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May 04, 2010, 03:16 PM
Registered User
Thanks again DJ - I have a spare motor and esc, so I'll pull them off and check them out on the bench. Actually, my motor came with the rotor end adapter, so I had to push the shaft through; and, I didn't replace the C-clip, so I can just pull the motor apart and take a quick peek inside.

Steve
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May 06, 2010, 01:22 PM
Philippians 4:13
Quote:
Originally Posted by sgomes
Something for you puzzleheads out there - Slap, I think you may find this interesting.

Flew two batts this morning. After second landing, I went to taxi it back to me, but the motor would'nt run. It would just stutter. Servos responded fine, nothing was hot, I've been putting back 70% so I'm certain the batt still had over 11 volts. Came home, put it on the bench, and it began running fine. Seems like some kind of thermal problem since it was 5 mins from the field to my house. Put another batt on it and ran it for a while, wiggling and tugging on the connections, but everything seemed fine....but, then it happened again. I've had motors do something similar, and it is usually a timing issue, and it is consistent, not intermittent.

Posted over at the power systems forum, but thought I would run it by you guys too.

Thoughts??

Thanks.

Steve
My 3542 did that so bad that even after redoing the connections I finally just sent it in to hobbycity for replacement and they said it was my esc. They sent a new motor anyway and it did the same thing. I tried 3 different esc's and it still did the same thing. I finally just realized that the 3542 motors just have this problem and I have learned to deal with it. It usually only happens when you increase in throttle quickly. I haven't been able to find a solution yet and I have been working on it for about a year.
May 07, 2010, 12:29 PM
Registered User
Well, mine's not a turnigy, but that's not so encouraging. Haven't had a chance to check it out, but I will post results here when I do.

Sorry to hear that.

Steve
May 10, 2010, 06:30 PM
Old F-4 Crewchief
fuzzyhead's Avatar
Still waiting for a chance to try the landing gear mod. Last weekend was booked solid. Been extremely windy today. Already have an aluminum landing gear mount and 2 1/2" wheels standing by if needed. Pulled off the blue checkerboard and added black stripes on the bottom wing. I'm all dressed up with no place to go.
Latest blog entry: The first F-4 I crewed.
May 10, 2010, 06:49 PM
Registered User
Well, I checked all the connectors, and everything seems tight and very well soldered. Then I pulled the ValueHobby 3542 and HeadsUpRc 40A esc off and ran the motor with another esc. The motor ran okay at first, but shortly began "clicking" and very briefly hesitating. It didn't present the same stuttering and stopping like before, but then I didn't run it very long. Frustrated, I decided to change out the motor, so I dropped in the Turnigy 3542-1100, and it ran fine for the few minutes I throttled it up and down.

Right now, I am thinking the motor is somehow bad, which is disappointing because I already returned the esc to ValueHobby - convinced that the problem was with the esc. Inspecting the motor, I noticed only that some of the magnets showed wear marks on the ends. Don't know if this is the problem, but I'm gonna try running the Turnigy and see what happens.

Very confused.

Steve
May 11, 2010, 10:24 PM
Registered User
Ran the Turnigy today without any problems. Pretty sure the motor from ValueHobby is bad. Alex - great guy - at ValueHobby said to send it back and he will replace it.

The turnigy is 3542-1100 vs 3542-1250 from ValueHobby, and I am surprised at the torque difference. I really like the 1000-1100kv range - it suits my flying style with adequate torque and plenty enough speed. Also, the motor, esc, and batt were noticably cooler - further convincing me the other motor had problems.

Still pretty nervous flying the Gemini, but getting more confident. The schoolyard where I fly, I have been landing only in one direction - there is a tree that makes landing in the opposite direction a bit tricky; but, today I tried a couple of times. Both times, I got it down okay but got a little disoriented just before touchdown - I'm sure just a mental hurdle. Anyway, a bit of wingtip scuffing - nothing serious, but kind of disappointing. Of course I know this means that I just need to vary my patterns so that any direction becomes more comfortable.

My average landings are getting much better. I'm coming in with a little more speed, and this seems to allow me to fly it right to touchdown. Today I was coming in at about 20' up when I needed a little more speed, so I just dropped the nose and the speed came up to allow me to fly it in for a perfect touchdown - no bounce at all, just the sound of the main gear as the wheels began rolling. Amazing, wonderful feeling!!

Great flying little plane this Gemini - hope I don't kill it anytime soon.

