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Old Dec 23, 2008, 08:41 PM
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Not sure what the 'formula' is for determining what the max discharge rate should be for a lipo/motor combo.

I am using the 2815-2000 and -1400 with 20c and 23c discharge lipos and have not had a problem at all. The batts I use are the Enerland Polyquest and Hyperion batteries.

You can actually fly a heavier battery if you want, I use the Polyquest PQ-2200XP 3c and the Hyperion LiteStorm VX 2200 mah 3c lipo in my MM, PZ Corsair, PZ T-28 and Stryker. They are expensive batteries but worth the money, in my opinion. I have a couple of DualSky 1300 batts that I use also. They do quite well and I use them when I want to fly into strong winds, just holding the MM into the wind and letting it sit in one place.

You mentioned the tendency of the MM to climb when you add throttle. This is to be expected due to the positieve incidence of the wing and the motor. You can help this a good bit by angling the motor downward and by adding a small piece of velcro at the rear of the wing, between the wing and the fuse. This will help to change the incidence of the wing to a less positive number.
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Old Dec 24, 2008, 03:54 PM
Take that runway!
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United States, AZ, Glendale
Joined May 2005
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slappySF,
Battery, ESC and motor matching have a lot of variables and gets confusing. One of the things I like about the forums is I can start with the combos people say they use and go from there. Let me try to answer your second question first.

Start with the motor you plan on using and note its normal operating amps. In your case the tech sheet says the 2815/2000 is efficient at 7 to 23 amps. You'll influence the amps the motor pulls by the prop size. Use a watt meter.

Another indication of the motor's amps is the recommended ESC. In this case it is 25 amps. So... if you prop your motor to run around 20 amps, you'll be in the motor efficiency range and under the ESC max.

Next the battery. An easy formula to compute the max amps for the battery is the capacity in millamps X the C rating /1000 (A = mAh X C/1000). Using your two batteries you'd get about 19.8 amps for the 1320 mAh battery and 18.7 for the 1250. I used 15C since you said 20C was the burst rating. If you were propped for 20 amps you'd be over amping your batteries. So to answer your first question, no, the batteries wouldn't be OK.

You can either lower the amps, increase the C rating or raise the capacity of the battery. Using the same formula a 2100mAh 15C battery would be safe to 31.5 amps. (That's what I use with my MM.)

Don't err and think that keeping the ESC less than full throttle will help. They don't work that way. There is a discussion on that going on at the Multiplex Fun Jet discussion group on that now.

Cheers
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Old Dec 24, 2008, 06:07 PM
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San Francisco
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Quote:
Originally Posted by jim12
slappySF,
Battery, ESC and motor matching have a lot of variables and gets confusing. One of the things I like about the forums is I can start with the combos people say they use and go from there. Let me try to answer your second question first.

Start with the motor you plan on using and note its normal operating amps. In your case the tech sheet says the 2815/2000 is efficient at 7 to 23 amps. You'll influence the amps the motor pulls by the prop size. Use a watt meter.

Another indication of the motor's amps is the recommended ESC. In this case it is 25 amps. So... if you prop your motor to run around 20 amps, you'll be in the motor efficiency range and under the ESC max.

Next the battery. An easy formula to compute the max amps for the battery is the capacity in millamps X the C rating /1000 (A = mAh X C/1000). Using your two batteries you'd get about 19.8 amps for the 1320 mAh battery and 18.7 for the 1250. I used 15C since you said 20C was the burst rating. If you were propped for 20 amps you'd be over amping your batteries. So to answer your first question, no, the batteries wouldn't be OK.

You can either lower the amps, increase the C rating or raise the capacity of the battery. Using the same formula a 2100mAh 15C battery would be safe to 31.5 amps. (That's what I use with my MM.)

Don't err and think that keeping the ESC less than full throttle will help. They don't work that way. There is a discussion on that going on at the Multiplex Fun Jet discussion group on that now.

Cheers
Thanks. That's a lot of information to soak up and study and make sense of.

