New Ds-7002hv Servo From Bk

Discussion in 'Industry News' started by utrinque, Jul 26, 2015.

By utrinque on Jul 26, 2015 at 12:12 PM
  1. utrinque

    utrinque Well-Known Member

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    • Operation Voltage: 6V – 8.4V
    • Weight: 66g (2.33 Oz)
    • Torque: 17 kg.cm (236 oz.in) @ 6V | 19.1 kg.cm (264.5 oz.in) @ 7.4V | 21.1 kg.cm (292.3 oz.in) @ 8.4V
    • Speed: 0.07 sec/60 @ 6V | 0.054 sec/60 @ 7.4V | 0.047 sec/60 @ 8.4V
    • Dimensions: 20x40x37 mm
    • Frequency: 1520us/333 hz
    • Gear Type: Metal
    • Motor Type: Coreless


    There is alternative:
    http://www.alofthobbies.com/kst-ds725mg.html

    Servo TypeDigital
    Gear TypeMetal
    Stall Torque13Kg.cm@6V, 16Kg.cm@7.4V, 18Kg.cm@8.4V
    Speed.o9sec/60°@6V, .08sec/60°@7.4V, .07sec/60°@8.4V
    Voltage Rating 6V to 8.4V, 17mm coreless motor
    Dimensions40.5 mm wide x 20 mm thick x 37 mm high
    Weight70 g / 2.47 oz
    [​IMG]

    or:

    $194.90 for 3 X KST BLS815 + 1 X KST BLS805 Tail & Swash Servos

    3 X KST BLS815 HV Brushless Tail Servo
    Operating Voltage 6.0V-8.4V
    Dimensions: 40.5*20*39.5mm
    Torque:
    14Kg.cm@6.0V
    17Kg.cm@7.4V
    20Kg.cm@8.4V
    speed:
    0.09sec/60°@6.0V
    0.08sec/60°@7.4V
    0.07sec/60°@8.4V
    weight:68g(with box:132g)
    working frequency:
    1520us/333Hz

    1 X KST BLS805X HV Brushless Tail Servo

    Operating Voltage 6.0V-8.4V
    Dimensions:
    40.5*20*37mm
    Torque:
    5.5Kg.cm@6.0V
    6.5Kg.cm@7.4V
    7.5Kg.cm@8.4V
    speed:
    0.048sec/60°@6.0V
    0.042sec/60°@7.4V
    0.039sec/60°@8.4V
    weight:
    68gwith box:132g
    working frequency:
    760us/666Hz


    [​IMG]
    http://www.rcchinamade.com/3-x-kst-...l-swash-servos-for-450-700-rc-helicopter.html
     
    Last edited: Jul 26, 2015

Comments

Discussion in 'Industry News' started by utrinque, Jul 26, 2015.

    1. Min

      Min Well-Known Member

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      Those are some sloppy alternatives! the KST is close in terms of torque but no where near as fast
       
    2. utrinque

      utrinque Well-Known Member

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      Both brands are Made in Taiwan. KST is half the price of BK (probably rebranded Servoking).

      Gartt 700 is half the price of X7 I got today...

      Will I fly like Dunkan Bossion? No :)
      Will buyers of BK servos fly like Kyle Stacy?:eek:

      One BK servo on X5 tail started to behave strange on me. I am not fan of BK. I like Bert a lot.
       
      Last edited: Jul 27, 2015
    3. Min

      Min Well-Known Member

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      I understand that both brands may be manufactured in the same geographical region but if you look a little deeper into the manufacturing processes you will find that the location doesn't matter, its the equipment and tolerances you specify. If you look on alibaba you can find many CNC suppliers that can may any machined part you want. When you want a quote they will request a drawing of the components you want made with the specified tolerances. After each part is made there is an inspection process where the part is measured relative to the datums set in the drawings and the ones that do not fall in between the allowable tolerances are chucked out. From the same factory you can specify the exact same parts to be made to +-0.25mm tolerance or +-0.01mm. This could be the difference between have a really nice set of servo gears that are smooth with no play or a set that is either notchy or has excessive play. Again from the same factory you can specify what materials you want the parts out of. You can choose the cheapest steel there is or the strongest alloy of titanium.

