2-stroke engine weights ....

I pursuit of perfection and a really small pusher I have ended up using simple APT or Limbach 2-strokes for one good reason...excellent power to weight ratio.

Typical 2-stroke aviation engine like Rotax would weight 45 kilos and produce 40 hp.

engine: http://www.ultralightnews.ca/rotax447/rotax2strokepdf/weightcg2strokenges.pdf

gizmos: http://www.ultralightnews.ca/rotax447/447info.html

I would really need 40 hp to carry all that extra weight compared to 6.5 - 7.5 kilo engines of 20-22 hp.

Thing is that Max III needs powerplant of non reduction geared engine because the transmission to the shaft has a possibility to do a reduction..in a very light way. Like in Bede-5B.

Also the internal systems of cooling and position are easily obtained with this kinda layout...another advantage is that the engine of this lightweight and size can be placed further in the fuse and a short shaft is needed; this will further reduce weight and vibration caused by this type of engine/shaft/propeller combo.

The best engine of all would be Axial Vector Engine for the incredible power output and torque. In fact an AVEC engine would produce at the same weight as Rotax 447 enermous 200 hp ( 5 times more ! ). I have hard time even imagining how fast that type of engine could propel MAX III type AC..certainly close to 400 mph with close to 1:1 power to weight ratio ( even the world fastest racers don't produce those kinda figures ).

Here is S Stefanuttis 1936 designed pusher with 15 hp 2-stroke engine:


Solid proof of the economy of a pusher.

Here is the original FLEA with 17 hp engine..this shows the small size brought avantage:


The Flying Flea was just as long as Max III 3.5 meters: http://en.wikipedia.org/wiki/Flying_Flea


  1. Why reinvent the wheel? Your design looks like the Vmax Probe, so why don't you just go ahead and build one?

  2. Yeah it looks like VmaxProbe...which had crisifix tail and was 4 ft longer and had fixed undercarriage. Also Vmax had 4 x times the output and was 60-80 kilos heavier.

    Like comparing Skyraider with a Bearcat...or fixed gear Ta-152 H-1 with a Heinkel He100D.

    Thanks for the comment.

  3. Most of all it's like comparing a well designed, top notch built, proven to fly aircraft with a one that's never going to be more than a 3-view drawing...
    BTW, you didn't answer the question - why not take a ready made good design of the VmaxP and build one according to their specs?

  4. See new topic to get some answers.

    Please use at least a nick.