a few more pics. The last one just to show it made it up into the air1

Nice job, Alan.

First of all, 48 ounces is not bad - but please tell us the voltage of your battery packs. Two 2100 mah in parallel should give you 4200 mah total. I run two 4 cell packs in parallel with my planes and they all weigh over 50 ounces.

Don't feel bad about the Zigras. I used mine for a couple of flights and had it turned upside down for one flight. Set all the switches to the exact opposite of what they should have been. Almost choked a battery pack. 

Take care,

Ron

Alan:
Kudos, looks like you are off to a good start.   

As I learned with our recent Oriental mod: converting an "slimer" ARF to E-power is probably harder than building the durned thing that way from scratch - so I got an idea where you are coming from with this conversion!

THANK YOU also for posting the Eagle Tree data.  Sounds like you should have plenty of battery to go the distance, hope you get a few more flights before the snow flies!

...and looking forward to more of your progress!

Igor,
You are probably right. When I bought this motor, I knew that I was close to the limit of rpm and battery voltage. Scorpion gives a table where they show static rpm for various props for each of their motors. The props included the APC11-5.5 and they show that for a 10.5V input, it will turn up to 9275 rpm. Now for this flight I had the rpm set for ~9800 rpm, so yes I was asking for a lot when the prop gets loaded down. Since I am dropping the rpm one notch, I am hoping that I will just be under the max load my 3s batteries can drive. This was the lowest kV of this motor that was offered (at least at the time, but I haven't checked lately)

If it is still an issue (= noticeable in flight), then I do have the kit version of this motor which I can wind myself. So I can be the BOM (Builder of the Motor)!

Alan, if you do not want to change motor and battery, you can still try another prop, for example Apc 11x7 ... it will need also little less power

Great table, so I see with 11x7 it gives 8800rpm and I expect that prop will need 8500, may be less. I think it will be usefull. Not optimal, that pitch for such a small diameter is not the best choice, but I think still better then to loose RPM overhead.

I think the key to a classic sized conversion is a quite feasible with 3 cells, 4 cells requires meticulous attention to battery load so as to use small batteries.

But I am with you, E-power is not just possible, I am beginining to believe it is the prohibitive favorite for CLPA.

Dennis,

The concern I have with three cells is we have to produce a certain amount of watts to do the pattern and with the limited voltage of three cells, the current will go up big time. I'm sure it can be done and maybe it just takes newer technology. My old 15C batteries could not do it very well; maybe the new 30C Li-Pos can handle the load.

I am a charter member of the "More EMF" club. I like having lots of voltage available. My current controller is limited to 15 volts  (4 cells), but I'm working on a new regulator so I can move up to 5 cells. Paul Walker went this route and I think it's the way to go with a 60-64 ounce ship.

Take care,

Ron

It's been a while since I had to do any math.    But IIRC, when I first started flying electric CLPA in 2005, we figured we needed 150 watts per pound to do a competitive stunt pattern. If we plug in that need with our formula, we will need roughly 450 watts to fly your 3 pound Nobler through a decent pattern. Take that, and divide by your nominal 11.1 volts (yes, the fully charged li-po gives you a little more), then you're going to need 40.5 amps average during the six minute flight, which translates to 4.05 amps/hour or 4050mah if I calculated everything right.

It's not so much the current drain I'm worried about, it's the battery life. Pull 4000 mah out of a 4200 li-po (or 2000 out of each 2100) and you will have a short-lived battery. Going up to 4 cells lets me do the pattern with 30.4 amps (or about 1500 for each 2100 cell).

Of course, that was two years ago and we have better batteries and more experience. I have over 200 flights on my Shocker Cardinals and my real life experience is giving me a decent pattern on about 425 watts (50 ounce plane). I rarely stress my 4 cell li-po much over 1450 mah (2100 capacity) and my battery packs are still delivering good performance. I know the common knowledge says we can pull 80 percent out of these with no damage, but I learned at my job that 70 percent is a better target number.

