Has anybody used a contra rotating prop setup yet?

Think of the possibilities.
No gyroscopic precession, and the look.......WOW!!!!!!
Scale Seafires etc.....can't wait!!

I got a Himax 650 watt system which is basically a set of 2814's or 35-36's whichever you prefer.  Both motors are 1050 Kv and specified to use 3S on a 12 x 6P front prop and 11 x 8 rear prop.  I ran on the bench and system runs quite well.  Problem is the weight.  The motors together weigh 10 ounces and would require (1) 3700 3s pack per motor so that would drive total battery weight to say 20 to 22 ounces.  Then add in (2) esc's and that is another 4 ounces. 

The reasoning for the smaller higher pitch rear prop was to first stay out of the front props tip vortices and second take the already accelerated air and move it faster.  I did try to run (2) 12 x 6's and was amazed at how loud the system got and also how much higher the current was on the rear motor.  This obviously confirmed Maxx Products claim.  The sound is amazing though!!!

I considered going to 4S and running smaller props, but the prop selection got dismally thin.  A 10 x 5 on the front and 9 x 6P on the rear ran very nicely on 4S, but still the total system weight was way too high. 

To me, the weight of the system and added complexity didn't justify any performance advantage.  The Himax contra-motor system is very nicely built, but I was going to have to change a few things to stiffen it up as I was not convinced it would hold up under CLPA loads.  The front motor does have a support bearing in the rear of the bell housing, but the 5mm shaft was ground down to 3/16" for the front prop.  The rear prop is driven by the front motor and rear motor drives the front prop.

I had drawn a 650 sq in Miss Ashley II for it.  I have always liked that airframe.

Archie Adamisin
Muncie, Indiana   

Hi Archie,
What you want to do is run the front motor at constant RPM, and then build a circuit that slaves the rear motor to match the current draw to that of the front motor.
Prop sizes are not of prime importance here, just that matched currents equal matched torques and no spiral airflow.

Dean P.