I am not familiar with that motor, but I think a 900kV motor is better suited to a 4s battery setup. On some of my motor tests with an 880kV motor running at 8000 rpm, the 3s pack ends up needing full throttle from the ESC just to maintain the 8000 rpm in level flight power levels, leaving nothing extra for maneuvers. A 3s pack needs a kV in the 1000-1200 range, depending somewhat on what your target rpm is--determined by prop load. The detail to remember is voltage available will be less than the nominal lipo voltage (just battery internal resistance) plus the drop in voltage as the battery discharges. Another detail is that at least for me, maneuvering power is about 30% higher than cruise power (as I recall, you can look at the peaks in the data plot I gave in response to your energy question). So you need to keep that sort of reserve available, even at the end of the flight when the battery voltage has dropped.

Here is a plot of a "typical" discharge. The horizontal axis is how much charge has been pulled out, the vertical axis is the battery terminal voltage, and you have different curves for different current outputs. Recall a 10C discharge implies that you have pulled out all the charge in 6 minutes.

I am not sure about constant power ---in our case we need more power for maneuvering. So the constant rpm mode makes sense--as the load goes up, the power increases to keep rpm constant. Not that it wouldn't be nice to get an extra boost in rpm when you needed it, but that requires something smart figuring out when to give you the boost (I call it Fox 35 technology!  ).  All the Castle Creation Phoenix ESC's have the governor mode. Their cheaper ESC, the Thunderbird does NOT.

Charles,
how many watts is the turnigy capable of producing? for sport flying and light manuevers something around 110 to 120 watts per pound of airplane would be ok,,, but for flyign the pattern the standard is to be able to generate more along the lines of 150 watts per pound so for an airplane that weighs 48 oz ready to fly ( three pounds) you want to be able to generate in the neighborhood of 450 watts

Thanks!

I ordered one of the 1100 k/v motors last night. Now I am mulling over a controller. They do a 40A one that has governor mode (with a little programming card)

Charles

If you want a Phoenix Todds Models seems to have about the best prices on them. The 35 amp is $62.99 and 45 amp is $79.99 http://www.toddsmodels.com/Castle_Creations_ESC_s/39.htm. If you prefer something else Hobby City has the TURNIGY Plush 40amp Speed Controller for $34.95 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=2165&Product_Name=TURNIGY_Plush_40amp_Speed_Controller and it's $6.95 for the programming card if you need it. I have a Turnigy but haven't used it yet. I am sure others can comment on its performance. See above which got in while I was typing this one.

I agree with Mark and only use the Pheonex speed controllers on the planes I fly more seriously. If I use the Turnigy at all it will probably go on a ARF Flight Streak that I will convert for my 12 year old son who is still learning his stunts. In any case I am home from work for at least a week or 2 with a broken finger and 3 stitches so maybe I will do some ground testing on the Turnigy.

CharlesF
As Mike indicated I have experience with the Turnigies - I have 5 Turnigy 40A ESC's - but they are now all in a box.   

The problem is that they do NOT govern to maintain a set rpm.  Thus your motor speed deteriorates as the battery wears down.  Will Hubin did some bench tests that show it MIGHT be feasible to use the Turnigy IF you also have a "throttle up" or compensating timer that increases throttle setting over the course of the flight.  There are a couple such timers out there (and I am not familiar with all of them),  Will has the FM-1A timer which actually ramps up the throttle over time to try to maintain a near constant RPM.  I have some FM-1A timers and I am going to try them with a Turnigy ESC in a OTS sport model this spring.  I have no illusions that it will perform like a Phoenix, but I am hoping this will let me recoup some of my investment in Turnigy ESC's!

My expectation is that the FM-1A timer with the throttle-up functionality will make the Turnigy ESC into a workable piece for a sport model - without the "throttle up" the Turnigy it is virually unusable for CL.  They should work OK for RC though.

Another problem both Will and I have noted with the Turnigy is that they seem to be a little unstable with heat - but that has been harder to pin down.  My brother the 'puter geek is fitting all my Turnigies with CPU heat sinks to nullify any possible heat issue.

On the plus side: The Will Hubin Timer with Turnigy is very easy to set-up.  Will's timer has easy to set controls - when you use it with the Turnigy controller all you need is a small Phillips screwdriver & a tach to set your target RPM - no PC required.  The Turnigy programming card is easy to use, and the ESC WILL let you set "governor" simultaneously with an effective prop brake.  One more plus - The The Turnigy "Sentry"(?) series has a connector that you can plug into your LiPo balancing plug.  The ESC actually monitors battery balance.  That seems like an idea other ESC's might some day copy.

In flight the Turnigy seemed to govern during manuvers.  I THINK (but I did not get a lot of experience with this) that the Turnigy governor might deal with short duration load changes to maintain more constant RPM.  However, because you do not program a target RPM into it it has no target to try to maintain as the battery wears down.

Depending on your intentions for your ECL bird the Turnigy with compensating timer MIGHT be good enough.  For a sport model - probably OK.  I'm cautiously optimistic that it will work in a OTS model I'm working on.  However, for ECL-CLPA there is no substitute for the Phoenix.

I ran 2 ground tests with my Turnigy today on my P40 and 1 in the air test as the weather cooperated for about an hour.(No I didn't fly the new one yet). On both ground tests I ran my usual downsized 8x6 that I use for on ground testing to set up my RPM's. This speed control even with a light load could not hold the RPM at the 9000 that I tried to set it for. I was using the FM-1a timer that Dennis A spoke about. On the second test I dialed a little throttle up into it and was able to hold it reasonably steady. I then put my 12x6 APC on it and went to do an in the air test. I didn't tach it but suspect that my RPM was not at 9000 as preset with the other prop.(This doesn't happen with the Phoenix). The flight was OK but a little light on the lines. The RPM did seem to hold close to where I set it. Like Dennis I would only use this speed control for sport flying and with a boost setting on the speed control. This will work out fine if I ever get around to converting the ARF Flight Streak for my son. If not maybe I can use it in an electric powered rc glider someday.

William,
have you ever given us the details on the P40 setup? I'm kludging a recycled glow one together, and may have it in a flyable state by next week. Curious to get a starting point on power settings--prop and rpm I guess!

Thanks,
That's more or less the hardware where I'm starting, so the rpm target is useful.

I have been flying a new Turnigy SK 35-48-1100 on 4s in a converted Q-500 for 3 weeks.  The motor is a beast.  The 800 watt rating is accurate.  I have tested it @ a sustained 675 watts for 2.5 minutes and it doesn't even get warm.  I am flying it on 4S and have used from a 9 x 7.5 to 10 x 8 and haven't over loaded yet.  (Of course it is at full throttle at all times @ flying over 100 mph during this test.)  I am going to now test it on larger stunt props because I plan to use it in a 625-650 square in CLPA around 50-54 ozs.  At max power, it would give 237 watts/lb at that weight.  This motor is no slouch.  I agree that on 3S, it will need as much prop as you can give it to make power.  This motor is like the polular AXI 26-26 series which many have used successfully in larger airframes on 4S.

My 2 cents

Archie Adamisin
Muncie, Indiana