brocja01

Hey all, I know that you guys are pretty sick of talking about the DNU. It has been some time since I've been out in the forums, (10 month old is taking up most of my time) but I have my DNU just sitting in the closet with a Black Widow attached to the front. It is very difficult to get out to the field and fly, so I would like to go electric. But I don't have the 1st clue on what size of battery and motor to put on the front of it. I would like the same performace I got with my Black Widow, maybe a little more.

Plus, as all of you with young ones know, the wife has put me on a budget, so I can't break the bank. I'm going to need battery(s), engine, charger, and Speed Control.

Thanks all in advance, it is great to see the core groups of people still posting on a daily basis.

rainedave

My Feedback: (1)

brocja01, you can spend $300 easily on brushless motors, lipos and a charger.

A quick and very inexpensive route is the GWS direct drive 380 with a 7 or 8 cell NiMH pack.

This motor turns an APC 5.7x3 at 16,000 on the 8-cell pack (650mah).

I have this setup on my Randy Randolph Bee-Tween and it flies really nice; as long as you keep the all-up weight under a pound.

Here are the Tower links for what I'm using:

http://www2.towerhobbies.com/cgi-bin...p?&I=LXHHN1&P=

http://www2.towerhobbies.com/cgi-bin...?&I=LXHVB8&P=7

http://www2.towerhobbies.com/cgi-bin...?&I=LXGBM2&P=7

And a photo of my Bee-Tween:

psullivan

FMA Direct has a motor/esc combo for somthing like $45

FMA also has nice batterys for cheep but not in stock until next month..

Justin

JasonFalls

ew...electric!

psullivan

I know...for shame for shame...

I might be getting a GP Riot though...

That would be wicked with a nice .04 on there....Hmmmm....

brocja01

I knew I was going to recieve some flak for wanting to go electric. But I can fly electric in the little field next to my house, those little Cox engines are waaaaaayyyyy tooooo loud to be flying in a sub-division.

rainedave

My Feedback: (1)

Simmah Dowwwwn.

If you took the time to look you'd have seen the glow fuel behind my plane.[8D]

That FMA combo is interesting. It's rated at 150 watts and should be 50% to 75% more powerful than my brushed motor. But, it produces its power with larger Slow Flier props. For 1/2A type props you want what they call an "Inrunner" not an Outrunner (that's a general rule of thumb, not a stedfast rule).

But, for a DNU, you will want a motor rated between 75 and 150 watts. My setup, according to GWS, is producing these figures:

9.6 volts, 13.80 amps, 15.17oz of thrust, and 132.48 watts.

Another merchant with good information is MPI (Maxx Prod). They have brushless combos and provide the glow equivalents. Scroll down to the "Combo 061." 90 watts and 17oz of thrust, and it's relatively inexpensive for a brushless setup:

http://www.maxxprod.com/mpi/mpi-264.html

Brushless motors require special 3-wire ESCs and won't work with brushed motor ESCs, so decide what you want before investing in a system. Honestly, if you don't mind the expense, brushless motors are usually more powerful tahn brushed motors. It's sort of like comparing a reed valve to a schnuerle front rotor. May be the same displacement, but totally different performance. Still, you can't beat my setup for the $30 it costs.

dieFluggeister

I'm in the middle of converting mine to electric. And to all you poo-poo'ers out there I got the express consent of the designer before I proceeded. With luck I should have some pics tonight.

My setup -

Motor Tower Pro 2408-21
and
HiModel 18A ESC combo $30

8x4 GWS Prop and a 1320mAh 3s Lipo $50
or
9x5 GWS Prop and a 1500mAh 2S Lipo $13 on sale

rainedave

My Feedback: (1)

I guess you can beat my $30 setup![X(]

I've been hanging out at another electric forum and the Hextronic motors are getting decent reviews, as far as the el-cheapo Chinese knockoffs are concerned.

Castle Creations (made in USA) and Scorpion are two good ESCs that get super reviews. The Scorpions are less expensive and come with a programming card. The CC requires an additional $25 programmer. Why is programming important? Because, unlike Ni** batteries, lipos are very sensitive to over discharging. The "Low Battery Cutoff" circuits in most ESCs will not kick in until the lipo cells get below 3 volts per cell. That is very bad. The Castle Creations, Scorpions and the new Thunder Power ESCs will let you set the voltage cutoff above 3 volts per cell. This will greatly increase the life of your batteries. Here're links to the Scorpions and the new Thunder Power ESCs:

http://www.innov8tivedesigns.com/Sco..._jan21_002.htm

http://www.rctoys.com/rc-products-ca...DER-POWER.html

The Castle Creations ESCs:

http://www.castlecreations.com/products/phoenix.html

rainedave

My Feedback: (1)

There is a lot to learn about lipos. They have almost nothing in common with Ni** batteries. I have been doing many hours of reading on the subject, and there are five rules that seem to be extremely important:

1) Never charge over 4.2 volts per cell. Fire will most likely result.

