skybuster97

Gentlemen,
I have an Electrifly 2100MA 3 C batt, Electrifly SS-35 ESC, Hacker 30-28S motor, apc 10 X 7 slo-fly prop. Just ran the motor for a few minutes and smoked it. What esc will work and any suggestions on prop sizes ? Thx

jzrf6c

According to the Hacker web site it looks like you should be fine.

Operating Current: 15
Peak Current: 25
Peak Watts: 250
Resistance: 0.068
RPM / V: 1140
Battery: 3 LiPo

I question the 3c battery though. Did you mean 3 cell 15c. In this case "c" stands for the "charge" which is used to provide the useful current charge/discharge rates. You may want to check out the connection configuration. Of course, the motor could have been defective from the start. Have you contacted the seller?

Normally, when you smoke a motor its because you have exceeded the current limitation. As you can see from above the max current you want to draw is 15 amps with a max of 25amps. Your ESC will allow at least 35amps with probably a max of 40 or so amps. So, if the prop load is such that you exceed the 25 amps the ESC is fine but the motor will get to hot and either the solder will mealt or (mostlikely) the wire will burn open. The other problem is that if you "had" a smaller ESC it would have burnt first. So you see it's a balance act. If the battery is smaller and can not "supply" the current the motor wants to draw then it does not burn just works poorly. You may want to check out the various motor calculators that are available online.

How long did you run the motor with the 10 X 7 prop attached?

rmenke

My Feedback: (13)

Skybuster;

Good advice above. Next, you gotta get a watt meeter. As you can see, for a good system, your controller is usually rated above the max. demand rating of the motor, and the battery able to put out even more. Now this can be a setup for disaster if you push the motor beyond its rating, or the controller, or the battery. One or two pitchen in prop size will spell disaster, or great. You want great, and the only way to make it so is with a watt meeter. This way you can check your new setups and size the prop based on the systems actual performance without damage. The old feel it for hot method is hazzardous to all your equipment and yourself. Get a meeter and learn to use it, its easy!!!

Dr Kiwi

According to Motocalc you may be drawing the max 25A with that prop. (more, if you have a good pack and your voltage was higher than this 10.3v) - and at only 50% efficiency that is a heck of a lot more waste heat than that motor can cope with. I have to ask - was this a few minutes static (an absolute no-no), or in-flight.

Motor: Hacker A30 28S; 1140rpm/V; 1.3A no-load; 0.068 Ohms.
Battery: Thunder Power TP2100 (ProLite) (15C); 3 series x 2 parallel cells; 2100mAh @ 3.7V; 0.018 Ohms/cell.
Speed Control: Castle Creations Phoenix 25; 0.0065 Ohms; High rate.
Drive System: Direct; 10x7 (Pconst=1.69; Tconst=1) direct drive.
Airframe: Anything you want.
Motor Amps = 25.0
Motor Volts = 10.3
Input (W) = 256.3
Loss (W) = 113.8
MGbOut (W) = 142.5
MotGb Ef(%) = 55.6
Shaft Ef(%) = 51.4
Prop RPM = 6864
Thrust (oz) = 33.9
PSpd (mph) = 45.5

skybuster97

Thanks Everyone,

The battery was a 3 cell, 20C Electrifly 2100ma. And, yes this was a static 2 min run...

Dr Kiwi

In reality, the 25A is burst current - meant to be used in-flight for only 5-10 seconds at a time with adequate cool-down time in between. In-flight you might be able to draw 15A continuously with good cooling, but in static mode even 15A is probably more than the motor can handle for as much as two minutes.

I have no idea how efficient light bulbs are, but let's call them 50%. That Motocalc computation suggested >100W waste heat from your motor... so imagine holding a 200W bulb in your hand for two minutes... very toasty!....that's your Hacker motor.