What on Earth is all this “High Hole –Low Hole Stuff?”

//What on Earth is all this “High Hole –Low Hole Stuff?”

What on Earth is all this “High Hole –Low Hole Stuff?”

With the Continental engine installation on the Stearman, there is a hole in the upper left hand corner of the left side engine cowl door.

This hole accommodates  the end of the crank bracket, the primer handle, and the pull handle for the clutch engage for the inertia starter.

Some Stearmans have this hole positioned with the top edge down 5/8 inch from the hinge line. “The High Hole”.

This position left a very narrow and sometimes weak piece of sheet metal between the hole and the hinge.

Later, beginning with the PT-27, this area was redesigned to move the hole down so that there was 2 1/2 inches of sheet metal between the hole and the hinge line. Hence, the “Low Hole”. Fewer cracks!!

OK, so far so good. However, there are more dominoes in this string.

Since it was determined that it is really preferable to have the crank bracket come through the side cowl where there happens to be a hole, there had to be two different brackets. One for the high hole and one for the low hole.

Still a couple of traps left for the unwary!!

Now when the crank is inserted through the bearing in the center of the bracket, the other end will have a universal joint installed allowing it to connect to the starter crank input.

 The crankshaft should stay pretty parallel with the bracket housing when the other end of the universal joint is connected to the starter.

 Since the starter has many holes that match the six studs on the accessory case, it is important to clock the starter, (before you put all those nuts on), so that the crankshaft lines up properly.  The high hole bracket and the low hole bracket require one hole different clocking of the starter to get the right alignment.

 So there you are. The cowl door, the crank bracket and the clocking of the starter all have to match either the “High Hole” or the “Low Hole” configuration.

 It is worth saying a few words about that bearing that is in the center of the bracket housing. A75N1-2863

It is a ball bearing with two outside races. One race swivels inside the other. This allows for some misalignment between the crankshaft and the housing.

To remove this bearing so that it can be re-lubed is a little tricky until you know the secret.  Don’t remove the outside race, it may be OK, and is difficult to get out and back in.

Put some oil all over the bearing in the housing and let it set for a while. Then with a long punch, tap one edge of the inside race so that it begins to swivel. Work it from both sides of the bearing until the center of the bearing is a right angles to the outside race. Then turn the bearing around in the outside race until it lines up with the two slots, one on either side. Now the inside bearing can be lifted up through those slots and removed. 



By |2016-11-13T09:33:33+00:00August 23rd, 2003|Flying-Wire|Comments Off on What on Earth is all this “High Hole –Low Hole Stuff?”

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