OX-5 #2

I was able to finish up the water pump overhaul for the OX-5.  Before I go into that, a few comments about the mighty Curtiss.  I won't go into the history of the engine - the web is full of that info, but I will mention a little now, and in other posts about the overhaul.  The Curtiss OX-5 had a reputation of not being a very reliable engine, but what has to be kept in mind is this is a 100 year-old engine.  I have to think that the mentality in the early years of aviation was to keep the engine/airplane operating with whatever methods were available - good or bad.  Applying todays engineering, parts and know-how I believe improvements can be made to any engine to increase its TBO, reliability, oil consumption, etc.  The OX-5 is no exception.

Now, I am not a pioneer in this.  Folks have been experimenting and improving this engine for many years.  I'm just fortunate to be able to apply these improvements that someone else has thought of, and maybe even get lucky finding some of my own.  One of the great things I've found about restoring old airplanes is - there are no secrets.  People seem to readily share anything they have learned or tried and I try to do the same.

Now the water pump...The original design had its drawbacks, and is a perfect example of how modern technology can improve on a 100 year-old design.  Many antique airplane people know Kent McMakin.  I'm fortunate to live close to kent and he loaned me a modified water pump so I could see what improvements have been made.  20 or so years ago, you could send out the water pump or buy a kit to upgrade it, but I don't know of anyone doing that now, so the parts have to be machined.

Original shaft on left, new one I machined on right

The shaft is one area of concern.  The original shaft is carbon steel which will, of course, rust and pit in the cooling water.  I machined a new one from stainless steel, and at the same time could get a nice fit, .0015" between the shaft and the bushings.  Getting those areas that ride in the bushings nicely polished will also improve its performance.

Lip seals installed in packing nuts

The other area of concern is the packing that seals the shaft where it exits the front and rear of the pump and prevents leaks.  This is important, as the water pump sits directly above the carburetor! The original packing was a typical rope-type, but modern lip seals fit directly in the packing nuts and fit the shaft - a definite improvement!

Grease retention groove in bushing

The shaft and bushings are lubricated with grease applied to the inside of the shaft.  Small holes at each end of the shaft where it rides in the bushings allow the grease to be distributed.  I machined small grease retention grooves in the bushings to help hold grease in this critical area.

The collar to the right of the impeller controls
the end play

The final area of concern is general fit-up.  Curtiss manuals call for 1/16" end play of the shaft - way too much!  I carefully set up the collar that controls the thrust with only .005" end play.  May not sound like much, but clearances will get bigger with higher temps and the closer end play will eliminate wear which could lead to impeller rubbing.

Measuring end play with a dial indicator

Collar adjusted for .005" end play

 

Here's a shot of all the components.  Had to make new gaskets as expected.  The hardware is all original.

A comment about the hardware and engine in general.  Properly restored, the Curtiss OX-5 is a thing of beauty.  All the steel components, including valve train, cylinders, hardware, cooling tubes were nickel-plated. The aluminum components were left natural aluminum.  The engine sparkled like a jewel!  This is how our engine will be restored.

Finished Curtiss OX-5 water pump

I also got a great start on the lower LH wing.  As expected, going way quicker than the first wing.  Next post will hopefully be fit-up of the crankshaft in the main bearings to check clearances.