View Full Version : Electra power

07-26-2005, 12:21 AM
Hello all!
I have had an Goldberg Electra sitting around for a long time now. Ive read that the Master Airscrew motor550/gear box 3to1/prop @12 x 8 is a good combo for this plane. Yes, no? If this is good for me what pack and ESC would be recommended. Id like to have a lite pack with good power. No lipos but NiMHs or NiCads. If anyone has a recommendation with maybe a link for where to get it, that would really help me out. the lighter the better.

Thank you wattflyers!

Jason T
07-26-2005, 01:08 AM

I do not know much about that motor. Do you know what the maximum amp draw of it is?


07-27-2005, 12:10 AM
This is all the info provided from Tower. I appreciate your help Jason. This plane has been sitting for years waiting for this. :)

Link from Tower.

Motor specs from Tower.
This is a 7.2 Volt 05 Electric Motor from Master Airscrew. This motor is designed for electric powered R/C airplanes. FEATURES: Made with Ferrite Magnets. 19-Turn Single wind, clockwise motor for 2-Meter Sailplanes and Sport Electric Airplanes under 56 ounces. Built-in capacitors Runs with 6-7 cells For both direct drive and geared systems
INCLUDES: One Speed 500 7.2 Volt ferrite motor. Built-in capacitors. One instruction sheet.
REQUIRES: SPST switch rated at 6A@125V Fuse rated 25A 7.2 or 8.4 volt 1400mah battery pack Wiring harness with switch and fuse (see above) COMMENTS: A vented motor mount is recommended


Jason T
07-27-2005, 04:25 AM

I think that motor will fine for that airframe. As far as batteries you could use some NiMH's. I like the 1950 FAUP cells or the new GP2000 cells. Both are kinda pricey but fairly light weight for the power they put out. Or if you wanted a cheaper lighter pack you could use the GP1100's. I buy my NiMH cells and/or packs from http://www.battlepack.com/

With a 7.2 volt motor I would recommend a 9 to 10 cell battery pack.

As far as the esc I would recommend the Castle Creations Sprite 25. You basically want a esc for a brushed motor that has a brake option because you want the prop to fold fairly quick after you cut throttle. Several places sell the Castle Creations controllers. I usually buy mine at http://www.atlantahobby.com

Let me know if you have more questions and I hope that I have actually answered some. :)


07-27-2005, 04:31 AM
Thank you much Jason! Im going to start putting together the order for the electra. I really need to finish this lazy day flyer before the summer comes to an end.

thanks for the info!


07-27-2005, 04:38 AM
Jason, one more question. The cells you recommended are GP2000 4/5 A. 4/5 A and not a sub c pack is this correct? Please excuse my ignorance with electrics and such. Is this a 1.2v per cell?:confused:


Jason T
07-27-2005, 04:51 AM

Yeah, the GP2000s are 4/5A which are not sub c. The GP2200's are sub c. The both of those cells are 1.2v/cell. The GP1100's will easily handle the motor and are lighter but the duration of motor run time will be less with the GP1100's.


08-08-2005, 05:07 AM
Keep in mind that the motor is offset and you will need to adjust the mount to accomodate this. The opening in the front former will have to be modified. You will have to cut a new opening in the former or I should say make the opening deeper to account for the offset. Also make certainyou use the lower set of slots for the rear mount support.

I have had several Electras with this set up and have had very good results.


William L Baker
08-09-2005, 12:44 PM
If you can find one (Tower no longer has) the Kyosho Magnetic Mayhem motor or the Kyosho Endoplasma motor are very good alternatives to the supplied Electra motor.I am flying Magnetic Mayhems in both direct and geared modes in a two meter sailplane and an old timer Kloud King respectively. The motors have fixed timing but were marketed in both standard and reversed timing. The Endoplasma has adjustable timing. I think either would give better power than the Master Airscrew rig but it
is ready to go so wins on being a quick and easy change. This airplane thermals well, mine tended to tighten its turn in tight thermal turns, cut a half inch off of the top of the fin-rudder to cure this.

