Multiplex Twinstar 2

[Dave Foster]

Hi Guys, I wonder if anyone can help me?

I have just bought a Twinstar 2 (radio ready version) and had my first couple of flights over the weekend. The aircraft is fitted with the stock motors and speed controller etc and the model shop sold me a 'Tornado TRC 4300 Nimh 9.6v Sub C Pack'. The first flight was OK, but after a re-charge of the battery pack the aircraft only flew for 2-3 mins before the engines stopped. After landing and being allowed to cool down the motors seemed to be running fine again, so I re-launched and again only managed a couple of minutes flight before the motors stopped again. I managed to make another dead stick landing and upon investigation found the battery pack and speed controller to be very hot. I am new to electric flight, but would I be right in assuming that the speed controller is over-heating and therefore shutting down?? And if so, does that mean that the battery pack is not suitable? Having looked in the instruction manual, Multiplex recommend a 7 or 8 cell pack of 3000mAh.  I can see from the user reviews on this website that others have had similar problems with the engines 'cutting out', but they do not mention how they overcame the problem.

Can anyone tell me which pack I should use in this plane please?? Thank you in advance.

[Frank Skilbeck]

You battery pack is OK, it's as you have said the electronic speed controller is getting to hot and has a thermal shut down protection.

The Nimh batteries will get warm during discharge, and it's made worse by the fact that it's a foam model with very good insulation properites.

What you need to do is make sure you have separated the battery and ESC and have a good air flow over these.

If the TW2 is similar to my original the air is taken in just under the canopy and exits by the rear of the wing, make sure air can flow between these two.

I had similar problems on my Twin Jet and cured it by adding a further air exit. Note the exit should be at least twice the area of the inlet for good air flow.

As anside I put a 3s Lipo in my Twin Star and performance was much improved....................... for several flights, but I can advise they don't fly very well on one motor as I found out after I'd burnt out one of the original 400 motors

[Dave Foster]

Hi Frank

Thank you for your response. I will take another look at the airflow and see if I can improve it.

Thanks again

Dave

[David Ashby - Moderator]

The critical question is what amp rating is the ESC Dave?

[Dave Foster]

Hi David

It is the standard ESC supplied with the kit, which is the M-32. I have taken the following information about the M-32 from the Multiplex website;

For standard 500 to 680-class motors.
• BEC receiver power supply (up to 8 NiXX cells)
• Power-on guard
• Overload and excess voltage protection
• Automatic low-voltage cut-off with NiXX batteries

Specification:
Cell count, NiXX, with BEC: 6 - 8
Cell count, NiXX, excl. BEC: 6 - 8
Pulse width: 1250 - 1750 μsec.
Permissible continuous current: max. 32 A
BEC voltage: 5 V
BEC current: max. 1.5 A
BEC dissipated power: max. 2.5 W
Pulse frequency: 6 kHz
Dimensions (L x W x H): approx. 60 x 16 x 14 mm
Weight (incl. cables): approx. 30 g
Motor / battery connections M6 / M6

My battery pack has the following printed on it  'constant discharge 25 - 35Amp Bursts (10 sec) discharge 35 Ap +'

Thanks in advance for your help.

Dave

[David Ashby - Moderator]

OK Dave so its a 32-amp. A brushed speed 400 motor draws about 12-15 amps on full song so x 2 and you' could be getting close to the ESCs rating. I would try a larger ESC, perhaps 40 amps. Like Frank I used 3s Li-Po in my model and used conservative throttle so the motors weren't damaged by 11volts.

[Dave Foster]

Thanks for your response David.

As I mentioned, this kit is the 'Radio Ready' version and therefore everything was pre-installed, looking at the model now I don't think I would be able to remove the ESC if I tried. It drives me nuts that the makers of the kit haven't figured that there could be a problem with the capacity of the ESC and installed a bigger one in the first place! 

So can I presume that there is not a problem with the size/capacity of the Ni-Mh pack that I have then??

Thanks again

Dave

[David Ashby - Moderator]

The pack should be fine Dave, assuming it's ok. In fact the Twinstar 2 benefits from the weight that NiMHs bring to the nose.

[Former Member]

[This posting has been removed]

[Dave Foster]

Hi Tom

I wish it was a simple as that.........

[Former Member]

[This posting has been removed]

[Dave Foster]

Thanks Tom, I will give it a go.......

it does seem a shame to have to modify a good loooking model though.....why don't the kit makers get it right first time?!

Frustrated of Aylesbury!!

[Former Member]

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