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| Medusa 028--032--2800 | |||||||||||||||||||||||||||||||||||||||||
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Specifications
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| My thanks to Mike of www.aurorra.co.uk for the supply of this motor for testing. This motor is a 2800 KV brushless motor suitable for use with either a 3S, 4S or more pack. The motor is in the middle of what I consider to be the weight class for a trex at 70 g. This is the small brother of the Medusa motor tested previously on trextuning. That particular motor proved to be one of the most powerful motors I have tested but unfortunately was a little bit hungry with regard to amp draw. Hopefully this motor will prove to be less hungry but have similar levels of power. This motor is also different to the most recently tested motors in that it has a low KV. In order to test this motor with a 3S pack I selected a 15 tooth pinion. This should give me ample head speed and hopefully not overload the motor. Initial spool up revealed a willingness for the head speed to climb into the realms of 2900 RPM. This should be plenty for use with carbon blades but in order to test with the wood blades I will need to back off the throttle curve on the transmitter to stay around 2400 RPM. This is motor will be tested with both wood and carbon blades and I will also be testing it on high voltage to see what performance can be gained with a hot setup. The test was conducted in an ambient 20 degrees centigrade, 68 degrees Fahrenheit. The pitch range on the T-Rex being from +/- 10 degrees. The power source was a Kokam 3S 2000mAh pack. The test are charts are created from the CSV data from the Hyperion Emeter which shows Volts/Amps and RPM on one chart and Watts on a separate chart. |
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| The Medusa recorded the following maximum values : 29.07 amps 12.51 volts watts The recorded minimum voltage was 9.4 volts during the 30 seconds of full pitch. The motor temp at the end of the test was 70 degrees centigrade, 158 degrees Fahrenheit. The lithium pack reached a max temperature of 45 degrees centigrade, 81 degrees Fahrenheit. All of this is well within specification and nothing of concern. During the 30 second climbout the headspeed dropped from 2430 RPM to 2220 RPM, a 210 RPM drop in overall headspeed over a full 30 seconds of full pitch. This is a very very respectable performance and is comparable to that of the 400DH. This puts this motor amongst the top performers that I have tested. Amp draw was relatively high on this motor, with 29.07 Amps maximum over the course of the test. This level of draw will of course affect flight times. Next is the carbon blade test, again utilising the Kokam pack and using the Align Carbon Blades..... |
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| The Medusa recorded the following maximum values : 36.54 amps 12.49 volts 345.67 watts The recorded minimum voltage was 8.6 volts during the 30 seconds of full pitch. The motor temp at the end of the test was 81 degrees centigrade, 177 degrees Fahrenheit. The lithium pack reached a max temperature of 55 degrees centigrade, 131 degrees Fahrenheit. These temperatures are all well within specification for the motor and the pack. During the 30 second climbout the headspeed dropped from 2310 RPM to 1905 RPM, a 405 RPM drop in overall headspeed over a full 30 seconds of full pitch. This is still a respectable performance and in line with motors of this weight class. Amp draw was very high on this test, with 36.54 Amps maximum over the course of the test. This level of draw will of course affect flight times. Also this is beyond the specification of the Kokam pack and therefore potentially damaging to the cells from being put under such an extreme load. However, as usual the Kokam pack stayed within its temperature range and only reached a maximum of 55°. Something else of interest in the graphs above is the fluctuation of power during the full throttle and full pitch test. At this time I am unable to explain this particular phenomenon. Certainly during the test I could not tell that this fluctuation was occurring just from listening to the helicopter and motor loading. The interesting thing about this Medusa motor is that it has a very low KV value (2800) which makes it ideal for use as a high voltage motor in a hot setup. Therefore I am also going to test this motor in 4S configuration. Utilising high voltage should reduce the amp draw and bring it in line with specification of today's high-power packs. Initial testing has been slightly unsuccessful in that the speed controller I was using was unable to handle this motor and unfortunately caught fire and has since been consigned to the bin. The belief at this stage is that one of the FET chips overheated. On checking with the manufacturer the documentation for the speed controller is going to be updated to indicate that it is not suitable for this type of high voltage application. I will hook up my external BEC to another speed control and complete the 4S testing in a few days time. After which I will do some flight testing to look at flight performance on both configurations... |
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