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View Full Version : T-REX Shutting down during flight


Adrian
10-19-2006, 11:43 AM
Flown the t-rex 3 times now & have had to auotortate it in 3 times:eek: 1st time was only hovering a couple of ft off the ground. 2nd time nose in head on, ended up caught by a football net behind me & 3rd time a heavy landing,which stripped the gears in a servo, each time it,s happening 7mins into flight Im using Pro Power 2100mah 18c 11.1v batt,s on std Align motor & esc which is set up. Brake disabled-mid timing & low voltage protection. (I've got a guy making me warning light which will kick in at 3v per cell so I don't damage li-po's) but there is plenty of power left in the pack, the problem is the motor just shut's itself down:confused: Anyone had a problem like this & any suggestions

stinkweed007
10-19-2006, 12:11 PM
I have an ESC which when my battery starts to go down, it cuts the motor to save juice for the servos... but thats for fixed wing... I can still glide.. with a heli.. I can see where it would be catastrophic..

It might be a clue as to why you can autorotate but have no main motor. servos good but no motor. it could be possible that your ESC cuts out to soon with regards to your battery/ESC combo.. (volts or amps)

When mine cuts, usually I kill my throttle then raise it again to get my prop back if I need it..

Some of the more Motor+ESC+Battery smart folks here might want to know all the details of your combo to maybe see if your ESC is doing its job give what it is working with..

I do have a question about your "Brake Disabled" setup.. I am only (I can be wrong) aware that Car ESC's have that function... Are you using the correct type of ESC?

RUSH
10-19-2006, 12:57 PM
The LVC is probably kicking in. 7 minutes is a bit low, but close to what you can expect for flight time. Check the gear mesh from the main gear to the motor pinion to make sure it is not tight at any point in the rotation. Also, make sure the tail belt is not too tight - it should be a little on the loose side. This should help with flight times a bit. Also, if you can tell us what motor/ESC you're using, that would help us figure out what flight times you can expect. Also, how much your Trex weighs will factor into the flight time.

You say there is plenty of power left in the pack - how much do you put into it when you recharge it? I run the Hyperion 3S 2100mAh packs and set the timer for 10 minutes - that's about all the time I can reasonably get. And, in fact, it sometimes runs below 9V before that when just hovering around (I have a light to indicate 9V, like you're talking about). Hovering takes more power than forward flight.

Tintin
10-19-2006, 12:59 PM
The LVC on that esc will pulse the power when you get low in voltage. It's not totally unlikely that you actually hit LVC after only 7 minutes.

A thermal shutdown will cut and might very well happen if you run a too low throttle setting. On Align stuff you should have at least 80% throttle at midstick/zero pitch.

I guess you have the 430 motor. Is it a 25 or 35A esc? The 25A is somewhat small for the 430 motor if that's what you have.
Is the heat sink properly installed or glued to the shrink wrap?

It might also be interference, several have had similar problems with cuts where connecting cf frame/boom or boom/tailcase or both have helped, lubing the tailbelt might also help as it can work like a van der Graf generator and it might be static electricity hitting your radio gear.

Brake off is normal on Align escs and is the proper setting for helis.
I'd set it to high protection untill you get that alarm as at low ith will cut 7.56 volts which is not healthy for a 3S lipo. The Align esc lets you land the heli if LVC kicks in unless you are inverted 10 cm off the ground.

Adrian
10-19-2006, 11:45 PM
After 4hrs of checking EVERYTHING + a little luck, found that my heli was one of many supplied with black insulating around ESC, then double sided tape with heat sink on top. exsuse me, but were Align having a "blonde moment" or what! I'm just learning to fly a CP machine, so the ESC is working so much harder(I'm no 3d god)), with all that c*ap on it, ESC overheat's & cause's my "autorotation" Out came the craft knife, superglue (double sided tape in bin) & ziptied back onto support, Also found belt drive too tight, which may not have helped on the batt drain. Put 3 batt's through in total 25mins,with no prob's. I'm a happy bunny:D

Tintin
10-20-2006, 11:24 AM
Good to hear, however don't make the error of so meny before you to think low throttle setting is good as you're new to it. That esc might overheat even with proper heat sink if you run 60-65% throttle. At 80-85% you might even not need a heat sink in fact.

You want a fairly constant headspeed, if 85% gives you more than you want then use another pinion instead of reducing throttle %age.

Adrian
10-21-2006, 06:35 PM
Im not running full head speed yet-I don't need too, as Im just flying it around in gentle circuit's at moment. (think it's about 1800rpm) Put 3batt's thru it the other nite & totaly trimmed it out. it virtually sit's in the air now, only drifting left (tail in) V V slowly, no overheating prob's at all. Put new blade's on it last nite, as old blade's had a few "ding's in them, from my "autorotations" Can't wait to get it in the air Monday nite! (would fly it outside, but it's October in England & it's blowing a hoolie!

redgiki
10-23-2006, 06:43 AM
Wow, only 1800RPM? I fly at 2600-2700 on my Rex (tach measured), and long for more head speed!

My flight times are about 8 minutes.

Glad you found the cause of your thermal shutdown. With my 15C batteries, I actually really enjoy the soft-cutoff (3.2V) feature of my Align ESC. It begins pulsing once the batteries hit 3.2V, and I have a few moments to kick down into Normal mode and bring it in for a landing. The batteries normally rebound to well over 10V because they hit 3.2V under load, and I put about 1600-1700mAh back in.

It's so nice to have an ESC with a cutoff that shouldn't damage either my LiPos or my chopper. I long for a 3.2V soft-cutoff for the ESCs on my airplanes now!

Adrian
10-24-2006, 08:52 PM
Have'nt actually got an RPM counter, so that may be a conservative estimate. Put another 3 batt's thru it last nite, including the new Flight power 2150. got approx 10mins out of it before it started bobbing up & down, boy did it bob on that batt, all 3 cells hit EMPTY together. New low voltage alarm fitted this aft, no more of that nonsense:cool: Off work Thursday, hope to get it out door's & get more hour's in.

Tintin
10-26-2006, 10:19 AM
Oh oh, do not fly untill the Align esc hits LVC unless you have the newest one and set it to high protection at 3.2 volts. You'll kill your batteries in no time if you do this with the older escs where high settings is less than 3 volts...I know, I have 6 packs to prove it's not smart...

Adrian
10-27-2006, 08:23 PM
The guy who built this little widget is an electronics eng, much wisdom fall's from his mouth. (& his finger's) 1/2 the club flie's on his alarm's, with no stuffed batt's from any of them. I will rely on his advice/set up of alarm over align's any day of the week! I've stuffed'n'puffed 6 batt's (1st 3 due to running them into the ground, other 3 due to leaving them for month's without charging them) due to ignorance & poor quality charger's, it WON'T happen again.

Tintin
10-28-2006, 12:12 PM
Wouldn't be a Customidea alarm would it ?

Adrian
10-31-2006, 10:25 PM
Never heard of it! Mine custom built by a man who supplies model manufacturer's with electrical part's. Quite good with a heli also!

Reflex
11-01-2006, 12:28 AM
It's built by Mike at http://www.customelectronics.co.uk/

Shoot him an email if you need more details.

Paul

Tintin
11-01-2006, 09:02 AM
Thanks for the link.

I use these in my smaller models
http://www.customidea.com/hrpolyx.php

And this for the TRex 600
http://cgi.ebay.com/Lipo-Voltage-Alarm-5-6S-for-Trex-600-size-Helicopters_W0QQitemZ190044425163QQihZ009QQcategor yZ84444QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Pretty good both of them, haven't lost a battery since I started using them a while back.