Help from power guru here

kaos · Post by **kaos** » Thu Jun 20, 2013 11:16 pm

I was testing my esc, motor, and porp. got myself a watt meter, trying to get the most out of my system.
I put a 55A Turnigy Trust ESC, a 2415 2700kv motor (http://www.hobbyking.com/hobbyking/stor ... oduct=6263), and a TGS 6x5E prop.

According to some review about this motor (meant for a 45 0heli), it will run up to 400 watt with a 5x4.75 or 4.74x4.75 and draws about 35A current. i was expecting to get a hot motor and high amp draw, so I put a 55A ESC and a 40C lipo to test it.

But when I ran my watt meter on it with a Nanotech 40C 2.2 Ah lipo, at max throttle the current draw was only 25A and the wattage is only 250 or so. Can't figure this out. also the watt meter showed the lipo voltage dropped to 9.6 volt at full throttle.
Did I over prop it and slowed it down, but why so little amp was drown compared to other' review? The motor does get a little hot after a while but not extreme. or I just have a bad lipo? which I think on a 40C lipo should not happen. and it was doing fine on my 450 heli.

This is the 1st time I am using a watt meter to try to make most out of my system, before i rely on other people's report. but 1st time run it already got some unexpected result.
Any thought? input?

Post by **Kilrah** » Thu Jun 20, 2013 11:24 pm

kaos wrote:Nanotech

Says it all

Post by **jhsa** » Thu Jun 20, 2013 11:39 pm

Yeah, they were supposed to be very good but apparently they're not.. I have 3 of them.. Next time >i will stick with the zippy ones. I bought the nanotechs because the zippy's had hard wire on the balance plugs and the wires break easily, but I think now they are using soft wire, so no reason not to buy them.. I still have my first zippy's after nearly 3 years..

João

Flaps 30 · Post by **Flaps 30** » Fri Jun 21, 2013 12:28 am

By the sounds of it. It does look like the Lipo has a high internal resistance or your wiring is too thin for the currents in question.

How about trying it out on another Lipo or a good car battery.

kaos · Post by **kaos** » Fri Jun 21, 2013 12:37 am

I think you are right. Probably a 'type' or qc issue. I just tried another nanotech 35-70C. and same set up, it went up to 350-370 watt, 30-35A. But there are some nanotech I have works really well, like the 600 mah 1S for my v959. The 300 mah 1S 45-90C also works better than the stock V922 lipo.
I have Turnigy, Zippy, nanotech. May be I will stay away from nanotech too. unless it is a type known to perform well. I do know I have another same type which worked well so far.

now back to 'power' thing. so this motor can work with 6x5 and put out 350 watt. question is after running for 10 sec, (plane is still), the motor mount and stand off becomes really hot, the rotory part of the motor is barely warm. Is that normal or OK? Like I said, this is the beginning of my power exploration. don't know what to expect.

pmullen503 · Post by **pmullen503** » Fri Jun 21, 2013 1:37 am

You could try a higher timing on the esc. 6x5 is probably too much on 3S.

kaos · Post by **kaos** » Fri Jun 21, 2013 4:06 am

I am pushing it with 6x5.

but I don't have a 5.5 x5 at the moment. only 5x5, 6x5 and 7x6. Have a 6x4 but mounting hole is not compatible.

I will try high timing tomorrow, if I don't burn up the motor or crash it into piece in the morning.

Post by **Rob Thomson** » Fri Jun 21, 2013 6:51 am

I have never had issues with nanotech. I have both zippy and nanotech - never noticed a difference!

Sent from my GT-I9300 using Tapatalk 2

gohsthb · Post by **gohsthb** » Fri Jun 21, 2013 12:39 pm

You can also try using a service like this (http://www.ecalc.ch/) to guess at what you should be seeing.
-Gohst

kaos · Post by **kaos** » Fri Jun 21, 2013 7:21 pm

well, this is the verdict of what can happen when you over prop a motor. the motor gets hard, big deal, you burn the motor, so be it. well, not just that, when it gets hot, it will loose power. I was in the air for 3 min and found out 100% throttle does nothing. Surely it happens on the way out of the field, trying to make one last turn around and won't make it and the plane drops. Let's see, the nose broke off, the canopy broke into 6 pieces.

Amazingly nothing else and the twin flimsy vertical fin is touched. This skyfun is a tough little booger.

Also I found out I really need to change the TRN switch to a light press button momentary switch. Earlier I was trying to trim it, while reaching out for the TRN, obviously I moved the ele/ail quite a bit (i have small hands), and put in a 98 off set in Tx (after wards found that out), the plane turn into inverted dive right away. was able to inverted it back and crash landed it. Because don't know how to fly that thing any more with 98 offset. wow, how did I put a 98 offset by doing instant trim. May be I should add a second parallel TRN on the left hand side.

will try 5x5 tomorrow.

will run the watt meter 1st to see if it gets hot again. No more hot motor for sure.

