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Old Jul 29, 2010, 01:14 PM
KF5LDN FPV Junkie!!!
Wizzard033's Avatar
United States, TX, Lubbock
Joined Nov 2009
1,704 Posts
Once airbourne I generally fly around at about 150 watts. Thats almost a minimal thought at 3.6lbs. With a throttle setting thats much it lower makes the tail drop in flight and the controls get just a bit mushy, or at least more so than I care for. I like my models somewhat over powered personally. 100 watts/lb is a good power setting 61 watts is less than trainer power but thats what you get if your model is 3.6lbs and 220 watts.
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Old Aug 04, 2010, 10:04 AM
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sylifis's Avatar
So. Calif.
Joined Nov 2008
464 Posts
Well, I have to say that I didn't like the way the plane performed at 4.5 lbs., plus I lost sight of my goal of using it for my 4oz. camera....which would be even more weight. I like bullet proofing and bells & whistles, but I went overboard, I think. Soooo, I tore it apart and rebuilt a new one.

2 Rimfire 35-30-1250's
4 hs-65mg's
2 e-flite 30A Pro's
2 2blade 9x6 counter rotating props
2 2350 3s 25C Rhino's

weight without the bats is 35.2 oz or 2.2 lbs.
weight with the bats is 49.78 oz. or 3.1 lbs.

No landing gear or flaps yet, I will just use programming for flaperon/spoileron action....I can add landing gear later after I observe the performance with and without the onboard camera.


I always thought this guy was pretty amazing at 44 oz. with battery:

Twinstar 2. movie (4 min 44 sec)
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Old Aug 04, 2010, 05:03 PM
Stantheman
LaGrange, Ky.
Joined May 2004
421 Posts
Need Some Advice

I have about 25 flights on my completely stock Receiver Ready Twinstar ll using 7 cell Elite 5000 mah Sub C NiMh battery packs (8.4v.). I have three of those packs and performance is adequate for the type of realistic, scale-like flight that I prefer. However, with the weight of those packs the twinstar ll is not as "nimble" as I would prefer. While not exactly a pig I feel that it probably would be recognized by other barnyard animals.
Today, at my LHS, I purchased a 2s 5000mah LiPo battery which has basically the same dimensions as my sub-c packs but, of course, weighs about 1/3 as much.
From reading this forum (and watching Jurgens video on 2s power) I feel that my voltage will be adequate but my concern is the stock ESC. Is it LIPO friendly and will it recognize this new battery without any "programming" on my part?
Any other warnings or suggestions would be greatly appreciated.
Thanks, Stan
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Old Aug 04, 2010, 06:10 PM
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sylifis's Avatar
So. Calif.
Joined Nov 2008
464 Posts
You'll probably get a few answers, but I would recommend you call multiplex USA at this number 858.748.6948 ....they are usually very friendly and helpful, afterall it's their warranty.
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Old Aug 04, 2010, 09:52 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
17,076 Posts
Quote:
Originally Posted by Stantheman View Post
...From reading this forum (and watching Jurgens video on 2s power) I feel that my voltage will be adequate but my concern is the stock ESC. Is it LIPO friendly and will it recognize this new battery without any "programming" on my part?
Any other warnings or suggestions would be greatly appreciated.
Thanks, Stan
I think you'll find the stock ESCs will work fine with your 2S LiPo BUT it is not LiPo friendly in the form of a proper LiPo LVC. You can still use them as is, just time your flights, say starting at 5 minutes, land, charge your battery and see how much charge they took. Increase your next flight time according until you find the spot where you don't exceed 75%-80% of your packs capacity. A LiPo friend ESC is a better option, but I'd bet your end up going brushless in the future and will never look back at brushed systems again.
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Old Aug 05, 2010, 12:59 AM
Stantheman
LaGrange, Ky.
Joined May 2004
421 Posts
Quote:
Originally Posted by Vantasstic View Post
I think you'll find the stock ESCs will work fine with your 2S LiPo BUT it is not LiPo friendly in the form of a proper LiPo LVC. You can still use them as is, just time your flights, say starting at 5 minutes, land, charge your battery and see how much charge they took. Increase your next flight time according until you find the spot where you don't exceed 75%-80% of your packs capacity. A LiPo friend ESC is a better option, but I'd bet your end up going brushless in the future and will never look back at brushed systems again.
The stock esc is rated for 6-8 NIXX cells. Are you saying that the low voltage cutoff would be set for 6 cell specs or that there will be NO lvc in case of lipo usage? If there was NO lvc with the 2s 5000mah I am assuming that I could safely get at least 10 minutes of just cruising around with that many mah's at my disposal and the WORST that I could do would be to RUIN the lipo battery pack.
You are right, of course, brushless would be the way to go but I am satisfied with the 2 s400's for now just because they are there! I just want to lighten their load but I was afraid that the lvc would prematurely end the flight, perhaps at an awkward altitude, long before I had reached the 80% capacity level (approx. 4000mah) since I would have started with only 8.4V (2s lipo).
I really hope that I am making sense since I am still on the slippery side of the learning curve with electric flight.
Thanks, indeed, for your help.
Stan
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Old Aug 05, 2010, 06:43 AM
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Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,019 Posts
Quote:
Originally Posted by Stantheman View Post
The stock esc is rated for 6-8 NIXX cells. Are you saying that the low voltage cutoff would be set for 6 cell specs or that there will be NO lvc in case of lipo usage? If there was NO lvc with the 2s 5000mah I am assuming that I could safely get at least 10 minutes of just cruising around with that many mah's at my disposal and the WORST that I could do would be to RUIN the lipo battery pack.
Your 2S pack fully charged will be about 8.4V, which is the same as 6 fully charged nimh cells. So the ESC (not being LiPo aware) is likely to set the LVC to 6V (1V per cell), which if you flew to cutoff would be right on the limit of over-discharge for your LiPos (3V per cell is the minimum voltage).