08-09-2005, 03:18 PM

Do yourself a favor and take William's advice. I'd hate to see you waste your money on a MA motor. They don't last long. They weigh about 2.5 oz more than a Magnetic Mayhem and won't put out 1/4 of the thrust. The Mag. Mayhem reverse is pretimed for gearbox use. The Endoplasma has even more power but requires you to time it. Either motor is WAY better than tne MA motor.

I have flown the Mag Mayhem reverse with a 3.5:1 MA gearbox/ 15 X 12 MA folding prop on 7 cells. It pulled about 27 amps and climbed well for such an inexpensive setup.

You also could try an MPjet inline planetary gearbox (Hobbylobby sells them) so you don't have to deal with the offset on the MA gearbox.

Ernie S.

08-10-2005, 10:16 PM
Are there any other car motors that work well on this gear drive?


William L Baker
08-10-2005, 10:48 PM
I am sure there are but I cant name them. The electric columnist for Model Aviation magazine for many years did some extensive testing of car motors for suitability for aircraft use, and the two best were the Magnetic Mayhem and the Endoplasma. Unfortunately 1) the magazine has seen fit to dump Kopski and 2)Tower has seen fit to dump Kyosho , who made the motors, and 3)I found a recent Kyosho website which did not list these motors in their lineup. .You might check with RC Car hobby shops in your area, as they may have some left. The Kyosho line up was extensive, and I do know that the two motors were both regarded by the car people as truck /4 wheel drive motors, by which I assume meant they were designed to handle high current.

08-11-2005, 12:32 AM

In addition to the Mag. Mayhem (22 turn fixed timing), Endoplasma (16 turn double wind adj. timing), there is the Atomic force (17 turn double wind adj. timing) which make good candidates for gearing. These motors work well because they have larger brushes than most other car motors and can carry the current better.

Trinity makes a line that works well also called Speed Gems. Look at the 16 to 19 turn motors for possible setups. You can estimate thrust/current and prop RPM by going to the P-Calc website.

Try different gear ratios that match the MA gearbox line (2.5, 3.0 and 3.5) and also the MPjet gearbox line (3.3 and 3.8). If timing the motor is no problem for you, I would go with one of the adjustable motors. They will give much better power than the Mag. Mayhem (which is still way better than the MA stock motor)

Ernie S.

08-11-2005, 02:11 PM
Hi....Im new to electric end of sailplanes but have flown for years off of a high-start to reach thermals. My question is that I was given an Aspire EP which after my first flight was obviously WAY underpowered to glide...let alone climb. It is a 2 meter which comes with a 550 motor,esc, 8/4 folding prop and a 7.2 Nicad battery. I really dont see a gearbox fitting in without front end re-constuction....can I increase from the 6 cell battery and run a larger prop???? Do I need to change to a larger (700) size motor and then larger battery and prop. Do I need to swapout the speed control also....or will it work with a larger battery set-up??? I really just need to get to Altitude so it can glide....looking for the easiest way to accomplish this with least amount of re-constructive surgery. The plane itself seems of good design much like my other sailplanes....just the difference of the electric motor. Thanks for your help and advice. Oh yeah...I live about 200 miles from anywhere so any recommendations on where to buy online would also be great......Peter

