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Help with understanding 4S to 6S gearing

Help with understanding 4S to 6S gearing

Old 04-19-2016, 07:28 PM
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Lightbulb Help with understanding 4S to 6S gearing

Can someone help me to see if my thinking and/or math is correct. I did post this in the 3.0 thread, but did not get a response.

I have a recently purchased Losi 8ight 3.0 with a Castle Mamba 2 and Neu 2200KV. I took it to the track Sunday and really had a great time. It was my first time racing in 15 years. I have been into planes during that time.

I have a lot of 6S batteries from my planes and only had 2 4S 4500mah to run in the buggy. I want to use my 6S batteries. In doing so, I want to keep the same amount of power with less amps. It should be the same principle as my planes....ie....if I go from 4S to 6S and to a smaller prop, I end up with the same amout of power with less amp draw which is less heat and more efficient.
This is a measureable amount and not theory.

Here are the numbers and I am not positive about everything.
  1. The stock system is 2200KV x 14.8V = 32,560rpms (no load)
  2. My pinion and gear is 15/43 x 3.3 (drive ratio) = 9.46 (Final drive ratio)
  3. 32,560 / 9.46 = 3,441 (rpm's for 1 revolution of wheel)

So if I can find a 6S system close to 3,441....it should be the same amount of power / watts.
  1. 2200KV x 22.2V = 48,840
  2. Pinion Spur is 11/45 for a final drive of 13.487
  3. 48,840 / 13.487 = 3618 (a 10 tooth pinion is 3288)

I realize this is all no load and perfect conditions, but if I do change to 6S and put a wattmeter on it, I should be close to what I had on 4S.......am I close?
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Old 04-19-2016, 08:11 PM
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I have a new in box monster x that runs 2s-6s, it's pretty rad, I have one on my slash thats stretched and widened

Last edited by 666thSlash; 04-19-2016 at 09:09 PM.
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Old 04-19-2016, 10:49 PM
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you try to get same wheel rpm by changing gear ratio. However, there is not any linear relationship that you get same power at specified rpm by alternating gear ratio. Brushless motors are more efficient at lower rpm range. Therefore, you may not benefit the advantage of 6s lipo at all.
i suggest you to buy 1500 to 1800kv motor to have a system pulls less amps.
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Old 04-20-2016, 05:11 AM
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Originally Posted by murat61 View Post
you try to get same wheel rpm by changing gear ratio. However, there is not any linear relationship that you get same power at specified rpm by alternating gear ratio. Brushless motors are more efficient at lower rpm range. Therefore, you may not benefit the advantage of 6s lipo at all.
i suggest you to buy 1500 to 1800kv motor to have a system pulls less amps.
2200x14.8 =32560RPM 1700kvx18.5=31450RPM 1400KVx22.2=31570RPM. Stay in that RPM range but the more cells just become more efficient. A 2200kv motor on 6 cell is 48840RPM, Who's going to Drive that?
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Old 04-20-2016, 01:13 PM
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just an fyi if you haven't already, confirm your track allows that. A lot of places only allow up to 4S lipo.
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Old 04-20-2016, 01:31 PM
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http://m.ebay.com/itm/SKYRC-TORO-1-8...534?nav=SEARCH
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Old 04-21-2016, 03:10 AM
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A 1400kv motor is just right on 6s. When we used to run nitros and elec together I was easily running 20 min mains on a 3000mah 6s. Almost every track has a 4s rule. It's a shame because the higher voltage battery is more efficient with a lower kv motor allowing you to use a smaller and lighter battery. With my 1900kv on 4s I was still turning my radio down to 80% so I've been running my 1400kv on 4s and gearing it up (18/46) and easily running our 10min mains on a 3000mah battery.
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Old 04-21-2016, 06:00 PM
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I'm not even running a 4s battery in my 8th scale. I'm running 2 2s hardcase packs in series. Eventually I will invest in a 4s pack thou. Everyone is going be running Gens Ace Lipos at my track. But I just bought some Common Sense Lipos to use.
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Old 04-22-2016, 12:17 PM
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In addition to the good comments above, I will add one more:
2200KV x 22.2V = 48,840 is very fast, you risk killing your motor.
Typically 50,000 is max rpm.

I ran 6S on 1400kv for years and loved it. But it is not allowed if you race.
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