The BEC has to do with the provision of power to the receiver through the ESC using the motor's battery. Otherwise you would have to have a second battery for the receiver. The BEC data (5 V/4 amps) has to do with the voltage provided to the servos and the maximum amperage that can be provided through the ESC to the servos. Those values have nothing to do with the LVC. The LVC is the voltage at which the ESC cuts off the motor to ensure the battery has enough power (volts and amps) to run the receiver and servos. Thus allowing you time to get the plane back onto the ground before you lose all power and, subsequently, control.

I will run the specs for your power system through motocal when I get home this evening and see what the model says about amp draw and post another reply.

You may have indicated before, but, what is the brand of ESC? I need that information to make the modelling more accurate.

Danny

P.S.: I just ran the numbers on a simpler model software and came up with an amp draw of around 54 amps. This assumes you are running direct off the AXI, i.e. no gearbox. If that is the case, you are mostlikely drawing more amps than the GP3300s can provide and greater than the motor's design maximum. I believe the GP3300s have a recommended maximum discharge rate of 10C or 33 amps and the AXI 2810/10 has a maximum design draw around 42 amps for 60 seconds. I need to check my specs, but I believe they are very close to correct. I will still run the numbers on my more detailed software when I get home this evening.

P.S.S.: Well, I ran the numbers on my motocal software and got a 38 amp draw assuming direct drive. I really believe you are drawing more amps than the battery can provide without a significant drop in voltage. When the voltage drops due to the amps drawn at WOT the LVC is triggered stopping the motor. When you decrease the throttle, thereby, reducing the amp draw, the voltage recovers to a level above the LVC. Once the voltage is above the LVC, the ESC allows the motor to restart. When you increase the throttle again to a point that the amp draw pulls down the voltage below the LVC, the process starts again. I believe you may need to either adjust the prop to lower the amp load at WOT or change batteries to ones which can handle the WOT amperage.

I hope this helps../////Danny

Danny this is a massive help,thankyou so much! However, the ESC is doing the same on a 1900mAh 8 cell which indicates the battery is not the problem. It's definately the over heating of the ESC though that is causing it to cut, motor and battery aren't even warm at this stage. The ESC takes 40amps continuous and 60amps max, however it is one from an electronics company in hong kong and maybe of inferior quality. A lot of people on this forum and other Magister forums are using the AXi 2810 with batteries like the GP3300 and they are using ESCs like the Jeti 40 or the CC Phoenix 45 with 11x7 props and don't seem to be having problems like me...I really think it's just because I have a budget ESC.

Does a larger prop generally mean the current is higher??

Kind regards
sam

If you increase the prop diameter and or pitch you will see a greater amp draw. The fact that you are having the same problem with the smaller battery (1900 vs 3300) would still indicate a possibility of drawing the voltage down because of excess amp draw. The 1900 mAh battery would have a lower maximum amp value than the 3300. Therefore, you would expect to see the same symptoms with the 1900. Anyway, the problem could certainly be caused by excess heat to the ESC as well.

I hope I was able to help some. Good luck.....Danny

Got rid of other ESC and just got my CC phoenix 45 ESC today, haven't had a chance to fly yet but she seems to work well without cutting out...I've also put proper hinges on all the control surface as part of my rebuild which has considerably maximised the travel. I have put a scoop (half spoon) in too but further back to keep the ESC cool and I've cut a 2cm square beneath it (just behind nose wheel) to allow efficient air cooling. The AXI motor doesn't even seem to get warm so just leaving that as it is.

Joe, are you running all six servos from the BEC on the Phoenix 45?

I am going to upgrade to li-po soon but not sure which pack to get, is it worth going for 4 cells or will 3 be adequate? and what mAh would be most suitable?

What type of hinges did you use? I have been working on my Maggie the last few evenings setting up my Optic 6 transmitter and have been thinking going to hinges would be a good idea. The pinched foam hinges on the Maggie are very restrictive. Did you cut the ailerons completely off? Also, did you hinge the elevator and rudder as well? Have you set up flaperons on the Maggie? I put a second aileron servo in and what set up flaperons to slow the Maggie down for shorter landing runs.

