Can't get off the ground. Looking for help!

[cwolfe]

I apologize this is a bit long. I recently bought a 28" J-3 Cub PNP from Hobby King. After a few really good flights my inexperience showed and I nosed her in. Bent the shaft on the motor and burnt the ESC. So, I went back to Hobbykings web site to look at what motor had come with it. It said that it came with a Hextronix 16gm 1700KV motor and 10amp ESC. So I bought two of these and a new 10amp ESC from HeadsUp RC. The motor arrived and I soldered connectors that came with the ESC to one of them. Checks looked good. Yesterday I'm out at the field and it wont seem to get off the ground. 40 feet or so of throttle and it just shoots across the ground. Head back home. No I was at LOW rate on my DX5E could that be it? It took off at 1/2 throttle before. I noticed a slight wobble in the motor. I don't know if that would do it. Or did Hobbyking state the wrong motor that came with the PNP? They look exactly the same except for the one that came with the plane has larger wires coming out of the motor. Thanks for taking the time to read this and thanks for any advise.

[FlyingBrick50]

It took off at 1/2 throttle before. I noticed a slight wobble in the motor. I don't know if that would do it. Or did Hobbyking state the wrong motor that came with the PNP? They look exactly the same except for the one that came with the plane has larger wires coming out of the motor. Thanks for taking the time to read this and thanks for any advise.

More power, check throws (trans), ...

[cwolfe]

Originally Posted by FlyingBrick50

More power, check throws (trans), ...

The throws on the trottle?

[NJSwede]

Could you have put the prop on backwards? Numbers on the prop should (usually) face forwards in the direction the plane is flying. Putting the prop on backwards makes it lose almost all power, so that would explain why it doesn't want to take off.

Also, you definitely don't want the motor to wobble. Do you get a lot of vibrations when you throttle up? In that case, don't fly the model until you've figured it out! You'll break it even more.

[cwolfe]

I'll double check the prop. The wobble is at the 5-10% throttle. I don't know where it's coming from.

[cwolfe]

with the prop and prop adapter removed I still get the wobble.

[NJSwede]

Originally Posted by cwolfe

with the prop and prop adapter removed I still get the wobble.

What part of the motor is it that wobbles? Can you shoot a video?

[E-Challenged]

Motor shaft bent a small amount. New motor?

[cwolfe]

Originally Posted by NJSwede

What part of the motor is it that wobbles? Can you shoot a video?

It looks like back by the mount.

I'm actually at work right now.(and working hard! LOL!)I can late tonight or tomorrow. Thank you that's very generous of you to take a look.

[Glacier Girl]

Along with Swede's advice, check the mount area on the fuselage. Could be that the foam and/or what ever holds the motor/mount in place got damaged when you boinked it.

Also in your post you said you bought two motors. You could swap the other motor on and see if your problem goes away or stays the same. If it goes away, your first motor is damaged. If it stays the same, you have a problem elsewhere, like the fore mentioned mount area.

[cwolfe]

Originally Posted by Glacier Girl

Also in your post you said you bought two motors. You could swap the other motor on and see if your problem goes away or stays the same. If it goes away, your first motor is damaged. If it stays the same, you have a problem elsewhere, like the fore mentioned mount area.

Yeah, I'm leaning that direction. The motor mount and fire wall was torn off in the mishap, but I've remounted the fire wall and this is the X mount that came with the motor. I think switching out the motors is a good idea.

[cwolfe]

Now, I did nose over when I reached the end of my run way. into the grass rather softly I thought. Is it possible that little bump bent the motor down by the mounting shaft? but that still doesn't solve my "I can't get off the ground issue".

[tom1968]

Sometimes a new ESC needs to "learn" the transmitter's throttle limits. The ESC may have instructions on how to do this. Also, was your battery damaged in the crash? Either of these can cause lack of power.

Did the servos get knocked loose, and does the elevator still line up with the horizontal stabilizer? Are the servos and control surfaces still moving freely and evenly? Maybe the elevator is not responding to "up" commands.

[colinb]

As others have said do a full check of all the various angles before flying a new model or after a big repair, so ...
- wing and tailplane at 90 deg to the fus. Fin at 90 to tailplane.
- wing incidence should be slightly more than the tailplane incidence, definitely not the other way round
- motor thrust line in line with fuselage or with a few degrees down and right according to model - definately no up thrust!
- all control surfaces at neutral when Tx sticks centred
- controls respond correctly to sticks, with adequate amount of movement
- motor responds correctly (you should use a tachometer and wattmeter to make sure all is well. These are cheap and essential for regular lekky flyers)

If you get this far then you can let it loose on the strip - full throttle and after 5 or 6 yds a bit of up elevator should see you in the air.

If you are still not getting take off, then play back in your mind your original model - how does the ground speed compare? If the mended model is slower, and you are sure you are getting the full revs from the motor then is the undercarriage binding somewhere and acting as a brake?

Bottom line is if the model is travelling fast enough, the thrust lines are correct and there are no control surfaces telling it to stay down, then it has to fly!