Thursday, October 30, 2014

Three steps forward... One step BACK???

The project to bring Curtiss Robin NR59H out of retirement has gone well thus far.  Up until September 21, we were making good forward progress toward our goal of returning her back to the air.  Occasionally, we have had small setbacks, but mostly things are moving along nicely. 

That day, on Sept. 21, we finished mounting the engine up to the airframe.  Afterwards, the three of us, Lon, Randall, and I were under the fuselage sitting on the floor... we were half-way resting, but half-way looking things over to decide what our next steps would need to be.  Randall saw it first... and uttered those ugly words..... Uhhhh Ohhhhh! 

With the owner's schedule looming in, the last thing we need is a major set-back.  Of course... that would be living in fantasy land.  So when we ran across this rusted tube on the airframe, it was almost enough to discourage the whole plan.  Evidently, despite the best of care given by Joe Erale over the past forty-some years were not enough to combat the adverse environment of some years of neglect and outdoor storage on Long Island New York in the 1940's and 1950's.

Here's the ugly truth we (Randall) found...


Of course, this prompted a whole 2nd effort to go over the whole airframe again with a tiny ball-peen hammer to tap on all the tubes.  It is hard to be 100% certain, but we think this is the only tube with major rust.  Something has to be done.





It didn't look any better after cleaning off the paint.  But we decided that this might be a candidate for a patch repair.  We tried that first.   It turned out there was just too much rust in the tube to accept a proper weld bead.  The whole tube must come out!


In the old days, this might have been considered a routine field repair by the old school pilot-mechanics.  Of course, they were probably dealing with an airplane of much less value, so they might have just dove right in and not worried so much about cosmetics.  We, on the other hand, are dealing with an Iconic aircraft of significant historical value.  The pressure is on.

As an engineer, I have never liked schedules.  Now, as the business owner and leader of this project, I was faced with some tough decisions.  So, after some discussions with our team here and with my friend and expert airframe weld repair expert, Craig Gunder, I decided that we need to proceed on with assembly of the wings onto the airframe and then to go ahead with the first engine run before we tackle this tube replacement.  That way, we will have the opportunity to identify whether any other major difficulties may crop up with either the fuel system, engine, or the general assembly of the airframe.

So here we are on October 30.  The wings have been installed.  This Saturday we plan to pre-oil this old Challenger engine and fire it off for the first engine run since 1984.  We will then proceed to weigh, rig, and inspect the airplane as though for final inspection.  Once deemed ready, we'll Bring in expert weld repair GURU, Craig Gunder from Red Lion PA. Craig is the operator of Gunder Restoration and Design and has made quite a name for himself repairing and building frames for vintage airplanes. Quite a lot of parts will need to be removed or partially disassembled.  But we're confident that this can be done and and back together pretty quick.  Perhaps we'll be airborne by Mid November.





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.

Installing 'packing' seal.
 
Repaired oleo assemblies with removed portions of upper tube that were replaced.
New paint for the re-built oleo struts
 

New Lester tires being installed
 

Leann Bowden doing paint touch-ups on the Fischer 28" x 4" wheels

The Majestic Curtiss Robin proudly sits on its repaired landing gear




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