First electro thoughts

1/ I think the best idea to cut off is timer. My nephew did first test with PIC (single chip programmable computer). It looks very simple to make short program for generating impulses for standard R/C equipment like brush or brushless engine (1 or 10 does not matter), for servos for retractable gears or even pilot signal for my favorable R/C gyro unit. It can include also 20 seconds of time delay allowing to run to the handle before flight (for alone flyers). I can imagine to do it also with two NE555 timers.

2/ I already wrote the NiCd and NiMh is not the best way. I got serious data for Kokam Lipoly. Here is one useful cell 1500mAh useful at 10A discharge time. It is for 6 min capacity 1Ah. It means the cell is after fly discharged only to 2/3 of its NEW capacity. Deep discharging is not recommended for LiPoly and the output voltage at end is still almost constant so there is no need to regulate it too much. Additionally partial discharge allows something called quick charge which results in only ~80% of capacity after charging. I will attach a discharge picture clearly showing the early cut off gives almost constant power delivery up to 100W. The voltage dropps only 0.2V for cell (we need 3 or 4)

3/ Small start up setup can be 3oz heavy brush less engine with 8to9x4 prop at 10 000 with brush less regulator and PIC generator (<1oz including cabling) and 3 cell Lipoly 1500mAh battery at 4 oz. It is 8 oz for power train. (with full tank )

4/ Electric engine does not shake too much and has very uniform torque. It does not need too strong fuselage. I see big chance for foamy models I did some first test for full foam model (no covering). I believe it can be up to 8 oz. The wing test shows 3oz heavy wing at span of 40” under the weight of 55oz. (supported at tips only!!!)

What you think?

I work hard to have serious regulator with constant rpm, I believe it will come soon. In that case I see real chance to have 350W power train with 4 cell battery with 3 parallel cells which can use 12x4 prop at weight of 6 oz for engine and 12oz for battery it is 18oz for good power train.

Thanks for doing all the research.

Thanks for letting us know that there appears to be the possibility of decent performance from an electric-powered CL model.

No thanks for the most depressing news I have heard since PW said he liked his Saito 56/Impact combination.

AWESOME foam work! How did you cut the fuselage parts? And the loading test is most impressive...

Nice Work!

Andy

The nose is little bit tricky. After cutting I cut little vertical cut out which later allows to make thinner rounded nose. It is visible on picture where one nose is open and another is already joined together.

BTW the CF does not run to the tip. It goes only to 2/3 of span on front spar and to ½ on back spar. This picture clearly shows how far it goes. The middle of wing is relatively straight, while tips are round:

Wow, great foam cutting. So it seems there's a bigger intrest in electrics then generally portrayed...

Your foam cutting work looks extremely innovative to me. Wow.

You realize, of course, that your foam techniques could be applied to conventional alcohol powered stunt models, to produce superior lightweight structures?

(Ooopps, you say you've been doing such all along, and beating us all with the results? )

Lovely stuff.

I'll look forward to your data and conclusions.

[photo not recovered: 3e69bb3870f12ad5.jpg]

"When I turned two I was really anxious, because I'd doubled my age in a year. I thought, if this keeps up, by the time I'm six I'll be ninety." -Steven Wright

If not else then it could be useful for short life beginner trainers.

I already did some successful tests with beginners wing, using foam LE combined with very simple “triangular” backside of airfoil covered by iron on foil. The guy was able to cut the foam and do model “by wire”. However he did several mistakes, but we solved them while building, and the result was his first succesfully flying model. (that uncovered on pictures) The rick is, that the beginner without a help typically cannot keep proper shape of LE and straight wing. All mistakes are payd by all kind of stalling rolling and so. While this construnction could be done on flat dest without any tools and LE is determined by templeate.

More progress, huh?

This continues to be a most depressing thread, to the point where I am having second thoughts concerning the overall value of the internet.

Glow fuel and gunky models forever!

Yeah, this level of inventiveness and engineering prowess does kind of take your breath away. I think I'll go bang some rocks together...

Andy

P.S. Nice going Igor. Let me know when I can send you a check for a complete outfit, ready to fly

AT

For those interested in the details, here's a link to a detailed data sheet for this part: http://www.microchip.com/download/lit/pline/picmicro/families/12f6xx/41190c.pdf

[photo not recovered: 3e69bb3870f12ad5.jpg]

"Thought is action in rehearsal." -Sigmund Freud

Shall I mention 4 units communicating by one pin, measuring 4 engines rpm and controlling them for optimal run by simple r/c servo and r/c carb by measuring the in-flight speed by R/C gyro unit and everything combined with automatically controlled retractable gears?

Igor,

You have no idea, nor any way of knowing, how many years ago I first tried electric power, how many hundreds of sub-C nicad cells I have consumed, motors fried, etc.

Let's just say that at one time 1/12 scale RC cars were *all* powered by either Cox reed-valve or front-intake (TDs) .049 motors. My family and I--four of us--raced these as a sidebar to 1/8 scale cars for three or four years before electrics came on the scene.

