motor shuf off at full power

[ropadope13]

Hey everyone,

My first post! I've got a question about the propr that comes with the float set. I took my sc up today (without the floats) and i was a hundred feet (or so) off the ground and gave it WOT. The motor cut out at that point and I was lucky enough to just bend the landing gear a bit from the unintended landing. I did some field testing and changed to another battery. I found that the motor will only cut out if I slam the throttle wide open. a slow gradual increase to full doesn't seem to affect it. No difference with either battery. I haven't had a chance to test it with the stock prop to make sure that it's the float prop yet. I don't yet have the gear to run tests on amps and whatnot, but I did hear someone mention that too large a prop can cause your LVC to trip cutting out your motor. Any thoughts? I've read a few posts with similar, but different problems. I do know that you shouldn't full throttle for more than 10-15 seconds with the larger prop and it's really just to help power the takeoffs with floats. thanks a bunch.

[ropadope13]

well... I'm the first to reply to my own post so I found a band-aid for the problem I had. I trim down the throttle so that 95% throttle is my new 100% and it never cuts out. Not sure if that's a good or a bad thing. Either way...it's working fine and I have no issues now.

[renard80]

Glad you got that sorted.

It's surprising how often the solution to a problem occurs soon after you post the question!

(Sometimes you don't get a prompt reply on here because people are busy. Other times they just don't know! ;D )

Good luck with future flying.

[ropadope13]

no worries at all. I still have to test with the stock prop without the throttle trim band-aid in effect to make sure that it's an issue of the extra load on the motor. Thanks for the reply

[ropadope13]

Finally threw the stock prop back on the cub and no cutting out anymore. Anyone else have that problem with the propeller that comes with the floats? I guess the first time i put it on the water i'll be trying the stock prop. I'd rather struggle to take off a bit than have my engine cut-off when I need it most in the air.

[freediverga]

Does it kick back on if you bring the throttle back down?

[flydiver]

This has a lot of the same issues freediverga brought up with his amps/thrust question.

PZ does not publish data for their RTF ESC. The old NiMh ESC was probably designed for ~10-11A. You need a bit of headroom over that so by guesstimate it's thought the old one was ~13A, but no one knows. I've called PZ tech support a couple times and tried to wheedle the info out of them but no one has ever budged.

If you go to 3S lipo on the stock 10x8 NiMh prop (same as the 'float' prop) you pull almost 20A.

That'll kill the ESC if you keep it up so it's only good for ~30sec.
To keep the ESC from burning up HZ down propped to a 9x6 likely keeping the amp draw to > 13A but I don't know of anyone that has tested a stock LP system. Trouble is newbies don't have test equipment and by the time they get it they've dumped the entire power system.

You could be cutting out because of battery sag and hitting LVC. If you can throttle down and immediately throttle back up successfully it probably is that. The stock lipo is theoretically barely able to sustain the 18-20A that are required for the 10x8 prop, which means in reality it probably actually can't.

You could also be overtaxing the ESC. I think if that was the case you would lose control along with throttle.
With a wattmeter you could test and tell. Without, you are guessing as am I.

I frankly continue to be amazed that PZ recommends that prop for floats. There are enough stories of the stock ESC burning up with the 9x6 prop let alone a 10x8. That's a huge difference.

[ropadope13]

thanks for the input. I've flown a few times since and I have no problems. I still haven't put the floats on the water yet. It's been cold, nasty, and by the time i get home from work it's dark. Maybe soon as far as the throttle perfomance:

It would only cut out right when I hit full throttle. Even if I brought it down immediately and put it back up it was still cutting out. no flight control problems though. I'm thinking i'm tripping the lcv somehow. with the stock gear I don't feel like pushing it and burning out the cheap-o electonics. I'm not really worried because with the stock prop it flies like a champ.

on a funnier note: my father-in-law and I flew last saturday. He took his brand new radian pro for it's maiden. I got to see him crash it into a tree. I filmed a bit of it, but missed the good part lol. After that I was trying to fly with him and was doing a great job staying close. So close, in fact, that I clipped his rudder with my prop and almost chopped it off. No bueno! good thing is, he brought it down relatively safely and the repairs were minor. That rudder tape is lame on the radian pro. fixed now with a decent hinge tape job. thanks again everyone.