Assuming you're not using mega-expensive packs I would go for it. Duration on 5000 mAh will be pretty good, and IMO you are unlikely to fly down to LVC very often. Hence the impact on the lifespan of your packs should be minimal.
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Old Aug 05, 2010, 07:48 AM
Sussex, UK
RobinBennett's Avatar
Crawley, West Sussex, UK
Joined Jun 2004
7,372 Posts
I though most old ESCs cut off at about 4.5 or 5v, because that was the minimum required to operate the radio and servos.

2s5000mAh should give a lot longer than 10 minutes, but without a LVC you'd have to leave a extra margin because you'll use more throttle on some flights than others.

Alternately you can get plug-in LVC modules, or low-voltage alarms that beep loudly enough to hear from the ground.
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Old Aug 05, 2010, 08:42 AM
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Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,019 Posts
Quote:
Originally Posted by RobinBennett View Post
I though most old ESCs cut off at about 4.5 or 5v, because that was the minimum required to operate the radio and servos.
Possibly some budget ESCs do/did that, but the majority work out a cell count from the startup voltage and set the LVC point based on that. Nimhs don't like being over-discharged either (nicds are more tolerant).
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Old Aug 05, 2010, 12:11 PM
Stantheman
LaGrange, Ky.
Joined May 2004
421 Posts
Quote:
Originally Posted by Bill Glover View Post
Your 2S pack fully charged will be about 8.4V, which is the same as 6 fully charged nimh cells. So the ESC (not being LiPo aware) is likely to set the LVC to 6V (1V per cell), which if you flew to cutoff would be right on the limit of over-discharge for your LiPos (3V per cell is the minimum voltage).

Assuming you're not using mega-expensive packs I would go for it. Duration on 5000 mAh will be pretty good, and IMO you are unlikely to fly down to LVC very often. Hence the impact on the lifespan of your packs should be minimal.
Thanks everyone! That is exactly the type of info/assurance that I was looking/hoping for. I will, indeed, go for it. I will time my first flight for 8 minutes then stay at altitude which would allow me to "make it home" in the event of lvc. My eventual goal will be 12 minutes at about 3/4 throttle. Only "timing" will tell.
Stan
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Old Aug 05, 2010, 01:28 PM
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Bill Glover's Avatar
United Kingdom, Bracknell
Joined Nov 2000
11,019 Posts
5000 mAh will give you 15A for 20 mins, so I'd have thought 15 minute flights would be fine.
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Old Aug 05, 2010, 09:20 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
17,076 Posts
I fly 3S 3200mAh packs on brushless motors with 8x6 props...I forget my exact amp draw now, but I can get 15-20 minute cruising flights. I usually just fly ~8 minutes and land...so sometimes go for two flights from one pack. You should have no problems with >10 minute flights.

Perhaps I'm under the old school, but I also though most 'non-LiPo friendly' BECs would run down to ~5 volts before LVC. If that's the case or not, time your first several flights and track how much charge the packs take and you should get a good idea of how long you can fly and land with reserve still left. Enjoy....
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Old Aug 06, 2010, 07:12 PM
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Joined Jun 2010
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Quote:
Originally Posted by Bill Glover View Post
5000 mAh will give you 15A for 20 mins, so I'd have thought 15 minute flights would be fine.
As a reference i run a 2S 4000mah lipo on standard motors and props and i usually manage between 25 and 35 of "fun" flying. The best i ever got was 48 minutes, sure i could go further though...

Regards
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Old Aug 07, 2010, 12:41 PM
my karma ranover my dogma
galaxiex's Avatar
Edmonton,Canada Eh
Joined Jun 2007
7,565 Posts
Does anyone know where to find the datum line for the TSII?

Is there a drawing or blueprint somewhere that shows this?

Thanks!
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Old Aug 07, 2010, 01:56 PM
Stantheman
LaGrange, Ky.
Joined May 2004
421 Posts
Quote:
Originally Posted by galaxiex View Post
Does anyone know where to find the datum line for the TSII?

Is there a drawing or blueprint somewhere that shows this?

Thanks!
To locate the datum line for the Twinstar ll one would have to go to the datum simulator and type in Twinstar ll which would provide the quadratic equation which would allow you to ascertain the hypotenuse and triangulation length of the parallel, diametric glossomar waves.
Then all you would have to do is enter Control-Alt-Delete!
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