Friday, April 11, 2014

March and April 2014

March and April 2014

Most of March was spent working for a living plus other projects. However, between these there was a little time to work in the shop. This photo shows a jig for building the trim actuator arm which is mounted in the rear cockpit. I piddled around with this thing way too long! The original builder fabricated this jig and cut a few of the components, but I'll have to finish the fabrication of this part which involves welding. I'm not that proficient in gas welding anymore, having had NO practice in many years. My old regulator went haywire, so I purchased a new oxy/acetylene outfit from a local welding supply store, but it only included a #5 nozzle, which is really too big for this job, so I ordered a few more. They were delivered. At least the USPS web site showed that they were delivered, but they never showed.

Another order and one is back ordered. And so it goes...

The 4130 tubing on the jig is 5/8" tubing and I don't have a die to bend that size and neither does anyone else I know. So I just heated it red and bent it around a small pulley. That worked, but the bend is flattened somewhat. That's okay; it is not a structural part and the bend is not visible where it will be mounted. Most of the other stuff is either made or easy to make. Just need to practice gas welding again to regain lost skills. This drawing is very detailed, so the actual fabrication should be relatively easy. There is an internal spring which forces the locking tab into the teeth. I'll probably have to make that spring, as well.

One of the major items that needs to be attended to is the fabrication of control cables for the elevator and rudder. This will require fitting the elevator to the horizontal stabilizer and the rudder to the vertical stabilizer. The rudder has been on for a while, but the elevator has not. I've been avoiding this as the elevator has six hinges, but fitting has to be done sometime so...

As you can see, the controls all fit very well. The elevator is a bit stiff since it has so many hinge points and it has not been assembled to this point before (to my knowledge).

Also the hinges are 1920s technology, meaning there are no rod end bearings, no roller or ball bearings, just steel against steel. There are, however, little oil holes in the steel straps for lubrication. I'm sure that in time they will "wear in" and become loose enough to be effective.

I don't want a stiff elevator. The ailerons are actuated by push/pull steel tubing, and that creates a very responsive aileron. From what I've experienced the Travel Air has fairly well balanced fight controls, which makes an airplane a joy to fly rather than a chore. Most pilots are not aware of just how important "control harmony" is to the "feel" of an airplane, but besides responsiveness, this is what makes all the difference.

Many of the older airplanes had terrible controls. Very sloppy control response and unbalanced control feel. But this is what is to be expected with such old technology. But the Travel Air was very successful in part because of the way it handled. Quite a testimony to the engineering skills of Mr. Lloyd Stearman. His original trainer design (the Model 6 Cloudboy) was a joy to fly. The one which the government ended up with does not respond nearly as well. It is a trainer, and should be harder to fly. I think this was done intentionally, but I could be wrong. I've had

people ask me about learning aerobatics in an RV-4, which I think is a bad idea. The airplane is just too good of an airplane...too easy to fly to be a good trainer. End of editorial.

With the tail feathers installed, I took the time to fabricate the two control sticks. Both have bends to bring them closer to the pilot, so another small tubing bending job and now there are two sticks.

I had to look pretty closely at the alignment of both control sticks before drilling their attachment holes. I realized that a small misalignment could throw the lateral position of the stick off quite a bit. Actually, I cheated a bit to the right on the rear control stick since I like having the stick offset just a little bit to the right so it fits snuggly in my hand with my arm resting on something like an arm rest or my leg. Maybe that's from too many hours flying formation, I don't know.

I finished making the two curved wood stringer supports a month or so ago, but never did fabricate the fittings to attach them to the frame. In the case of the forward attach point, I used a tab that was welded on the frame to form the aft wall of the baggage compartment. Since I extended the baggage space to the next bulkhead aft, like the original Travel Airs, that left three of these little tabs free for whatever I wanted. I cut off the center one and used the two outboard tabs to attach the support forward arch. A piece of scrap aluminum angle acts as an adapter.

The rear most arch is attached to the frame with an adel-style clamp and two little aluminum plates also from the scrap bin. I used four attachment holes, which may be a little overkill, but so what?

The arch will be attached to the stringers with some rib-lacing cord or similar material. I didn't want to make a hard attachment considering any movement might result in cracked wood. They only have to support the stringers in one direction with the pressure of the shrunken fabric pulling them inward.

Fabricating control cables requires some fore-thought to avoid buying unnecessary fittings, which run to the ridiculous expense-wise. I cannot believe how much turn-buckles and those little shackles cost! My daughter was with me when I picked up my order at Aircraft Spruce. I showed her the small bag of fittings and said $350 worth. She almost chocked. Me too.

The rear stick actuates the elevator and a control arm transmits that movement to the front stick. The original had four little steel "tangs" to adapt the round tubing of the stick to the fork on the turn-buckles. Those four little tangs took me over an hour to make using a "ziz-wheel" on a die grinder to cut the 4130 plate steel. I really could use a good metal-cutting bandsaw. My old horizontal is just not a very good saw, and doesn't work well in the vertical.

One very bright spot in all this expense was finding an old box of aircraft cable that I bought a few years ago at a hangar sale. Most of the cable is 1/8" which is what I need. AND, every cable in the box has some kind of an end swaged onto it. Most of them are 1/4-28 threaded stud ends. Jackpot!! All this stuff is new surplus. Some of it is coated with cosmoline or some other gooey protectant. A quick run through the parts washer and they are ready to be measured and thimbles nico-pressed to the other end. This is not as easy as might be first imagined. The extra-strength fuselage with it's extra 4130 tubing welded into almost every frame bay, creates an obstacle-course through which I must run these cables. It will take some creative use of pulleys and fair-leads to get them from point A to B. Actually, the original Travel Air had pulleys under the next-to-aft bulkhead, but free travel there after. Mine will have to run through some fair-leads at only one point and have some kind of protection where they criss-cross. Not a big deal, but I'll have to run string first for measurements, then make the actual ends on the bench.

One more little item of interest... I opened a box looking for cable fittings (to no avail) and found this box full of parts, the use of which I am uncertain. Some are fabricated steel fittings and some are manufactured fittings along with other flotsom and jetsom. One of the fabricated items is the retainer for the bungee cords on the landing gear. I'll have to discover the rest looking through drawings. Or maybe I'll be fretting over how much some item will cost and then realize: "I've already got that!!" Lets hope so anyway.