bob_nj

My Feedback: (62)

I posted this on another board, but can't seem to get an answer to what I thought was a relatively
easy question for the seasoned electric gurus.

I've been at this a year or so, and get around foamies pretty good. I don't fly any bigger than 3S 1320 packs and run AXI 2204/54, 2208/34, and 2212/26 motors.
Basically I am asking how to interpret the AXI ratings in the motor literature so as not to "amp" the motors.
I don't need all of the power, all of the time, but do need to know what my limitations are.
I'd like the motors to last awhile and just need some help.

OK, so here is the aforementioned post:

The AXI 2208/34 is listed as a Max Eff of 4~7A, with Max Load of 8A/60s.
I'm not exactly a neophyte, but I do need some guidance here.
Which ratings do you use?
Some say this is a 5amp motor.

Here are some numbers on a test stand with APC props, 3S TP1320 Pro Lite packs and WOT.
None of them fall within even the 8A range?
What am I doing wrong, or do I need to use a really really small prop?
I like the largest diameter prop I can get away with for 3D.

APC
8x3.8 9.9A
8x6 14.2A
9x3.8 12.6A
9x4.7 11.8A
10x4.7 16.15A

What props are you guys using, and what ratings are acceptable for the AXI?
Is it the 3S packs that are pushing me over the edge?
Do most flyers use the 8A/60s rating as a guidline and not use WOT?

Thanks for any help_bob

jooNorway

Your numbers look right.
This motor is meant for slow planes. It would propably give you the best efficiency-numbers at 6-7 cells NiCd, spinning a 9x3,8 prop. It can sure be run on 3S LiPo, then a 8x3,8 is a good choice not heating this motor too much. In fact I use this motor myself in a Microbat, running 3S and 9x3,8SF. Drawing more amps than recommended but the motor get a lot of cooling and have worked fine for a long time.
It is a 8Amp, not 5Amp...

wright3

I've been running my 2208/34 motor with 3S and 10x3.8 for about a year now. Performance has not degraded although the set-up sucks down about 15 amps at WOT. Because this is more than twice the recommended draw, I don't use it except for extended verticles and punching out of a hover. You're way past warranty if you draw it down like we do but all 4 of us have been using this motor this way and the smoke has stayed in every one.

Likewise, I've been *****g my 2212/26 to 18 amps in a little pattern plane. Frequent flyer for the past 3 months with no problems.

I think we can safely assume that these motors are underrated and very tough. We also know that we are on our own because of the power levels we impose on them.

Randy

bob_nj

My Feedback: (62)

Thanks for the reply Randy.

I too use close to full power on extended verticals in a couple of routines.
It's just the nature of the beast I guess?

Are most other brands rated and used in the same way?

Take care_bob

Glacier Girl

My Feedback: (4)

amps = heat, the more amps you run through a motor the hotter it gets. That is what will kill a motor. Cooling the motor by way of it's location can allow you to run higher amps.
An enclosed motor will not last as long as oppossed to one mounted out in the air flow, From my own experience, Mega motors, they are rated at aprox 28 amps, yet due to location of them in my planes, I've run 50 amps through them with no harm.
Just like the engine in your car, with out cooling it isn't going to last long.

wright3

My pockets aren't really deep enough so I must really be a dumb s---! I recently decided to put an E-Flite 370-5400 to a distruction test. This motor is a smaller version of their 400 motor. I used a 5.4/1 gear ratio and started adding pitch, starting with a 10x3.8. This was set up in a mini funtana. I was looking for speed and I really found it when I got to a 10x8. My watt meter said I was pulling 25 amps which is rediculous for the little 370 (factory says 8 amps; it's very happy with up to 15). I bolted up a heat sink and flew it. Great speed, wonderful verticle, a very nice pattern set up. I forgot all about the fact that it was pulling over 3 times the factory max and just enjoyed it. After about 10 15 minute flights, it was just beginning to loose it. It still flew the plane after 15 flights but it was no longer ballistic. In retrospect, It was a hard 225 minutes for that little motor and the experience tells me that if we would just keep our amp draw within reasonable limits, we'll see that these little brushless motors have incredible lifespans.

Randy

bob_nj

My Feedback: (62)

Thanks Randy.

Other than slowing down, did it "shake", "rattle" or roll?

wright3

Shake, rattle, and rolling is what they do after you smack 'em in real hard. I've lots of experience there. My unsmacked motors, when subjected to amp abuse alone, have just slowed down. It's hard to sieze the ball bearings; not so hard to heat the windings to the point where they begin to fry.

In retrospect, I sure could use the three motors I slowly fried. They were an e-flite 370 inrunner, a 370 outrunner, and a himax 2025-4200 inrunner. It makes no difference who makes the motor, if overheated, it will fry.

These days, I'm a bit more careful although my 3D set-ups generally pull about twice the recommended continuous current at wide open throttle. 2 Axis and 2 e-flite motors are still running fine after many, many hours of use.

Randy

bob_nj

My Feedback: (62)

Interesting!

I guess I'm too literal at times.

Thanks Randy_bob