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  1. #1
    RC Turnbuckle Jr.
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    Brushless Motor Voltage Questions

    Based on a motor with a max RPM of 60000, you would want to find an option with the Rpm/Volt closest to the following w/o going over, right?  Question 1

    Using 3.7v per cell
    6s option =60000/22.2=2702r/v
    5s option =60000/18.5=3243r/v
    4s option =60000/14.8=4054r/v
    3s option =60000/11.1=5405r/v

    …or is it better to use the max voltage of the cell (4.2v)  Question 2
    6s option =60000/25.2=2380r/v
    5s option =60000/21.0=2857r/v
    4s option =60000/16.8=3571r/v
    3s option =60000/12.6=4761r/v

    Also…
    I have read that it is better to run a lower Rpm / Volt motor and use more volts. In other words a 6s on a 2702r/v would be better than a 3s on a 5405r/v.
    Is this true? If so, then why?  Questions 3, and 4

    So if using a 1515 Neu motor, your ideal options would be…
    6s = 1515/1y 2200
    5s = 1515/1.5D 2700
    4s = 1515/1D 4100
    3s = 1515/1D 4100
    in that order…correct?  Question 5

    Oh yeah….why am I posting this here?
    Because, I am looking for brushless options for the E-Revo and Mamba Monster I have on pre-order.


    OK..now let me have it!
    I know you are all opinionated about this and I want to hear it all.
    Just please don’t bash each other for having different ideas on the best set-up.
    Whatever your idea is…I’d like to hear it

  2. #2
    RC Turnbuckle Jr.
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    Right-ish, wrong, see below and wrong.

    1. 60,000rpms is the maxximum for Neu or other high-end motors, but in reality running it that fast for length of time will kill the bearings rather quickly. Best to aim for 40,000-50,000rpms at most.

    2. Always use the nominal, or 'resting' voltage, not the fully charged voltage.

    3. A lower kv rating motor draws less current (amps) than a high kv motor, and it also turns more slowly. Therefore, using the slower motor on a higher voltage will produce lower temps & longer run time due to lower amp draw (amps = heat).

    4. 6s = 1515/2.5D 1650kv
    5s = 1515/2D 2050kv
    4s = 1515/1Y 2200kv
    It is possible to run the 4s motor on 5s, it makes great power but run time will suffer, as will temps a bit. The 5s motor would also be good on 4s, but topspeed will suffer a little, buit temps & run time will be much better. The 6s motor could also work on 5s, but again top speed will suffer for better temps and runtime.

    You would never use a 3s lipo system or motor in an MT, regardless of what some noob who works for a magazine may tell you (I saw the youtube promo vid too). The single VXL system can barely cope without over heating, and that is when its geared reasonably- no chance of racing or heavy bashing as the temps will sky rocket.
    READ THE FAQ!
    or else.....

  3. #3
    RC Turnbuckle Jr.
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    Suicideneil,
    Based on your suggestion to aim for 40,000-50,000rpms, these numbers seem to be conservative.

    6s = 22.2 using a 1515/2.5D 1650 gives 36630rpm
    5s = 18.5 using a 1515/2D 2050 gives 37925rpm
    4s = 14.8 using a 1515/1Y 2200 gives 32560rpm

  4. #4
    RC Turnbuckle Jr.
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    With the emphasis on 'conserve'

    Unlike the Hvmaxx motors, you dont have to gear down Neus or most other high-end motors, you actually tend to gear them up. This way, the motor spins at a comfortable speed, and you still get that good topend you are after. if you wanna have a look at some common setups using Neu motors and compare the voltages/ cell counts, have a look here:

    http://www.rc-monster.com/forum/showthread.php?t=6423
    READ THE FAQ!
    or else.....

