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PostPosted: 25 Jan 2013 04:59 pm 
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Location: Hong Kong
K.Y.Mak wrote:
many pilots are using pull spring nowadays :o



Hey Mak,

Did you mean "pull string" instead of "pull spring"?

I built my Longshot using pull string years ago. I couldn't remember where I purchased those string from and what kind of material it was. Can anyone point me to where I can get this pull string?

I checked with many build threads for Akcent 2 on RCGroup, it seems that most pilots are still using metal (musical) push wire, is it because it is easier to build? :? :?


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PostPosted: 25 Jan 2013 05:30 pm 

Joined: 02 Aug 2004 10:14 am
Posts: 621
Hi Stanley, if you are talking about the "Pull-pull" system, the string is "Dyneema" which is mainly using if professional kiting sport.
The European uses the pull spring. The whole system is light and slop free, though many don't want to see the servo being loaded all the time. US uses the push rod system but the whole system is heavy and you need to handle the tubing carefully (they are using thinner wire , not the heavy 0.7mm and thick tubing from our local market). Try something new la!

Johnson


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PostPosted: 25 Jan 2013 09:33 pm 
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Joined: 20 Apr 2011 10:02 am
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Location: Vancouver/Yuen Long
Stanley, I would really recommend setting the voltage alarm to 3.7v, below that is quite risky, especially going all the way to 3.4v I think. I find that some chargers do not charge 1s properly for some reason (including both of mine) and display 4.2v and cut charging enough though that battery is only ~3.9v. The only way I was able to remedy this was to charge at very very low amps (0.1). I wonder if that is the case with why there's a voltage difference between the charger display and the telemetry? Do you have another way to test the cell voltage?

Personally I use pull spring on all my planes (unless pushrods come already installed hahahaha) because it is so simple and light.

If you use pushrod, you should be using 0.5mm stainless steel wire, with thin etched teflon tubing.

Thomas


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PostPosted: 25 Jan 2013 11:14 pm 
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Hi, I charged the 1S battery with my charger at 4.2V. After fully charged, I measured it with a digital voltmeter, the reading was 3.85V, and when it was loaded into the reciever, it dropped to 3.8V and when the servos were moving, it intemetantly dropped to 3.7V or 3.6V, so I think we need to set the alarm at least down to 3.5 or 3.4V to be safe.

Thomas, can you show a photo of your pull spring system? I have read some articles in RCGroup but still couldn't figure out how it works! :oops: :oops:


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PostPosted: 26 Jan 2013 01:50 am 
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Yes, basically know how the pull spring system work and will try to install this.

One question, did you guys build a ballast system for your DLGs?
What is the pros and cons for having ballast to the perforamnce of launch and thermal cruise? :oops: :oops: :?


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PostPosted: 26 Jan 2013 06:36 pm 
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Location: Vancouver/Yuen Long
I'm worried your charger is having the same issue as mine, indicating full charge even though it's not. I suggest to thoroughly test the battery at those voltages inside the plane before usage, <3.6v on a 1s setup is very scary regardless of what the charger says. I think the digital voltmeter and possibly the telemetry is more accurate.

If you havemore questions about the pullspring let me know, I have lots of pics on my comp i can email you.

Depending on your physique, reasonable ballast can improve launch height, and increase L/D, and decrease turbulence effects on the plane. Min sink obviously increases, so ballast with caution. Remember, in thermal soaring, do not use too much ballast that the plane will not go up in the round's thermals. It really is a black art.

Personally I do not use ballast often, although some of my next planes will have a ballast provision again because of the Denmark weather.


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PostPosted: 28 Jan 2013 03:27 pm 
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Joined: 20 Apr 2011 10:02 am
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Location: Vancouver/Yuen Long
I just ordered 10 pcs 1s 750 35c lipo from a friend's hobby shop in china, he said he tested them and they are very good. Specs and size seems to be the same as my turnigy nano-tech 1s 750 35c packs, so I am wondering if they are the same. If they are then they should be quite good, will keep u guys updated when they arrive. Maybe put it in my new Blaster 3 and XXLite planes to try first when they arrive.


