E-Power 101

Discussion in 'Giant RC Plane Forum' started by TManiaci, Sep 4, 2008.

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  1. Sep 8, 2008 #61

    TManiaci

    TManiaci

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    I have seen this bird fly many times. Mike (Mithy) has awesome power on this thing. If you calculate based on his numbers here, he has:

    2700W / 184ozs = 14.7 W/oz<---- nice!
     
  2. Sep 8, 2008 #62

    snap

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    499.00 dollar Airframe
    1800.00 Motor bat and esc

    10min of quite flight ........ priceless
     
  3. Sep 8, 2008 #63

    TManiaci

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    Finally, with the Wattmeter wired in our system, we run it with a starter propeller. That prop selection is probably best selected by using the one close to the motor manufacturers recomendation, or a step up from there.

    Then, I always buy a few props that step up from there in 2-3 increments. Prop load on the system, or wattage is related directly to the Diameter and Pitch of the prop. The relationship is represented in the following equation:

    Watts = (Const) x RPM x D^4 x P

    Where (Const) is a factor that accounts for atmospheric and other conditions, D^4 is Diameter to the 4th power, and P is Pitch.

    You can see clearly that Diameter has a much greater impact on load than Pitch, so think of these variables as course and fine tuning steps respectively. If you are way low, step up in Diameter. If you are close, step up in pitch.

    Also, consider your Prop Type. The E-Type (Thin Electric) props are far more efficient at high RPM. If you are running design RPM below 9000, you will get better 3D performance from the SF Props, but above that you are washing out, flexing the blades flat, and losing a lot of the potential thrust that the motor is consuming wattage to make. Using a tach is also a good tool in determining the real system perfomance.

    Do all of your testing with a fully charged battery. Don't run more than 2-3 short WOT tests on one battery, because the max loads will not be possible as the battery fades.

    This is a test-and-retest iteration process to get the perfect setup. Yea, you are gonna buy a few props you don't need, but they aren't that expensive. As you do this more often, your feel will improve on stepping prop selection up or down to get that perfect point where the load matches your system design goals. You're getting all you can out of it, and you are running just below failure risk points on the system components. This is the best way to get a light build to perform at it's best.
     
    Last edited: Sep 8, 2008
  4. Sep 8, 2008 #64

    Altavillan

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    I had to test myself with some of the stuff I'm learning here so today I ordered another plane. A Sebart Sukhoi 26s 30E (just had to have one). Last week a Cermark 49" Sukhoi and a few weeks ago a PA extra. So did I get it right? If the prop don't work get another plane???? And this weekend it's 4 days of RENO baby! Stop by for a beer, West RV lot space 40.
     
  5. Sep 9, 2008 #65

    TManiaci

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    Villan... When you're ready, let's see how you go about setting up and buying your gear for those birds.
     
  6. Sep 9, 2008 #66

    TManiaci

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    I recently did the prop search to test load my new BAF Yak. I'm running an AXI 2820/12 (990kV, 37Amps/60sec). With AXI, I plan for 150% Burst, since they don't publish that way. That's 55Amps, of course I will treat this as a Burst and use it sparingly.

    The two batteries I am running are the Impulse 3S1P 3200 mAH 20C (64A Cont., 220g) and the Thunderpower Extreme V2 3S1P 2200 mAH 25C (55A Cont., 170g).

    I started with the 12 x 3.8SF before my other props arrived. My target load was 50-55 Amps. After I got the props I ordered, I tested as follows.

    APC 12x6E...... 395 W @ 39.2 A
    APC 12x3.8SF... 468 W @ 42.4 A
    APC 13x4.7SF... 538 W @ 49.8 A
    APC 14x4.7SF... 564 W @ 53.3 A

    I am flying the 13x4.7SF now with a Phoenix 45 ESC, and as soon as my 60A ESC arrives, I'll step up to the APC 14x4.7SF. I am wating for a few larger APC E-Series props to arrive so I can check them out too. I want to make a fair comparison of the E-Series to the SF props making same wattage. I expect to find the right E-Series prop will be 15 inch diameter.

    I ordered a 15x4E, 15x6E and 15x8E. Unfortunatly, there aren't any low-pithch 16 inch APC props available.

    With the TP 2200 on board, I have 13.1 W/oz now. That's dead on the wattage/load I expected using the methods we have discussed. It's pull-out is nice, not ballistic, but damn good. I'll get a few more Watts out of the bigger prop, 13.7 W/oz.
     
    Last edited: Sep 9, 2008
  7. Sep 9, 2008 #67

    CA$HEY

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    Thats intresting,,i have never seen a 12,13,14, size SF props here, except GWS,,very intresting
     
  8. Sep 9, 2008 #68

    bdavison

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    Yeah, biggest Ive seen is 12x6SF, but Ive heard they make a 12x8SF...

    Never heard of em going bigger than 12" in SF because of the thin blade root, and possibility of slinging blades.

    Tman, where did you find the SF APC props that big?
     
  9. Sep 9, 2008 #69

    TManiaci

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    Hobby Lobby stocks them. You can see them HERE.
     
  10. Sep 9, 2008 #70

    bdavison

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    Hmmm...interesting...
    Anyone know what the bigger props are rated for RPM wise?
     
  11. Sep 9, 2008 #71

    TManiaci

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    APC does not publish ratings. They boast that thier products are tested carefully, but they provide no data or guidelines for use on thier line. So, it's unlikely anyone has good data that will help us.

    I will tell you it was scary turning that 14x4.7SF prop at 560 Watts. I was very worried about the prop breaking and tearing me and the big foamy apart. It seems to be strong, and I didn't notice much flex. I think I may find better performance with the E-Seris props, but I wanted to do a little of my own testing to see how Thrust and Wattage correlate with SF vs E-Series props. Should be interesting work.
     
