120sr TAIL WIRE DRAWING TO MUCH POWER

brettskywalker48 · 05-11-2012, 07:49 PM

My mcpx has been collecting dust the past few months, after becoming frustrated with the tiny wires. I went back to my b400, the past 2 wks I've been waiting on various parts for my 400 so I dusted off the mcpx in attempt to further evaluate its problem. The last thing I did to it was replace main motor & replace tail motor wiring, which snapped from to much handling, the heli would fly fine at a constant throttle. Give it full throttle & it would just drop out of the sky. I thought maybe a mosfet was burnt, I've seen pics of them but mine did not look like they were scorched. So I thought I may have burnt the tail mosfet completely off. At my lhs today they had 2 mcpx v2s, so I opened 1 up & looked at the main board, it appeared no different than mine. I soon remembered I had replaced the tail motor wire with 120 wire. & then it hit me, COULD THE USE OF THE 120SR TAIL WIRE BE DRAWING MORE POWER, CAUSING THE MAIN MOTOR TO BOG & EVENTUALLY NOT HAVE ENOUGH POWER TO SPIN THE ROTORS AT ALL?? My lhs had a complete tail assembly that I quickly bought & installed. Haven't done a full throttle test but it seems to be running much better. Let me know your thoughts please. All electronics are stock

Talesin · 05-11-2012, 08:01 PM

Unlikely... more likely a bad solder joint on the new wire, or a short, if it's tail-related. Fly it around first; if the heli flies fine with the stock tail, then ask again, and it'd be a reasonable thing to check if so. But without basic troubleshooting, it could be moon-mice hiding their cheese in your old tail motor. Or the old tail motor just dying, or a bad FET, or... tons and tons of things. Need to know if the new stock tail fixed it before any actual guesses could be reasonably made though, or things to check be suggested.

brettskywalker48 · 05-12-2012, 12:08 AM

Very true, I definitely need to do more than cruise through the warehouse at work to test its performance. The new tail assembly may have solved the problem, but I won't know until I get a chance to really fly it. I ll try some pitch pumps to see if It shuts down. Will try tomorrow or later in morning

UKHeliBob · 05-12-2012, 02:32 AM

It does not matter how thick the wires are that you use to conduct current to the tail, they will not cause excess current to be drawn.

The most likely cause of the original "dropping out of the sky" problem is that the main motor is drawing too much current when you give it full collective. To prevent this the mCPX manual suggests that you set the positive and negative pitch Travel Adjust to 75%. Try reducing this and see if it improves things. Don't forget to do both pos and neg.

brettskywalker48 · 05-12-2012, 08:50 AM

Sweet info ukhelibob, I'm pretty sure my travel adjust is set to 100%. I'm going to change that right now & give it a whirl in a bit

brettskywalker48 · 05-13-2012, 09:51 AM

I think ukhelibob hit the nail on the head, after installing a complete tail assembly with new tail motor & checking my pitch travel adjust which was at 100%!!! I quickly changed it back to the stock 75%, I can once again reach full collective without the main motor stalling. Which particularly helpful in strong wind gusts that bounce the little heli several feet up & down. I was ready to scrap, sell, or store my mcpx, now I will continue to irritate my wife by buying upgrades every once in a while. Its ridiculous that some of the metal upgrades for this are 4 times smaller than 450class but cost the same! Oh damn, just started raining, well at least I got to run through 4 batteries this morning

05-11-2012, 07:49 PM	#1
brettskywalker48 Registered Users Join Date: Feb 2012 Location: south carolina	120sr TAIL WIRE DRAWING TO MUCH POWER My mcpx has been collecting dust the past few months, after becoming frustrated with the tiny wires. I went back to my b400, the past 2 wks I've been waiting on various parts for my 400 so I dusted off the mcpx in attempt to further evaluate its problem. The last thing I did to it was replace main motor & replace tail motor wiring, which snapped from to much handling, the heli would fly fine at a constant throttle. Give it full throttle & it would just drop out of the sky. I thought maybe a mosfet was burnt, I've seen pics of them but mine did not look like they were scorched. So I thought I may have burnt the tail mosfet completely off. At my lhs today they had 2 mcpx v2s, so I opened 1 up & looked at the main board, it appeared no different than mine. I soon remembered I had replaced the tail motor wire with 120 wire. & then it hit me, COULD THE USE OF THE 120SR TAIL WIRE BE DRAWING MORE POWER, CAUSING THE MAIN MOTOR TO BOG & EVENTUALLY NOT HAVE ENOUGH POWER TO SPIN THE ROTORS AT ALL?? My lhs had a complete tail assembly that I quickly bought & installed. Haven't done a full throttle test but it seems to be running much better. Let me know your thoughts please. All electronics are stock

05-11-2012, 08:01 PM	#2
Talesin Registered Users My HF Map location Join Date: Jan 2012 Location: Kansas City, MO	Unlikely... more likely a bad solder joint on the new wire, or a short, if it's tail-related. Fly it around first; if the heli flies fine with the stock tail, then ask again, and it'd be a reasonable thing to check if so. But without basic troubleshooting, it could be moon-mice hiding their cheese in your old tail motor. Or the old tail motor just dying, or a bad FET, or... tons and tons of things. Need to know if the new stock tail fixed it before any actual guesses could be reasonably made though, or things to check be suggested. __________________ *Blade*: mCX2, mSR, mSRX, Nano-CPX, 2x mCPX (v1), mCPX-BL, 120SR, 450 X Spektrum DX8, DX6i

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05-12-2012, 12:08 AM	#3
brettskywalker48 Registered Users Thread Starter Join Date: Feb 2012 Location: south carolina	Very true, I definitely need to do more than cruise through the warehouse at work to test its performance. The new tail assembly may have solved the problem, but I won't know until I get a chance to really fly it. I ll try some pitch pumps to see if It shuts down. Will try tomorrow or later in morning

05-12-2012, 02:32 AM	#4
UKHeliBob Registered Users My HF Map location Join Date: Aug 2011 Location: UK	It does not matter how thick the wires are that you use to conduct current to the tail, they will not cause excess current to be drawn. The most likely cause of the original "dropping out of the sky" problem is that the main motor is drawing too much current when you give it full collective. To prevent this the mCPX manual suggests that you set the positive and negative pitch Travel Adjust to 75%. Try reducing this and see if it improves things. Don't forget to do both pos and neg.

05-12-2012, 08:50 AM	#5
brettskywalker48 Registered Users Thread Starter Join Date: Feb 2012 Location: south carolina	Sweet info ukhelibob, I'm pretty sure my travel adjust is set to 100%. I'm going to change that right now & give it a whirl in a bit

05-13-2012, 09:51 AM	#6
brettskywalker48 Registered Users Thread Starter Join Date: Feb 2012 Location: south carolina	I think ukhelibob hit the nail on the head, after installing a complete tail assembly with new tail motor & checking my pitch travel adjust which was at 100%!!! I quickly changed it back to the stock 75%, I can once again reach full collective without the main motor stalling. Which particularly helpful in strong wind gusts that bounce the little heli several feet up & down. I was ready to scrap, sell, or store my mcpx, now I will continue to irritate my wife by buying upgrades every once in a while. Its ridiculous that some of the metal upgrades for this are 4 times smaller than 450class but cost the same! Oh damn, just started raining, well at least I got to run through 4 batteries this morning