Good flyin everyone.

Steve
Last edited by sgomes; May 11, 2010 at 10:33 PM.
May 12, 2010, 03:31 AM
Sailplane Mafia

Good job Steve!


Sounds like you are having a great time with your Gemini. It has been my first plane and I have put it through hell. Lots of CA repairs and CF reinforcement. It is still flying fine. Broke the nose completely off in one crash.

Yesterday, I ordered foam and some more building materials to scratch build one of these. https://www.rcgroups.com/forums/showthread.php?t=579000

I figured it would be cheaper to be able to make my replacement parts instead of buying another Gemini kit.

I'll post updates on my build when I get to it.

Good luck with your Gemini and I wish you many more wheel down landings! Bending the landing gear foreward 1-2" made all the difference in my being able to land without nosing over.

Later, Crash Master

Quote:
Originally Posted by sgomes
Ran the Turnigy today without any problems. Pretty sure the motor from ValueHobby is bad. Alex - great guy - at ValueHobby said to send it back and he will replace it.

The turnigy is 3542-1100 vs 3542-1250 from ValueHobby, and I am surprised at the torque difference. I really like the 1000-1100kv range - it suits my flying style with adequate torque and plenty enough speed. Also, the motor, esc, and batt were noticably cooler - further convincing me the other motor had problems.

Still pretty nervous flying the Gemini, but getting more confident. The schoolyard where I fly, I have been landing only in one direction - there is a tree that makes landing in the opposite direction a bit tricky; but, today I tried a couple of times. Both times, I got it down okay but got a little disoriented just before touchdown - I'm sure just a mental hurdle. Anyway, a bit of wingtip scuffing - nothing serious, but kind of disappointing. Of course I know this means that I just need to vary my patterns so that any direction becomes more comfortable.

My average landings are getting much better. I'm coming in with a little more speed, and this seems to allow me to fly it right to touchdown. Today I was coming in at about 20' up when I needed a little more speed, so I just dropped the nose and the speed came up to allow me to fly it in for a perfect touchdown - no bounce at all, just the sound of the main gear as the wheels began rolling. Amazing, wonderful feeling!!

Great flying little plane this Gemini - hope I don't kill it anytime soon.

Good flyin everyone.

Steve
May 12, 2010, 08:30 AM
Registered User
Yeah, from the outset I cross-braced my landing gear, increased the forward rake, and used rubber wheels; and, I've had no problems whatsoever with the bouncing/hopping that others have experienced. And, since I put in the aluminum motor mount there has been zero vibration.

That foam scratch-built looks pretty nice. Unfortunately, I have no modeling skills, so it's out of my range to even try; but, I really like the smaller planes so I can fly close to my house. Good luck with the build.

Steve
May 16, 2010, 11:15 AM
Old F-4 Crewchief
fuzzyhead's Avatar
Finally got a break in the weather this weekend to try the landing gear mod. Didn't go as good as expected. When I raked the gear forward my bends were not that good. So I had one side higher than the other. That led to wing tip overs on landing. No bouncing but I was starting to chew up the right wing tip. Decided to chuck it all and install the aluminum gear I bought. Followed Steves idea. Cut off the forward two wire slots. The new gear slid into the aft slot. Installed 4 screws. Also used slightly larger 2 1/2" wheels.

Took her out this morning and perfect. No bouncing. Tracks straight on taxi. Do need to max out the rudder throws. Would like her to turn sharper on the ground. Did have a nasty oops today. On takeoff she caught a line in the street and pulled hard left. Pulled the stick back hard to avoid the curb and get airborne. Worked great until the gear caught the high weeds and flipped her over. Major damage was the upper wing attach bolt pulled out. Canopy also pulled off. Any suggestions how to secure the attach housing other than just reglue? Maybe make it stronger.
Latest blog entry: The first F-4 I crewed.
May 16, 2010, 07:21 PM
Registered User
Fuzz, that gear setup certainly looks stout - nice job. Regarding the wing bolt, did the bolt strip? Either way, it seems like regluing and possibly replacing the bolt should do the job. I would examine the wings to make sure there are no hairline fractures.

Hope you get it back in the air soon.

