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Armattan Oomph 2205 2550kv
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This is the hyper little brother of the Oomph 2206 2300kv, trading weight for KV.

Check out the full list of motors in this series here

Summary

Published: Mar 7, 2017

Armattan Oomph 2205 2550kv<br />

Tested KV:2540kv
Weight:29g
Stator W:22mm
Stator H:5mm
The Armattan Oomph 2206 motor came across the bench a while ago with some innovative features and some interesting design approaches. This 2205 version follows on that design, simply scaling down the stator size.  The reduced stator size allows the motor to reach sub 30g weight.  I was hoping for a bit less weight given that many 2205 motors are hitting 26 or 27g fairly easily, but the thick shaft and fairly substantial bell design definitely make that weight range harder to reach.  The increased diameter of the internal shaft and decreased lever arm of the shorter prop shaft should result in better durability especially when combined with the bell design, so it is a tradeoff between weight and robustness.  Other than that all the comments about the design of the previous Oomph motors apply here.  Definitely a quality build from Brother Hobby combined with Armattan's unique perspective.

Results

Coming down from 2206 to 2205 on this motor definitely has an impact on performance.  The reduced stator height trades torque for higher RPMs, but practically speaking that means this motor will be more focused on lighter loaded props like the 5x4x3 or Cyclone 5x4.5x3.  While it is certainly capable of pushing heavier props thanks to the relatively conservative 2550kv, the lack of torque will impact the transition speeds, and you'll be more likely to get difficult to remove bounce-back on hard recoveries, and the characterstic "snap" of the high torque 2206s will be missing.  The 2205 and higher KV also trades off some of the impressive efficiency of the 2206s. On the 5x4x3 it actually outperforms the 2206 variant, but at significantly higher current draw, just over 1300g at 33A for the 2205 and just over 1270g at 28A for the 2206.  On the 5x4x4, a slightly heavier prop, the difference is even more pronounced, with almost identical thrust at just under 1400g, but 35A on the 2205 and 31A on the 2206.  That current draw difference minimizes at lower throttle but never completely goes away.  Still some very impressive performance from a 2205, matching the original RS2206 2600kv quite closely with a bit better efficiency, which given the significanly lower KV is an interesting analysis.