As the bandwagon drove by, we jumped on, rode along for several more years.

As a result, I would never consider electric-powered models of any sort when it comes to competition and the resulting competitive atmosphere. Not even CL Stunt.

As a sport-flying option? Of course. No problem.

I wish you well in your research and development.

I have really no idea how it looks at you, but if I remember well then for example also Claus Maikis got the same idea – he presented his small stunter in some thread here. He is also experienced flyer, builder, contestant and still playing with “other” models. For me it is way how to do “something” on weekend and not invest several months of effort. I do not think the “magic” is in electricity, I think the magic is in simplicity.

I think you and I are on the same page, as I can be found to be flying some sport FF (CO2-powered models or HLG or something similar) while out with serious Stunt equipment.

Again, electrics for sport flying are fine. But when one mixes electric power with a competitive event, things can get really ugly very quickly. To the point where I simply would not be interested.

I continue to enjoy you and your erudite approach toward comments you make on this site. Most enjoyable.

Dan,

I'm not quite on the same page here. If you level the playing field so the intent of the event is for everyone to compete with electric-powered models where is the "ugliness"? I'm not sure if you are referring to the technology (cumbersome? inadequate?), or the human interactions (IC Chauvinism?) as being "ugly". I'm just dense I guess...

The utopian (definition "Utopia": "Nowhere") vision I have is for electric models to attain a level of performance sufficient to allow "serious" competitors to practice for competition and compete, and "sport" flyers to have fun, and both to have the option of using electric power for their purpose. The dream is to have models so clean, and so quiet, that everybody from Walker Cup winners to Soccer Moms can appreciate their grace, and tolerate them in the maximum number of venues (parks, ball fields, big back yards). No more fleeing civilization to the outer wastelands to fly. To be welcome and accepted. I must be nuts...

Andy

But I do not afraid too much of such problems. Our models are not based on power train (even less than R/C). I think until we see Jurassic 4-2-4, pipe and 4C engines successfully compete together, I do not see too much problems. But you have good point, we should watch F3A carefully. Especially if actual draft of new FAI rules allows electric power plants.

>>>What language do you program in?<<<
It depends on chip. I do not want to invest lot on money, so we use free compilers. There are compilers for native assembler, Basic and also for C. It depends on chip type, which you must choose first depending on your application.

>>>How much is a setup (compiler and pc interface).<<<
You can have trivial parallel port programmer which you can build yourself (for one time job – you can find plenty on web) and you can have also professional device for quick duplication. It also depends on chip type – especially if it has flash memory (expensive – good for one piece), you can have in circuit programmable chips and you can have very cheap versions but you need special programmer. But I think the limiting feature is debugger/emulator. If you want make better than trivial program, you will need a way to trace the program or full debugger. It is always disappointing if you write a program, you start it and it does not do anything and your black box is still black

>>>i wanted to use one the make an analog to digital, n-1 mutiplexer, with internal counter. i guess it would consist of many loops and an external ADC.<<<
You can have also internal ADC and external multiplexer, of if n is small enough it can be pin by pin but I think if n>2 then the multiplexer is better.

I probably did not answer your questions, but I think the proper way for you is to look to that home page, to choose proper type and then search on web for its name. You will get tons of price offers, but you will also find some “how to” pages for that your type, compilers and programmers/emulators.

I also saw Mike Palko fly his AXI powered Twister. Although he didn't pull really hard maneuvers, the motor had very little speed variation. It just churned along with no perceptible change in pitch other than the prop making wowing noises. He used NiMh cells, so it was a little heavy. With what we are seeing now from the LiPoly batteries, an electric should be a pretty decent performance setup(if you don't mind the initial cost)

The typical synchronous AC engine rotates and thus make on winding sinus wave. Feeding comes from another sinus wave. If those waves are in coincidence, the engine does not make too much power, does not have too much consumption. If you load it, you get a phase shift, so those waves are not in coincidence, what makes voltage difference on winding and thus also makes current giving lot of power. But the rpm in allowed range of load is always equivalent to the feeding current frequency.

But brushless engine works different way. You have permanent magnet and winding. It also makes similar wave from rotating. Until now the same, but now comes different feeding. Now I expect it is a star. The controller does electronic comutator. It feeds two of three input wires and as the rotor (magnet) rotates, the third wire changes its polarity as the pole crosses the winding. It gives information to the unit what is the position of winding to the magnet and the unit rotates “virtual comutator” inside the program and under its position synchronized with the rotor feeds winding EXACTLY same way as comutator does – by rectangular pulses.

The result is, that is works same way as DC motor does. The biggest advantage is, that there are no loses of improper contact on comutator, and efficiency is higher thanx easier timing regulation regarding actual rpm – that is not possible on DC engine, you can make only constant timing. It is also reason why the rpm is more stable – loading does not force the engine out of optimal efficiency, but certainly not constant. But the comtation handled by computer, so that is the way how I am trying to control it – I would like to use device developed for Heli application with collective head. It already exists it just need little change of firmware in unit, but it needs cooperation of producer … it will take some time.