Post by **MikeB** » Fri Jun 21, 2013 7:30 pm

Check your motor, if it got VERY hot it could weaken the magnets.

Mike.

kaos · Post by **kaos** » Fri Jun 21, 2013 7:46 pm

that is what I am going to do this afternoon. make sure it does not get hot again or just change out the motor.
this is a outrunner motor, the magnets is on the outside turning part, it barely gets warm at all times, but the motor where the wire winding and mount got really hot. well, you learn most from failures.

Mike, How do you check the motor/mangnet?

Post by **jhsa** » Fri Jun 21, 2013 7:53 pm

If it got that hot it might have burnt the enamel from the wires and now it could be shorting.. that could mean that the ESC is next..

kaos · Post by **kaos** » Fri Jun 21, 2013 8:11 pm

That is what I am trying to ask. what signs are for a damaged motor without obvious visual defect like burned enamel.....

Post by **MikeB** » Fri Jun 21, 2013 8:18 pm

If the magnets have weakened, the the RPM/volt value will increase. It will try to turn the prop even faster, and so take lots more current.

Mike.

Post by **jhsa** » Fri Jun 21, 2013 8:37 pm

trying to find that motor in drive calc, but maybe is not there cos is a heli motor..

kaos · Post by **kaos** » Tue Jun 25, 2013 10:50 pm

retested the motor on the ground, it is still way hot, pulling about the same amp with 6x5 or 5x5. I guess it is just not suited for my use, unless I go with 4.75x4.75. it looks like when overheated the motor just lose power or stops.
I replaced with a Turnigy 2636-6 2200 Kv with a 6x4 (yes, found a drill to make the right hole for prop adapator). this one I saw at youtube recommended for a 6x4. put a masterscrew 6x4 and ran the watt meter, pulls 25 amp at full throttle and 250watt. The motor is hot but not burning hot like the other heli motor. I guess I am going to fly with this motor for while.

Now my question is the 2415 heli motor is rated to be used with 40A ESC. The stock motor is a Skyartec 2500kv with a 25A esc (which is probably much less than 25A capable, some say <20A) but the stock prop is a APC style 6x5. The Skyartec motor is much less robust than the Turnigy 2200kv motor. Obviously the 6x5 master air screw is already the limit for the Trunigy 2200kv motor. How the stock motor can run a 6x5 without problem and with much less amp?
Is it the motor design? the type of prop besides the length and pitch?

Post by **ShowMaster** » Sat Nov 16, 2013 9:07 pm

Some educated guessing.
The wattage rating on the motor I find is the max and not to be exceeded. It's also not to be run at that full time. Magnets when heated will lose their gauss and recover if not heated beyond a certain rating. Overheating them will not only have their magnetism sag off resulting in power loss to the prop, but usually not fully recover when cool again. Many slowly cook their magnets and the result is complaints of loss of power at the field. Some add an extra cell to their battery pack to regain this power only to cook the magnets more or have smoke pour out in flight. We've all seen that I'm sure.
So a watt meter is the best tool to make sure you're not maxing out the wattage. It's also wiser to select a motor or prop that doesn't have to pull the rated wattage and has some headroom.
Next is the esc,
Many motors are wound to produce max power, or max speed, or wound to give both. These windings are also used for the sensor less timing feedback to the esc. Most esc's are set for a timing that's in the middle safe range that guarantees a fast start and a reliable rpm range and can't have this timing changed like the thunderbird esc series.
Some motor windings require a timing change to make the motor run efficiently and not stumble or worse overheat.
Wire length to the motors from the esc can mess with timing. Keep them all the same length, short as posable and don't coil one wire and not the others. There is inductance and inductive kickback at work there.
Not all motors are equal and if the application is critical it may be wise to use a brand name with a rep that you can contact about your application. This goes for the esc as well.
I'm sure the high end Heli guys can better explain about motor and esc selection or failure and brands.
I have a brushless motor test stand that pushes on a digital scale I use for matching brand name to no name motors. I can measure rpm, wattage, current draw, and case temp all at the same time. I can tell you that there is a big range of posted ratings and hype when I compare them.
A lot of work so I try and go with recommended brands.

I found this Q&A with a google search

Will Neodymium magnets demagnetize if I heat them?

Yes, if heated beyond 176 degrees Fahrenheit (80 degrees Celsius) the magnets will quickly loose their magnetic properties. Sustaining these temperatures for a length of time or heating the magnet significantly higher than this will permanently demagnetize it. Other types of magnets such as Samarium-Cobalt have higher heat resistance. There are also other types of Nd-Fe-B magnets that are not as susceptible to heat induced flux degradation.

openrcforums