Curtiss Jenny Restoration

Welcome! We hope you enjoy following the restoration process of a 1918 Curtiss JN4D Jenny. Once completed, the aeroplane will be flown and displayed at the Candler Field Museum in Williamson GA (30 miles south of Atlanta). You can contact me below by clicking on "VIEW MY PROFILE"

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Location: Peachtree City, Georgia, United States

Sunday, May 03, 2015

Engine update

Progress on the Hisso continues! 

Last week, I happened to have a work trip to Charlottesville, VA.  We were only on the ground a few hours, but John Gaertner met me at the airport and I went to see the Hisso.

Where do I start?  OK, how about the valves.  As mentioned before, all the valve guides were worn beyond tolerances.  We decided the best course of action was to make threaded sleeves.  Here you can see two sleeves and one sleeve already threaded into a guide.

The bottom part of the sleeve was machines to match the guide.

The sleeved guides were inserted into the cylinder banks.

The valve seats were re-cut and the valves hand lapped into place.

Both banks were painted.

As were the valve covers.

On to the camshafts.

The left camshaft gear was missing a spacer.  Not anymore.

Also one of the end caps was missing.  A new one was made.

Pistons - since the rings in the engine were worn out, new rings were ordered.

Each piston was cleaned, inspected and measured.  Seven of the pistons were fine.  But the eighth one......

It was trashed.  As you can see, part of the piston was eroded away.  Blow by from the bad rings?  I don't know.  There was no way we could use this piston again.  So, a call to Ross Pistons in California was placed and eight more pistons are being made.

They no longer make the long, heavy original style pistons as you see on the left.  The new ones are shorter and have one less ring.  I worried about the difference until I talked to my friend John Saunders.  John has two Hisso's of his own, knows a ton about them and assured me the pistons would work fine.  Jack Kearbey has been running a set in his SE5A powered Hisso for a long time without any problems.

More bad piston news.  Several of the piston pin caps were deformed.

New ones had to be made.

They were made oversize so when the new pistons arrive, then can be machined to match.

The case was split apart and the crankshaft was removed.

More unpleasant news. The center three bearings were way out of tolerance!  

New babbitt bearings had to be made.  John designed this jig.  

It is a fake crankshaft surrounded by the Hisso bearing shells.  A gap is formed between them.

In this gap, the molten babbett is poured.

The edges were machined away....

And the bearing is ready to be split and bored.

Good news - the connecting rod bearings checked out fine.

The rest of the case has been painted.

There are still a few more things to do but for the most part, the engine is waiting for reassembly.  All we need are pistons!

A few days before I arrived, the OX-5 that John overhauled for a customer left the shop.

Lastly, I got a nice email from Earl Haury in Katy, Texas.  It was this type of email that makes me feel this blog is doing some good.  Earl wrote:

Hi Brian
Congratulations on the completion of your Jenny!.....Thank you for documenting the process in your blog, an invaluable document for anyone wishing to build a Jenny, full scale or model. I though you might enjoy knowing how your project helped mine.
I’m a modeler and primarily interested in precision aerobatics where I’ve competed for 40+ years. I occasionally take on something different, as you can see from the attachments, the current project is a Jenny. This all started half a dozen years ago with the purchase of a popular Jenny kit and the acquisition of documentation of a Barnstorming Jenny on display in an English museum. I quickly realized that the kit was lacking in the hardware and detail to really do the airplane justice. In further research I found your blog which offered the level of detail in parts and construction I wanted. I’ve spent hundreds of hours lurking and copying (in 1/6th scale) the parts and pieces from your project.

April 10-12 I completed a bucket list item by entering the Jenny in the Weak Signals model show in Toledo, OH where it was awarded Best in Class. Please note that your blog is credited with a detail source in the display presentation. The history of the original airplane is quite interesting – well traveled to say the least.

 It would take too many words to describe all the tooling built to make parts, most the same as yours – just smaller. The bead roller for the fuselage cowlings, tooling to fabricate 100 shackles, hand forming the brass radiator, etc. The stick assemblies are ball bearing mounted, as are the rudder tiller bearings and elevator bellcranks – all operated by servos hidden beneath the rear seat. Even the aileron cable pulleys are fitted w ball bearings. One thing for sure, 1/6 scale provides many challenges as parts are small – lots of 00-90 capscrews.

I haven’t flown it yet – wanted to get Toledo checked off first – and I’m way behind the curve on my precision aerobatic competition prep, but the Jenny is fully flyable (electric powered) and will fly this summer.
Earl Haury
Katy, TX 

You are welcome, Earl.  Beautiful model.




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