Bottom line is, until I can get my mitts on a 2100mAh 15C battery (which I can afford about 75 bucks from now! ) then if I continue to fly on one of the above batteries, am I at risk of damaging the motor? \

And by over amping the battery, do you mean ruining it immediately and causing it to puff and or become dangerously volatile? Or do you mean it will just not last very long, and reduce flight times and longevity?

Only reason I ask is that I just hate to be out of the sky completely until I can afford another 75 dollar lipo.
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Old Dec 25, 2008, 12:31 AM
Bumpy Cp
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Israel
Joined May 2007
244 Posts
Quote:
Originally Posted by slappySF
Thanks. That's a lot of information to soak up and study and make sense of.

Bottom line is, until I can get my mitts on a 2100mAh 15C battery (which I can afford about 75 bucks from now! ) then if I continue to fly on one of the above batteries, am I at risk of damaging the motor? \

And by over amping the battery, do you mean ruining it immediately and causing it to puff and or become dangerously volatile? Or do you mean it will just not last very long, and reduce flight times and longevity?

Only reason I ask is that I just hate to be out of the sky completely until I can afford another 75 dollar lipo.
You can always try the Hobby City Zippy LiPO http://www.hobbycity.com/hobbycity/s...idProduct=6330
Iv been using it for 5 months now and its a grate pack. and a bit more friendly to your wallet.
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Old Dec 25, 2008, 01:28 PM
Take that runway!
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United States, AZ, Glendale
Joined May 2005
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By over amping the battery I mean that you run the risk of puffing it or worse. Pulling to much current from the battery to fast is bad for lipos. I agree with Roish on the batteries from Hobby City/Hobby King. I have several and am pleased with them. I have 4 of the ones he linked to. I have found them to be a good multi-use battery used in several of my models. I use two in parallel to power my Magister. Even if they end up lasting only half as long as a $75 battery you are still money ahead.

You won't hurt the motor.
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Old Dec 26, 2008, 03:38 PM
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Quote:
Originally Posted by jim12
By over amping the battery I mean that you run the risk of puffing it or worse. Pulling to much current from the battery to fast is bad for lipos. I agree with Roish on the batteries from Hobby City/Hobby King. I have several and am pleased with them. I have 4 of the ones he linked to. I have found them to be a good multi-use battery used in several of my models. I use two in parallel to power my Magister. Even if they end up lasting only half as long as a $75 battery you are still money ahead.

You won't hurt the motor.
Thanks for your help, Jim and Roish. I will check out those lipos.

And Jim, thanks for the heads up. I will be looking at all my power systems on my foamies, and breaking out the calculator to make sure everything is on the up and up.

Thanks again, gang.
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Old Dec 31, 2008, 03:44 AM
Ultimate 10-300!
Los Angeles, California
Joined Oct 2008
62 Posts
Very HAPPY!

Quote:
Originally Posted by Jurgen Heilig
Hi Larry,

The Easy Star is probably the best model for a beginner. As a second model he (or she ) had to chose between the Easy Glider or the Twin Star II. Both models are much bigger and need different batteries. For those who don't want to go the Easy Glider route, the new MiniMag might just be the right model. I hope to have the model ready for our clubs New Year Fly In.

Jürgen
I am very happy, that I don't have to get an Easy Star, because I don't like it & it is way overpriced! I just saw the MiniMag, lastnight on nesail, & was delighted to see there's an aileron option.
I have 3 biplanes & I have never flown BUT, I have alot of time spent on G4 & other flight simulators. So, I doubt I'll be needed anything with 3 channels or less.
A few threads I've started with info as to what I was planning to learn with, has resulted in many suggestions for me to start with a Traditional Trainer, or the Expensive EasyStar. So, I will be taking a word from the more experienced, as I'll be purchasing a Mini-Mag to get my feet wet.
Oh yeah, that's another PLUS!+ It has optional floats also!
& it is NOT so Mini! Very excited & happy to have just learned about the Multiplex MiniMag!

Happy New Years to all RC Modelers out there! Peace & Take Care. Soon enough, I'll be winning some Championships. You watch.
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Old Dec 31, 2008, 03:52 AM
Ultimate 10-300!
Los Angeles, California
Joined Oct 2008
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Color?

