Thursday, April 16, 2015

Engine Rear Case

Just feeling better after a nasty virus. Work continues as able.
Since the center engine case is installed in the fixture and mated to the nose case, the next procedure calls for installation of the tappet bodies and lifters. It amazes me that this 1930/40s technology radial engine has these nice little roller tappets while "modern" engines use a solid tappet that rubs continuously against the cam in operation. Maybe I'm naive, but it sure seems an improvement would be in order here. I guess it all boils down to money, as usual.

Jim's Handy Bearing Capture Device (Low-Tech)
Rotated for Access to Rear of Case,

Here's the "back side" of the center case with Jim's handy-dandy low-tech bearing capture device still holding the rear bearing in place after mating the case halves. With the engine rotated into position for installing the "cam ring," as it's called on a radial engine, the cardboard tube and nut is removed.  

Cam Ring in Place for Checking Play

Installing Tappet Bodies

Now we can install the cam ring and center gear for the purpose of checking for the required amount of space between the cam and it's spacer. The book calls for .008"-.012". This one measures .010"—perfect! With the cam removed again, we began installing the tappet bodies, which are aluminum tubes that  are held in position by studs and nuts. Jim had previously layed in the gasket with a thin film of Tite Seal on both sides. He likes this stuff as it never hardens, but provides a nice seal for surfaces like these. The roller tappets will be installed in these tubes, rollers mounted on cam ends, and circlips installed on the outside end

View of Roller Tappets Installed
This is How Roller Tappets Engage the Cam Ring

Once all the tappets are installed, we can lay in the cam ring and center gear. It was slathered well with STP/engine oil mixture. This is what everyone uses when building up an engine. I've used this same mixture on airplane and auto engines that I rebuilt. Good Stuff!!
There is a BIG nut that holds this gear in place. It has to be torqued to a very high setting and a keeper installed with a safety added to hold the keeper. This nut is important.
With all this in place we can move on to assembling the accessory case and mounting it to the rear of the engine. I don't know what I would do without this fixture...and Jim Friedline!

Friday, April 10, 2015

More Engine Work

With improving weather and matching schedules, Jim Friedline and I began assembling the major case parts of the engine. This is where experience really becomes important. You can follow an overhaul manual to the letter, but there will still be procedural nuances that can only be learned from experience that make the whole process proceed smoothly. Jim has this expertise and is overflowing with facts gleaned from many engine rebuilds. Knowing that this will not only be done right, but quickly and with no common errors is a load off my mind. The man amazes me with his keen memory of details and numbers. So, with his chain hoist in position, his home-made bearing capture device in place, and oven on, warming bearing races, the assembly begins.
Forward Thrust Bearing Pressed into Cage

Heating Bearing Race

Crank Mounted on Jim's Stand

Jim has several home-made devices, actually. One shown here is the stand that holds the crankshaft in the vertical position to make placement of bearings much easier.  The mid-bearing race must be heated to around 250ยบ F to expand it just enough to slip onto the crankshaft. Once dropped into place, the race cools to the temperature of the crank almost immediately and is shrunk to a very tight fit. This, of course, is known as a "press fit" or "interference fit."

Jim Places Race on Crankshaft

Race Installed and Very Tight

 Once the race was installed, the bearing slipped right onto the race and will be held there by a sleeve.
Mid Bearing in Place (Roller Bearing STC)
With all this done, it was time to lower the Nose Case onto the crank. The front bearing was installed in the nose case and the whole assembly heated in the oven to allow for an easy fit onto the crank. Once the Nose Case is lowered onto the crankshaft, the cylinder base openings trap the rods, so the rods were spread to their final positions to allow for the correct cylinder to mate with its rod. Number one cylinder is straight up on this engine and contains the master rod.

Nose Case Lowered Into Position
Rods Spread

The front (thrust) bearing is a tight fit also and will easily slip out of the cage if not trapped in position as it is lowered onto the crankshaft. This is another one of those little tid-bits of knowledge that makes Jim an expert, and would have caused me to repeat the procedure multiple times.
Whole Assembly Lowered Onto Mid-Case
Another one of those experience-born procedures was the low-tech cardboard tube (not shown) that holds the rear bearing (also a roller bearing) in place so that the assembly can be lowered onto the mid-case without the need for seven hands. Once this is done the cardboard tube is removed and the rear bearing is trapped in its housing in the mid-case. Using a chain hoist to assemble the nose to the mid case made the whole procedure easy. Worked like a charm!

These photos show the nose and mid case parts mated and bolted together while in the engine fixture where the rest of the assembly will be done.
This was one of the most enjoyable learning experiences in the whole project.
Now it's on to the rear (accessory) case, where the cam is located. Once I'm over this nasty little virus my wife shared with me, that will be done.