William L Baker
08-11-2005, 04:14 PM
The problem you have : there is a lot of that going around, due to the industry shamelessly pushing cheap can motors in ARF planes in order to sell to the unknowing on the basis of low price.The first and simplest thing you can do is go to 7 or 8 cells, highly recommend Sanyo1300CP for this, they are a lot of capacity for weight, and they can handle a 3 to 4 C charge. If you got a cheap charger, designed for 6 cell car packs, it will charge very slowly if at all.The motor will handle this this increase in cell count with short 30-45 second burns without overheating too much. It may wear out faster, but it is cheap anyway. Forget the speed 700, they are much larger and heavier than the 550-600 cans. There are some good motors intended for RC cars and trucks that are not cans, but have adjustable timing, ball bearings(some do) and large external brushes. so they can stand high current.The best ones seem to be off the market just now which is why you can read about the Magnetic Mayhem and Endoplasma, and Atomic Force in these pages. Check the car shops. However, what you really need is to get a good set up with a brushless motor like the Jeti 15/3 or 15/4 which will fly your ship direct drive , with matching ESC, and a good charger such as the Astroflight 110D if you are really going to enjoy electric soaring. Costly but good stuff. But, to use what you got, increase battery cell count, even if you have to get smaller capacity cells, they often put large 6 cell packs in, so the power to weight ratio suffers even more than it would from the inadequate motor. You dont need larger than 1300 CP cells because you dont need more than a couple of minutes of climb power (when you have adequate climb power). The other thing you can do to use the motor etc you have is to add a gear box, and turn a larger prop, like a 3/1 box and 11/7 prop, that with more cells will get you up. Assuming the charger will handle the cell count. That brings up another thought. If you can check the battery voltage after charge, you may find they are not really charged if the charger is as weak as I suspect it is. A NiCd just off the charger shoud have a no load voltage of about 2.6 per cell should measure about 16 volts. If not, then likely it is undercharged, or there is a bad cell or some other problem .

William L Baker
08-11-2005, 04:26 PM
The voltage of a fully charged nicd cell , no load should be about 1.6, so a 6 cell pack would measure 9.6 volts under no load.Sorry for the mental glitch

08-11-2005, 04:51 PM
Thanks william...I feel Im getting somewhere now. Will I have to swap out servos or anything else If I increase the cell count....or will it all still work. Should I try a bit larger folding prop blades with the increased cell count or will that defeat the purpose.....I will do some research on chargers....I have 2 now. One an older on for a car...7.2 volt charger...and a quick charger which came with the plane.....do I need a reverse motor to run with a gearbox???? or can I change polarity of the elctric motor. Thanks for all your help......Im sure I will solve the problem....and the High start seems prety simple now.....I still like the idea of just being able to hand launch....climb...and fly...Peter

William L Baker
08-11-2005, 05:45 PM
I can agree that high start flying is so simple and trouble free, BUT takes a lot of space. Electric you only need enough space to land in, and the cows, kids and cockelburrs dont get into your line. And you get more than one climb per flight with electric.Servos ? If you mean the increased volts from increased cell count for power pack, no this will not affect servos, assuming the servos get fed their juice form the ESC-BEC. On the other hand if there are large servos, going to a smaller lighter servo such as the Hitec HS-85 would benefit the overall performance due to weight reduction.Increasing prop size when increasing cell count: I would do one thing at a time, increase cell count and see what that does then try going up an inch in prop size. Check the motor after a flight if it is too hot to touch, maybe best to go back a bit on prop. Warm is fine, too hot to touch you may demagnitise the magnets, and be worse off.Folder versus non folder. Yes, use a floder. Years ago my OFB (old flying buddy) each had Goldberg Electras, identical 8/4 props. These were marginal in climb but we got some good flights and then I changed to a 8/4 folder. With no thermals I consistently did 10 minutes and he got 9, which I translate into about a 10% improvement. Reverse motor for gear box by reversing polarity: yes that is what you do and it will work if the motor timeing is neurtal which is like on the cheap motors found in most ARFs. But for best performance, the timing needs to be advanced, and if advanced for "normal" rotation it will be way retarded for reverse rotation and performance will be poor and it will likely overheat. Certain car type motors are sold with adjustable timing, and others can be bought with reversed rotation, which means the timing is advanced in the reverse .direction. It is likely the low performance motor you have is neutral timed and doesnt care which direction it runs, and if so you could reverse polarity to use a gear box.

