Dynomometer build (for air-screws)

1/2A Nut wrote:Dumas uses 1/8in solid steel drive lines, 1in prop with 1in pitch so at .062in you are pushing it. When the flex cable winds up under load you have to make sure the raps are going the right direction to tighten as the prop loads up the line. A cut down Octura 27mm x 1.4in pitch to 24mm dia may keep the cable from breaking. 2mm wire drives can handle 70 to 100w tops you're at 1.6mm If you use a reed engine you maybe ok should be about 65w given a TD can do up to 80w.

Thanks for that info! Yes.. the .062" cable-twist is in the correct direction.. so it shouldn't bind inside the tube. I also really enjoyed reading the 1/2A boat thread over on RC Universe. Lots of great tips there!

I have the Dumas H5-2306 running hardware kit.. but I wanted something lighter in weight. I'll also be using the "Ace-style" venturi throttle on the engine. Not sure how I'm going to connect the cable fittings yet. A small collet assembly would be great on the engine-side.. and would allow for replacing a broken cable. Octura makes a coupler for 1/8" shaft with .062" collet for music-wire. A 5-40 screw has an approx. dia. of .123" so I guess that would be the one to get.

I'm still unsure of how the entire drive-line "mass" will affect a throttled engine. I will use a flywheel of some kind, to facilitate starting the engine.. but I don't know if or.. how much rotational/inertial mass is needed to keep the engine running. Where I will have throttle control.. the concerns of over-revving can be dismissed. I do enjoy the challenges associated with trying something different.