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Old Sep 09, 2014, 05:20 AM
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Sverige, Värmlands Län, Filipstad
Joined Jan 2009
1,177 Posts
Hi,
I use Futaba S9551 (44 gram each) standard low-profile digitalservo with metal gear for ailerons and for rudder in my MythoS 125E. For elevator I use Futaba BLS153 miniservos with nylon gear (26 gram each) that is also digital but has also brushless motor.
You can use nylon gear servos on all control surfaces if You want since they usually has less or no play (that metal gear servos tend to have or get, more or less).
In my larger MythoS Pro (2M) I use for ailerons and rudder Futaba BLS551 (metal gear) with same seize and weight as S9551 but it has brushless motor=BLS, and elevator servos are same as in MythoS 125E, Futaba BLS153.
I think Futaba BLS153 servos is discontinued now and replaced with the Sbus.2 servo BLS173SV (that is more expensive).
Futaba S9551 is also avaliable in a new S.Bus2 version, S9570SV.
Futaba BLS551 is still avaliable.

Check for servos with similar specifications (weight, torque, speed etc) as Futaba S9551 and BLS153 and You will be OK. There are many other good servos out there from JR, Savox, Graupner, Hitec etc. Maybe try to avoid to cheaper servos, assuming some relationship between price and quality. 6 volt or HV (High Voltage=7.4 volt) capable servos is good to use for better torque and speed then 4.8 volt only servos. Digital servos is also natural to choose for higher resolution (less deadband, more accurate positioning), faster control response (increased acceleration), constant torque throughout the servo travel and increased holding power when stationary. That is what Futaba has to say about the advantages of digtal servos.
Whether brusless motor in the servos can be justified (more expensive usually) is a more open question but it has some advantages that Futaba lists.

No play in gear, good precison, high resolution etc servos is nice to have in F3A model since it is about precision flying.

/Bo
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Last edited by bossee; Sep 09, 2014 at 07:33 AM.
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Old Yesterday, 05:39 AM
al murray
Joined Oct 2014
2 Posts
Been following this thread for a while now.By the way, I am new on this forum. I am also a Sebart fan,I have about six, from Angel to a new Mytho S125 waiting to be assembled ( well you can't call it build really) .The Mytho is the best yet in my opinion. I also have Suchoi 29S 50, early one,good little model, but the flat tail feathers and the way the the fin is stuck on (reminds me of models we used to build in the '70's. Did have a Suchoi 140 with an Axi 5320 /18 on it a-la Gernot Bruckman style, was not bad ,on six cell, In the end I converted it to petrol ( gas) with a Mintor 37, a lot better. But last year I decided to give up the "infernal combustion engines and stick to electric. Now to the "nitty gritty" I still have the Axi and had thought of trying it in the Mytho S 125, on six cell 5000 ma battery with 18×8 prop, not quite as much power as the Hacker 5XS but quite close, I think I can mount it straight onto the bulkhead without disturbing the mounting holes for a Hacker. If I decided to go the Hacker route, I might go to 8 cell battery,wee shall see. My question is, there is a choice of Hacker SXmotors,5, 6 or 7,which do you think would be best, by the way I have a Castle Phoenix 100amp esc,which i will probably use in the Mythos. Hope you can help me out of my quandary
Allan Murray
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Old Yesterday, 06:18 AM
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Sverige, Värmlands Län, Filipstad
Joined Jan 2009
1,177 Posts
Allan,

It really does not matter if You run on 6 or 8 cells, it is the watt You get out of the setup that matter more and You can achieve same watt (power) in both cases, It is with a 6 cell setup You have to take out more current (amp) to achieve same power as a 8 cell setup can produce. Remember You get the power(watt) from voltage times current. On a 6 cell setup You have approx 22 volt nominal and on 8 cell almost 30 volt nominal. 8 cell setup vill draw less current so You do not need an ESC that must cope with as high current in 8 cell scenario as a 6 cell setup.
I have 8 cell setup in my MythoS 125E.
Others have 6 cell setup with MythoS 125E and it seems to work fine, but 5000 mAh then is maybe little low in this case, I think You should have 6000 mAh or little more LiPo battery if using 6 cell setup if You want to fly the Schedule with MythoS 125E without worry to much about draining the capacity below 20%.

Castle Phoenix ICE or Edge 100 amp ESC is for max 8 cells if I remember correct. 100 amp ESC is probably not enough with 6 cells on a MythoS 125E, current draw is probably over 100 amp at full throttle with a more optimal prop. You want some current margins also for the ESC.

Since a Phoenix ICE or Edge 100 ESC can cope with up to 8 cells but it has a limit of max 100 amp it would work better with a 8 cell setup with a MythoS 125E since You probably will not draw over 80 amp with a suitable prop on a 8 cell scenario. With my MythoS 125E with 8 cells, Master Mezon ESC and Faclon V2 carbon prop 19x12 with Hacker A60-7XS I get max 77 amp on full throttle.

Hacker A60-5XS and 6XS is for 6 cell, A60-7XS is suitable for 8 cell.

With Phoenix ICE or Edge 100 ESC that can handle 8 cell LiPo You can use it with a Hacker A60-7XS. I think this ESC is not suitable for a 6 cell setup in a MythoS 125E since the current drain can be in nighbourhood of what the ESC can handle then.
Check what user jfetter has in his MythoS 125E 6 cell setup (if I remember he has a Castle Phoenix ICE or Edge HV 120 and Hacker A60-5XS, 6 cell ThunderPower 6600 mAh LiPo etc).

/Bo
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Last edited by bossee; Yesterday at 06:26 AM.
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Old Yesterday, 07:04 AM
ltc
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United States, MA, Mendon
Joined Mar 2010
2,464 Posts
Allan,
Welcome to the forum.

FWIW, before I buy, I always run my proposed battery, ESC, motor and prop thru eCalc. www.eCalc.ch

It has proven to be very useful at playing "what if" games with different motors, cell counts and props. It is also rather accurate when compared to actual in plane measurements.

I tend to try and "standardize" around power setups that are 8 or 10s, since most of my batteries are 4s or 5s.
My Powerlab6 with MPA or Cellpro 10XP charges these without a problem.
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Old Yesterday, 08:54 AM
al murray
Joined Oct 2014
2 Posts
many thanks guys.

Many thanks, for the useful info,according to propcalc with the 5SX you are a bit limited to an 18×8 or maybe 10 prop that keeps max amp draw to between 70 odd amps or in the case of the18×10 80 odd amps, power to weight on the 8 pitch is about 150:1 ,on the 10,about 170:1, my wind 50S has about 190:1, ( these are propcalc figures) so I am looking for a setup to give me approximately that, looks like the 8cell would give me a better chance,many thanks again.
Allan Murray
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