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Old 12-29-2003, 05:38 AM   #31
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OK, I basicly asked Josh Cyrul the following question... 'Tell us about what differances to expect on track under ideal conditions/gearing when you would use a 19 turn motor, vs. when you'd use a 12 turn motor'... and the following was his reply.

"DynoMoHum - I would say that on a 10 second a lap track a 12 turn would be about .1-.2 faster per lap than the 19 turn. More top speed and at least the same or more bottom end."



Pretty much backs up what I've been trying to explain.


I'd be more then happy to try and further enlighten people as to what some of the theoretical reasons I maintined the posisition I did if anyone cares to listen.

If your looking for me to humble myself first, I offer this... My comments about lower turn motors generaly being more effcient then higher turn motors is really a bit deceivng and really should be revised a bit. I'll try and explain it better... the short version is that low turn motors are clearly more effcient at high amp loads, at lower amp load they have simmilar, perhaps slightly lower effciency... again however this depends on many factors such as timing.


If you want more contorversial opions of mine on this subject of 19 vs 12 turn motors... stay tuned and I could try and explain why I feel it's misleading to state that low wind motors have lower torque then high wind motors... in fact depending on how you look at it, it's not only misleading, but it's down right false.
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Old 12-29-2003, 09:16 AM   #32
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Dynomo: Thank you.
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Old 12-29-2003, 11:56 AM   #33
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If 19 turn motors are faster than 12 turn (which I know from experience they are NOT) than why would anybody run them instead of a 19t? Only under certain track conditions is a 12 turn motor going to be slower, and that certainly has more to do with the driver than the power of the motor. If your going faster on the straight, and are overshooting every corner, and getting your car out of shape, then maybe a stock motor would be best for you. There are a number of times that I have run a stock motor in mod truck, because the track was really dusty or loose, and won because the other guys running mods couldn't come out of a corner straight.

Lower turns equal more power. Don't forget that 19 turn uses laydown brushes which will make the power numbers look higher because of the brushes shorting across the comm. The Kr has a larger comm to eliminate this.
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Old 12-29-2003, 02:13 PM   #34
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PitCrew,

What do you mean when you say 'that 19 turn uses laydown brushses which will make the power numbers look higher because the brushes shorting across the comm' etc...


If your refering to the data I had in my graphs, I don't beleive the data is destorted in anyway as a result of the brush overlap. If anything the effciency would be lower if there was exsessive shorting, but the output power is what it is, the accuracy of the output power numbers should not be effected by comm wrap in anyway.


BTW, I am pretty sure that that C2 in my graphs had the Trailing Edge of the brushes trimed by about .015" inch, as that is pretty much standard procedure for me when I tune a motor with laydown brushes.
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Old 12-29-2003, 02:32 PM   #35
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Calm down there dyno.

What I was saying is that the numbers shown on a dyno for a laydown can be be inflated (ie.. power output in watts) because as the comm rotates, with laydown brushes and a standard diameter comm, the comm material creates a short between the two brushes for a very brief amount of the total rotation. But you also get more overall power because of the lack of cogging; one pole of the armature not being energized for a brief amount of time.

I do believe I am agreeing with you on this, that a 12t motor is going to be fasterthan a 19t, if thats what you are saying...
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Old 12-29-2003, 02:34 PM   #36
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Maybe I am thinking of power consumption, which as you said would decrease the eff #, but power output of a slave motor (being used as a generator) is what it is.

Sorry.
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Old 12-29-2003, 05:19 PM   #37
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Some brush overlap can indeed be a good thing, that is it can increase output power... too much overlap just tends to use more input power then you gain in output power and amp input goes up while effciency goes down. I personaly belelive there is little or no reason to ever have brush width greater then about .175", which is what you wind up with when you trim a laydown brush by .015". A really high RPM motor will typicaly bennifit more from a slightly narrowed laydown brush then will a moderate RPM motor will...

Interestingly enough, a D5 motor has brushes that are about .175" right out of the box. However most Mod guys won't even use them that wide, they typicaly narrow them to about .150 which is the width of a standard stand up brush....

Since I didn't dyno the D5 Mod motors in those graphs, I have no idea if the brushes were trimed or not. My assumption would be that the brushes were full sized P-94 brushes, simply because there was no notation that the brushes had been altered.

So... the brushes on all the motors in those graphs, may very well be juat about the same width.
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