Oil Pump "Pack"


After the oil tank was fabricated, work proceeded on the electric pump assembly to provide power. Keeping things modular, this unit was designed to be mounted in place with thumbscrews and can be removed in its entirety.

  For a pump, I used my old Orbit pump which has successfully run my MW-54 for so many hours. A custom top plate was made of aluminum for the fittings seen here. Due to the odd shape of the pump, slots were cut in the 1/16" aluminum channel so that the pump lays flat. A single FHCS secures the pump to the channel
Plumbing was bent and fitted for both the pump feed and output. These tubes can be tricky to make... rarely has the first attempt been successful - either the tube kinks, or the bends are incorrect. Persistence pays.

Here, the lower tube carries oil from the tank to the pump, and the upper tube delivers oil to the gearbox.

Before finalizing everything, I did some tests to find a suitable battery combination. A single cell, either NiMH or NiCD, provided a rather weak flow. A 1600 mAH NiMH provided this flow for perhaps 11 minutes, marginal at best. A much better combination was a pair of cells, for a 2.4V source. 2 ea 1600 mAH NiMH batteries in a nylon holder provides a strong oil stream, and the higher voltage appears more efficient, powering the pump in excess of 20 minutes. That's when I terminated the test.
In action, but without the big prop gear. The arcing upper oil stream would intersect the mesh of the small pinion to the missing prop gear. No problems at all draining the oil. In use, the rotation of the gears would spray a lot of oil on the walls of the gear box, but in this static condition, the level of oil, witnessed by the sight glass, dropped only a millimeter or 2.
With the batteries selected, the 3 important components were fixed in place. The pressure switch can be seen in the fore. It is a very simple device, not as sensitive as Mike's, but more compact. A piston of diameter .420" is driven by pressure to actuate a microswitch. An O-ring on the end of the piston seals under pressure and prevents leaks. It closes at perhaps 1.5PSI, which is well below idle pressure, and since it is tied to the propane line, it will be positively closed during the startup sequence.
The final location of the "pack" was on the left side, as viewed from behind. Note the brass thumb screws which hold the unit in place. The aluminum angle acts as both a mounting bracket and a heat shield.

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