View Full Version : Radikal Gear Ratio Testing

James Kovach
12-27-2009, 07:41 PM
So far I have flown the Radikal with the 6.0 and 6.4 gear ratios. I have been loggin in flight RPM and Engine Temps to find the "sweet" spot of the stock Zenoah G20. Here are my findings so far.

The first graph is about the engine temps. I lost the data for the other flight that I will be referring to, but you will get the picture. Notice during that flight how the temps are staying pretty consistent no matter how loaded the head is. That particular flight was with the 6.4 ratio at 1900ish RPM. I had another flight logged, which I lost the files for, that was on the 6.4 gears at 2050ish rpm. On that particular flight, the engine temps were even more consistent. This tells me that the engine is "happiest" running at that particular engine RPM, 2050*6.4=13,120. So that is probably a good "target" rpm for the engine.

The second graph is RPM logs from 3 different flights as follows:

- 6.0 gears at 1900ish RPM
- 6.4 gears at 2050ish RPM
- 6.4 gears at 1900ish RPM

The thing you will notice is not matter what I have my limiter set to, when the head is loaded during flight, they will all fall into the same RPM range and stay there. The only time it will go back up to a higher RPM is when the head is unloaded. So looking at the graph, it seems that 1800-1900 RPM is going to the max this engine can sustain when loaded. I know it is falling below that in the graph, but I have not flown the 6.9 gears yet, so I am making a little bit of an assumption.

What you cannot see that well in the graph because it is pretty cluttered is how the RPM recovered after being loaded. The 6.4 ratio definitely recovers quicker. I suspect that the 6.9s are going to be even better as you will be able to run the 1800-1900 rpm with the engine being up in the Higher 12k to lower 13k range. I fully expect that when I get to loggin the 6.9 gears, you are not going to see it fall off the target RPM as much and when it does it will recover very quickly.

I will post more info when I get a chance to fly the 6.9 gears.

12-29-2009, 10:24 AM
James, for a sport flyer should I just stick w/the stock 6.0 gears? Going to use ThunderTiger 620mm Carbons and a AR7000r. Got it setting on the bench to build, but haven't even opened the box. Long time ATTF/INHE listener.

James Kovach
12-29-2009, 12:53 PM
It will fly just fine with the 6.0 gears. This video was shot using the 6.0 gears running 1900rpm


It flies just fine. But if you want to get the most out of this engine, you will want to get the 6.9 gear ratios. That will require buying the 90T main gear and 13T pinion.

12-30-2009, 10:17 AM
Thanks, I think I'm going to do like you. Fly it stock till us mere mortals can get hands on a TotalG.

01-01-2010, 07:55 PM
Been flying the 6.9 gear ratio for 2 weekends and it is working very well, with rt 620 widechords and 12 /12 pitch it pulls like a tractor:YeaBaby:running 1900 headspeed the motor is very happy and holds headspeed very well.

01-27-2010, 06:29 PM
^^^That's the same set up I plan on using. I bought a Century Radikal LT Carbon. I am going to use 6.9 ratio and the Century Flybarless head. I plan on running RotorTech 620's.

01-27-2010, 08:55 PM
^^^That's the same set up I plan on using. I bought a Century Radikal LT Carbon. I am going to use 6.9 ratio and the Century Flybarless head. I plan on running RotorTech 620's.
the flybarless should really add some pop.