Steve
May 16, 2010, 08:27 PM
Old F-4 Crewchief
fuzzyhead's Avatar
The bolt is ok. The housing that it is in is what pulled out. Upon further inspection there was way more damage. The fuselage was cracked on both sides just behind the cockpit. The motor shaft was also bent. Reglued the fuselage crack and the wing mount. A small piece of foam came out around the bolt housing. Filled the gap with Gorilla glue after the ca cured. Whats so puzzling is that it didn't hit that hard when it flipped over. No more than 3 feet off the ground.
The motor is a different story. Could not get the grub screw out to change the shaft. Tried everything. I'll order a new motor for now.
So the saga continues.
Latest blog entry: The first F-4 I crewed.
May 16, 2010, 11:33 PM
Registered User
slappySF's Avatar
Stuttering motor problem -- fixed!

The ol' process of elimination did the trick.

Found a loose gold plug on my ESC when I cut off the shrink wrap. Re-soldered it on. Tested her out.

No go. Still stuttering and not spinning.

Thinking it was the motor now, I plugged the ESC into a brand new 3542. The new one stuttered as well.

I had a spare ESC, but instead of tossing this one I gave it one last ditch effort, by clipping off all 3 gold connectors and re-soldering.

Bingo!

Motor spins great.

Weather permitting, I got no excuse but to maiden her next weekend. Hooray.

I'd love to try and do a gear mod before then. Prolly Steve's mod by bending the wheels forward and wiring/soldering a brace.

But if I don't get to it, I'm going to maiden her anyway.

Waited too long to take her up.

Quick question though.

On the rudder/elevator control rods, I have very little extra sticking out past the barrel connectors on the control horns. We're talking like 1/8 to 1/16th of an inch. Closer than I have on other planes. Those germans are very precise! Would hate for one to slip out and lose control of a surface. Did your pushrods come trimmed that close? And is it still OK to fly? Or ought I visit the hardware store and get a couple lengths of piano wire and cut some new ones? A much quicker mod than the gear. Whaddya think?
May 17, 2010, 01:55 AM
Registered User
Slappy, 20 points out of 10 for perserverance. Great bit of info.
Re your rods. i don't have a Gemini and i assume you are talking EZi Connects with a srew adjustment. The screw has to lose its grip for the barrel to slide off the rod.
I would prefer threadlock or hotstuff on the thread of the adjust screw, once the adjustment is correct. Even the old typing correction fluid - white out - will hold stop the screw loosening.
Cheers
John
May 17, 2010, 03:04 AM
Sailplane Mafia

Good job troubleshooting!


Glad you found your electrical problem. They can be frustrating to narrow down. Good job!

On the linkage length, I have about the same amount of rod extending beyound the fastener. Sounds like it's normal. I use loctite on the fastener screws to prevent any slipage.

Good luck on your maiden! Look forward to a report.

Crash Master

Quote:
Originally Posted by slappySF
Stuttering motor problem -- fixed!

The ol' process of elimination did the trick.

Found a loose gold plug on my ESC when I cut off the shrink wrap. Re-soldered it on. Tested her out.

No go. Still stuttering and not spinning.

Thinking it was the motor now, I plugged the ESC into a brand new 3542. The new one stuttered as well.

I had a spare ESC, but instead of tossing this one I gave it one last ditch effort, by clipping off all 3 gold connectors and re-soldering.

Bingo!

Motor spins great.

Weather permitting, I got no excuse but to maiden her next weekend. Hooray.

I'd love to try and do a gear mod before then. Prolly Steve's mod by bending the wheels forward and wiring/soldering a brace.

But if I don't get to it, I'm going to maiden her anyway.

Waited too long to take her up.

Quick question though.

On the rudder/elevator control rods, I have very little extra sticking out past the barrel connectors on the control horns. We're talking like 1/8 to 1/16th of an inch. Closer than I have on other planes. Those germans are very precise! Would hate for one to slip out and lose control of a surface. Did your pushrods come trimmed that close? And is it still OK to fly? Or ought I visit the hardware store and get a couple lengths of piano wire and cut some new ones? A much quicker mod than the gear. Whaddya think?
May 17, 2010, 08:46 AM
Registered User
Slap, good to hear the fix is in; and, the same here on the ez connectors - very little rod extending through. Yup, blue loctite on the threads of the grub screws; but, also a dab of ca on the ends of the bolts that hold the ez's on the control horns.

If I'm not there with you on the maiden, I'll keep an eye out for a yellow one on this side of the Bay.

Believe me, if you soften your surface control a little you will be surprised how predictable and compliant she is.

Best of luck.

Steve


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