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Mega 15T brushed motor

Discussion in 'Electronics' started by Skaxis, May 28, 2015.

  1. Skaxis

    Skaxis Well-Known Member

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    My wife and son were bashing about in the (flat) back yard tonight and on the street. Mix of two surfaces: short St. Augustine grass and blacktop. I put pack #3 in and the steering worked, but no power to the rear tires. The light on the ESC was working. So I unplugged the motor and tried a spare I had in my box. Viola, power. I tried the motor included with the kit and nada. :( I've never seen a motor burn up in just two battery packs. Seriously not impressed.
     
  2. mrbelloso

    mrbelloso Moderator
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    If you were using Lipo, the motor will get burned really fast. Contact Arrma and ask for a replacement under warranty.
     
  3. Skaxis

    Skaxis Well-Known Member

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    No LiPo, 3800 mAh NiMh. I've emailed them. Will report on what they say.
     
  4. Unusual RC

    Unusual RC Moderator
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    Grass creates a lot of friction. Compare it with driving your real scale car into a cornfield!

    I am not saying you should not do that, but my own experience is that the brushes of the stock motor are of poor quality.
    They get overheated very quickly.

    The most cheap option would be replacing it with a brushed motor with replaceable brushes, or upgrade to a mild 2-pole brushless system
     
  5. Skaxis

    Skaxis Well-Known Member

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    That's a great analogy. I gotta say, I've run my 1/10 buggies in the backyard for more battery packs than I can count and they have never burned up a motor. Some of them are just using the stock 540-J "silver can" motor, others are using more hopped up motors. I'm going to chalk this up to either a) a defective motor or b) Arrma Mega motors aren't so mega. ;) I'm in the process of an RMA request from the vendor. While I'm working through that I'm going to keep running the Tamiya Dirt Tuned motor in the Fury. It fits the bill as it's cheap and has replaceable brushes. I can tell you that the Arrma motor was pretty hot after a pack of pure pavement driving and the Dirt Tuned was cool as a cucumber after a pack on grass.
     
  6. Unusual RC

    Unusual RC Moderator
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    It all depends on how long the grass is, the amount of ground clearance, and last but not least the size of the tires (diameter).

    But most important is proper gearing. Possibly your other cars are geared "conservative", which means lower geared than might be optimal.

    Arrma for some reason (I can make a guess why) gears the mega models a bit on the optimal side. And their used motor has poor quality brushes.

    Indeed some other simple closed can 540 like motors perform better and last longer. Kyosho comes to mind for example.

    I did get the motor replaced under warranty. Never used it though, and went straight for a brushless replacement.

    I might use it in a vintage boat I have ;)
     
  7. mrbelloso

    mrbelloso Moderator
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    Some of the other people have commented that is better to call Arrma than emailed them. Email response could take up to 3 months and by calling they have their problem resolved on one phone call.
     
  8. Darren Wes

    Darren Wes Well-Known Member

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    Yeah...i can just imagine how well rc cars would run on a fresh cut 18th green...but on that note i find any grass taller then the tires has got to be a steady low speed.... a 2 pole brushless does help a bunch with the tall grass. But so would lowering 1 pinion. Also not running a lipo on the stock setup... i find beingmindful of scale helps the most... you do have me thinking that someone has made a10th scale tall grass tire!... hummm.goingswimming....

    Edit: Solved the file issue
     
    #8 Darren Wes, May 30, 2015
    Last edited by a moderator: May 30, 2015
  9. roger nelson

    roger nelson Well-Known Member

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    I called them and they say return the motor with copy of receipt and return address and email.
     
  10. James

    James Well-Known Member

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    Same issue happened to me. Burned out my motor within a few days. I emailed arrma support and I did get a reply telling me that they'd send me a motor.. but then no confirmation email to say whether they sent it or not. That was long ago. I'm assuming it wasn't sent. I ended up just buying a replacement from my hobby shop and then ended up buying a brushless system. Not so impressed with the support over email. Calling may have been better but I'm passed that point now
     
  11. Skaxis

    Skaxis Well-Known Member

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    I contacted the vendor first, and after a back and forth a couple of days they ended up just telling me to call Arrma. FYI, Arrma is a Hobbico company. I sat for about 25 minutes on hold waiting for a CSR to pick up. The gentleman I spoke to was polite, courteous and apologetic. He asked for my zip and name. He quickly found me in their system (creepy) and said that a replacement motor would be sent ASAP via UPS. I'll post back when I get it.

    Oh, BTW here is a pic of the truck on the grass we were running it on. Hardly scaled down "corn fields". ;)

    06.02.2015-11.20.png
     
    #11 Skaxis, Jun 2, 2015
    Last edited: Jun 2, 2015
    joe kidd likes this.
  12. Unusual RC

    Unusual RC Moderator
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    The grass comes halfway the diameter of the wheels, which can be considered corn field height for a real scale SCT ;)
    This kind of grass is really a high strain for the poor 15T brushed motor I am afraid...

    Nice field though ;)
     
  13. Djinn

    Djinn Well-Known Member

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    I had the same problem check the connection to the motor, my wire had popped off little solder and all fixed.
     
  14. joe kidd

    joe kidd Well-Known Member

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    I went to local rc shop today for upgrade on short course but all they had was scorpion brushless upgrade said it would make it a 50mph truck. Not looking to fling it apart just want about 10mph added speed from stock anyone have any ideas that won't cause a major upgrade
     
  15. Darren Wes

    Darren Wes Well-Known Member

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    Ummm a brushed motor probably wont give you 10mph more. Well unless you put in a higher pinion and unleash the beast on maybe a 12t titan or something. Wont last long but possible.

    What you sound like you are wanting a cheap brushless upgrade.
    But yeah a esc and motor could cost like 55 bucks as opposed to a 20 dollar brushed motor
     
  16. joe kidd

    joe kidd Well-Known Member

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    Appreciate the info does anyone know what size brushless motor I would need to make it about 35mph
     
  17. Darren Wes

    Darren Wes Well-Known Member

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    Depends on what kinda battery you wanna use. You gotta choose wisely if you want speed.
    You could go 3s with a low 2000kv motor but you will probably break your transmission. Since you wanna go 35mph you might wanna stay away from high 2000kv
    Lower 3000kv is nice for driving speeds
    I use high 3900kv and i go about 33ish with 2s and low 40s on 3s.
    I wouldnt recommend anything higher than 39kv for 3s (at least not cheap stuff) and well.... i haven't used anything higher but a 43~47kv brushless would do that on 2s.
    You could go higher then 5300kv buttttyt.
    You would probably fry it in 2 min
     
  18. Unusual RC

    Unusual RC Moderator
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    You can actually calculate in advance what kind of kV you need for your set-up, in order to reach 35mph.

    On the official Arrma forum I did put the calculation down there.

    You need to know the reduction of the Arrma gearbox. Then diameter of your rear wheel and the spur/pinion combo.

    With that info you can calculate the theoretical top speed, given your battery type.

    I am on my cell right now. But if you want I can redo it here for you!?
     
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  19. Skaxis

    Skaxis Well-Known Member

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    Is there a web form for this calculation? You know the kind I mean, where you fill in all but one field and hit a button and the web form calculates the missing variable? If not, there should be!
     
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  20. joe kidd

    joe kidd Well-Known Member

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