2) Never discharge below 3.25 volts per cell. You will drastically shorten the life of your batteries.

3) Invest in a Balancer. Packs with individual cell voltages that are not in balance can be dangerous. If one cell is lower and you don't use a balancer it is very possible to overcharge one or more cells. See Rule #1.

4) ALWAYS charge in a fireproof container and DO NOT leave the batteries unattended.

5) Never store packs that are fully charged. Charge or discharge to around 3.8 volts per cell when not in use.

There is no such thing as a 100% automatic and totally safe lipo charger. The FMA Direct Cellpro 4 comes closest, but it can still set packs on fire.

I am trying to scare people. Lipos are not like Ni** batteries in any way, shape or form. Watch this video and do as much reading as you can before using them. PLEASE be extremely careful with lipos. The margin for error is in 100ths of a volt.

http://www.purehobby.com/images/Misc./LipoSackv.wmv

brocja01

DieF...

I just found that deal on your motor and esc [link=http://www.rchotdeals.com/Products/rc/Brushless_Motors_ESC/BrushlessMotorsandESC.html]here[/link].

I'm thinking about picking it up, and then picking up some lipo's and a charger.
I'm thinking I would like the 2S approach, a little easier on the wallet.

Let me know what you come up with when you get done setting your DNU up.

rainedave

My Feedback: (1)

Aside from the very serious safety issues concerning lipos, there are some real world, practical issues, too.

It's probably safe to say that today the single area of greatest false advertising in electric r/c is with lipo discharge "C" ratings. The top of the line, expensive packs will probably deliver their advertised discharge rates, but the cheap, budget packs will never do it.

Budget packs rated at 20C are in practice more like 10C packs. So, a 1000mah budget pack rated at 20C will actually only deliver around 10 amps, never 20 amps (20C means the pack is supposed to be able to deliver 20 times its rated capacity in mah).

Second, it's bad for any lipo - high quality or not - to be pushed to its discharge limits. If your motor/prop system wants to draw 10 amps then either buy a high quality 1000mah or higher pack rated at 15C or more, or buy a budget pack of 1500mah to 2000mah or more. What you want is headroom with lipos. A 1000mah pack that can only deliver 10C is not going to last very long.

It's better to carry an extra ounce of battery weight and have l;onger flight times and longer battery life. Granted serious competion fliers will push their equipment to its limits, but that's the same with any area of competition. The DNU is not an FAI pylon racer.

What I said above is all true. In my opinion, however, I would buy a high quality pack with a discharge rating of at least twice the amps my system will be drawing. If you want to go lightweight with a 10 amp system, use a 15000mah pack with a legitimatet 15C rating or more. That will give you a relatively light pack with 22.5 amps of available current. You won't stress your pack and your flight times will be longer.

Raymond LeFlyr

My Feedback: (2)

Once you get all the lekky stuff worked out, I think you'll be pleasantly surprised.

dieFluggeister

Well, here she is.

14.5 oz using the 1320mAh 3s Lipo. It lifts right out of my hand and accelerates vertically. Slows down real nice too, in fact it flies level at 1/4 throttle![X(] I havent gone through a whole battery yet but I expect a loooong flight time.

Trying to post a vid but my computer is being stupid.

rainedave

My Feedback: (1)

dF, I really like that a lot. Very cool indeed!

How is the throttle control with the HiModel ESC? I know that with some of the inexpensive Chinese ESCs there's not much smooth control below 1/3 throttle. Also, are you timing your flights or relying on the ESC's LVC setting? Apparently, from what I've read, if the LVC is set at 3v per cell, or 9v for a 3S pack that's too low for lipos to discharge.

dieFluggeister

Dave, I've found the throttle response is not bad. I believe the ESC is 'self adjusting' by revving up to full throttle it defines the upper and lower limits. My Tx has the ability to put some expo on the throttle to help fine tune the low end but I've never found it necessary.

I have used the LVC a couple of times and I've worried about over discharging too. I believe the LVC kicks in when the voltage spikes below 9v on a hard throttle up etc. I land immediately and when I test the batt it still has more than 9v. I also run a much larger capacity batt than I need so I dont run into that problem as much. I get 10min flight times and still have well over a 10v test.

