My contribution: Axi 2808/20 data and Dymond Raven performance - RC Groups
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Apr 04, 2004, 09:30 PM
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ohms's Avatar

My contribution: Axi 2808/20 data and Dymond Raven performance

My contribution: Axi 2808/20 data and Dymond Raven performance

So it was that a few years ago I bought and flew a Dymond Raven a few times and then decided to get out of the hobby. I sold my Astro motors, speed controls, batteries, all my radios/receivers, most servos, but not the plane. Well, that insubordinate plane stared at me defiantly from the storage closet for years until I finally couldn’t take it anymore and decided to give it another shot. I now have an Axi 2808/20, an 8-cell 1050 NiMH from CBP, and an 8-cell 1300 SCR pack from MEC. Here are the measurements using Graupner scimitar props at 15 seconds of motor run:

Prop Battery RPM Amps
09-5 8C1050 8700±100 12.8±0.1
09-5 8C1300 9400±100 14.5±0.2
10-6 8C1050 7000±150 17.4±0.1
10-6 8C1300 7700±060 21.0±0.5
11-7 8C1050 6000±200 20.6±1.5
11-7 8C1300 6400±100 25.4±1.3

The values represent the averages of three independent determinations and include standard deviations. Packs were peak charged with an Astro 110D charger.

Dymond Raven flight performance: The Axi fit easily into the Raven’s nose after removing the stock motor mount. AUW was 39.8 and 34.3 ounces with the 1300 and 1050 packs, respectively. Since the Raven’s sister ship Crazee has already been reviewed by Ezone, I won’t go into details, but I can say this setup matches very well with this plane. With the 10-6 prop the climbs are steeper than before and the duration has improved. I can get about 3 or 4 minutes of usable motor time (mostly WOT). It doesn’t go vertical, but it does climb quickly at a very steep angle. It really floats with the lighter pack without too much loss of duration. The results are impressive for a motor that weighs less than 3 ounces. I have read some mixed opinions about Axi outrunners, but I am quite satisfied with my experience. Hopefully I’ll make a flight video and post it. And hopefully others will find this info useful, as I have found an abundance of useful info on Ezone. Happy flying!

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Apr 05, 2004, 04:53 AM
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Bruce Abbott's Avatar
I put your setup into Motocalc. The predicted current and rpm were very close (±2%). With the 10x6 and 8x1050, Motocalc predicts a climb rate of 735ft/min, run time of 3:49, and 68% motor efficiency.

The only thing that's a bit worrying is the motor loss of 40.7 Watts. Presumably this is OK for short runs, provided that the motor is allowed to cool off between climbs.
Apr 05, 2004, 08:10 PM
Registered User
ohms's Avatar
That's interesting... I hadn't looked closely at the Motocalc numbers, but 68% efficiency is 10% below what the instruction booklet states for this motor. Any ideas on how to improve this? Presumably if I keep the amps closer to the max efficiency current of 10-15A that would improve things. I haven't tried flying with the 9-5 prop yet. But I was under the impression that these motors could be pushed a bit harder.

One other thing--after a 7 min. flight the motor and battery were very warm but not hot. However, the Jeti 30 speed control felt quite a bit warmer than I would expect. I don't know if that means anything, but it concerns me that the controller might fail mid-flight. Any opinions? Thanks.