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Tom's Web Site
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Date: 8-8-2009
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Number of Hours: 3.00
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Manual Reference:
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Brief Description: Trim Wheel -- tubing bushing reducers
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QB Fuselage #59 is unique as the trim wheel supports were made from 0.500" tubing. There might be three other fuselages as I think they are built in groups of four, but my tubing ID is approx 0.380". NOTE: Drawings specify "T4" tubing in that location 3/8" x 058" wall. So ID is close to 1/4" for AN4 bolt.
Bob Barrows has a recommendation for mouning the Avipro trimwheel, but is based on different size tubing. I have a hard copy someplace, alas ECO are not published on the web but by newsletter only.
Back to my solution. Using tubing to size down the ID to 1/4" for AN4 bolt just means that tubing will spin around. Loose cables, or a loose trim wheel, both can cause flutter. So needs to be addressed. If the trim tab is loose (flops a little) STOP FLYING! Find out why, and fix it.
Picture 1 -- started off with 1" wide 0.063" 4130. Idea was to bend to capture the tab. Once further down the road, realized a simple 5/8" strap would be a better solution.
Picture 2 -- with 5/8" strap welded to some 3/8" tubing (OD 0.375 - 0.065 wall -- ream to 0.250") Brass bushing to take up the space. Two 0.010" shims will be made.
Picture 3 -- everything fits! AN742-8 clamps (two) will be used. This allows the bolt to be adjusted to give approx 3# pull force at the trim wheel.
Only one strap is required as it will prevent rotation.
Other option was to cut off those 1/2" tubes, grind the welds down, and weld on the correct T3 & T4 drawings.
BEST OPTION: Just locktite the new tubes in place. Actually locktite just one, so you can still R&R the washers as needed
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This idea didn't work as planned
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brass spacer machined to size
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Need to add straps. Shim bolt for proper pull force
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