Aero Question For Ted, Brett and Igor

What if you could really have a constant RPM? I was reading through the instruction manual on my electric speed control (ESC) from Castle Creations and it shows a governor mode used for helicopters. It is used to keep a stable rotor speed for the more advanced adjustable pitch (collective) rotor heads. It tries to keep the same RPM all of the time regardless of load, and will as long as the required power to turn the rotor is below or at the max motor output power. SO, what if we then use one of these on a C/L Stunt plane in constant RPM mode? Level, up, down and everywhere in between we get the same RPM. We should then have an almost constant airspeed. It seems to me that this should be a good thing. Or is it a bad thing?

Thoughts??

Mel, did you see this:

http://www.slovanet.sk/orsia/electro/electro.htm

Yes I think constant RPM is probably best way for electric power train. I also tried to make some positive feedback on base of prop load to make similar boost of power at load. You can very easy measure power on shaft and regulate output on that base, but it leads to troubles. Adding is easy but back step is difficult and can depend on model /prop. It could be difficult to adjust. BTW we have same problems with piston engines. It jumps “on” easy but going back can make problems.

So I think the constant RPM run is best, however it will cost stronger engine and to find proper prop. Unfortunately prop for this type of work is different than we are used on piston engines and it looks it will need little more development. I was surprised after first tests with electro – if I compare it with piston engines it looks “everything is different” – what I learned on piston engine, does not work on electric (no I do not mean priming or oil type ).

I do not think that regular Heli regulator is useful. At least I did not find any useful. I tested some of them and I always found "some" small trouble preventing serious usage. It needs regulator for planes, but with regulation of RPM instead of PWM power. So I decided to have different software in the same hardware. You must just convince producer to do it for you or convince him to burn your software to the unit. It is not finally finished yet, but I think it is on good way. Actually I wait for newest test version. But basically after tests of older version I can say yes it is good thing. It works well and it is far better that usual constant power R/C mode.

However it IS more expensive solution and I would like to see it on brushed engines. It could be more price effective. … (Yes I am working on it … slowly but safely.)

Hi Igor,
Interesting! I am going to email the guys at Castle Creations and see what they have to say about a C/L specific software revision for their speed controls. The really nice thing about their speed controls is that they are programmable by the user from the CC website with the purchase of a $25 adapter. You can set all of the programmable features as well as download the very latest S/W for that model of controller. They will need to know what works best and what we want, so when you get results that are positive (or maybe even raw data), let me know. The CC guys are nice people and their customer service is among the best in the industry. Maybe we can get lucky and they will listen.
You make a VERY good point about props. I may even edit the "thoughts on electrics" post above to make sure it does not get lost. I have found that the props developed just for electrics are MUCH more efficient than nitro props. There has been a great deal of development by APC and some of the high end folding prop manufacturers. Blade shape, size and pitch over the length of the blade have optimized for R/C and now we need to re-look at them for C/L. APC might even be willing to hear some thoughts about an C/L specific electric prop.