  12. Sep 9, 2008 #72

    bdavison

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    Per APC here are their recommended RPM ranges for the props....straight from the source.

    Glow and E props - 190000/diameter of prop = max RPM
    SF props - 65000/diameter of prop = max RPM
    Racing Props - 290000/diameter of prop = max RPM

    So for a 14" SF prop
    65000/14 = 4642 max RPM
    Thats kinda SLOOOOOOOW.
     
  13. Sep 9, 2008 #73

    TManiaci

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    WOW... I had heard somewhere that the SF props were limited to 8,000 rpm, but that factor really pushes down the limits. I don't know anyone running props that slow. None of the popular outrunners even have kV ratings that will work with that range. Sounds like a Liability statement to me, not a specification!
     
  14. Sep 12, 2008 #74

    TManiaci

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    Ready for some more E-Power 101?

    This may seem a little too basic, but I have seen some pretty bad wiring and solder jobs on airplanes. A bad connection can take a plane down. It's important to do good work here.

    First, get a decent Soldering Iron. Those cheesy 25 watt soldering irons you get at Radio Shack don't cut it. You need a good bit of heat to do a decent job, so get a Soldering Iron that has at least 40 watts, better at 60 watts.

    Soldering is an art, and there are things you can do and use to make the finished product much better.

    First, using the right solder is important. For general electrical work, 60/40 is best. This is the ratio of Tin to Lead, or Sn/Pb ratio. Don't use "Flux Core" solder, use the solid non-flux core type solder. This allows you to better control the soldering process. You need very little flux to do a good job. But, if you need a healthy solder joint with lots of solder, the excess flux that Flux Core solder supplies is just way too much, and inhibits good flow.

    IMG_5789.JPG

    Flux is a key factor in soldering with quality results. A good Rosin Paste Flux is ideal for soldering. Using it sparingly, and applying it only to the area of the solder joint is best.

    IMG_5790.JPG

    Clean materials is also a key issue. Corrosion and contamination will impede solder flow and adheasion. Make sure you have clean soldering surfaces, and cut back into fresh wire on cables.
     
    Last edited: Sep 12, 2008
  15. Sep 12, 2008 #75

    TManiaci

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    The first step is to prepare the components by "Tinning" them. After applying a bit of flux, heat the wire and flow in a generous amount of solder until the wire end appears solid and all the way around so it's a nice cylendrical shape without any frayed wire strands hanging out.

    Then, Tin the contacts with a nice bead of solder pooled on the contact area.

    IMG_5793.JPG

    Notice that I am holding the connector with some small vise grips. It's really helpful to immobilize the part so you can manipulate the wire into a proper position.
     
  16. Sep 12, 2008 #76

    TManiaci

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    Now, hold the wire head on the solder pool and apply heat, you'll find when the melting point is reached, it all flows together very nicely and leaves a solid bridge of solder all the way around the joint. Add a little more solder if necessary to make it fill.

    IMG_5796.JPG

    Note that on the Utra Deans connectors, the Positive is the crossed contact. Don't forget to slide on a piece of shrink tubing before soldering, douh!

    IMG_5797.JPG

    Also, when soldering the Female on a Battery, do them one-at-a-time and shrink the shrink-tubing on before attempting to solder the second lead. This will prevent accedental shorting of the battery, a bad day if you do that. The power in the Lipoly battery is enough to weld the contacts or soldering iron solid, and you will have a lipo meltdown, puff and possibly a fire!
     
    Last edited: Sep 12, 2008
  17. Sep 12, 2008 #77

    bdavison

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    Here is a video I made to show how to solder different connectors.
    [ame]http://www.youtube.com/watch?v=EmrFAgPuieI[/ame]
     
  18. Sep 12, 2008 #78

    CA$HEY

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    For the dudes that tend to put to much heat into there dean's plug when soldering,,and the pins start to move and not line up anymore,,,I aways leave a DUMMY end on,,in other words i leave the male and female plugs joined together when soldering,,but i dont have bare termanals hanging out,,there just DUNNY plugs,,when finished thay will all ways plug in very easy
     
  19. Sep 13, 2008 #79

    TManiaci

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    I used ot do that too Ca$hsy, but with a high-power soldering iron, it's not necessary any more. When you can get the heat in fast, the rest of the brass contact doesn't heat up so much and soften the plastic body.
     
  20. Sep 14, 2008 #80

    TManiaci

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    More E-Power 101... Charging Stuff.

    As we diversify our aircraft hanger, we need to deal with a lot of recargeble batteries of various types and styles. I got hung up on the Great Planes Triton Chargers myself, because they suit all the various battery types, they are easy to use, and they provide all the information that you need to know. There are several chargers out there that do all this and more.

    I was always frustrated with all the various connectors that we deal with, so I started making adaptors for each type of battery. The variations got pretty hard to manage until I finally put it all in a kit. Now I always have it all together and nothing gets lost.

    Adaptors.JPG
    Adaptors for all Nitro, Gasser and E-Flight equipment, including both types of Tx connections and many others. Everything I have to charge has a custom made adaptor that uses the Ultra Deans connector that I have on the Charger leads.

    Field Charger.jpg
    Keeping it all in a stackable kit.

    Home Charger.jpg
    At home a second Triton with a Radio Shack 15Amp 12VDC power source. The Triton is velcro attached, and I can take it with me any time.

    Field Power.jpg
    My home-made field power pack. This is a gang of six 2.4AH gell cell 12VDC batteries, wired parallel to provide 14.4AH (14,400 mAH) of charge capacity. I use this, rather than lifting the hood of the car to steal power from my vehicle.
     
    Last edited: Sep 14, 2008

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