ehelibuff

I just bought a 4100KV brushless for my speed 400 pylon plane. It's a gold 4020U inrunner with cooling fins for planes/heli.

I'm running a Ripmax 25amp ESC and Multiplex 1600mah 11.1V lipo 20C/(25C burst) battery. I'm turning an APC 4.7x4.2 prop.

The motor screams bloody hell at full, but at full throttle, the motor gets extremely hot in about 10-15 sec at 100% and the batt was getting a bit warm, but not too hot yet to let go. I was holding the battery in my hand, so I can feel the battery if it were discharging too fast, i'd shut down. But I mainly noticed the motor getting so hot, it would burn you!

Am I over loading the motor with too much pitch? prop it down? Or is this just so fast, I need to only do full bursts and fly const. at 50%? I thought about Cropping the prop down (reducing some pitch) and surface area, then rebalancing as we do in gas pylon carving our props.

I just bought a meter but never used it yet. I think I need to run it in series to test. So i'd have to buy new connectors to see what I'm pulling. It may be pulling way too much....

At 50% or so i'm fine.. It's just when it's opened up this happens... Everything is brand spanking new! the motor specs are:

Dimensions: 20x40.5mm
Load Current:16A/60S
KV:4100RPM/V,1700r/min
Idle Current:1.8A
Max Current:7.1A
Max Efficiency:86%
Max Power:90W
Suggested prop 4.75x4
Weight:58gr.

Suggestions.....

I'm fairly new to electrics; I've been flying gas for 30+ yrs

Eric

jzrf6c

It sounds like your drawing to much current for the motor. Check the propload for your prop vs motor. I'd use something like the Motor calculator found online. Don't always believe the mfg specs!

mrasmm

yeah, unless a part is defective or something, if that motor is only drawing 16A, then the battery shouldn't even be getting warm in that time frame. That's 1/2 of what the battery is rated at. If that prop is more than doing what you want, then you might try going down a bit on the prop and see if that doesn't fix the prob or something.

The other thing I don't really know is if you need some sort of gear reduction or anything. On a 3s lipo at 4100kv, you're looking at 45,000 rpms WOT. That's probably real close to making that prop explode, but I dunno too much about the small props and high performance pylon racing.

rmenke

My Feedback: (13)

Appears you are giving the motor manufacturer's specs. What does your watt meeter say as to draw. I not sure how the motor should react at these rpm's. All my gear is ballanced and barely gets warm, motor or battery while doing 3D. Have seen similar sized motors and batteries get quite hot when over proped, but return to normal temps with the load reduced. With hot pylon stuff, you need to experiment with all sorts of props not only to see what the motor/battery combo likes, also the airframe. High speed is high maintenance and R&D to get fast. Worse yet, almost every motor/engine even from the same manufacturer will like something different. Nuf to drive you, not me, nuts. ENJOY

Flypaper 2

Running it statically gets very little cooling, plus the prop unloads in the air. Fly it for a few minutes, land it, then check the temp.

ehelibuff

Thanks guys,

Yeah the first thing came to mind was that the specs were not as seen in my garage. I haven't hooked up the meter yet. I had to run to work, so ran out of time. I'll get that set up.

Yes, pylon jobs normally run at ballistic purportions.. My other 3D jobs don't even get warm...

I do think I need to first crop the prop down, and see if that helps.. I could be loading it, and yes unloading in the air will make a difference, plus cooling vs. static thrust.

I wouldn't be suprised if i'm pulling as much as 80 watts. I should tach it as well next time.

I'm thinking of going to layed carbon fiber prop on this motor.. I have some Quarter Midget Formula 1 props around somewhere that would work great on this plane. They were on .15 (2.5)cc nitro racers that turned 35K+

Hopefully I still have them somewhere...

I'll give an update on this set up once I do some testing...

Eric

ehelibuff

Ok guys.. the motor is junk..

I just ran it on a meter and in 3 seconds it was at 350+watts, and 40 amps! Yes, I know I did everything right... That's the actual readout. It got hot in those 3 seconds.. The motor is drawing way more than it should.. Oh well, was $17.01 at my door from ebay. The guy has excellent feedback. I wrote him about the motor. We'll see what he says..If I eat it, oh well...

Good thing I never flew it!..

Anyone want a cheap high input motor? It's a screamer! [&:]

I think i'll go buy a new name brand motor from the store....

Eric