But back to engines. Producers typically give no load PRM and resistance of winding. So you can easily calculate how you must load the engine at known shaft loading to reach wanted current. The current depends on engine, they always provide max current - giving thermal loading of winding (resistance of wire * current ^2), and max efficiency current where you have to keep. The second number is typically not very important, as the efficiency is relatively good in wide range. It is 70% in worst case and typically 80%. It means 10 cells NiXx gives say 8V (average under load), at current 30A you have 240W on engine and it gives 180W on shaft (at 75%) what is enough to handle 10x4 prop at 10 000. On 165g heavy engine. Unfortunatelly the battery for 6 min comes to 20oz.

More info is here:

http://www.megamotor.cz/en/motor_detail.phtml?prod_id=42

later,
Mel D.

P.S. Here is a sample output..............

Static Analysis - TEST
Sea Level, 29.92inHg, 59°F

Motor: Hacker C40 11S; 3818rpm/V; 1.7A no-load; 0.0175 Ohms.
Battery: Thunder Power TP2100; 3 series x 2 parallel cells; 2100mAh @ 3.7V; 0.022 Ohms/cell.
Speed Control: Castle Creations Phoenix 45; 0.0026 Ohms; High rate.
Drive System: Gearbox Efficiency Curve for 10x6; 10x4 (Pconst=1.31; Tconst=0.95) geared 1:1 to 4:1 (Eff=95%).
Airframe: Accord Rock & Roll; 770sq.in; 33 oz w/o powertrain 47.9oz with; 9oz/sq.ft; Cd=0.045; Cl=0.15; Clopt=0.42; Clmax=0.98.
Filter: 35A max; 45A max (ESC).

NC Gear Diam Pitch Weight Batt Motor Motor Input InPLd Loss MGbOut OutPLd MotGb Shaft Motor Prop Thrust PSpd RofC Time
Ratio (in) (in) (oz) Amps Amps Volts (W) (W/lb) (W) (W) (W/lb) Ef(%) Ef(%) RPM RPM (oz) (mph) (fpm) (m:s)

3 3.20 10.0 4.0 47.9 34.5 34.5 9.9 340.2 113.7 51.7 288.5 96.4 84.8 75.4 35394 11061 51.5 41.9 579 7:19
3 3.30 10.0 4.0 47.9 32.3 32.3 9.9 321.5 107.4 48.6 272.9 91.2 84.9 76.1 35830 10857 49.7 41.1 468 7:48
3 3.40 10.0 4.0 47.9 30.3 30.3 10.0 303.8 101.5 45.8 258.0 86.2 84.9 76.7 36233 10657 47.8 40.4 360 8:19
3 3.50 10.0 4.0 47.9 28.5 28.5 10.1 287.2 96.0 43.3 243.9 81.5 84.9 77.2 36606 10459 46.1 39.6 255 8:51
3 3.60 10.0 4.0 47.9 26.8 26.8 10.1 271.7 90.8 41.1 230.6 77.0 84.9 77.6 36951 10264 44.4 38.9 155 9:25
3 3.70 10.0 4.0 47.9 25.2 25.2 10.2 257.1 85.9 39.2 217.9 72.8 84.8 77.9 37271 10073 42.7 38.2 58 10:00
3 3.80 10.0 4.0 47.9 23.7 23.7 10.3 243.4 81.3 37.4 206.0 68.8 84.6 78.2 37567 9886 41.2 37.4 -36 10:37
3 3.90 10.0 4.0 47.9 22.4 22.4 10.3 230.6 77.1 35.9 194.8 65.1 84.4 78.4 37842 9703 39.7 36.8 -125 11:15
3 4.00 10.0 4.0 47.9 21.1 21.1 10.3 218.7 73.1 34.5 184.2 61.5 84.2 78.5 38096 9524 38.2 36.1 -211 11:56

Note: Motor performance calculations do not take ambient temperature and heating effects into account.

Generated by MotoCalc 7.00, 1/19/2004 7:40 PM.

However, regarding engine selection, I would really go the way of no gerabox. It means it will need a producer givig wide range of types (number of winds) giving chance better match the battery voltage and the prop. The example can be that Mega from my sheet upper, but also Phasor or your mentioned Axi or PJS has that chance. But there is one problem. Types with outer magnet like PJS and AXI can make problems in tight turts because of gyro moment of rotating magnet - also bushing is not the best in that construction. On opposite side the Phasor and Mega has magnets "inside" and long shaft. It is better I think.

The measured amperage gets adjusted to a certain amount, enough to keep the plane aloft. If it drops below the motor stops.

How long are the average flights per battery pack?

I agree with Igor. Current is more difficult to measure and less useful in this case. The main reason the current decreases is because the battery voltage drops and voltage is much simpler to use.