Today all major components were finally finished. After some polishing and cleaning we started assembly. This photo shows two gear-wheels before a housing was put around them. Later it will be filled with transmission fluid to lubricate the wheels.
Our gearbox reduces high RPM from our engine to an optimal rotational speed for our rotor.
To protect our sensors from the environment, we, as a start, created a mould.
Into that we lay special glass fibres which are almost transparent to radiocommunication.
Finally we could assemble all individual parts to create Ephemerons center structure and core.
It houses our engines and most of our drive system. Also our tank and gearbox are attached here.
Our payload compartment will be similar. From these two parts, struts will be attached to support our duct and control surfaces aswell as our landing gear.
Our first rotor blade was supposed to be nothing more than a test for the process of building other rotor blades. However we were curious whether it could hold up to aerodynmaic forces so this blade could create thrust for our test rig.
Our test rig’s goal is to obtain values for aerodynmaic forces of our rotor and duct. For that we need a rotor with the correct geometry. Our first test rotor is very heavy and has a weak point at it’s root. Therefore we were suspicious whether it could hold up in our test rig.
However, we were proven wrong: It was able to carry four times the load which it endures in our test rig. Actually we didn’t have enough containers of water to simulate aerodynamic forces, so we filled up extra large containers which fit 12 kgs of water each.
For hovering, Ephemeron’s whole rotor will create 25 kgs of thrust. Our rotor blade for our test rig has proven capability for loads beyond 100kgs.
Having planned all day for work on our duct mould, the whole team gathered to prepare and conduct laminating with glass fibres and epoxy based resin. As previously planned, we couldn’t make use of our hot-wire-cutter as our foam was to resistant to it and styrofoam on the other hand would not have survived a pressure differential greater than minus ~0.2 bar. To achieve good compaction at least -0.8 bar would be desireable.
For that reason we bent strips of foam around the existing foam to approximate our final mould and it’s gaps were filled with milling flakes. Then we split work between actually laminating woven glass fibre layers ontop of the foam, mixing resin and cutting glass fibre layers aswell as “peel ply” which will allow spatula to adhere to our laminate after curing.
The glass-fibres will give our mould enough strength and rigidity to withstand enormous forces from vacuum. This will be necessary when finally laminating our duct in order to use the pressure differential to really press our laminate into the mould.
Next week we will start applying spatula which will be shaped by our milled duct-profile.
All day until late in the evening we began setting up our workshop and started building a mould for laminating a carbonfibre-reinforced-plastics (cfrp) duct for aerodynamic tests. Later we will use the same mould to do an infusion of our final duct made from sandwich cfrp.
Due to its size and to achieve a nearly perfect circle we use a cnc-milled aluminium profile which is fixed to an arm, rotating around the mould’s centre. Initially foam was cut roughly and tommorow we will add a layer of styrofoam which will be hot-wire-cut to approximate the shape of the duct. Then spatula will be shaped by the aluminium profile to accurately model the mould. Ultimately glass-fibre-reinforced plastics will be laminated ontop to provide enough strength to the mould.
We are excited to see how far we can get during this weekend.