Second aircraft engine being unpacked

The engines needed to be run for a little over 5 hours before they were ready for use.  Here we are breaking the engine in on the Mark I frame.

A 105hp engine puts out a lot of wind when it's running

The propellers were driven by two belts, but they never caused any problems

Wiring up the new control box by scavenging some components from the Mark I control box

The electrical system was complicated to say the least

The original wheels couldn't handle the weight and had to be replaced several times

The original design wasn't strong enough for the gears, and you can see the steel tube simply bent under the pressure (it was straight before the test)

Those magnets hold the bar in place as it's being welded

View from the pilot seat of the gauges (left) and power controls (right)

Eventually gearboxes were made to prevent the gears from becoming misaligned

In early tests the duct flexed and the propeller ground away the fiberglass!

That rough area shouldn't be there - at one point the engine wasn't putting out as much power as it should have and we discovered that one of the plates holding a bearing was being ground down.  A small spacer soon took care of the problem!

At one point we tried measuring thrust while it was running, but instead it simply destroyed the scale the foot was on

Eventually the control flaps were also controlled by servos so the entire device could be controlled by remote

The remote control servos, and the computer that controlled all the remote components

The Mark II remote control box - hand made from clear acrylic

3D printed duct when glued together and mounted

3D printed duct when glued together and mounted

The 3D printed duct failed at full power and was utterly destroyed

Aftermath from the 3D printed duct exploding - there were plastic pieces everywhere...

This is all that was left of half the duct - the rest was smashed to pieces smaller than a dime

Ducts were made by pouring expanding foam into a 3D printed mold and then fiber-glassing over it

Sometimes ducts didn't come out at the exact right size and a spacer was needed to widen the duct (so the propeller could fit inside!)

Each side has various power switches and start/stop buttons for the engines

Pieces of a towel that was shredded on the first successful test

This was what remained of a full-size bath towel that went through a propeller