Discussion Extreme Flight Aircraft power systems discussion

[gyro]

Hi guys, first post here. I would like to tap your collective brains to guide me on a power setup. I am looking for the optimum 3s power setup for one of the 48" 3 lb birds that are out there. My issue/problem is that all of my 3s packs are nanos 3300s (yea, I know) but I have a dozen of them and they fly all of my airplanes on them. The batteries are 10.5 oz or 300g so the issue is that they are heavier than what most of you are using. It looks like I might need some advice on an airframe as well to perform with a little extra weight. I don't need all out 3D performance but I am looking for an all round optimal package on a larger 3s pack. Thanks for reading.

Welcome to the forum!

To me, your 3s pack weight is the same as most 4s2600 packs, which is what most (including me) use on these planes.... So the weight is a non-issue it you ask me.

So all you need is a motor wound for a 3s LiPo that'll spin a 13x6.5 prop, and an ESC that can handle the higher amp load... Like maybe a 85a Gecko from ZTW.

And one of the best brands out there makes a perfect motor for your needs: the motrolfly 2820-950. It'll put out more power on 3s than the stock torque motor on 4s. Check it out:

DM2820-950

3D planes up to 60 oz

3s Lipo Max 800 W

13x6.5 to 14x7 on 3s

Here is the link: http://shop.subsonicplanes.com/product.sc?productId=17

 

[SnowDog]

snowman, you finally made it!!!!

welcome to our little home on the internet!

I'm sure you will get lots of responses to your questions

FYI, I have a DM2820 that will be going in my 3DHS 49" Su-26 if I ever manage to find time to build it!

 

[snowman]

Thanks for the great information! I have ordered the Motrofly 2820-950 and the EF 300 48". I will be shopping for an ESC (70-80 amps, thanks again for the tip) and servos when we go down to the Toledo show in a couple of weeks. There is still a pretty good chance that I can get it ready to go before the snow melts up here! We're looking at late April before we can get to the field this year! Thanks again, will talk to you all soon.

Oh, anything I should know on building the 300? I'll probably catch you guys on some of the EXP threads here!

 

[SnowDog]

Snowy, you are gonna really like that plane/motor combo!

Be sure to look at the ZTW Gecko 85A ESC - very reliable and reasonably priced...a number of our site sponsors carry them.

http://www.quantumhobby.com/ZTW-Gecko-Series-85A-SBEC-8A-p/g-ztw85asbec.htm

http://www.altitudehobbies.com/ztw-gecko-series-65a-brushless-esc-w-8a-adjustable-sbec

http://www.buddyrc.com/ztw-gecko-85a-aircraft-esc-with-8a-sbec.html

Buddy RC also sells Glacier batteries which are a very good value as well.

What kind of servos are you planning to use?

I've got an EF 60" Extra that was given to me by a fellow RCer after he crashed it...I'm rebuilding the motor box and battery tray, and I've got a Motrolfly DM4315 for it...can't wait to get it going. It's my first EF airframe, but I'm sure it won't be my last.

 

[3dNater]

[MENTION=3034]snowman[/MENTION] Im happy to see you responding to the call of the electric power system. I have to admit the raw power stirs primal urges. Dont worry... what happens on rcg stays on rcg

You are going to truly love that plane

 

[snowman]

Thanks again, I am really looking forward to this combination. I really have the confidence that this is going to be great! I will certainly be dropping by to see Dale at the Buddyrc booth in Toledo in April to see his ESCs and 'what's new'. Great guy and product line! I have heard about his batteries but I have a mitt full of 3s 3300 nanos at the moment so they aren't on my list....yet...... As for servos, I have a set of TGY-393V HV Metal gear Coreless Digital Servo 4.3kg (67oz) / .10sec / 22.5g (.8 oz) that I ordered in error last year. They are heavy, hopefully not too heavy but they are just collecting dust at the moment! I have tested them all under load and they seem great at the moment. Starting to see some grass around the edges of the snow banks!! Thanks again, will be in touch, Doug

 

[snowman]

"and an ESC that can handle the higher amp load... Like maybe a 85a Gecko from ZTW"
I have a question about these ZTW ESCs. When I read the manual on buddyrc's site, I found that the voltage cutoff for LiPo is 2.8v/50% to 3.2v/65% or nothing. I find that voltage too low for Lipo especially for a 'reduced power' cutoff. The percentage numbers are even more confusing. Are they suggesting 50% remaining at 2.8 volts? The manual even used a Lipo as their example with these numbers so it isn't like they were thinking LiFe or something. Did I find an old manual, or is this the way it is? Not too sure I like these settings very much or am I out to lunch on everything I thought I knew. Thanks again!

 

[3dNater]

Hi snowman, I apologize, I thought you were someone else the first time you posted.

Anyway, the general philosophy amongst most of us that fly a lot of 3d is that we fly to our timer and effectively disable the LVC. Most of the time if you were to hit LVC on a 3D plane it means damage. Be conservative on your flight time and you should be fine. Dont push it to the limits of battery capacity. The Gecko is as good as anything available in terms of reliability and throttle response. You will love it if you follow good practices.

 

[gyro]

Hi snowman, I apologize, I thought you were someone else the first time you posted.

Anyway, the general philosophy amongst most of us that fly a lot of 3d is that we fly to our timer and effectively disable the LVC. Most of the time if you were to hit LVC on a 3D plane it means damage. Be conservative on your flight time and you should be fine. Dont push it to the limits of battery capacity. The Gecko is as good as anything available in terms of reliability and throttle response. You will love it if you follow good practices.

Good points, and I agree. I disable the LVC in all my planes, after it's caused me a few crashes while first getting started.

I use RC logbook on my iPhone to record my flight durations and what I put back (mah and volts) into my packs. It then can show me where to set my timer based on how much remaining mah I want to land with (usually 75-80%).

 

[snowman]

Thanks guys, great advice as always. It certainly makes sense to disable the LVC and I will make it my goal.

What I couldn't understand was how ZTW could get those settings so (dangerously) wrong. It's like they haven't a clue about LiPos. 2.8 volts??

I parallel charge a lot (but not always) so it is harder to use GYRO's tracking program. I fly with a timer and I have a pretty good idea what I am consuming but not enough to turn off that last 'land now before you fry your battery' warning. Every once in a while, I get caught having too much fun like the last time I was practising large consecutive KE loops triggering the LVC way before my timer went off!

As suggested, a conservative timer setting is the way to go so that eventually I can turn off the LVC but for me, not yet so I won't be going ZTW this time. One of the things I am shopping for this year is a proper 'pack voltage' or 'Watthour' telemetry system. Wouldn't that be nice if they can get it cheap, accurate and light enough? Thanks again guys. A great place to be!