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Old 04-22-2007, 12:33 PM   #1
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Default Brushless and Gearing

Today our national series started and ofcourse everybody was running Brushless.

But I also found out that nobody really understands the right gearing for brushless.

I started out with a 5.5 Bonded (LRP) and stuck to LRP's 8.8 for a big track. But this was way to slow and 19T stock could almost match my laptimes.

Changed to a 5.5 Sintered but still no speed. Only when I finally geared it to 5.3 I got the same speed as the others (4.5's and 5.5's).

But this seems like to high for a sintered motor as even the 4.5 in the LRP manual says 7.8.

So, what should be the right gearing for a large (1/8th gas) track?
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Old 04-22-2007, 01:58 PM   #2
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i have a 13.5 with sintered rotor not the same power as 4.5 or 5.5 but the ideal is the same , the ? is do you run carpet or asphalt , i find alittle hard to gear my car based on final ratio do to sometimes it doesnt work the same as NOVAK recommeds to gear this motors , i gear my car based on roll out and track size,
the track that race at its not big at all only 70'*40' where rpm isnt to much of a factor but torque takes a mayor part , i have a xray t2 007 us spec and normal gearing on that car is 116spur with pinion starting around 29 or 30 for stock , however with the 13.5 i had to gear the car with 100spur and starting with a 36
pinion depending tire sizes for foams of course ,,, last time i race the car i didnt
change pinion all day with 3 heats and a main and the car was just getting faster every qualifier also keep in mine the motor temp due that sintered rotor let you gear higher than usual also remember that novak brushless do have lots of power but rpms are not as high as a well tuned brushed motor so there for you have to gear higher,,,,, BTW temps on brushless motor are around 140 to 155 of course if it is gear to the moon hope this little info helps.
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Old 04-22-2007, 03:50 PM   #3
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These are the unloaded RPM #'s per volt from NoVAK on their B/L motors

3.5 = 10,500
4.5 = 9,000
5.5 = 7,400
6.5 = 6,400
7.5 = 5,800
8.5 = 5,000
10.5 = 4,300
13.5 = 3,300

Most of them average about 16% rpm drop per extra wind from the 3.5 up. That number seems to decrease as the # of winds increases. As you can see from the 10.5 to the 13.5 is only about 23% with a 3 wind jump.

I've found under load these motors drop approx. 30-40% of their unloaded RPM depending on the track size and style.

16% = about 3-4 teeth on the pinion gear. So a 4.5 motor should be around 12 teeth or so less than a 8.5. Most of the higher wind motors will run similar top speeds, but they need to be geared up...and the 3.5 and 4.5 type motors really need to be geared down. (6 cell = approx 7.32 volts under load x 6825 RPV loaded = 50,000 RPM loaded and almost 77,000 unloaded w/ a 3.5)
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Old 04-22-2007, 04:07 PM   #4
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i ran my 5.5 with a bonded rotor at around 10.25 FDR...
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