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Old Mar 13, 2006, 02:02 PM
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53859 Niederkassel, Germany
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Quote:
Originally Posted by Bill Glover
Was that with the same motor? Any before/after tacho and amp draw figures? A couple of years back I tested four neutrally timed Permax 6V S400s with the same prop and same input voltage (8.8V), and got quite a spread of results. If I'd been flying the worst (13,900 rpm) and switched to the best (15,200 rpm) I'd have got a significant improvement without any tinkering whatsoever!
There is a page with a lot of testing of Permax 400/480 - measuring the effects of wet break-in, timing, flux ring etc. (unfortunately it is in German only):

http://www.frach.de/

Jürgen
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Old Mar 13, 2006, 02:17 PM
elaporaholic
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Staffordshire, England
Joined Aug 2004
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TT, I see you are still nervous about Lipos.
I am too and I just don't trust myself with them. So I have changed from nicads and nihms to Saphions now (no thermal runaway). I use 3s2p in my TS with the stock setup and have found them to be ideal. 1p is good for 18amps cont. 2p good for 36amp cont. etc.
Why not try a 3s1p in your EZ?..... 3s1p gives you 9.6v 1200ma and weighs 130grms, you have to charge with a Lipo charger (don't need a balancer) but can use standard Escs.
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Old Mar 13, 2006, 02:19 PM
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Quote:
Originally Posted by flieslikeabeagl
...
Let's look at something as objective as can be. I looked up the motor constants for the Multiplex Permax 400 6V on the web, and found them at Motocalc.com. They are: Kv = 3026 rpm/V, Io = 0.700 A, Rm = 0.3570 Ohm. I plugged those numbers into a program that calculates the motor performance as a function of current, and I've attached a graph of the results, with the motor run at 7.5 V, representative of a 7-cell pack under light loading (efficiency gets worse as the battery voltage drops, so at WOT when the battery voltage drops below 7.5 V the actual performance will be worse than the graph shows - I wanted to be nice).
...
-Flieslikeabeagle
You really rely on figures from MotoCalc? MotoCalc often is quite far off from real world figures. Why not use the original data from the manufacturer of these motors?

70% efficiency at 6V and 4A. At higher voltages the efficiency gets better, and the peak point moves towards higher currents. A 7 cell pack of good SubC sized Nicads or GP2200 NiMH provide at least still 8.4V at 10A.

How much the motors actually see from this voltage depends on connectors, ESC and wiring.

Jürgen
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Old Mar 13, 2006, 02:23 PM
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Quote:
Originally Posted by Sooty100
...
Why not try a 3s1p in your EZ?..... 3s1p gives you 9.6v 1200ma and weighs 130grms, you have to charge with a Lipo charger (don't need a balancer) but can use standard Escs.
What gives you the idea, that you don't need a balancer for a 3cell LiPo pack or that you can use a standard ESC (i.e. an ESC designed for LiPo usage)?

Jürgen
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Old Mar 13, 2006, 02:35 PM
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Here is a link to a thread explaining about them

http://www.rcgroups.com/forums/showthread.php?t=403527
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Old Mar 13, 2006, 02:44 PM
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By standard esc I mean an esc designed for nicads and nimhs and I was refering to the fact that whilst it is important to balance lipos for saftey reasons saphions don't need to be. Soory if I was wasn't very clear.
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Old Mar 13, 2006, 02:44 PM
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Quote:
Originally Posted by Sooty100
Here is a link to a thread explaining about them

http://www.rcgroups.com/forums/showthread.php?t=403527
Those are not "normal" LiPos and although safer than standard LiPos should still be treated with proper care.

Jürgen
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Old Mar 13, 2006, 02:50 PM
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Quote:
Originally Posted by Sooty100
By standard esc I mean an esc designed for nicads and nimhs and I was refering to the fact that whilst it is important to balance lipos for saftey reasons saphions don't need to be. Soory if I was wasn't very clear.
Of course you still need to have the cells balanced. In an unbalanced pack, the fullest Saphion cell will still get damaged when the overpressure valve ruptures.

Jürgen
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Old Mar 13, 2006, 04:23 PM
Honey,just one more thing
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Quote:
Originally Posted by flieslikeabeagl
So: Yes, I will fly the Twinstar II with the DX6. Happy flying!
-Flieslikeabeagle
I'm with you. I am going the same route. I have had one on a small gyrocopter for awhile, and have had it up till it was a speck and far out, no problem at all.Bud
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Old Mar 13, 2006, 04:45 PM
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[QUOTE=Jurgen Heilig]Those are not "normal" LiPos and although safer than standard LiPos should still be treated with proper care.