Danny

I just used ordinary plastic hinges with a little metal rod in them. I completely cut off all the control surfaces (ailerons, elevator and rudder)...then made sure the edges were smooth. To fit the hinges I just cut little slots in the EPP to allow for them to snugly fit in. CA glue was used to hold them in place.
Although I have a second aileron servo, this was just installed for better aileron control as I only have a 4ch transmiter thus can't use a flaperon feature...Though I don't really feel this plane needs flaperons, but I guess I have a lot of space where I fly.
There is so much travel now I have put hinges on...so much I had to tone it down with the ATV on the transmitter. She doesn't fly so well with huge amounts of travel, after all she's not a 3D weapon! but I definately recommend installing proper hinges as it offers a very cheap and worthwhile upgrade.

Great infor, thanks. Looks like I have more to do. I did something similar to my Space Scooter and it made a big difference is trim and control.

Danny

Just a word of warning when installing the hinges...
The mistake I made was not putting enough hinges on, and once they're on they are on for good so theres no more adding hinges at a later date!
When you cut off the control surfaces they are very flexible and you will prob need 2 small hinges on rudder and 3 or 4 small hinges on the each aileron and elevator.

Thanks Sam. I did one aileron the other night. I used four Dubro heavy duty pinned hinges. I plan on doing the same to the other aileron and was indeed planning on using 2 of these hinges for the rudder. I hadn't decided on three or four for the elevator.

I cut slots at mid-depth (thickness) of the trailing edge of the wing and mid-depth of the leading edge of the aileron and CAed the hinges into the slots. This placed the hinge point at the center of rotation for the control surface. There was enough depth (thickness) on the wing and aileron for this to work well. I will have to surface mount the hinges on the rudder and aileron (I think) because of the thinner material. But, I love pinned hinges. Much more effective control surfaces and much less amp draw.

Let me know how your Maggie flys.

Danny

Greg,

I have the Magister kit, and am starting to accumulate the mechanicals for it.

I purchased the Kokam 3C 3200 mah (20C discharge rate), and a Himax brushless outrunner motor (the HC3522-0700). I printed the instructions for the motor off the 'net and noticed that it stated it would power planes up to 84 oz for aerobatic flight, but that the recommended accessory was a 35-45 Amp ESC, and a 14.4V LiPoly, capable of 29-40 Amps. Himax makes a similar powered motor (max 400W), the 3522-0990, for aerobatic flight up to 84 oz, which recommends a 45 or 60 Amp ESC and an 11.1V Lipoly, capable of 38-54 Amps.

I'd like to make sure the battery is correctly matched to the motor. I'm concerned that the 0700 recommends the 14.4 Lipo (a 4C which I hadn't seen til I looked it up on the 'net).

Motor (purchased)
HC3522-0700
35-45 Amp Esc
14.4 Lipo capable of 29-40 Amps

Motor (other option)
HC3522-0990
45-60 Amp Esc
11.1 Lipo capable of 38-54 Amps.

Do you think I should exchange the motor or the battery?

Thanks for your help.

Dave Ferguson

Joe,

On your magister AXI addition, did you modify the firewall or just bolt the AXI directly to the provided firewall?

Dave F.

Dave,

I can't say that I'm familiar with the Himax outrunners but a 3-cell Kokam 3.2AH pack is lighter and provides plenty of power with the correct motor for the Magister.

You may be interested in my latest upgrade project. I will be testing the new [link=http://www.hobby-lobby.com/magister.htm]Hobby Lobby Magister Upgrade[/link] as a "Part 2" article except using a 3-cell Cellpro Kokam [link=http://www.fmadirect.com/Detail.htm?item=2077&section=45]3200mAh pack[/link] which is the same as your Kokam pack except with a node connector for balanced charging.

Greg:

When do you anticipate the review being published? I am looking forward to reading what you have to say. I will be repowering my Maggie over the winter and would really like to know your thoughts on the AXI upgrade.

Thanks

Danny

Greg,

I am totally interested in your latest project! I hope to be able to follow that as I construct my Magister. My outrunner looks very much like the AXI; I had gone to the Local Hobby Shop to ask for the AXI but they didn't carry it and suggested the Himax. From photos, they look very similar, so I will be following your modifications closely.

I purchased my battery from stock at the LHS, otherwise I would have purchased one with the extra wire.

Dave F.

