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Kurt Haller RV-9A
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Date: 8-11-2018
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Number of Hours: 0.00
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Manual Reference:
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Brief Description: Jacks and jack points
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Made two jacks based on HF long body bottle jacks, as several other VAF-ers have done. (Image 1). Didn't keep track of hours making them at home.
For the jack points, I turned a ball-end on a 1/2" rod of O1 tool steel. I turned about 2/3rds of the rod to the proper starting diameter for a 3/8-16 threading die. When threaded into the tie-down extrusions, the shoulders of the 1/2" rods will bear almost all the load. Once finished, the jack points were heated in Karl's propane forge to glistening, non-magnetic heat, quenched in oil, then tempered in a 400F oven for an hour. Finished part is the inset in Image 2.
To receive the jack point, I cut up an Avery tools mushroom bucking bar into two, 1.5" dia steel cylinders. (I bought the bar with a goose-neck backriveting tool that never worked all that well on the wings.) I turned a 1.25" bore on one end of the cylinder to fit over the end of the bottle jack's ram. In the other end, I drilled a hole about 1" deep with a 0.75" dia drill, which formed a 120 deg cone at the bottom of the hole. (Image 2.)
I would have preferred a smaller included angle for the cone. To help keep the ball end better centered, but allowing several degrees of tilt in any direction, I got some soft (Shore 20A) 1/2" id tubing, and put two layers on the 1/2" diameter part of the jack point, leaving the ball end exposed. (Image 3.)
Ironically, when I brought the jacks to the hangar, the left main was flat as a pancake. Jacked it up and got the wheel apart--nothing apparently wrong with the tube. Dunked it in a sink full of water--no bubbles EXCEPT the out of the valve. A piece of schmutz created a slow leak, maybe? Not having another tube, I blew out the end of the valve with compressed air, reassembled the wheel, inflated the tire, and screwed on the rubber lined metal valve cap tightly. [Tire was full a week later...]
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Big red jack
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"Ball and cone" jack point
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Jack point installed in wing
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