model:
1750g heavy
6s1p A123 battery
axi 2826/10 motor + APC 11x5,5 prop
lap time 5.2s
lines 19,5m

model does complete pattern except level upright laps an inveted flight between loops

http://www.olive.cz/pub/igor/1.jpg

http://www.olive.cz/pub/igor/2.jpg

It is  very interesting that you can so clearly see all the manouvers in the graph, even what part of teh manouver you were in :-)


Regards

Randy

Not only can you see the manuvers - looks like he bobbled the LAST corner of the triangles!    Also looks like he did a couple outside loops to unwind the lines after the pattern!  (oK that's a little extreme)

If I am reading this correctly his power requirement was about 95W/lb on average, with a peak (after take-off) of 490W or 127 W/lb - with data like this motor and battery selection really start coming into focus!

do you think the the motor is maybe under the efficency rating of the props?

That motor is for 4 cells. Now I have 6 cells A123 it gives 16V end of flight. It definitelly gives lower efficiency. Unfotunatelly Axi 2826/12 has too little RPM/V for 16V and 5.5 pitch. I have another motors Like MVVS and Dualsky 4250/6 with 840RPM/V that can be better match. Unfotunately they does not fit instead of LA .46 into my model.

But I plan to build first "electro only" model winter so I will make different airframe. I must save 200g and I will make fit for all those motors, they have same screws in "reverse" mountig and it also allows usage of fans.

Actually I have motor mounter on firewall (where was Os max .46LA before). So I can use only this AXI. I do not have any other motor to use in this model.

I plan to make another model and I definitelly plan to use front mounting. It wil allow fan on AXI, or it will allow to use and to test more motors with lover rpm/V which I have with A123, like MEGA, dualsky or phasor, but especially my new MVVS (with integrated fan) which does not allow firewall mountig. MVVS makes special adapter which allows firewall mounting, but it is too large for nose of my model, it was designed just to fit small LA engine and its pipe, nothing more.

data is from prop APC 11x5.5 on governor at 10100

ESC is yeti SPIN 66A, battery is almost cold (colder than ESC and far colder than motor). We have relatively cold air now here, so I covered pack by PS foam against too low temperature. Pack temprerature in that condition was 45 deg. Celsia after 3 flighs (flight, immediate charging by 10A, then again immediate flight, charging an last fligh) ... it looks heating and discharging makes approximately the same amout of heat. Starting temperature was 19 deg. C. It shows, that even withou cooling (summer thin hot air) A123 can survive that killing usage. Try to tell R/C guys you can do full cycle of batteries in only 20 - 25 minutes :-)) ... they play game with "C"s but i reality they fly over 10 minutes. The only issue is weight, I hope I will find better way to use them in lighter model and with more efficient powertrain.

I fly 5:10 for whole pattern, but no problem to go to even 5:30. A123 works great till end of its its capacity, the voltage drop after discharging is almost instant (unlike slowly weaking lipos), so it is necessary to be carefull in 4leaf. It gives chance to drain it really almost to 100% of its capacity (once again - unlike lipos). However I have only 10 flights now, so it is too early to estimate how long it can work well, but F3A guys says after 200 flight no signs of capacity differences or higher iterna resistance, or some other problem.

>>>Is the cost of the batteries you are using similar to the LiPos we are using?<<<

They cost less and if you add far longer life time, then it is no question. The only problem is weight, nothing else.

It is difficult to compare. The cell is 70g heavy, capacity is 2,3Ah and voltage is 2,6V (empty under the load).

The 4Ah lipo has end voltage 3V and weight 100g.

So if I compare the w/g capacity, I am in ratio (4 * 3 / 100)  : (2,3 * 2,6 / 70) = 120 : 85 = 1.4

Means lipo can keep 1.4 time more capacity in the same weight. But A123 can be drained more than 90% of its capacity, while lipo only less than 75%, what makes that number little better: 1.4 * 75 / 90 = ~1.2 ... means A123 is in any case 20% heavier. So yes, more wiring and, longer cables and so will meake 100g more than lipo.

Unfortunatelly it is not whole story, other problem is that they make only one size 2,3 Ah. 8 cells 4s2p is too heavy and too little voltage, too high current, too slow charging. Usefull combination is 6s1p and that is not enough capacity for 12x6 prop (with motors I know). Usefull prop is 11x5.5 and that needs smaller plane. I would say under 1500g, or even better 1400g and if I count well, 450g battery, 200g motor, 50g esc and battery protection makes 700g ... means the power train must be half of the whole model or by other words, the trimmed airframe with landing gears and all hardware must be at 700-800g. My lightest airframes (for IC engines) are at 900-1000g.

So I see two chances, I either fing better motor with 10% better efficiency (and that looks difficult) or I just must build lighter model ... I prefere the first choice, because I have two such planes with exchangeable motor.

Hi just a few questions i have some 2700 mil amp cells coming they are similar to he a123- 79 grams these are for a cardinal size plane 580 inch if i can optimize this set up will they have
enough  mil amps to complete the pattern i was going to make them up as 4 cell packs they are 3.2 volt per cell, also would it be good practice to put a balance lead on them,
chargers i have a 2 amp  lipoly charger balancer can i use this as it states that they can be charged at 5 amps  i have a 4200 ma4 cell lipoly weight 433 grams the lithium ion would be 100 grams less last cardinal weigh 40 oz hope to keep it reasonably close to that
also how many poles has a 2628 axi got
    also i was thinking of trying a 10x5 3 blade and repitch as needed .
sorry to go on abit just trying to give you the general picture
thanking you Pete Beddows .

Hi Phil,
And therein lies the rub. I don't think it needs to weigh 4 or 5 ounces, but between 2 and 3 for sure. I'll bet the weight is a wash.
As you say, the key is distance between the shaft bearings. I am also contemplating either a small steel spur gear and Delrin/polyurethane large gear, or aluminum pulleys and a cogged belt. Belts don't really want to run over pulleys at 40,000 RPM as in the case of the best efficiency inrunners, but outrunners with Kvs that are 2 or 3 times too fast for us will have very good efficiencies. In Igor's case, a motor with a Kv of 1700 or 1800, less than 45 or so milli-Ohms, and a continuous current rating of just 20A will do just fine on a 6S A123, if belted down about 3:1.
The domestically produced NeuMotor 1900 "ORK" series will probably be the ticket, even if they ain't cheap.
By the way, the Pattern guys are beginning to see the lifetime data come in: soft mounts extend the life of their planetary gearboxes dramatically. The cogging torques are beating the gearboxes to death, now that they have moved the output shaft bearings farther apart. Polyurethane output gears and belts will accomplish the same thing. You'd be amazed how much of our remaining noise is radiated from the prop itself.

later Friends,
       Dean

thanks for he heads up Igor the cells as advertised are 20/30c  with a maximum charge rate of 5 amps  the charger i have is for lipolys 4 cell 14.8 v these cells would be 12.8
a 2volt difference  would this be a big problem as long as the amps are right having said that i will buy a new charger ,
have i got this right i will have 2700mil amps to use looking at what others are using to com pleat the pattern   its about 2500mil amps if i go up to5cells this uses the power up faster and i have more power so i can throttle back  but now i am heavy the sweet spot for the motor is between 20 to 30 amps with 12.8 volts do you think it will push it over the 30amps  propped to do a 5.4 lap .
i should not read your posts you give me to many ideas how to spend i have a yak shockflyer to convert for indoors .
                  thanking you Pete Beddows.