By Allan Flowers
This project started almost a year ago on a Google Image search when I discovered a very strange and interesting airplane. Having been thinking of starting a new project, I was intrigued by this odd challenge.
The Gallaudet was powered by a mid fuselage propeller driven by a ring gear – by no less than twin Duesenberg engines. The first version of this design, the D-1, actually flew in 1916 and was a proposal for the US Navy, which subsequently commissioned the Gallaudet Company (Connecticut) to build two more, the D-4s. One later crashed when the propeller failed, killing the test pilot. The other flew for several years, ending its life as a Schneider Cup racing plane. These were quite large planes, with wingspans of about 48 feet.
My first design was to be 1/6th scale at 96” WS. Along with the issue of the unusual drive mechanism, the ability of the single main float to provide sufficient buoyancy for a 20lb model was a concern. My CAD program has a mass properties function but it wouldn’t give me consistent answers so I solicited some help from fellow modelers on RCSB where I had started a “build thread”. Based on their calculations, combined with measurements of my Scion (which had to be used to transport this thing), I decided to consider a different scale. Around this time, a gentlemen who had seen the build thread, sent me some info from WW-1 Aero Magazine, which showed a drawing of a smaller Gallaudet proposal for a “hydro scout” (also from 2016). It had a 28 ft WS and larger a tail-fin and ailerons. This plane could be made in quarter scale with a larger float but smaller wingspan than the D-1.
The United States was soon involved in WW-1 and lost interest in the hydro scout programs. Thus the Scout was never made but the drawing had enough detail to interest me in a build.
The early CAD designs established the parameters of the drive mechanism and enabled a search for components, mostly from McMasters-Carr – which provides CAD models to download and pop into my system. The main parts were the roller bearing and sleeve which could be slid over an aluminum tube which would join the front and rear fuselage sections. Also important were some thrust bearings and seals to complete the drive.
Next was finding sprockets and belts to power the thing, and a suitable electic motor of small enough diameter to fit in under the main aluminum tube. That boiled down primarily to a few Hackers and Neumotors. The final choice was a Neumotor driving 13 and 44 tooth sprockets through a 15mm belt. Because of the gear ratio, a high KV motor was a necessity. E-calc was very helpful in researching the motors, ESCs and propellers. The later was a big challenge because there are no multiblade props that would work with the unusual hub design.