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PostPosted: 28 Jan 2013 10:36 pm 
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I charged and discharged my 880mAh and 650 mAH batteries a few times for testing, it seems that they are all ok with sufficient capacity. So I will install 650mAH battery in my Akcent 2, this should be sufficient for at least 3 hours of flight after fully charged.

Most Lipo chargers will set the charging voltage for 1s cell to 4.2V, I did monitor the battery voltage using my digital voltmeter during charging. With a 0.2A charging current, the charging voltage rose up to 4.2V gradually, and then stayed there while, in turn, the current was gradually reduced until it reached zero, then it stopped. So I believe it was fully charged, but still when I removed the charger and measured the voltage of the newly charged battery without connecting to a load, the reading was 3.85V only.

I will do another test to discharge the battery to just before empty and then connected it to the receiver to see the absolute minimum voltage this receiver can operate before the 1s battery was fully drain.

I think I will not build a ballast system for the time being, if I found that ballast is really needed, then I think I can build it later.

Cheers! :P :P


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PostPosted: 29 Jan 2013 12:27 pm 
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Joined: 26 Feb 2004 07:54 pm
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Location: Tai Po, HK
Stanley,

don't discharge the battery below 2.8v (empty ! ?)
that'll damage the battery.


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PostPosted: 30 Jan 2013 01:15 am 
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K.Y.Mak wrote:
Stanley,

don't discharge the battery below 2.8v (empty ! ?)
that'll damage the battery.



Hi Mak,

My charger has a discharge mode, the minimum discharge voltage for 1s is fixed at 3.0V.
I am still checking the minimum voltage my RG831B receiver can still function properly, so that I can set a warning voltage in my transmitter later on. I will report this once I found it out. 8)


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PostPosted: 30 Jan 2013 11:42 pm 
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I have just tested and evaluated the minimum voltage my RG831B receiver can operate.

After my 1s 650mAh battery was fully discharged, I measured its voltage without load at 3.23V, then I connected it to my receiver, its voltage dropped to 3.18V, and all servos (2 Waypoints, 1 Hyperion DS09 and 1 Sanwa 94761) connected were still functioning, blue lights on the receiver still on. After a while the voltage gradually dropped to 3.08V, then the Sanwa servo was not moving, but others were still ok even the voltage was further dropped to 2.95V.

So I can confirm that JR RG831B receiver, Wavepoint W-038CL and Hyperion DS09 are ok with voltage as low as 3V.

However, I did notice a strange thing that I can not explain.
When I monitored the telemetry voltage on my transmitter, it showed a value fluctuating at 3.6/3.7V when I moved the tx stick with servo movements, even though my digital voltmeter had a reading of 3.1V. A constant reading of 3.7V was there when the voltmeter reading of the battery was down to 3.0V and lower. Really strange, that means there must be a voltage regulation circuit within the receiver!

I repeated the test using a fully charged 1s battery, and the telemetry voltage reading was varying between 3.7/3.8V while my voltmeter reading was similarly varying at 3.6/3.7V.

So what does it mean?
My conclusion is there is no point to set the warning voltage at 3.6V or lower because the telemetry reading never down to that level even the battery is lower than that!

Then what is the cut off warning we should set? If we set it at 3.6V, it doesn't give a true indication the battery capacity remains since even a fully charged 1s battery also gives this value

I know some of you guys are using XG8 and there have been accidents that the low voltage alarm sounded because of servo malfunction. Which warning voltage you guys set? If you are using 4.8V NiMH battery, you probably have set the warning at 4V, have you ever tried lower this to 3.0V and it still works?


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PostPosted: 01 Feb 2013 11:31 am 
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Joined: 20 Apr 2011 10:02 am
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Location: Vancouver/Yuen Long
No, my fully charged 1s batteries on all my planes read 4.2v on my telemetry. The only time it reads lower than that is if I try to quick charge and the charger doesn't put enough back into the plane before the charger thinks it is 4.2v. I don't know why but many guys are having this problem with their chargers.


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PostPosted: 01 Feb 2013 11:46 am 
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Stanley,

Did you do a discharge test on your battery,
to check the total amount of Amps from full to empty?
If Amps output is less then the qouted capacity of that battery, it's an indication of charging problem.


