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MJX T34 Co-axial rotor heli helicopter - 12/5/2012 6:09 PM   
ghost123uk



Posts: 242
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Joined: 11/29/2004
Last Login: 3/22/2013
From: Chester, UNITED KINGDOM
Status: offline 		Firstly, here is a picture =



I usually fly r/c gliders or control line aerobatics, this "was" just a toy, but read on...

In brief, local super store having a clear out sale, picked it up for £39 (~$45) supposed to be around £80 (~$100)

Early on learnt :-

NOT to try and fly it in ANY wind.

NOT to crash it, they do break (unlike the blurb) fortunately spares are easy to get.

They NEED a bigger tail rotor (easy to source) to make then fly forward and backwards properly, though this mod makes them a bit harder to control = less like a toy though

Then I discovered how much fun it is to fly one in the (fairly large) "beer garden" at our local village Pub in the evening . The ultra bright LED "nav lights" make it fly'able in the dark once you get used to it = great fun and the regulars love it

So, all in all a good toy for grown up boys to play with.

BUT The batteries that come with it are 2 x 1100mAh Li-on cells (= 7.4 volt) - but the current draw is over 5 amps and this rapidly kills them, like in 10 x 10 minute flights [>:]. Standard batteries are ~£14 . I assumed the r/x would have the usual low voltage cut off, so I bought a decent 13,00 mAh Li-Po (same weight). It lasted around 6 flights I then found out the r/x doesn't have a low voltage cut off. NICADS are too heavy. So, a shame as it was fun but I ain't going to keep spending on batteries at that rate !

Just a blog really - unless anyone has any ideas ?

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JB in N.W. UK - (if you are into control line in my area, get in touch)

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RE: MJX T34 Co-axial rotor heli helicopter - 12/19/2012 2:27 PM   
ghost123uk



Posts: 242
Score: 100
Joined: 11/29/2004
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From: Chester, UNITED KINGDOM
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Sorry for the "back to back" posting

I now discover that the LiPo is not cream crackered, it is summat to do with the Heli

I put it on a 10 amp bench power supply @ 8.4 volts and it is simply lacking in power. Now the funny thing = I completely stripped it down and checked everything. I swapped one of the motors for a spare I had, re-assembled, taking great care to check everything for alignment and / or binding etc.

I took it out for a test flight = great - it worked fine

I then did have a bit of a crunch on landing, no damage but blade(s) will have been stalled against the ground very briefly.

Now it's back the same, not enough power to take off even. I have checked the battery and tried the Heli on the bench PSU again, but no go. It's not connections as I have checked voltages under running conditions at all relevant points.

Very frustrating as I like "messin about" with this bird, at night, in the local village pubs beer garden (it has nice bright nav lights )


I wonder if there is a similar craft but better engineered ?

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JB in N.W. UK - (if you are into control line in my area, get in touch)

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RE: MJX T34 Co-axial rotor heli helicopter - 1/18/2013 9:54 PM   
jeeper80


 

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From: Kekaha, HI, USA
Status: offline 		One thing about Lipos is that you have to let them cool for a while before putting them on a charger.  Don't try to charge them hot.  I don't know if a power supply is the thing to charge them with.  Lipo's are not like Nicads on Nimh.

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RE: MJX T34 Co-axial rotor heli helicopter - 1/19/2013 9:23 AM   
ghost123uk



Posts: 242
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Joined: 11/29/2004
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From: Chester, UNITED KINGDOM
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quote:

ORIGINAL: jeeper80

One thing about Lipos is that you have to let them cool for a while before putting them on a charger.  Don't try to charge them hot.  I don't know if a power supply is the thing to charge them with.  Lipo's are not like Nicads on Nimh.


Ah, no, you misunderstood, I used the bench PSU (an expensive and accurate one) to "phantom power" the heli, no LiPos were in it at the time, just to see if a hefty ampage @ 8.4 volts would prove / disprove whether a lack of supplied power was the problem. It wasn't. btw, I do use a proper balence LiPo charger as I use one for my fleet of electric R/C planes (I also fly Nitro planes too, both R/C and Control Line aerobatics)

Now, I should have posted back, (sorry) because I did find the problem. It was the cog for the upper blade slipping upwards on the shaft causing the upper spacer (just under the upper blade) to "bind". I stripped it right down (again !) and re-seated the cog, tightened the screws up as tight as I dared and used some Loctite thread-loc on the actual shaft to cog mating surfaces. I now have 1/2 a mm up and down movement of the upper rotor compared to the lower one and all is fine again.



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JB in N.W. UK - (if you are into control line in my area, get in touch)

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All Forums >> Radios, Batteries, Clubhouse and more >> Toy-Grade RC Products >> MJX T34 Co-axial rotor heli helicopter
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