Wednesday, November 30, 2022

Half-Scale Build #71


I completed the foot-well having elected to cut out an 8" diameter hole in its topside to facilitate passenger ingress. Meanwhile back at the top end there is a use for these sockets that are more normally used to fix poles in wardrobes. They also help locate our own poles during assembly in the field, whilst bolstering rigidity to some extent.

You might be wondering why I've chose to fix the rotorhead in position rather than have it rise into place with rotors turning prior boarding? Well at full scale that will be a flyer, the aircraft poised for lift-off and me racing to board under fire in my fatigues, looking very much like Robert de Niro in the Deer Hunter.

The mannekin though will race nowhere on fibreglass legs and if the vehicle won't fly with him anyway, we've more serious issues than whether the rotorhead is sliding to spec.

Top tip: orient the sockets as shown so the rivets don't catch the tubing inside.

Half-Scale Build #70


With mannekin centre-stage, mark around the feet. We'll be including a circular hole, as I don't want to take bespoke tailoring so far as shoe-size. Nonetheless it allows as economical a cut-out as possible, so as to preserve the structural integrity.

There's a twist crept in somewhere, mainly because at at this rapid prototyping stage I'm working to a millimetre. Airbus do have rulers that measure microns, but we don't.

Half-Scale Build #69


Here's the new 9mm ply pattern bolted into place, and doesn't she look pretty? You'll have noticed there's a serious omission in the form of a hole to stand in, which we'll get to next.

Half-Scale Build #68


Get my best ideas at three in the morning generally and figure I can lower the profile of the foot-well by using an identical pattern to that of the mid-riff retainer aka flight-deck. To do that I've taken an inch off the uprights at each corner (now 2.75" each) so as to include a threaded M6 insert. If you've been following my instructions and can't believe this is the second modification to the wheel-well, then bear in mind that it's a character-building exercise you'll get no place else.

Tuesday, November 29, 2022

Static Load Test


One for archives? The rotorhead took a bit of walloping with a rubber mallet to knock it into place, but I've built dozens of frames and they rarely needed wrapping in cotton wool. I did carry out a risk assessment for this exercise that concluded it might end in injury or death, but as it wasn't my 'cock on the block' I gave it the go-ahead.

That's 40kg or nearly 90lb up top, supported by sixteenth-inch tubes 19mm diameter. Engineering students among you will know that the columns would eventually fail by splaying apart, buckling and crushing Monty in the process. What prevents this is the flight-deck, set at 500mm above the foot-well and cutting the effective length of the columns by 50% to increase their strength disproportionately.

They test airliners to destruction during development, bending wings up with hydraulic rams until a horrendous BANG as they fail at the root. I'm not going to do that here, but I have decided to up the width of the columns anyhow to a full inch. Yes it's over-engineered, but I prefer to come at it from that direction than the other.

Half-Scale Build #67


I've made the decision to test the prototype in the first instance with the rotor-head locked in the uppermost FLIGHT position, and as a result I've been able to reduce the circular tubes to just 1050mm and need only drill the centre-section of the top end at 6mm instead of 20mm or thereabouts. Here I am allowing for the internal width of the alloy sections and positioning a bracket to match the bottom and middle sections of the air vehicle.

Quiz


Study the above carefully. It's a...

    (a)    Minecraft Polar bear

    (b)    Personal air vehicle safety-restraint

(4 marks)