08-11-2005, 08:33 PM
Thanks William....this clears up a lot of problems..I will take your advice and go one step at a time. So if I add 2 more cells ...this is more like a 9.6 nicad set-up and I should get an appropriate charger for it?...I will also step up the prop a size or two to experiment with and look into the gearbox installation. Thanks again for all your input...Peter

08-11-2005, 09:58 PM
Hey...one more thing...I just saw a motor on the RC Universe site. It is an E-Flite 600 that is already geared to 2.8:1 and comes with an 11" folding prop. How do you think this set-up would work with a battery upgrade as you suggested...seems like an easy and complete fix....what do you think....kind of covers all the areas that need attention. Thanks....Peter

William L Baker
08-11-2005, 10:39 PM
Well, I dont know anything about this particular product, but taken at face value it would seem to be an easy fix.amd most any 600 motor will give better results with a gearbox and 11 in prop than direct drive. You will want at least 7 cells though. Power is watts, and watts are volts times amps.. so to get more power from a motor, you have to either increase the volts, or the amps, or both. Increasing the size of the prop makes the motor draw more current, therefore developing more power. Turning a large prop with a gearbox does not necessarily increase amps, but it does increase propellor effeciency. and thrust, because a big prop moves more air . there is quickly a limit on more power from adding volts and prop, that limit being the heating of the motor to destruction. warm is OK, hot is not ! I grew up in a rural seting, and was dependent on mail order, and in those days the mail was slow, so I know. I trust Hobby Lobby and Tower, with the warning that Tower has been guilty of selling some kits and ARFs with really inadequate motors for the model in my opinion, so you really have to know what you are buying. Thermals

08-12-2005, 12:37 AM
Thanks William...I think Ill go for the geared motor with the 11" prop and the 8 cell battery....should do the trick and be the easiest fix....Thanks for your input......Peter

10-07-2005, 01:45 AM
Gosh, you all got me thinking about my old AF 05FAI that's been sitting on the shelf. Now I'll probably have to drag that out with the 12x8 and 8-1250SCR's. But what to put it in.......?

12-14-2005, 01:08 AM
MARS, I have been there before!

I started with a Windstar EP 600 direct drive and spent all my charge trying to climb. The first thing I did was put a proper ESC on it then I got the Graupner redrive and S600 combo, about $50 and used a 13" prop or so. What a difference! Now I could shut down and climb again several times and never lacked for climbrate again.

The biggest mistake I made from my earlier experience was to put a battery pack that was too heavy in it thinking I needed to reclimb a lot- 8, then 10 3000Ma NIMH- which made it so heavy that soaring was difficult at that wingloading.

Better to go with 1000 ma or so and enjoy the lightness- and not defeat the purpose. I believe it pulled 25 amps with a big 13" folder, ESC was Jeti 30 A.

Hobby Lobby has a new MP Jet 600 class brushless redrive motor that won't waste half the batteries' capacity as with the 50% efficient ferrite brushys- for about the SAME PRICE!

Pick yer poison, lad, and good flying. Redrives rule!

12-14-2005, 03:04 PM
I probably would go with 7 CP1300SCR's for and the 12-8 with that motor/gearbox. It will work well and it will last.

William L Baker
12-14-2005, 03:24 PM
right on, the 1300 CP cells are low internal resistance so they can accept fast charge (3 C or about 4 amps) without overheating and can give strong current for the same reason, plus they have greater capacity to weight ration than about anything other than lithiums. Other people continue to make the mistake of puting in very large high capacity cells which are too heavy, and usually have high internal resistance and so give low power, the worst of worlds :excess weight and low power. For Sailplane 1300 CPs are the way to go.

12-15-2005, 12:56 PM
They charge well at 5 amps. The Electra dates from the time when we were transitioning fron N1200SCR to N1400SCR cells. They were full sub c's. GP2200's are also worth considering but are larger. After you get better at thermaling you will find you don't need as much battery capacity as you thought. The higher capacity is a good thing for beginners because it gives them more stick time to develop their skills.