Keep in mind that this is a definate hop-up from an 049 and is much more than is needed. It really gives it 3D capability for power but not the control surfaces to realize it. So in my opinion a lot of the upper end is wasted. Like most outrunners it is very torquey (is that a word?) power but is not as speedy in the air. It is pretty cool through to lauch it straight up and have it accelerate away!

dieFluggeister

FWIW I just ran the batt down to the LVC. Tested the batt and it was 9.82v.

rainedave

My Feedback: (1)

dF, that sounds reassuring. I'm far from an expert with lipos - I'm just one of those people who's read too much for their own good.

dieFluggeister

Finally got my cam to talk with my computer. Here's a quick vid.

http://www.rcuvideos.com/view_video....a9075b5bb8070a

Raymond LeFlyr

My Feedback: (2)

Jeeze Mike, its a shame you didn't use a motor that had enough power. Maybe next time huh?

I didn't know you had so much sand up yonder. Purty white color too. That looks like a very baggy T-shirt you've got on. Does it catch the breeze and keep you cool?

I just finished murdering my myrtles about half an hour ago. Yeah, yeah I know just wait til Summer.

I suppose I shouldn't reveal this since the other displaced Yankees in the CC might pounce on me, but there are times when I miss snow, cold, sleet, ice . . . well, maybe its not that aften after all, but some snow now and then wouldn't hurt.

rainedave

My Feedback: (1)

Yeah, it needs one of these:

Specs:
Weight- 4.6 lbs
KV-166
Peak Amps-200
Prop-27x12
7500 RPM at 174amps
14S-7700mAh Lipo

Big Al-RCU

Anyone that can fling a plane 100 yards underhanded with just a flick of the wrist is someone to be reckoned with in my book.
Al

ptulmer

My Feedback: (5)

[sm=lol.gif] That's pretty crazy. Um, dF, you've got good vertical performance, huh?

voodoo_chicken1

I know this isn't a lipo forum but I had to throw in my 2 cents about lipos:

1. They are experimental, dangerous, and care should be used at all times. But then again, the same can be said about the aircraft we fly which is why we have AMA cards.

2. "C" ratings are misleading. However, I disagree that expensive packs perform best and are more reliable then "cheap" cells. Based on personal experience and the experience of many people I fly with, Thunder Power is the most over rated, over priced and poorest performing battery I've come across. The most current issue of FlyRC came to a similar conclusion when it tested Thunder Power, PolyQuest and A123 lithium Ion packs. Thunder Power simply couldn't hold voltage anywhere near what it was rated by the manufacturer.

Polyquest=Hyperion may be a bit heavier, but they perform a heck of a lot better than Thunder Power. My 1500 Hyperion outperformed a 2100 Thunder Power in a T-REX. To top it off, my new "cheap" Hextronic 3 cell 1700mah outperformed the Thunder Power 2100 as well. How much was the Hextronic 1700 3S1P? $32, shipping included, from China.

3. Figuring out which motor to use isn't as difficult as everyone makes it. Like a fuel guy putting a .46 in a .40 airplane, electric folks should do the same. It isn't about pushing the limit with a smaller, less expensive motor mostly for budget reasons. It is about efficiency and flight duration. Get the slightly larger motor. An ounce or two isn't going to destroy flight characteristics. The added power and flight times make up for the extra weight.

4. Selecting your battery isn't as difficult as everone makes it either. Use the 70% MDC (Max Declared Current) rule. So, a 2100mah pack rated @ 12C constant should not be pushed more than 17.64 amps (0.70*2.1*12=17.64). 70% is conservative. 80% isn't too bad either, but I wouldn't go any more than that on any of my set ups. Again, it's not about pushing the battery to it's rated max burst discharge. The goal is to maintain voltage. Without volts, power lags and packs go bad pretty quick and more money will jump out of your wallet.

Hope this helps,
RAY

tangerine-jack

Cool. What's all that white stuff on the ground? Is it cotton? What's it for???


I am also doing the electric bit and I found the following to be true:

1. Use an ESC that is rated for 5A above the maximum rating of the motor. This prevents erratic throttle control and extends the life of the electronics. Don't get an ESC that is programmable unless you are going to use that feature, it only adds expense and complication otherwise.

2. Fire danger from LiPos is overrated. Use approved chargers and follow the instructions like everything else in the world. Did you know that glow fuel is flammable? So is the gasoline in your car, but nobody is panicking over that.

3. You get what you pay for.

4. Having fun is the most important thing, period.

I got this information from electric flyers in my area, real world information in other words.