Anyway - that's my thinking and the reason I did everything possible to stuff as much voltage into the plane as I can fit.    I realize it's very difficult to fit a four cell pack into a Nobler (or an Oriental) and that's one reason I eventually went to a bigger airframe.

Please don't let anything I say deter you from flying electric power. Your own empirical data will be your best guide. I'm a computer engineer, not an EE and I graduated from the TLAR school of design.   

Take care,

Ron

Rom:
There's a thread called "Shocking the Oriental" that covers what we have been doing so far.  I put it together but my Nephew, former e-pylon team member has been doing all the hard work.  What we have been doing solidly backs up Alan's claim that 3 cells will do the deed for a "Classic" size bird at up to 50 oz.  We do not have data recorder stuff, but gross numbers indicate roughly 2500 amps to fly the 50 oz bird through pattern at 5.5 lap times; performance comparable and possibly superior to my similar Oriental with LA40.  Average power (probably a usless parameter!) is only 90 W/lb.  Now here's the kicker, we started using Brodak SuperClown system, but replaced the ESC & timer to enable us to us a bigger prop at slower speed to control the airspeed & wind wind-up still using Brodak motor and batteries.  This is NOT a hi-tech set-up!

After our experience and from discussions with Bob Hunt, I am convinced that 5 cells will be impractical (too durned heavy!), at least until the NEXT leapfrog in battery design.  But no matter, 3 cell and 4 cell systems can definitley do the deed, and folks adding their experience with 5 cell (& more???) will continue to expand the knowledge base.

I'm trying to figure out what to do with my accumulation of slimer engines..!

Mike:
I'm thinking too heavy for any.  Seems like when you start with the big pack it spirals through big motor, big ESC, big prop, big airframe.  That big airframe has to gt stronger in areas like controls and landing gear - pretty soon you have a 70+ oz bird. 

Put a better way, (and counting recent history) I'd rather got to battle with a 52 oz bird than a 73 oz bird - the lighter airplane outperforms the heavy one every time. In fact I'd take a 42 oz bird over a 52 ouncer 10 out of 10 times - if I could ever build that light!

Historically I have always been one of the low-power guys.  I'd rather design to power available than stuff more power in. (you can put a candle in a cow pie but that don't make it a birthday cake!)  I have always believed that there are limits to how much power you can expend in a 70' hemisphere, especially when the practical limit is the speed that corresponds to a (roughly) 5.5 second lap time.  E-power systems and data loggers now can show us to the 3rd or 4th decimal point how much power we are really using and how much we need.  Old "slimer" concepts like "reserve power" are obsolete - power carried and not used is WEIGHT.

Now if you can start with the 5 cell and turn all those volts into a teeny tiny lighter pack - now you're talkin - but that is not what I'm hearing.  With folks like you leading the charge E-power is making phenomenal progress.  Yet 5 years from now, we will all be shaking our heads over how big and heavy everything was way back in '07! Maybe in e-CLPA we should have our own Classic series for airplanes from 5 years ago!

OK I'm ranting like a reformed alky (please forgive me!).  You most assuredly have the e-power background and experience - in short, "you got the chops".  What is your thinking on the subject???

Let me just make one comment. I don't think 4s or 6s is too "heavy". Basically the energy a battery contains is proportional to its weight. If you need 400 watts for 6 minutes, then a 3s or 6s battery that can provide that power should nominally weigh the same (adjusting for the fact that the physical sizes commercially available are nominally fixed.) Of course the motor would have different number of wire winds, but to first order, that doesn't matter.

So what I am saying is that a 6s 2100mAhr battery is equivalent to a 3s 4200 mAhr battery in terms of stored energy and weight. This is an obvious statement if you consider making the packs out of six 2100 mAhr cells, the first arranged in series, the second being two 3s packs in parallel--just what I am running now. If I had a 24 wind motor (for the 6s pack) instead of the 12 wind, my flight power usage (and rpm) would be the same.

