Monday, August 13, 2012

Painted Parts, Spark Plugs & Propeller

 While I wait for the needle for the carburetor, the air box is painted and baked in the sun.  They came out nice.
 I bought a new set of 4 Champion spark plugs, but I also have a used set of 4 plugs for the other magneto.  The problem was I could not identify who made them or whether they were legal to use on this engine.  Three of them were to rusty to read the markings but obviously identical.  The fourth on had markings still but there was no way to read them.  After Caleb helped make sure they all are working I had an idea on how to figure out the numbers. I lightly filed the flats with the numbers until they were just readable.  It became obvious the one flat had "BG" on it.  Sure enough BG was on the TC data sheet (E-233) and the Continental service letter on spark plugs (SIL 03-2B).  Careful filing of the flat with the number revealed 706SR.  I have no idea what the SR stands for but the plug is on the data sheet so I've cleaned them up and they're ready to install.  I've highlighted the numbers here so they show up better.
I didn't know anything about BG plugs but it turns out they've been in business since 1918 and still make plugs and igniters and such.  They were big into aircraft plugs in the 30's and 40's.

While Caleb helped check the plugs I found out he needed a propeller for the C-150.  I came back here and carefully checked the numbers on the prop for the Fly Baby.  It turns out it's a McCauley 1B90-CM which is the right prop for the C-140.  It's still 71 inches long and was re-pitched to 44 inches so as long as the static RPM is within limits I have a prop for the plane.  I wanted a climb prop so this is perfect.  I always wanted to make a wood prop for the Fly Baby so I'm thrilled.

Sunday, August 5, 2012

Rusty Carburetor Air Box

The carb. air box was dented and had a couple small cracks.  Once those were fixed I needed to get rid of the rust before repainting it.  Normally I would just grit blast it. I was concerned that I wouldn't get all the grit cleaned out well and some might get into the engine.  I decided to use Naval Jelly to remove the rust.  I don't think I spent any longer than I would have blasting it and then treating it with Phosphoric Acid before painting.  Naval Jelly is Phosphoric Acid in a jelly form so it doesn't run off the part and it doesn't dry out as fast.  It to about 30 minutes total to clean the box and it stayed wet through the whole process despite 90 degree heat.  I scrubbed with coarse Scotchbrite to get it worked into the rust and scrub the rust off.  Just like treating with Phosphoric Acid before painting you need to flush it off with water and quickly blow it dry so new rust doesn't form.  It's primed and I'll paint it when the other parts are ready.  It really came out great.

Friday, August 3, 2012

F&M TAF Oil Filter Adapter

The F&M oil filter adapter is back on.  I had to order a new gasket from them ($15).  I'm not convince it's much different from the one in the overhaul set.  They're both paper gaskets.  Their's is .032" thick and the one in the set is .030" thick.  Their STC SE7562SW is based on their gasket so it needs to be done with the approved gasket.  Also unlike Continental's service letter for most of the gaskets, the STC requires this one be put on without any sealants.  A assume its an effort to stop any sliding of the casting due to vibration.  Having worked as an oil filter engineer at AC Spark Plug it's amazing how much things can bend and move around when an engine is running.

Having worked on filters as an engineer I've seen a lot of problems people create installing them.  Always coat the gasket and casting with a thin film of clean oil.  Rubber vulcanizes at about 170 degrees F.  It will make a great bond to the metal casting if there is no oil between them and you will not get the filter off.  If you've ever seen rubber shock mounts, that's how they bond the rubber to the metal.  Also don't over torque the filter.  Pressure adds to the bonding process and makes it all the harder to remove the filter. With everything clean and dry like this, or a new installation, also put some oil on the threads of the stud and filter.  You want the filter to unscrew off the stud easily when you change the filter.
The filter holds about a pint of oil.  Fill it before installing it.  You want to minimize how long it takes for oil to get to the bearings in the crank and cam.  Why make them run without oil while the can fills when you can do it before installing the filter.  Be patient filling it.  The oil has to flow through the paper and then the air has to get back out.  It takes several refills before it's actually full.
When you screw a filter on first tighten it snugly by hand to seat the gasket.  Back the filter off until the gasket is just clear of the casting.  Gently screw it back on until you feel it touch the casting.  Start counting you turns (3/4 or 1 or whatever) from that point.  For this Tempest AA-48108-2 filter there is only a torque spec.  The old filter had a torque spec. and 3/4 -1 turn.  That's plenty of compression on the gasket to prevent leaks.  Over tighten it and that gasket may be there when you die of old age.
I like to write on the can with a felt marker when I changed the filter (date & hours).  Do it on the end of the filter when you first take it out of the box.