Quote:
Originally Posted by jim12
Howard, In addition to LouieB's explanation about the motor Kv another part of your why question has to do with the space in the nose and the prop size. First the space. A 28MM inrunner will slide neatly into the motor mount and simplify motor installation. An outrunner may need extra space and the associated carving to get it to fit. Many outrunners labeled as 28MM have actual outside diameters that are larger though if you've upgraded your SuperCub you probably know that already. For example an AXI 2820 has an outside diameter of 35mmX48mm. The 28mm inrunner I use has an outside diameter or 28.2mm x 37mm and just slides into the mount. The other issue is the prop. The SC comes with a 10X something prop. It is turning slower requiring more torque. Inrunners produce high RPM at the cost of torque so the typical MiniMag will run with a much smaller prop turning at a higher RPM. The Multiplex people recommend a 5.5X4.5 prop. I'm running a 6X4 APC thin electric on mine generating about 20 AMPS and 190 watts. It can go pretty fast but I keep it more scale-like at about half throttle.
In the picture you posted of your nice looking MiniMag, how did you get color on the foam? Regular spray paint? Or, is this some type of foam safe paint? I would like to paint mine also, as soon as I get it.
No worries. I won't do the same color scheme. I am always, all for originality, & keeping it that way. Thanks if you can please let me know.peace.
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Old Jan 03, 2009, 04:48 AM
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Pendle Hill NSW
Joined Oct 2008
155 Posts
Quote:
Originally Posted by digger12
Thanks guys a lot for the reply's! Especially LouieB for the great post.

Ok so it looks like it will fly again with a bit of TLC! This plane is second in line for work, but I will let you know how it goes for sure!
Hi guys, Happy new year!

Its been a while since I looked at my ebay mess of a MM. Can you believe I'm still waiting for the guy to send some missing pieces...canopy and new motor mount. Well he says he is going to throw in some extras to make up for the delays. Will wait and see on that one!

Anyway I've now ordered a set of 9gm servos, extension leads. Fixed a small crack in the elevator with CA. It came out nice.

Boy this poor plane has had a hard life. But hopefully I will have the bits and pieces this week. Can have another look at the front damage and sort out something with the mount he is sending.
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Old Jan 03, 2009, 11:34 AM
Take that runway!
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United States, AZ, Glendale
Joined May 2005
216 Posts
junglist1soljr,

There are a lot of threads that discuss painting Elapor foam. Just a couple of highlights. Elapor takes most spray paints though some report some potential for damage from the propellant. I use the very inexpensive "craft paint" found in stores like WalMart or Michaels. They are usally about 99 cents each. I normally apply with an inexpensive airbrush (Harbor Freight) I connect to a 2 gal compressor. When I paint I sand the surface to remove the molding marks. The lettering on the MiniMag is vinyl lettering from Staples. Cheers.
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Old Jan 08, 2009, 02:56 PM
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Barcelona
Joined Dec 2006
155 Posts
Just finished a mini mag for my son (12) and had to ditch the RR setup as only produced 105 watts on a 1300 Mah 2 Cell lipo. Installed a AKE sky dancer 1500 KV motor which with an 8x3.4 prop put out 257 watts on a 3 cell 2200 pack. There was quite a lot of vibration above 60% throttle so we just kept it below that setting. It flew well and needed a bit of rudder to couple with the ailerons to ensure a smooth turn. It did not need a single click of trim!
I have strengthened the stock motor mount by adding a piece of plastic to the back of the mount and epoxying it in place. There is now no vibration.
In the standard color it can be quite hard to see in a flat light so we will be adding some bright spots at a later stage. Nice plane! I guess i will put the brush less controller and motor on Ebay as it is no good to me! How it could fly on the RR setup is a mystery!
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Old Jan 09, 2009, 03:36 PM
GLM
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Check Six!
Joined Oct 2003
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MiniMag On Skis

Hi All,

Ever since I got the MiniMag – with the exception of the first few flights – it’s been an outstanding aircraft to fly.

