Ko BMC Speedo

Old 03-25-2011, 02:34 PM
  #1216  
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hooked up my 13.5 up, but not in car, turned my throttle travel from 150 to 50, turned it on, pulled trigger down for 45sec and I could not touch it anymore, super hot. I think its broke
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Old 03-25-2011, 02:46 PM
  #1217  
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were you doing this with the tires off the ground, if so that is the worst thing you can do for the motor and speedo.
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Old 03-26-2011, 06:58 AM
  #1218  
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nope motor was just sitting on the table, but I am curious why would it harm the speedo/motor to gas the throttle while the tires off ground?
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Old 03-26-2011, 07:07 AM
  #1219  
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i have personally seen someone do this and there rotor exploded and shorted out the motor and burned up the speedo. also free reving anything is bad.
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Old 03-26-2011, 03:22 PM
  #1220  
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hmmm.... there must have been something else wrong. Can you explain in detail why a motor would expload and speedo give out, just by testing it on the bench????
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Old 03-26-2011, 03:30 PM
  #1221  
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Originally Posted by synap2012 View Post
hmmm.... there must have been something else wrong. Can you explain in detail why a motor would expload and speedo give out, just by testing it on the bench????
The motors are not designed to go to full revs with zero load. I dont have specifics of the physics involved, but they are designed to have wheels on the ground. Even going to full revs with the motor in the car with the wheels in the air for prolonged periods is not a good thing.
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Old 03-26-2011, 03:58 PM
  #1222  
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Originally Posted by synap2012 View Post
hmmm.... there must have been something else wrong. Can you explain in detail why a motor would expload and speedo give out, just by testing it on the bench????
In a brushless rotor the magnets are glued to the shaft. Most have a failure point in the RPM range. You will most likely never achieve this range if the motor is under load. However on the bench there is nothing preventing it from spinning up past what it is designed to take. When you do you will have failure in rotor, which will most likely short out the stator windings and cause failure. It doesn't explode like in a hollywood movie. But the rotor does delaminate. I have had one rotor fail while running. It was not catastrophic as only a small portion of nickel plating came off. But is was enough to seize the front bearing and grind the whole thing to a halt.

Running the motor up and down for a couple of seconds though should not cause the ESC to get too hot to touch. I have been testing mine right now and it just gets a little warm. Unless I put the timing on 12 then it gets hot but I can still touch it.
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Old 03-26-2011, 04:05 PM
  #1223  
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Originally Posted by synap2012 View Post
hmmm.... there must have been something else wrong. Can you explain in detail why a motor would expload and speedo give out, just by testing it on the bench????
It's just like reving a real car's engine to redline while in neutral. All the power that the motor produces has no where to go, so it is applied to internal components of the engine. So on a brushless motor that is rev'd to it limit, it applies all the power to the rotor.

When the rotor explodes, I am sure the sensors don't read correctly. So the Speedo may fire poles in the wrong order. When that happens you could fire a single pole in both directions meaning +/- and -/+. Or the back end generated from a frozen rotor could be enough feedback to really damage the Speedo.

Last edited by theisgroup; 03-26-2011 at 04:51 PM.
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Old 03-26-2011, 04:12 PM
  #1224  
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I actually saw a racer explode a rotor when his car barrel rolled at the end of a long straight, he didn't let of the throttle and when it unloaded it broke up. It was like a 2 cycle kart when the piston seizes at the end of the straight.
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Old 03-27-2011, 09:51 AM
  #1225  
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Makes some sense but, every engine that comes from a factory has been on a dyno of some kind with no load! I check to see if a motor is balanced by setting it in my hand/table and giving a blip of power, the motor if its in good balance wont jump all over the place. Something I have done for years!

I mean yes, if you turn everything up and slam the throttle for obscene periods of time I can see things coming loose, but checking electronics out of the car has never givin me problems! been in the hobby 16+ years
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Old 03-27-2011, 10:13 AM
  #1226  
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I just provide the info. I have never shattered a rotor or had a prob with any of my brushless speeds. Do with it what you will
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Old 03-27-2011, 10:18 AM
  #1227  
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Originally Posted by synap2012 View Post
Makes some sense but, every engine that comes from a factory has been on a dyno of some kind with no load! I check to see if a motor is balanced by setting it in my hand/table and giving a blip of power, the motor if its in good balance wont jump all over the place. Something I have done for years!

I mean yes, if you turn everything up and slam the throttle for obscene periods of time I can see things coming loose, but checking electronics out of the car has never givin me problems! been in the hobby 16+ years
But you held the throttle for 45 seconds, not just a few blips!

People are giving you the answers, but your choosing not to take them. And good dyno's have a load of some sort.
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Old 03-27-2011, 10:19 AM
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Originally Posted by synap2012 View Post
Makes some sense but, every engine that comes from a factory has been on a dyno of some kind with no load! I check to see if a motor is balanced by setting it in my hand/table and giving a blip of power, the motor if its in good balance wont jump all over the place. Something I have done for years!

I mean yes, if you turn everything up and slam the throttle for obscene periods of time I can see things coming loose, but checking electronics out of the car has never givin me problems! been in the hobby 16+ years
Actually good dynos use some kind of load.
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Old 03-27-2011, 10:42 AM
  #1229  
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Originally Posted by synap2012 View Post
every engine that comes from a factory has been on a dyno of some kind with no load!
Uh...by it's nature, if it's a dyno, it applies a load. A "dyno" with no load is a test stand.

As far as free-revving, a short blip probably never hurt anything (unless dealing with a low wind mod motor), but you describe a 45 second torture test.

If you have doubts about the veracity of the information you are receiving, have a look at

http://www.teamnovak.com/tech_info/f...g_warning.html

From Novak's own site. I'm figuring they know more than you, I (25 years in the hobby now) and anyone else who has posted in this thread combined about brushless motors and failure modes therein. There probably isn't much they haven't seen.
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Old 03-27-2011, 12:40 PM
  #1230  
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you guys are right, I mis-lead, my 45 sec test was just blipping the throttle while having my end trim points down from 150 to 50. It took the ESC about 45 sec to become to a point that I could not touch it.

While the speedo was in the car it only lasted about 10sec before it was to hot.

I am sorry for not being more precise about my post.

O-by the way who said I was not listening to their answers??!??

I am completely aware of what they said

Thanks everybody!

p.s. sent esc to KO I will here about what was wrong in a few weeks
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