a couple photos of mine. You'll see that when the plane is leveled up (with the top longeron as the datum), the rake angle is actually negative. When it's in the three-point attitude on the ground, the rake angle is just a few degrees positive. I've been very pleased with how it tracks. Cheers, Ken

[bob turner]

Thanks. Yours looks like a better design. I will most likely be installing a real aircraft tailwheel, to gain full swivel capability. But for now, I have a good angle, and a way to get the towbar on there for rearward positioning.

On the colors - we are in the most crowded airspace in the world for GA aircraft, and a lot of the newer aircraft are equipped with heads-down displays. Even when our eyes are 100% outside, we are finding it difficult to see dark colored aircraft below us - a local flight school has black aircraft with just a hint of purple here and there, and when they are below us or on the black runway, they literally disappear.

I am so concerned with visibility that I covered a friend's L2, with the caveat that as long as I am alive it will never be olive drab. Safety of flight item.

[taildrags]

Bob; I'm currently building a single-place high-wing experimental with a VW engine. For visibility, you might like the paint scheme that I'm planning to use on it.

-Oscar

[Chuck in Indiana]

am so concerned with visibility that I covered a friend's L2, with the caveat that as long as I am alive it will never be olive drab. Safety of flight item.

I once had a Bellanca 14-13 that was camo with roundels, etc. we called "Spitlanka." It worked *entirely* too well.

[bob turner]

Mine is going to be Cub Yellow and Colorado Red, with a gentle sunburst on the wings and forward fuselage. I will get a photo of the scheme as used on a low wing. I probably won't be ready to spray until April.