1353

Item 1353

DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Root End Layout

Mockup Picture:

Sketch:

Drawing:

It will be rotated 22.5º so that it can be split vertically, with four bolts on each side.

Note:

Spar Attachment Bolts: Place the nuts inside the spar and have the spar root flange stop them from rotating. The bolts are located on the outside and are wire tied.

Spar Root Flange: A second flange will be required between the tow and the pitch horn so that the root pitch horn has something solid to be tightened against. Alternatively, this flange could be a part of the root pitch horn.

Spar will probably have to be prepreg tow and wrapped in cooler/freezer because of the long time between the start of wrapping and shaping for the curing. Or the towpreg will be at room temperature and require heating to cure.

If 0.70 in²is area of carbon thread at blade root, at top and at bottom, then there are a total of 1.4 x 1773 = 2482 /2 = 1241 strand looping around the upper studs and 1241 strands looping around the lower studs. Note that 1241 strands is 620 loops. If they loop around 9 studs then there are 69 loops per stud. If there are 9 tows per layer then there are 69 / 9 = 7.6 layers. The pin to pin gap is only sufficient for 4 (possible 5) layers, therefore there must be 2 sets of (9 * 4 = 36) groupings per pin.

Tip Pitch Shaft: What about having the Tip Pitch Horn connected to the Root Tip Horn by a bearing. Then have the shaft to the Torque Tube firmly affixed to the Tip Pitch Horn and float inside the Torque Tube.

Problems:

Are the eight bolts strong enough?

How are they replaced when nuts have been removed?

How does the bearing go in?

Possible solution:

Wrap the tow around pins that are covered with a release agent and are the same diameter as the bolts to be used. This elimination of a tubular sleeve will optimize the bolt size and wrap area.

The root end of the torque tube will be 2 or 3" shorter than the spar root. This will allow the eight bolts to be inserted from the inside.

The pitch arm will have a post which is round close to the pitch arm, to take a pitch bearing. further out it will be square and fit into a square hole in the root end of the torque tube.

Re Bolt Strength to handle centrifugal force. See following sketch; Note instead

Tapered 2-part sleeve inside tapered 1-part sleeve with bearing riding on outer sleeve

If electrical control consider electrical linear motor located inside the the spar for root control ???

New Notes Related to Change of Shape of Root Flange: August 1, 2005

Tow Tape Width:

360º / (8 * 2) = 22.5º

(2.5" dia * 22/7) / 16 = 0.4911"

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Last Revised: August 1, 2005