Lube and Air Manifold


Continuing with my plans for mounting the turboprop on a set of rails, I needed to leave as much space as possible directly beneath the gearbox for the oil tank. To this end, I designed a lube/air manifold which mounts on the rear of the gearbox, rather than the bottom. This manifold, which is separate from the gear oil system, is needed to deliver cooling air and a fuel/oil mix from the main fuel pump for use in the turbine shaft tunnel. Since both of these lines come from the gas generator, I oriented them facing to the rear of the turboprop.

  An aluminum manifold blank was machined. Here, a boring head is used to create the radius which mates with the shaft tunnel diameter bolted to the rear of the gearbox. This will be easier to visualize in subsequent photos as the manifold/gearbox comes together.
The air and lube lines, once plumbed, are more or less permanent. I visualized these lines as drawn copper, gracefully bent from the gas gen. service ports and traveling below the entire turboprop, terminating here at the manifold via detachable brass pressure fittings, seen in the next photo. These fittings are commonly used in the steam hobby, and can handle hundreds of PSI in a leakproof fashion while being detachable for maintenance. Here, one of the two ports is being tapped for the fitting 3/16 x 40 Imperial.
In place on the gearbox. I am visualizing the path the two lines must take to deliver their precious cargo to the tunnel.
Two mill cuts were made as shown. This will allow the delivery lines to bend in a kinkless fashion and clear both the tunnel mounting diameter and the hot exhaust front. A hole is contined downwards to the port to make the path continuous. At final assembly, the delivery pipes are smeared with a sealant compound and slid in a wringing fashion into these holes. I considered internal drillings to deliver lube and air into the tunnel, but discarded this as too difficult and prone to error; thus, the actual delivery pipes will enter the tunnel very much like Mike's design.
Three securing countersunk holes were drilled in both the manifold and the gearbox.
The completed fitting except for the delivery pipes.

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