kennydee

I have an AXI 2808/16 motor that is on my Great Planes Foamie Sukoi. I had intended to run this motor using a 3 cell Li-pol and an APC 10/4.7 slow-flyer prop. I had the motor connected to a Castle 25 amp controller. This set-up wouldn't work, the motor would shut off a few seconds after start. I then borrowed a meter and checked the motor. It was hitting nearly 40 amps before the controller cut it off. I switched the controller to a Castle 35 amp and checked it again. Got the same result, 38 to 40amps, much more than suggested by the AXI info(25 to 30amps). I changed batteries, went to a 2S 2P 4200 mill-amp Thunder power. According to AXI, the lower voltage should result in lower amps(on the same prop). This set-up ran at about 25 amps (still more than the suggested 19 to 20 amps). I flew the plane this way for a few weeks(maybe 20 flights). I was getting 15 to 20 minute flights until just recently. All of a sudden, the flight time dropped to 2 or 3 minutes. I dropped by my new adopted Hobby Shop (Fliteline in Summerville SC) and we checked the amp draw. It was up to 30 amps. That's about 10 amps more than it should be pulling on the 2S2P pack and 10/4.7 slowfly prop. I had to drop down to an 8/6 prop to get the amps down to about 25. The plane still flys but I've lost the vertical ability and a lot of power. I've tried to call Hobby Lobby but, so far, haven't been able to get the tech. I also suspect that the high amp draw has weakened my $100 2S2P pack. Is this motor defective?

Matt Kirsch

My Feedback: (21)

According to the specs at www.modelmotors.cz, the 2808/16 isn't designed for a 3S LiPoly, which is the equivalent of 10 cells. Specs say only 6-8 cells, or a maximum of 2S LiPoly. These outrunner motors are very sensitive to their limits; you don't want to push the motors much beyond their specifications. Since the windings are inside that thick outer can, insulated by a thin layer of air between the windings and the magnets, they can't dissipate the heat they generate to the outside world. You have to be careful.

Unfortunately, pushing the voltage 50% beyond what the manufacturer recommends also pushed the Amps 50% beyond what the manufacturer recommends. That's how electricity behaves. It probably damaged the motor early on.

What surprises me is that you're having trouble contacting Hobby Lobby. One of the local guys here got a dud 4120/18. He called HL, and they had a new motor to him in a few days. Since it was out of the warranty period before he used it, they gave him the new motor at half price, which is their policy. I'd expect them to offer you the same deal.

Just chalk this one up as a learning experience; a very expensive lesson

Billy Hell

My Feedback: (2)

Our tech was out last week. He is back in and returning emails and phone calls at a furious pace.

kennydee

Thanks for the reply. My experience with Hobby Lobby in the past has been very good. In fact, I think they provide the best customer service of all the vendors I've dealt with. Just couldn't reach them last week. The only time I ran this motor on 3 cells was very briefly during set-up. We found out quickly that it pulled too many amps. I only ran the motor on 3 cell Li-pols three or four times and only a few seconds each time. The motor never got warm. After that, I switched to the 2 cell li-pol (with the 10/4.7 slow fly prop) and that's how I flew the plane for the next 20 or so flights. I ordered this motor over the phone and I was told it would run on 3 cells. That was about 6 months ago and my electric knowledge was still in the embryonic stage. Now, I've at least progressed to the Toddler stage (but I still need diapers). I'll call back and see if they will replace this motor, or at least give me a good deal on a new one. I think I now understand what may have happened. Thanks again for the informaiton.

Spastic

Yeah Chuckauger loves this post, i think Matt is right you either tosted it in that short time or you had a dud or your ESC in not set for the right timing,
regardless, i'm running the 2808-24 with good results with a 10x3.8apc slowfly prop, getting about 25amps and 40+ oz thrust, got about 20 flights with no prob, Oh tanic 2500mAh 3s1p Tanicpacks.com flights are about 20min hard3Din on a 22oz plane

kennydee

Just a follow-up on my AXI problem. I recently spoke with David at Hobby Lobby. He didn't think that my brief experimentation with the 3 cell lipol caused the problem. I got about 20 good flights using the APC 10/4.7 slow fly prop and the Thunderpower 2s2p 4200 millamp pack. This set-up was pulling about 22 to 23 amps at first. As soon as my flight time abruptly dropped to 3 or 4 minutes (from 20 to 30 minutes), I checked the amp draw. It had suddenly gone up to nearly 30 amps. We went all the way down to an 8/6 prop and was still pulling 23 to 24 amps. David didn't think this was right and suspected a motor defect. Anyway, they asked me to send it back and if they confirm the high amp draw, they will send me a new one. Boy, I love those Hobby Lobby guys!!

kennydee

I still like those Hobby Lobby guys, but maybe Love was too strong a word. David called to tell me the problem with my AXI 2808. He told me it looked like someone had taken a screwdriver and jammed it hard into the front of the motor. After a minute or two of conversation, I could tell that a free replacement wasn't going to be in the cards. David seemed to be suggesting that the damage was due to abuse or negligence on my part. I tried to explain that the motor had not been abused and added that the plane it was on hadn't even landed hard. They did offer another motor at half price and I do appreciate that but the motor had to be defective. They suggested that the motor might have injested something in flight but that seems implausable to me. I don't blame Hobby Lobby at this point but I am frustrated with the high cost of Electric flight.