taxi

[Fl90]

I have been taxiing a conventional gear setup, trying to get the hang of it.

The mains contact the ground 12* forward of the cg, I have a 60* tip angle, mains are 48" apart, and wheel base is 53". The tail wheel is full caster, no toe on the mains (no adjustment). Rotor spinning, on grass.

A LOT OF WORK.


Any body out there with a tail dragger willing to give me a wheelbase and a short description of the workload involved just before rotation? I'm at the point of converting to tricycle gear, but I love the weight savings that this setup yielded.


Thanks in advance, Phil.

[Timchick]

Phil,
Are you using a pusher engine?

[Fl90]

Yep, it makes a tiny package......just like a squirrel. Unfortunately, it handles like one.

Something I had to try. It's doable, but I think my wheelbase is a little short. Extending the wheelbase would require a taller mast, etc.....so am not willing to.

If you know someone with a Pitbull single, let me know, I have some questions.

Thanks, phil

[Mike Jackson]

Try to get hold of Warren Traweek. He's got a BMW powered Pitbul here in AZ and has some good insight into its ground handling qualities. He's in the Member's list.

[chuter]

Phil,

Mine's a tractor tail tragger; I had some squirrelly taxi problems that took some working out. I finally got it satisfactory.

I'm not sure what my wheelbase is without measuring, but I think it's around 10 feet.

At first I had a tight, almost solid, connection between the rudder and the steerable tailwheel and it was real twitchy.
I finally tried some softer springs between the rudder and tailwheel and it made a big difference.

Does this help?

[Fl90]

chuter,
Thanks, yes, it helps. My short wheelbase is most likely the culprit. My tail wheel is not linked to the rudder.


Thanks Mike, I've heard of him....I'll drop him a note.

Phil

[Bob Gregory]

Tail wheels. Phil, you and I have traded comments on tractors before. Must be working on similar projects.

Read any post by "pbool" as in Pitbull.

Read any post by Warren Traweek.

Jim Bede,.............http://www.bd5.com/BedeDesign01.jpg

On third page of "Mast sizes" you, Mayfield and I have some comments about tail wheels.

My opinion after working with a tail wheels is at least a
10 inch tail wheel,
it must be trailing,
it can not be castering,
soft springs as Chuter and pbool say,
The mains must be absolutely straight or slight toe in (set with a laser).
Put 10 to 15% gross weight on tail.
Have mains 15 to 17 degrees in front of cg.
You have traded pilot weight for engine weight being a pusher.
Might have to angle the fin to compensate for torque or offset engine to right or left according to right or left handed propeller as "Aviomania" mentions
There are reasons for all of these, but this is the short version.

http://www.rotaryforum.com/forum/showthread.php?p=180899&highlight=tail+wheel#post180899

[mabik]

Do you have a picture of your machine? I've been thinking about a similar design. I'll have to get my gyrobee finished first, but i like the idea of a pusher taildragger.
doc matt

[Fl90]

Hi, no I didn't take a picture with the axle setup. Sorry. I could taxi, but it was a lot of work. It makes a very short machine and I think the wheelbase was just too short at 54".

I've heard of others that have tried and not had favorable results, but I had to give it a shot. Sometimes you do things that have been tried by others and it works for you. If you build one that works, let me know. I'd like to use the conventional gear, but not at the price of stretching the machine.

Phil

[mabik]

Just a thought, but could you put the tailwheel on a long leaf spring (maybe fiberglass)? Or add weight and complexity and make the tailwheel fixed and steer the mains?
doc matt

[docrob]

I think your short wheel base is a major part of the problem. Many years ago, Champion (Aeronca) built a Citabria which had a wheel which looked exactly like a nose wheel (6 inch tire, oleo stut, etc.) located about under the baggage area, which made it fall some 4 to 5 feet behind the mains. It sat slightly nose high on the ground, about half way between the pitch angle of a tail-dragger and a nose dragger. Besides being ugly as home-made sin, it was a real bitch on the runway. It would ground-loop at any speed, including parked with the parking brake set. The story is that just a few weeks after it was released, they sent a mandatory service letter to each buyer, which required removing the third wheel, installing a conventional tailwheel and spring in the normal location and shipping the third wheel back to the factory, freight prepaid. The airplane went back to being the good old honest airplane it had always been.

Dr. Rob

[mabik]

Making a scale model with adjustable wheelbase and trail on the tail wheel is useful for experimenting with different layouts and their ground stability. Leggos work pretty well.