Barnstmr's Random Aeronautics

Thursday, October 30, 2014

Moving closer toward first flight - step-by-step

The team at CAP is steadily moving Curtiss Robin NR59H closer toward its first flight since 1984. This refurbishment and modification project has included a long list of steps and tasks that we are continuing to knock out each weekend. We've been so busy, there's been little time to keep this blog up to date. But here are some photos of some of the recent work. Several weeks through August, September, and early October 2014 are included here.

With the fuselage lifted, Lon prepares to remove the temporary skid dolly.

Randall bringing the LH axle into position after RH gear is already in place.

Randal says... with the gear installed, this bird looks so much more "Majestic". I agree.

Challenger engine mated with Horseshoe Engine Mount.

One of the most difficult challenges with the modernization project for this airplane and engine was the goal to convert the magnetos with shielded harness and park plugs. The folks at Radial Engines Ltd built up a new harness and shrouds for the mags using the cast bronze distributor covers from a later style mag. They had to do some tricky machine work to get them to fit. Once we got them here to CAP, we ran into some clearance issues which forced us to do some additional machining on the covers. Here we have the mags installed and timed to the engine.

Mags installed.... we had some clearance issues with the horseshoe mount.

We also removed the original hand-crank inertia starter and set out to modify with an electric starter. Fellow antiquer Tim Talen sold us a Bendix-eclipse model F-141core, which we had overhauled bu Aircraft Accessories of Oklahoma.

Completing the Bendix F-141 Electric Starter conversion - thankfully it clears the oil tank.

What a day... we got the engine installed after a lot of little issues that had to be overcome. Anytime you modify something, you have to be ready for many issues that you've unknowingly created. Be prepared to fabricate.

Here's the CAP modification/fabrication/refurb team... Terry, Lon, and Randall.

Burning the midnight oil... installing tail parts.

Randall and Lon adjusting stabilizer and elevator

The Robin on its Roost after another productive weekend... tailfeathers installed.

By this time, many who are watching this project unfold have figured out that the new owner is making plans for some interesting NEW history to be made. We will write more about this in future postings. For now, I'll just say we have a wonderful group of people to support this fascinating project.


Ray and Jim readying the wings for installation.

This past weekend, on October 25th, we had an excellent crew of folks on hand to help install the wings on this magnificent old airplane. I will attempt to name them all here...Texas team members on hand that day were.... Ray Mattix, Guy Matthews, Jim Elsey, Leon Carr, Randall Green, Carolyn Carr, Leann Bowden, Travis Lightfoot, Rachel Lightfoot, Hannah Lightfoot; And the Costa Rican team on hand for this event were.... Everardo Carmona, Jr, Everardo Carmona, Sr., Alejandro Neito, Carlos Mazzalli, Carlos Macaya,

It takes a Village.

Marine PFC, Travis Lightfoot manning the safety rope while Carlos looks on.

Where did Ray go?

We found Ray!!

Glad to have her back together!!

Thanks to our most excellent "wing hangin' crew".

Thursday, September 4, 2014

Oil Hydraulic Struts... Repairs and Reassembly

Previously I posted about the disassembly of the "Oil Hydraulic Struts" as removed from a Curtiss Robin, NR59H. Well, A few weeks ago we finally finished with the repairs and re-assembly of these strut assemblies. Here are some photos of the process...I am happy with the results and believe we have a repair that should last for many years of continued service.

Portion of tube insert for repair.

A decision was made to cut out the badly pitted portions of the upper tube. We designed and fabricated a replacement tube to be welded in place of the removed portion. We found an "off-the shelf" material that was perfect for the job. It is a close-tolerance seamless tube made of 1020 steel chrome plating applied during the raw material fabrication process. This material is commonly used in the manufacture of hydraulic cylinders. The chrome plating will hopefully resist the kind of pitting that caused us to tear down the oleos in the first place.

To ensure a proper repair, the design concept for the repair 'insert' tube was to machine a step-down of the outside diameter and to give it a three-inch insertion length to allow the insert to self align to the existing tube. The insert was expertly machined by our friends at Madden Manufacturing, LLC, China Spring TX. We were a little worried about causing too much stress in the upper tube and the potential for cracking during the press-fit-up operation. The shop's owner, Dennis Thom, came up with the right approach for this by effecting a taper of the stepped-down OD from a 0.000 inch fit at the insertion point and gradual taper to 0.0025 interference fit at the last 1.5 -inch of tube to the bottom of its shoulder. The results were spot-on.

At the shoulder, the repair was finished off by welding the interface joint all around. Then the weld bead was ground and polished down smooth and flush with the tube OD. Rosette welds were deemed unnecessary due to the interference fit design which pre-loaded beneficial stress into the assembly.

Tube 'insert' welded in place and polished smooth.

Re-assembly of piston on upper tube with spring-lock clip in place.

The original design of this oleo assembly did not utilize a rubber o-ring seal as would be expected in a similar/more modern oleo. Instead, a packing material was used. Originally, this packing was most likely a degradable cotton or linen rope material of a round cross-section with graphite flake coating. We found that the modern materials used in water pump packing applications are far better than that of the old-days. We managed to find a synthetic graphite impregnated rope material with 1/4" x 1/4" square cross-section. This seemed perfect for the job (short of a re-design for o-rings). We used 24 inch lengths of this material to seal each oleo. The slight compression of the packing material riding against the smooth chrome OD should be an ideal seal and wear-resistant surface.