Mike,
Yes if you need more power for the same amount of time (a bigger plane), then the battery needs to be physically larger. So I definitely agree with you there.
But you can always trade off amps for volts in the P=I*V equation, and adjust the motor kV to suit for a given propellor and rpm. That's all I meant to say. Only when the current gets so large that the i^2R in the connecting wires/connectors becomes important (and if you keep that wire gauge the same) does a higher voltage system begin to beat the high current system. As long as the amount (=weight) of copper in the winds of the motor stays the same, no more resistance heat is created there either in the two cases. Of course you need the higher amperage ESC (which will usually have a lower resistance), and that usually costs you more ($), as long as the high voltage system doesn't force you to a HV ESC (also =$).
To me the choice simply was what would fit in, and to a secondary extent, the 3s 2100mAHr packs are pretty standard and I can use them in some of my RC applications as is.

Alan,

Thanks for sharing this info. The only thing I can think of for the load difference would be line drag, but since you're trying to compare real flight data with static load data, I'm not sure if any of it compares.

As an FYI, back in my younger days, I was comfortable flying a glow powered Nobler on 58 foot lines with a 4.9 - 5.0 lap time. You are right about there. 

Thanks,

Ron

You might have some interference with the slipstream hitting the cowl and fuselage, but once you are in the air that should not be seen at the motor.

On some of our experiments, we hardwired the ESC to the motor. This eliminates those bullet connectors because they can get dirty and noisy. Even though these are downstream from your data logger, there should be some difference in the current draw passing through to the motor.

I guess a lot of this depends on just how much drop you are seeing. We have a lot of connectors (I'm running parallel packs in my setup), but if the difference is tenths of an amp, I wouldn't worry too much. As long as I can get enough power to the prop and don't kill the battery in the process, I'm okay. I have my controller dialed down quite a bit right now as it is.

Take care,

Ron

Dean,
Thanks for the post. It is good to deal with modeling issues rather than politics, global warming, and BOM  .

I flew yesterday with the lower throttle setting and also with a few changes in the CC ESC parameters. As a background comment my CC ESC was setup to run governor mode on the Brodak Super Clown with its stock motor with high kV (except that I had changed the governor mode from the SuperClown Low Governor mode to the High Governor mode for the E-Nobler). Anyway up to yesterdays flight the ESC parameters were:
Auto Lipo detection, Soft Cutoff, Heli Governor High, Forward Direction (yes I know this doesn't matter unless the plane moves backwards!), and more importantly:
Motor Start --Custom (75)
Throttle response--Medium
Motor Timing --Low   (was hoping to conserve battery power--although CC says this is best choice for outrunners  (??)
PWM rate -- 13kHz (default)
Current limit --insensitive (especially since I am pushing past 35A with this 35A ESC!)
Governor Gain--Medium  (50)--this was necessary on the Super Clown because I was getting motor power oscillations on hard square maneuvers
Spool-up speed ==High (but even that seems like an eternity!)

Yesterday I changed the following parameters:
Motor Start --Medium (50)
Motor Timing--Standard
Governor Gain---Custom  (70)  (this is higher than before)
Spool up--Custom (9)--still takes a long time!

Also I flew yesterday with the Zigras at a "16" setting (32% full throttle)---this works out to ~9100rpm

One comment, is that the lap times were pretty nice a little slower than before, and the rpm was held steady (same 11-5.5 prop as before). Overall felt pretty good, but I will admit the wind was relatively calm, so if there was some wind I might have need for more power. I don't have the 11-7" APC prop, but I agree that I should try it. It would move me down more into the power region of my particular motor kV and battery sweet spot. As a matter of fact, that was what I was doing with the Super Clown, moved from the suggested high rpm 9-4 prop to eventually the lower rpm APC 10-7.5.