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PostPosted: 01 Feb 2013 11:58 am 
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That's strange! I set my charging current at 0.2A with upper limit on 4.2V for my 1s 650mAH battery, once fully charged, the voltmeter reading is only 3.85V and the telemetry reading is 3.8V.
I fully discharged the battery at the lowest limit of 3.0V and then charged it again. The total capacity pumped in is about 560mAH, which I think is reasonable for a 650mAH battery.
Perhaps, I should lift the upper limit of charging voltage to 4.3V to further pump in another 100mAH, but to do that it would certainly reduce the lift time of the battery.

By the way, has any pilot set the telemetry warning voltage lower than 3.6V on XG8 and it still works?


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PostPosted: 01 Feb 2013 12:26 pm 
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Weird, when I set my charger to 0.2A I am not getting that problem. Do you have another charger to try? Of the 3 devices you have I would trust the voltmeter reading the most.

I am very interested in hearing the outcome of your testing, it is very interesting.

No, lowest I have heard is 3.6V, most of the people are 3.7V though.


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PostPosted: 01 Feb 2013 01:01 pm 
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Stanley wrote:
By the way, has any pilot set the telemetry warning voltage lower than 3.6V on XG8 and it still works?


Stanley,

Even if it work at lower then 3.6v, it doesn't mean it'll last long.
At the end of discharge, the voltage can drop very fast.
You don't want your battery drop dead before you landed your dlg.
Do you ?

Better be safe then be sorry :wink:


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PostPosted: 01 Feb 2013 02:21 pm 
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Mak,

What I really mean is;
No matter what value (below 3.6V) I set on the telemetry warning voltage, even with the input voltage to the receiver is as low as 3.0V, the telematry reading is always a constant at 3.7V, very strange, can't explain this! :? :? :?

So I just want to ask if anyone has set the warning voltage below 3.6V and it still works :?: :?:


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PostPosted: 01 Feb 2013 02:31 pm 
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Are you sure about that?
That makes the voltage warning function of the JR radio useless :roll:

Bring your new gears and battery with you this Sunday, to test it against other JR radio.


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PostPosted: 01 Feb 2013 02:41 pm 
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Yeah, pretty sure!

It works for input voltage above 3.6V. I have tried to use a 4.8V NiMH pack and set the warning at 4.4V, then when the battery voltage dropped to 4.4V, it sounded.

This is not the case for 1s battery voltage dropped below 3.6V, the telemetry reading just stayed at 3.7V and never sound! :? :? :?


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PostPosted: 01 Feb 2013 03:06 pm 
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That's interesting, I set mine to 3.7v and it will sound....
Yes, please compare it against other JR tx's and see if perhaps there is a problem? That is very strange.


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PostPosted: 02 Feb 2013 09:08 pm 
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I tested the lowest warning voltage again last night and confirmed that the telemetry warning can work down to 3.7V only, below that the reading is kept at 3.6/3.7V and therefore never give a warning sound.

So don't set your warning voltage at 3.6V, it will never give you warning sound

However, if you set your warning voltage at 3.7V, it will sound when your 1s cell has only pumped out about half of its capacity - too soon!

So beware of this! :x


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PostPosted: 08 Feb 2013 04:51 pm 

Joined: 08 Feb 2013 04:44 pm
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I was given a link to this site in regards to the issue of what battery warning voltage is appropriate when using a single cell LiPo. When using my XG-8, I set my battery warning voltage to be at 3.6V. When the warning goes off, I recharge the battery and typically put in about 80-85% of the rated battery capacity.

I've not done much quantitative testing, just a few quick tests when I first got the radio. My first tests indicated that the telemetry display of the receiver voltage will not go below about 3.2V (or something like that). To me, that suggests that there may be a minimum voltage regulator in the circuitry.

Originally, I used 3.7V for my alarm voltage, but found that I was only putting in ~60% of the battery capacity when recharging. Someday I'll try 3.5V to see how much closer it gets to the edge!


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PostPosted: 08 Feb 2013 05:45 pm 

Joined: 02 Aug 2004 10:14 am
Posts: 621
JW, welcome to our forum.

Johnson.


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