Model Engine Dyno

I am also a R/C modeler and have flown U/C speed years back. I did a lot of modifications to engines and ran across the same problems your having. I used a "simple" method of keeping track of modifications by just using a simple model engine tach and known propeller sizes and pitches. For example I would note the rpm of a given prop such as a 10/8, make the mods and simply remeasure the rpm. This won't tell you the horsepower but will certainly tell you if your mod has made an improvement. Try to do this under the same conditions as far as temperture and humidity goes as this has an effect on the performance of an engine. When doing the testing I try to reset the needle valve each time to similate flying conditions. A too lean engine may give you higher rpm but will not develop more power as the prop tends to unload as the engine is under flying conditions. This is just a simple means to see if your heading in the right direction. It gets to be confusing because when you do a mod it might be nessesary to change fuel such as the nitro content as that will have an effect on the "timing" of the engine. Good Luck

We used a spring scale tied to the tailwheel and recorded the different readings. Adding a fan blowing through a simple duct with reducing dimension to up the wind velocity and some vanes in the duct to clean up turbulence provided simulated airspeed. This rather agricultural system was really effective in: 1/ tuning the motor. 2/ finding the best propeller setup for the motor as tuned for the area of performance we were looking for, stunt, combat or outrite speed. Happy tinkering and good flying. Bush Driver, South Africa.

I bet you could measure the electrical output on a small motor driven by the RC engine .I have a nose type starter on my airplane that could theoretically be a driven generator maybe a less torque motor like an old sewing machine style could be adapted and measure the electrical output .It could be put under load to simulate conditions as well using different known hp driven electrical motors to verify output or large bulbs to visually see brightness .

Watch your fingers !!!

How about a hydraulic motor paricidic load.

http://www.land-and-sea.com/images/dyno/eddy%5Fcurrent/micro%5Feddy%2Dcurrent%5Fdynamometer.htm

I run R/C race boats, and several of us have built inertial dyno's good for up to 40k rpm. The difficult part is the coupling to the engine. Also, if you use a multisegmented optical disk for the rpm pickup, you can see the change in angular velocity through 1 cycle. You might be surprised by the level of variation in RPM through a single 360 degree cycle. We had to settle on a single slit on the optical wheel. Different drums are used depending on the target HP and RPM.

A small inertial dyno is interesting. Please join CD4 and become an active contributor. I'm sure you will find like minds in this eclectic group.