  5. #5
    RC Turnbuckle Jr.
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    I'm no expert, but I would highly recommend the 1.5d on a 4s setup, and it is great on 5s and 6s for 'playing around'. The 1y will be a bit slower on the 4s setup but reasonable, will thrive on the 5s setup and 6s for 'playing around'. The 2d would be nice on 6s setup only, I'm not sure who would want the 2.5d at 1650kv, unless you had a specific race track in mind and with a 6s setup it worked out to the perfect max top end and get bonus high tq and low temps.
    eRevo Neu 1515 1.5d MMM Maxamps 4-2s2p8k 2-3s2p8k

  6. #6
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    Agreed. I'm a fan of the 1.5D...have now several more for other projects. Killer motor on anything from 4S to 6S
    3906 8XL
    3905 Neu 74.1mph
    XTM MMT -80.4mph

  7. #7
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    I think that the intended primary use also should be a consideration.

    If your going to be doing mainly high speed runs on the street with a little offroad then your going to want the higher kv motor.

    If you were planning on running on a track a lower kv motor would give you more usable power and longer runtimes. If your running 6s in the e-revo and limited to 5Ah packs this would be a major consideration in this case.

    Just for reference the 1515 1Y can easily pull enough amps from a 5s 5Ah pack to bring runtimes under 10 minutes when pushed hard non-stop. I'm curious to hear from stumblin if the 1.5D is much more power hungry or not.
    [QUOTE=Billstmaxx]if the water can't get out how does it get in??[/QUOTE]

  8. #8
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    What motor is best for you depends on how your going to use it and what you expect from it.
    1515's can also pull a lot of gearing with out any issues, so you don't need high rpm to get good performance for racing or general bashing. Even 30 000 rpm will give you 35-40 mph racing speeds with out issues, and ~45mph for bashing in larger areas.
    I race my 1650kv 2.5d on 5s and I can gear it to have more power than you can use on the track, 6s gets hard to control on the slippery tracks I race at. Even on 4s you can gear it to be competitive on the track, but it's not the best option. On 3s it's about the same speed as a stock e-maxx and stays cool.
    On 5s http://www.youtube.com/watch?v=ZMZeTJFA2f4
    There is a 1515 2d (2050kv) on 4s at my track, it has good power and stays very cool geared for ~40mph. You don't need any more power than that has on the track.
    Personally I don't see any reason to go past 40 000 rpm for racing and normal bashing (up to 50 mph) with a 1515. For very high speeds runs then I see the point.
    Last edited by Patrick 86; 05-11-2008 at 05:27 AM.

  9. #9
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    Neus in general are quite happy at rpms well over 40k. The advantage to running a higher rpm motor is that you don't need to gear quite as tall, so each motor revolution is not doing quite as much work. Also, slow speed control (and no cogging) is better too since there are more revolutions for the ESC to sample rotor position.

    But yes, Nues CAN pull a tall gear no problem, but a heavily loaded motor (via gearing) pulls more current and taxes the ESC and battery more.

    I recommend getting the highest voltage your wallet and ESC can support. Then, select the motor size based on vehicle weight/size. Then, get the motor wind that will run at the optimum rpm at this voltage; for Feiagos, 35k; for Neus, 40-50k is fine.

  10. #10
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    agreed.

    My experience with high RPM motors is, they run extremely hot compared to something spinning slower. Id rather load a lower kv motor to build the power. Voltage is always king, and with more voltage you can build the same power with less amps. Less amps = less heat. Less heat means you are saving power instead of making heat. The downside to voltage is, the more voltage you have the smaller problems you need to create a big fire. 6s is playin with fire, I have yet to see one last any length of time and actually be run hard. They are out there I am sure, but they are rare birds.

  11. #11
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    i know this is an old thread but what are: 2.5d. 2d, 1.5d, 1y... etc?

    Quote Originally Posted by HoovHartid View Post
    Suicideneil,
    Based on your suggestion to aim for 40,000-50,000rpms, these numbers seem to be conservative.

    6s = 22.2 using a 1515/2.5D 1650 gives 36630rpm
    5s = 18.5 using a 1515/2D 2050 gives 37925rpm
    4s = 14.8 using a 1515/1Y 2200 gives 32560rpm

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