Here is data-logger plot but the volt and amp plots were pretty strange--they were way off as if the datalogger was using a different scale for the data. This could have been due to my screwing around the day before with a 4.8V nicad setup to let me use a RC setup to look at throttle settings. I didn't reset the data logger before the flight. Anyway I think it is working ok, but operationally it doesn't expect to see major cell count changes for one the multiple data sessions. Anyway l left the pack voltage and current draw off this time becasue of that. But in the plot, the top trace is airspeed, the next is rpm, and the lower (green) is the altimeter reading. Now I hope you realize I wasn't flying underground!---there seems to be a drift due perhaps some pressurization due to airspeed. Eventually I'll track it down. Now it is useful to tad the high points of the flight and correlate airspeed with the pattern.

Hi Alan,
Keep cranking on the governor gain until just before the oscillations. Presently we set to 80, and haven't yet tried a new optimization after the most recent prop change. I've talked to Patrick at Castle about the spool-up time. He understands.

If I had to pick 3 parameters that tell me what the setup is doing, I'd pick Current, RPM, and Airspeed. If I'm looking to see how we are treating the equipment, it'd be Current , Voltage, and Cumulative Current/Capacity. Like I said, we are looking for 50% crest to valley current variations along with less than 250 RPM variation from the average.

It looks like maybe the pitot or static pickup tubes are angle sensitive or something. Where is your static port for the airspeed indicator?

Thanks again for the flight data. Could you picture this just a handfuil of years ago?

later,
Dean P.

Lookin' good Alan!
The 4S 2100s sound a little thin to me: assuming all else stays similar, you'd be using 78% of the 4S 2100 each flight.
That's using them pretty hard, but pack wear-out won't be so expensive either. Now you need 1 afternoon of Summer weather to see how much battery you would use in that condition.

Happy trimming,
Dean

Wow--That certainly is a clean installation--makes mine look pretty kludgy (which it is!). Your motor is a little smaller (and lighter) than mine which has 20 mm long magnets (more or less equivalent to the AXI 2820 series). We are both running very similar rpms---maybe due to the same timer and ESC (forgot which ESC you are using).
Right now my Nobler weight is down to just under 44 oz with the single 4s2100mAHr battery (weight is ~200g). Seems to work ok, but I do need to get the plane trimmed up better. First flight needed just under 1650mAHr to fill it back up. However tomorrow they are predicting snow flurries, so probably only a few more flights are likely this season.
My lap speeds are ~4.9 s --and I may be able to slow a little, but yours are very slow by comparison. Of course with that weight the motor can keep the speed up in the verticals.
Really nice.

Igor,
I am not sure what you are referring to---the only thing I see is what I think is a Zigras Ztron timer---but maybe I am not looking at the right point.
Actually I've been trying to figure how to tie my airspeed indicator into the throttle. Boy that would bring out the old-timers union I bet!

Sorry I do not know Ztron, it just looked like that device, I heard someone from Germany wants to use it for stunt to add power overhead, so I wanted to ask Bruno if it is already reality. I tried centrifugal regulator, but it did not work well, I hoped someone has working solution.

I mean this device:
http://www.freescale.com/files/sensors/doc/data_sheet/MMA7260QT.pdf

Igor,

So let me see if I understand your question. You want to know if someone is using an accelerometer to adjust the speed of the motor in control line electric flight? That's the question right?

Nope, never heard of anyone doing such a thing.   


Kim.

Hi Gang,
I would think that all you want to do is raise the RPM up to 5% (maybe even 10%) if the line tension/centrifugal force drops below some threshold value. A mechanical accelerometer would possibly be more robust and drift-free. Let's see what "leads" the loss of line tension, usually? Loss of airspeed, of course ... Rapid control movement?

The trick is to keep the fast RPM governor control, and to make the smaller adjustments to the RPM setpoint with the possibly laggier line tension/airspeed feedback.

The loss of airspeed thing is the heart of much of this thread. If you have a setup that averages 25 Amps, but has the headroom to easily double that if the RPM bogs a bit, then you get to keep your level flight speed, everywhere. Line tension up high will still drop of due to "grabbity" but you get to keep more of the level lap tension than if speed drops of substantially.

later,
Dean