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UM T-28 motor problem

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Old 04-13-2011, 06:39 AM
  #1  
acdii
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Default UM T-28 motor problem

Beautiful morning for flying, just a whisper of a breeze, so tried the T-28 again, found it had too much positive pitch, which is why it looped like crazy yesterday, managed to smack the tape fence where I was flying and cracked the tail. Two pieces of tape and a tweak on the elevator pushrod, and back in the air it went, NOW it was flying nicely. Made a few passes around to get the feel of the plane, managed to lose it in the sun for a few moments, managed to gain it back without crashing, and proceeded to make a nice aproach and landing. YEAH, Got it back up and fly it around a bit more then lost it a few times, no damage, then while Ihad it up and doing a couple loops and rolls the motor started to sputter, so Ibrought it down, then managed to overshoot and smack the fence again. Cracked a wing this time, but other than that the plane is holding up well.

SO to find out why it was sputtering I held the plane and gave it throttle, it spun up and stopped. OK maybe thats what it does when the battery is low. So grabbed a fresh one, put it in, and no throttle. None whatsoever. Tried a different battery, same thing, no throttle, everything else is working. Ibrought it in, thought mabye I knocked the connector loose, and pulled the canopy off. Nope connector is snug and tight. Did the motor quit? Went and grabbed my mSR which is apart at the moment waiting for new blade grips and plugged the motor into where the main drive motor goes, put in a battery and connected the radio, motor fired right up smooth as silk and ran fine. So I put it back together, and noticed it has a 3 connector plug, and plugged it into the left and center pins, plugged in the battery and the motor took off backwards. Pulled it out, put it into the correct pins and put the battery on. Nothing, no throttle still.

Ithen decided, not really know why, to turn off the TX, and then back on. Motor started up and I had full throttle. OK This is crazy, so I pulled the battery, and taped the canopy back on, plugged the battery back in, no throttle. Ifiddled with the TX a few more times, and eventually got throttle again. Iran a full battery through, took about 5 minutes to deplete it, and the motor started to stutter and then quit. Not much warning, I would thing it would wind down first before it quit, but it just quits. Popped in a fresh battery, and again, no throttle. A dozen flips on the TX , still no throttle. Tried to rebind it, no throttle, picked a new slot on the TX, bound it, no throttle, Reset it to the original position, no throttle.

What the heck could it be? It didnt hit that hard, and everything moves smoothly, and the throttle, when it did work, was 0-100% just fine, no vibrations, nothing loose. Could it just be a flakey main board? The nose gear had clipped the fence on the last hit, and slotted the cowl, and that is about the only visible signs, other than a couple pieces of packing tape where the wing and tail cracked, but no dents or other damage, since Iflew at only half throttle and wasnt going very fast at all.

I really like how this plane flys, and am really not happy that I barely got one battery out of it before it quit working. I highly doubt the crashes caused this.
Old 04-14-2011, 07:51 AM
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Tommygun
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Default RE: UM T-28 motor problem

I'm trying to understand what exactly you tested with the Blade MSR. The T-28 has a larger, brushless motor, the MSR has a small brushed motor, not sure how you intermixed the two. Anyway, assuming you meant some other model and successfully tested the T-28's motor, then your most likely culprit is the ESC. While they are reliable components for the most part, they do go bad. I'm trying to picture exactly what happened in this crash with the tape fence, but I can tell you if you crashed, and didn't IMMEDIATELY get that throttle stick down to low/off, that a stalled prop can damage the ESC. Also, ESCs hate any kind of water, so if there's a possibility you got it wet somehow, that can cause damage too. Be careful if you choose to keep trying to fly it like that; I've had an ESC start going bad on the motor side, then quit on the BEC side, causing a loss of control crash.
Old 04-14-2011, 08:34 AM
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Saburo Sakai
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Default RE: UM T-28 motor problem

acdii, that's solid sounding information from Tgun. Anyway, from your forensic description of the situation I think you'd make a great FAA accident investigator. It's very American to figure things like this out, to go for itand come up with solutions, and it's good to see folks thinking and acting! Good detective work, great feedback,and keep flying!
To VICTORY!!!!

Jimbo aka Sakai
Old 05-02-2011, 05:52 PM
  #4  
acdii
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Default RE: UM T-28 motor problem

I think you confused it with the larger T28. This one has a 8mm brushed motor, same size and voltage as the coreless on the mSR. Considering they share the same battery, I figured it would work. Iflew it for 4 more minutes after the incident with the fence, and I had chopped the throttle the instant I knew it would hit too. Itook it out of the box the other day, popped in a battery and no throttle, but flip the switch on the TX and it works just fine. Did it a few times to make sure. Pretty strange.


Should it whine when it binds? Seems like the ailerons are vibrating at a high frequency, if I give just a touch left or right the whine goes away.
Old 05-04-2011, 01:14 PM
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acdii
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Default RE: UM T-28 motor problem

Called HH support. Found the problem and resolved the no throttle problem. The radio needed slight tweaking for the throttle off position, now she starts every time. Hoping its calm this weekend, I want to get r flyin again.
Old 05-08-2011, 11:25 AM
  #6  
Voodoo101
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Default RE: UM T-28 motor problem

There is also a very good chance that you lost bind when you disconnected the aircraft battery and then plugged it back in without turning off the transmitter.

I'm not sure thatyou did this. However,doing what I described above will cause a loss of bind and when you plug in the battery the throttle may not work. This is a safety feature built into the system.

Everytime you unplug the aircraft battery you need to turn off the transmitter and then turn it on again before you plug the aircraftbattery back in. This is the only way to achieve a proper bind between the Tx and Rx.Without a complete and proper bind the throttle should not function.

Good luck with your flying.

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