They are not Lipos that is correct that was my point, as they are a safer alternative for those of us like myself who are still too nervous to use Lipos. Although heavier than Lipos they have thier advantages and the link is there for anyone who may not be aware of them yet.
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Old Mar 13, 2006, 04:46 PM
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Quote:
Originally Posted by Bill Glover
Was that with the same motor? Any before/after tacho and amp draw figures? A couple of years back I tested four neutrally timed Permax 6V S400s with the same prop and same input voltage (8.8V), and got quite a spread of results. If I'd been flying the worst (13,900 rpm) and switched to the best (15,200 rpm) I'd have got a significant improvement without any tinkering whatsoever!
Hey now,
Well since you can un-break in a motor and breaking it in after the damages has been done wouldn't work either, I used two motors, but I picked two that static tested the same from a large box of them, so they were close. The timed vs non timed was the same motor.
RobII
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Old Mar 13, 2006, 04:53 PM
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Hey now,
There's no need to be afraid of LiPos. They as safe as anything if used properly. Don't over discharge them, don't over charge them and if you smash them up in a crash don't just toss them in the car.
I've been using them for a couple years now with no problems of anykind.
Now, I'm not stupid about it either. They live in an ammo can like my other batteries and I keep each pack in it's own poly bag (just like all my other cells). If I charge them in the house I charge them in a glass baking dish with a lagre baggie of sand on top just in case, still I've not needed to so far.
The difference in power and weight is well worth taking a little extra safety precautions.
RobII
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Old Mar 13, 2006, 05:34 PM
Got shenpa?
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Los Angeles
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I just received my copy of Model Aviation (the AMA magazine). There is a discussion on improvements in lipo safety in it. The column refers to a large indoor meet that was held recently, where virtually every flyer was using lipos - IIRC the author of the column estimates that perhaps 1000 batteries in all were used during the entire meet.

Safety precautions (ammo cannisters to contain the lipos, sand buckets to extinguish any fires) were put in place. None were needed - there was not one single lipo fire or "incident" during the meet, despite a few crashes and attendant damage to lipo packs.

Please note: the above is an indication that lipo packs are getting safer, not an invitation to disregard safe procedures. As always, lipos should be charged and stored in a suitable flame-proof container, charged at appropriate rates with a lipo-safe charger, and checked for balance periodically. Damaged packs should be soaked in salt water for a day and disposed off in the trash.

Like Elfwreck, I too have been using lipo batteries since my second RC plane, circa June 2004 or so. I have damaged a few in the inevitable crashes, and have promptly disposed of those after the appropriate salt-water bath. The only "incident" Ive had in all this time was one unused cell which puffed up while in storage in a fire-proof box - it's noteworthy that this was an old Etec 1200, now a few generations old.

-Flieslikeabeagle
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Old Mar 13, 2006, 06:54 PM
Honey,just one more thing
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Quote:
Originally Posted by flieslikeabeagl
As you can see, Elapor models powered by small electric motors are not in this category, and can be flown quite safely with the DX6. Elapor (a mix of polystyrene and polyethylene) is quite transparent to 2.4 GHz RF, and the electric motors and lipo pack are too small to cast any significant RF shadow.
-Flieslikeabeagle
How about a 8cell nimh pack? Kind of got me thinking again. Unless the placement of the receiver is in some location that wont be affected. Its not like I don't have other receivers and radios to use, just want to try this out in it. I already have it set up to do spoilerons and such. Bud
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Old Mar 13, 2006, 09:31 PM
KY3JBD
lebanon, PA
Joined Dec 2000
560 Posts
Hello, well i flew my twinstar saturday with the twin 400xt motor setup on 3 cell 2100mah lipoly and 8x6 slow fly props. It flew great! not sure how it performs stock, but a nice gentle toss and it flew right out, nice climb angle, and a good amount of speed.......I was flying around inverted pulling outside loops from level flight and and making really big loops from level flight. I cranked up the aileron throw and it rolls actually better then i thought it would having such a big wing. Anyhow i am going to try 9x6 props and see if its better, but i am really happy with the performance so far. And to have a motor cut out you would really have to run the pack down pretty far and im not even sure it would be much of a issue at low throttle settings because this thing flys so well. Now time to rig up my camera........
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