Electric Open B is reality in 2007 Q&A

Want to discuss OPEN electric combat items? Come on in! This is the place.

Moderator: hbartel

Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Electric Open B is reality in 2007 Q&A

Post by Lee Liddle »

For several years this thread has gone almost unused. The only threads being about little 1/2a sized open style electrics, powered by park flier systems.

Well, in 2007 Open B, E style, has become a reality. And, last weekend, saw the first time an Open B contest was won by an electric plane. Also, it looks like Drewjet took 2nd at an Open B meet in Florida.

So far this year in Open B, I`ve flown 4 meets, flown 34 heats and (when the Jettero scores are posted) I`ll be in 3rd place in the NPS standings. I may also make the trip to Florida to fly the last B meet in 2007.

The cost is fairly reasonable. Motor aprox $35, ESC aprox $35 and 5s2p 4400 battery pack aprox $100. Unfortunately the motor has sold out for now. There is a similar, but higher quality, motor available for about $85, and there will be others, but even $85 is not bad.

Now the window for AMA rule changes has closed for another 2 years, and the E-phobes will have to wait before they start their "Limit Electrics" campaign for "OPEN".

So if anyone is sitting in the shadows wondering about electrics in open. Here`s the place to ask. I`ll be glad to help, as long as the monitors don`t allow the thread to be hijacked.

<font size="4">If you want to start an E-Phobe thread, do it some where else. This is a Q&A thread for combat pilots intrested in high performance electric combat. </font id="size4">
drewjet
Posts: 1101
Joined: Fri Mar 16, 2001 5:24 am
Location: USA
Contact:

Post by drewjet »

Lee, Great thread, Congratulations. I took second so as to set the record straight. Grasshopper beat me by about 400 points. I had a zero round in round 7 due to a failure in my electrical system. Had that not happened, or if I had Lee's abilities, it would of been very close.

Alex it can be done, though not in a legal RCCA open B Combat plane, even with the extra 8ozs allocated to electrics in open B. But to me it is obvious you are not serious, or have no clue. Typical nitro Open B planes are turning a 9X4 prop at 19000 RPM, not a 12X6.

The power requirement for a 12X6 @ 19,000 RPM is 6500 Watts. It would take 170 ozs of battery and motor to do that.

To spin a 9X4 @ 19000RPM would take about 1300 Watts and a battery/Motor weight of about 40 ozs.

Obvious neither of those solutions would give you a plane that would make the weight requirements of Open B. To use electrics you must disregard what nitro engines do, (Not try and match them) and start with a clean slate. You need to understand the strengths and weaknesses of electric systems and design your power system and plane around that.

The plane I was using over the weekend was running on about 500 watts on a system that I have been tweaking and optimizing for a few years. I was not the fastest, but I wasn't the slowest either. There were a few planes that had weak engines and non-moose cans. They were my favorite targets.

I will be happy to answer questions as well. Great job Lee, congrats.
drewjet
Posts: 1101
Joined: Fri Mar 16, 2001 5:24 am
Location: USA
Contact:

Post by drewjet »

By the way those numbers come from here http://brantuas.com/ezcalc/dma1.asp a great free online tool to help set up an electric system. It's info is not always exact, but it gets you in the ballpark then you tweak with real world numbers after that.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

Thanks Drew, If I`d have had to fly against Chris, I might have been second too. Too bad about the goose egg, but it happens, even with electric.

Good response to Alex`s "serious" question. Weight is the key limiting factor.

I`m launching at about 900 watts in. That`s 18.5v and aprox 50a. My batts/motor/esc combo weighs about 30oz including the motor heatsink. The batteries are cheap lipos that I`ll be lucky to get 30 or 40 cycles out of. If that`s the case it will make for a "fuel" cost of between $2.50 and $3 per heat. 50 cycles would drop that to $2. I`ll have to wait on that to give a report.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">I would like to put an e-motor turning an 12x6 prop at 19,000 RPM on my Open B plane.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

So would I Alex, but until the miniature nuclear reactors become available to the modeling public, I guess I`l have to wait. PS..this answer is about as serious as your question.