Here is a movie of one with a brand new set of skis doing their thing!

Mark's MiniMag Movie HD (5 min 1 sec) (5 min 1 sec)

Or here for a bigger version of the movie

Cheers!

Gary
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Old Jan 11, 2009, 10:38 PM
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San Francisco
Joined Mar 2008
1,214 Posts
Any ideas what's going on here?

Radio glitch?

Flying my Multiplex MiniMag/Brushless Himax 2815-2000/3S Lipo battery setup. Real powerful motor, so flying at about half throttle, otherwise it goes nose up in a hurry.

About a month or so ago the thing took an epic dump...from about 35 feet up, flying just fine, slow, about half throttle, and it goes from level to pointing straight down, plummeting nose first into the concrete. No warning. It's like it made a 90 degree turn straight down. Couldn't throttle up or pull up. Just speared straight into the ground. Thought it might have been a downdraft from a nearby hill that did it.

Got a new Himax motor and motor mount, re built it and flew it again a couple weeks ago. Went OK, no trouble. Still a little tail heavy and porpoise action. So I added some nose weight, rebalanced, and got her ready to fly.

Today was the big day...and same problem. Flying slow, making my first pass and from about 30 feet up--blammo. Plummets straight into the ground. No warning. 90 degrees. Slammed into the concrete schoolyard nose first. Another Himax trashed. Broke the fuse and motor mount. AND trashed a lipo. Grrrr... It's like it got hammered out of the sky. No response. No control. No time to regain altitude. Nothing. Just WHAM, straight down.

Does this sound like an RX glitch? The RX in the minimag is the AR6200 that came with my Spektrum DX6i radio.

I don't think it's my TX because my two other planes have been flying just fine for the past couple months. No glitches. Using AR6100s in those planes.

Any other ideas on why this is happening?

Getting kinda tired of shelling out for brushless inrunners. This is my third for this plane....

Thanks in advance, gang.
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Old Jan 11, 2009, 11:06 PM
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Joined Jan 2007
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This is pure speculation, but I had the same thing happen. Mine was from 200 feet. I got to watch for a pretty long time. Wing bounced back up 10 feet.

At first I thought the elevator servo pulled out. It was after the crash. But the crash could have done that.

Now I strongly suspect an ESC problem. If you run too many servos and too much voltage through an ESC it can't take it. In my case I was running a 4s A123 battery and 4 servos. The max for most park flier type servos is 3S and 3 servos. After that you should put in a separate BEC. Even though it's 4S the A123 puts out about like a 3S as it starts at lower voltage.

In the Spectrum case the load can tax the system and you can have the same ESC problem OR you might get a case of what's called 'brown out' where the voltage to the RX drops below a critical point and you lose binding. The older versions of the RX were more prone to this problem.

Read this:
http://www.wattflyer.com/forums/showthread.php?t=39138
Follow some of the links.
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Old Jan 12, 2009, 05:09 PM
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San Francisco
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Quote:
Originally Posted by flydiver
This is pure speculation, but I had the same thing happen. Mine was from 200 feet. I got to watch for a pretty long time. Wing bounced back up 10 feet.

At first I thought the elevator servo pulled out. It was after the crash. But the crash could have done that.

Now I strongly suspect an ESC problem. If you run too many servos and too much voltage through an ESC it can't take it. In my case I was running a 4s A123 battery and 4 servos. The max for most park flier type servos is 3S and 3 servos. After that you should put in a separate BEC. Even though it's 4S the A123 puts out about like a 3S as it starts at lower voltage.

In the Spectrum case the load can tax the system and you can have the same ESC problem OR you might get a case of what's called 'brown out' where the voltage to the RX drops below a critical point and you lose binding. The older versions of the RX were more prone to this problem.

Read this:
http://www.wattflyer.com/forums/showthread.php?t=39138
Follow some of the links.
Others are suggesting this, too.

Probably going to sink the dough for a TB 36 ESC when I get the new Motor. Looking over LouieB's posts in this thread for prop size specs for this combo, too.
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