Prop Shaft Housing Part I


Part 158, the prop-shaft housing, is machined from another chunk of wrought aluminum alloy.

  A slug of appropriate diameter is chucked and faced.
  The exterior is then profiled. I am going to deviate a bit from Mike's process and cut the "undercut" portion later. For now, the nose of the housing is turned to a constant diameter. This will allow for a firmer chucking when the piece is reversed.
The nose is bored for the largest bearing in the pack, that which supports the prop shaft just aft of the propellor itself. Once again, take care for the appropriate fit, in this case a reasonable hand press fit. The bearing can be removed with minimal effort, but there is no play at all when installed.
Successful test fit of the bearing. When finally assembled, there are two "wavy" washers which bear against the outer race and provide a bit of preloading. Thrust will be absorbed by the cowl. In my case, since I am not going to install a cowl, a bearing retainer ring will be installed with 8 SHCS.
The housing must be parted to face the rear and bore for the rear prop shaft bearing. Whenever larger diameters are parted, it is good practice to part with more than one "start", shown here. Note the width of the slot in which the final parting will take place. This minimizes rub and allows chips to clear. To do this, simply plunge the blade in two locations, side by side, to create one larger channel. The final part takes place in the middle of the channel. Obviously leave enough stock on the part for cleanup to dimension.
Flipped around, we work on the rear of the housing. The major diameter disk is faced to the correct thickness, and the bearing hole is bored.

Again, before doing this, ensure the part is running 0 TIR with either an adjustable 3/6 jaw chuck, or using a 4-jaw.

Ready for the mill and the bolt-circle holes. Final turning still needs to be done... the undercut portion aft of the front bearing. This will be done later.

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