This is a Pro-Electric thread. It is intended to HELP those who might be seriously intrested in trying electrics in Open B.

I`m not surprised that the first response was from you or one of the other two or three e-phobes who troll these forums. I`ll leave your "serious question", because of Drew`s good response and it`s a good example of what will not be welcome on this thread. Maybe you thought it was funny. I didn`t.

Any further posts of that nature will simply be deleted.
drewjet
Posts: 1101
Joined: Fri Mar 16, 2001 5:24 am
Location: USA
Contact:

Post by drewjet »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Lee Liddle</i>
<br />Thanks Drew, If I`d have had to fly against Chris, I might have been second too. Too bad about the goose egg, but it happens, even with electric.

<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

That was a part of my point. Electrics are not a guaranteed perfect run every time.

If you look back historically at my performance in the NPS, I have remained about the same going from Nitro to Electric. Since flying electric my planes have gone down in performance from my glow planes, they are either heavier, slower, less durable or wont last 5 full minutes of combat. Usually a combination of these. Currently I am 30th in NPS, however that is with only 16 rounds in the books, (there are only 2 guys above me (Both Wengers) with 16 rounds or less. I am hoping to make a big jump when these 7 scores get entered and maybe with some luck make the top 10 with the Boca contest next month.

Overall I am happy to be flying electric and owe it all to Alex Treneff who told me "why don't the electrics fly in open classes where they are already allowed"
Fred420
Posts: 277
Joined: Thu Feb 10, 2005 8:36 am
Location: USA

Post by Fred420 »

Hey guys ...... I used to fly electrics back when we all used brushed or cobalt motors, threw in a 10 cell 4400 Nihm or KAN's, everything was so easy. Now, with all of the brushless with all of these different winding and wire size, I am confused with watts and all of the other measurements that are now used in determining what to use.

When I read Alex's question, I did not see it as not being serious. I do not know what the requirements that are needed to turn a prop a certain RPM, and I am guessing that he did not either. So maybe this RIFF between elec end IC can end. It seems as if there is some personal animosity between a few of the pilots. Let's just fly and let the best flyer win, regardless of powerplant. I am ALL IN FAVOR of electrics in every class. Just meet the wieght, size and the other requirements that are required for that class.

Is there a site I can go to and see what brushless system or setup I need to upgrade 5 electrics from parkies to a scale .40 that is now with a colbalt? Or to make the switch to elec in Lim B and SSC?

Thanks.
drewjet
Posts: 1101
Joined: Fri Mar 16, 2001 5:24 am
Location: USA
Contact:

Post by drewjet »

Fred, the reality of electrics is that they are not easy. There is no direct equation of converting nitro to electric. Eflight came close with their series of electric motors, they have 15 25 46 etc sized motors. But the reality is if you want to fly electric, one of the best ways is to copy what someone else is doing, or spend the time and money to find something that works for you. If you have a specific question, for a specific plane, I will try and help you with it.

SSC is a relatively easy switch to electric as the power requirement is not so big, about 300 watts. There is plenty of info in the eSSC threads. Limited B takes a large amount of power (about 650 watts)because you are trying to replicate a nitro engine with a specific prop and RPM and that is just something that electrics don't do well, but can be done.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

Alex, if I misunderstood your statement that you`d like to run a 12x6 at 19,000, and your question about the rules, then please clarify it for me.

You and I know each other pretty well. I know that you don`t fly Open B. I also know that you aren`t very intrested in flying electrics. If you were, you should start with 3696 where it is cheap and easy to do, and there is already tons of info posted as to how to get started.

I`m pretty sure that you knew your statement/question was at best counter-productive to the thread and at worst quite inflammatory.

If I`m wrong, let me know.
Alex Treneff
Posts: 941
Joined: Mon Jun 06, 2005 2:00 pm
Location: USA
Contact:

Post by Alex Treneff »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Lee Liddle</i>
<br />If you were, you should start with 3696 where it is cheap and easy to do, and there is already tons of info posted as to how to get started.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Lee, I'll post some pictures of my 3696 mustang later tonight if I can. Should be able to test-fly it over thanksgiving weekend.
BenJammin
Posts: 527
Joined: Wed Sep 05, 2001 1:07 pm
Location: USA
Contact:

Post by BenJammin »

I would like to hear what setups you guys are using.

