Monday, 2 May 2011

Close is easy, Identical takes longer

Next were the aileron hinges, 3 of which are required on each lower wing.
I was not looking forward to making these, as I knew that there could be no allowance for error, and they would have to be identical.
The ailerons are mounted on the lower wings only, and they are attached via a round tube spar to 3 hinges bolted to the rear spar.
The ailerons are of a mixed construction, with a steel tube front spar, steel plate and tube hinges, steel rib attach fittings, and aluminum ribs, rear spar, leading and trailing edges.
They are almost full span on the lower wings.
And they seem to have be very suseptible to potential binding, maybe that is why the original never fluttered. :)
The hinged section seemed like the natural place to start, and as they must all be identical, another assembly fixture was required.

This is the first fixture I built, it allows the first part of the aileron hinge to be welded up. Shown behind are the tubes all cut and shaped to size to fit inthe fixture and mate to the larger spar hinge tube.
I then made a separate fixture to sand the forward tube ends to mate to the U shaped bracket accurately.
Once the first part is welded and match sanded, I then needed to make the U shaped sections which fit over the spars, and there is NO room for error with these. each must be an exact press fit, which is harder than it sounds when you are working with wood to metal, but in the end (after about 15 which did not work as well) I ended up with 6 exact U shaped sections, bent to the correct dimensions and drilled.
The lower wing spars have a 7 degree upper taper and a 3 degree lower taper, which must be bent correctly in the fittings, then they are bent to flat after the spar to match the attach block. (otherwise the bolt head and nut would not be parallel to the fitting)
I then built this fixture to weld the U brackets to the spar attach tubes accurately. After I tried to weld the first one, I had to change this, and substitute a steel spar section for the wooden one shown due to the wood burning. It took almost a week to have the steel spar section machined up by a shop to the finish spar dimensions.
It is now a completely useless block of rather expensive spar shaped steel.

The final hinges are all indentical, and once attached to the real lower spars should hopefully line up accurately with the front aileron spar.
To build the 6 hinges three separate fixtures had to be built. It took much longer to make the fixtures than the actual hinges.

1 comment:

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