      The price difference is due to all these factors. If the factory stuffed up the gears slightly, the more budget company will just go she'll be right and sell it when for the more expensive product they will be rejected and chucked in the bin.
      The higher the quality, the higher the rejection rate and these rejected parts are just complete loss. It costs just as much to make a rejected part as a good part.
      Better/stronger materials also drive the price up. When you have a stronger metal it is strong all the time and that includes when you want to machine it. This means the tools will blunt faster and in some cases the tools will blunt while you're machining the part. This means you either have to sit and work out how fast the tools wear and then account for it when machining which costs a lot of money because not anyone is able to do that or you just have a really high rejection rate which as mentioned before costs lots of money.

      Don't think things are expensive for no reason. When you buy a cheaper product you have to think about where they are making the savings. Is it because it's a straight copy therefore no R&D cost or is it because of substandard materials and manufacturing.
       
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    4. utrinque

      utrinque Well-Known Member

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      Probably BK brand sells better than Servoking. What if those are the same servos?

      We often pay for brand.
       
    5. Min

      Min Well-Known Member

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      Not sure which servoking servos you've been looking at but the ones that I saw look nothing like BK servos. Even if they had the same internal design, those manufacturing standards I mentioned before still apply. If they are the same servos, the BK rejects might make their way into the servo kings.
       
    6. utrinque

      utrinque Well-Known Member

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      Last edited: Jul 29, 2015
    7. Min

      Min Well-Known Member

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      A forum post is not a reliable source. I could claim Hobbyking makes Kontronik Kosmiks.
      Even if Servoking manufactures BK servos it doesn't mean they are of the same quality or even design. Like I mentioned before, it is possible to have a wide distribution of quality coming from a single factory.
       
    8. utrinque

      utrinque Well-Known Member

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      @Min I do agree.

      I do not want to say I have many bad RJX HV servos. I have found a thread at HF: "RJX HV servos - any good?". Some say they are awesome, some had failures and crashes related to them.

      I put them in new X7 and hesitate to maiden it after what happened yesterday.

      I have seen reports of servos with missing bearings. I had such servo. I have seen reports of burned big brand expensive servos. I han a few which burned on me. I have seen reports of cold soldering of potentiometer wires in servos. I had such servo once. I had big brand servos stripping gears.

      Lets share what we know without bias. In my opinion it is difficult to make informed decisions without considering failure rates. No one has them for comparison. We share opinions, recomendations and warnings.

      I just do not agree with "you get what you pay for" statement. Not always expensive means better, more reliable, problem free. I tried both expensive and cheap.
       
    9. MadBird

      MadBird Well-Known Member

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      RCHN episode 143. Bert says that same company who makes RJX servo's makes his servos, but to his specifications.
       
    10. utrinque

      utrinque Well-Known Member

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      [​IMG]

      BK funboys warning.

      Three RJX servos failed on me causing two serious crashes of 700 helis. Two of them burne itself.

      One BK tail servo failed on me in X5.

      KST are awesome in 450 (306G) and in 700 and 800 (315BLS and 305BLS). Survived hard 800 crash (alu horns). Never failed on me for year and a half. I use them on tails of at least six 550, 600, 700, 800 helis.

      What is your experience with BK servos made by Servoking?
       
    11. josh

      josh Active Member

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      Last edited: Aug 2, 2015
    12. utrinque

      utrinque Well-Known Member

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    13. simon

      simon Well-Known Member

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      Meh...Whingers will whinge, you can find a Youtube clip on anything if you look hard enough. I am not really sure what you game is pal.
      Simon
       
    14. marcust

      marcust Member

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      I've seen videos of Ferraris on fire on youtube, they must be junk shiz cars.
       
    15. utrinque

      utrinque Well-Known Member

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    16. MickyD

      MickyD Well-Known Member

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      Dude.... Actually I take that back. Oi, hobbyking has a special forum for this type of posting. Please go and share your passion there and not here.
      Thanks
       
    17. utrinque

      utrinque Well-Known Member

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      Compare number of views of my thread:
      [​IMG]
      with views of all Goblin 600-750 threads:
      [​IMG]

      Which of your threads has comparable views count?

      I compare KST servos with BK.

      Please show me KST branded servos on HobbyKing.
       
    18. Min

      Min Well-Known Member

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      It's such a shame you don't live in Melbourne. I would be more than happy to meet up with you one weekend to show you why I use expensive gear.
       
    19. utrinque

      utrinque Well-Known Member

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      I get it.

      BK servos are not particularly expensive. Middle range. MKS 8X are more expensive.

      Expensive gear... it is relative. Do you use turbine engine?
       

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