I thought I had a combo found early in the season. I was using a Welgard 2820-6, 5 cell emoli and a 9x6 ma prop. I flew one contest with this setup. We flew 8 rounds, I had to sit out the 7th so I could do a motor swap. I did manage third place. Every thing seemed to work well there. As the summer went on though I had problems. The motors developed vibrations. The motors have a 4 mm shaft and it wasn't a good fit between the motor can and shaft so it allowed it to move. On top of that I am not feeling the joy from the emolis. They don't seem to be making the power they were when I got them and they are heavy.

I do have one of the motors left. It has not been through combat so I mounted it on a sport plane that weighs 3 lbs. With a 4S 4000 mah lipo and a 10x6 prop it has way more power than it did on the 5S emoli. I flew it last weekend. I made two 4-5 minute flights for a total of 8-10 minutes on one pack. When I recharged it, it took 2000 mah so I still had half the pack left.

I believe that setup would work in open B, but I wish the motor was more durable and I hate to damage a Lipo.

So what are you guys using?
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

Sounds like your motor is an outrunner. Outrunners are very efficient, but not as durable as in runners.

I`m using a Quantum Drive 36-55 inrunner. It`s rated at 50a and has a 1400 kv. The batteries are 5s2p4400 lipos of various brands. The esc is a Tower Pro 70a for 4s to 6s. I add a second set of input leads to the esc and plug each 5s2200 directly to the esc, no "y" cords. So each side pulls about 25a static.

I`m running an 8/4 prop, either MA or APC and set the EPA so that I`m pulling 50a at full throttle. This usually gives me about 20.5k rpms depending on the day.

I`m drawing 11c on the ground and probably 10c in the air. I have an Eagle Tree now, so I plan to get some actual in flight numbers soon.

I had problems this year because most of the batteries that I bought were some of the bad batch that everyone dealt with this year, but with good batts it will go 5.5 minutes with no problem.

The speed is faster than most Open Bs, except for the Webra powered flying wings. I can keep up with them too, but not for 5 minutes.
drewjet
Posts: 1101
Joined: Fri Mar 16, 2001 5:24 am
Location: USA
Contact:

Post by drewjet »

BenJammin,

I tried the emolis but found them like you did, to loose capacity and punch after a few cycles at 10C. I really think they are more of and 7 to 8C battery.

I so far am finding the A123s to be longer-lasting, hold voltage better under heavy loads, and faster recharging.

Currently the two setups I am using for Open B is a Scorpion 30-14 outrunner. It has a 5 mm shaft and so far seems to be very durable. I have had many lawn darts and haven't bent a shaft yet. I run either 4S2P for my heavier ship or 6S1P in my lighter plane.

I have been staying away from lipos as my experience with them in combat is that they are usually turned into accordions after a midair. If you can avoid midairs then they have a higher power to weight ratio than the A123s or emolis. But for me they are just too expensive and too fragile for combat.
BenJammin
Posts: 527
Joined: Wed Sep 05, 2001 1:07 pm
Location: USA
Contact:

Post by BenJammin »

Thanks for the feedback guys. I hadn't seen any inrunners that could spin a big enough prop but that sounds like an option. I did have my eye on the Scorpion 30-14's. Are you rolling your own Drew? As for batteries, I think I'll wait until spring and see what happens. It's too dang cold to do much flying around here anyway. Maybe A123's will come down in price or something better will come along. I see Ryobi has a lithium system now. I haven't heard for sure what chemistry they use but they are rated at 2.4 ah. Dad has an 18v Ryobi chainsaw, I'm planning on getting him a lithium kit to go with it for Christmas. You can bet I'll be taking the cover off one of the batteries to see what's inside.

What's the highest amps you can draw with a 1P A123 and still fly a full round?

Electric combat is so darn nice I just hate to have to go back to slimers.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">What's the highest amps you can draw with a 1P A123 and still fly a full round?
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

That would be about 25a static.
Post Reply