You guys know that I always use the forums as a workspace for my "works in progress". I'll either post it right here or start a new thread in this forum in a week or so.

The Hobby Lobby [link=http://www.hobby-lobby.com/magister.htm]Outrunner/Lithium Hop-up[/link] for the Multiplex Magister really makes this plane come alive! By replacing the old technology stock power system with a new AXI 2820/12 brushless direct drive outrunner and a 3-cell Lithium pack, the magister will drop an incredible amount of weight and increase both power and flight duration.

With the Hobby Lobby power system hop-up, this plane makes a great aileron trainer with solid flight performance, capable of aerobatics. It has plenty of power for short takeoffs on grass and strong climbs, and can easily aerotow sailplanes like the Multiplex Easyglider ([link=http://www.hobby-lobby.com/easyglidersail.htm]MPX4205[/link]).

The hop-up starts by removing the stock power system. I had a burr in my motor shaft which made it difficult to remove the prop adapter but otherwise the removal was easy.

The motor mount cage faceplate can be easily unscrewed. The holes used by the stock geared Speed 680 motor are not the same ones needed for the AXI 2820 motor. A second set of existing holes is almost a perfect fit for the AXI motor so you only need to very slightly enlarge them to create a perfect alignment that matches the motor.

The new AXI motor weighs only 5.2oz compared to the 11.4oz stock geared motor. Already, we have an incredible 6.2oz drop in weight so we are off to a great start!

The proper mating connectors need to be soldered on the battery pack, ESC, and AXI motor. The Jeti ESC supplies the connectors for the motor but you need to select your own power connectors. My favorite connector for this level of power is the Dean's Ultra.

The stock 8-cell, 1900mAh NiCd pack weighs 16.5oz and the replacement 3-cell, 4000mAh Lithium pack weighs only 9.8oz. We dropped another 6.7oz in weight and added the voltage of two more NiCd cells.

The incredible benefit of new technology like brushless motors and Lithium power has not only increased performance but reduced the weight by an amazing 12.9oz!

I needed to slot the upper middle hole in the motor mount slightly towards the outside edge. This allowed the motor to mount easily with three M3x10mm screws. The motor mount plate was then installed back into the frame in the fuselage.

The Jeti ESC is held with Velcro and I used a Tywrap to secure the motor wires. The On/Off switch sat in tha same position as the previous ESC for brushed motors.

I made an EEP foam step to cover the ESC and support the battery pack. It has Velcro on both sides.

The lighter pack fits nicely across the receiver and ESC. I check the CG after installing the wing and it was just a bit nose heavy which will be perfect for testing. It was originally flying a bit nose heavy with my stock power system although it is not likely needed as these trainers are very stable flyers.

Outstanding stuff, Greg. Keep it coming. I can't wait to hear the details of the flight testing.

Danny

The parts recommended for the spinner and prop adapter did not play well for me so I used a different 5mm prop adapter I had on hand. The adapter and prop could be used but not with the spinner. We are currently sorting this issue out at Hobby Lobby as they claim otherwise.

I measured 30amps and 300 watts at full throttle. This is good power and can be left at full throttle the entire flight without hurting any of the components. It also allows for the possibility of using a 13" prop, if desired.

I hope to test fly it today if the wind cooperates.

Hey Greg,

Great thread you have here. Hate to be one of those barge-in-and-want-an-answer kinda guys... But I am trying to buy a XMas gift and time is short. I have been looking for a bird like this for my Father-in-law. This is probably perfect, but a bit bigger than I had in mind. We have some gear I was trying to match to a new bird for him.

The stuff on his Hirobo Extra (a boat anchor and way too advanced for him) is the AXI 2808/24, Phoenix 35, 3S HD 2100 mAH 12C. I know it sound a little light to me, but this setup will turn out nearly 300 watts with a 10x5E. I measure well over 40 ozs thrust once on it. That's pushing it a bit, but I run the same setup on my Mini Funtana and it barely gets warm, even after vigorous 3D flights.

He won't be aerobatic at all... just big circles and maybe a loop now and then (when he gets up the guts). He needs a plane he can "see in the air" (read 40 size for poor eyesight) and flies with stable forgiveness. So, whattya think? Will it get off the ground with reasonable authority? I can't seem to find anything that gives a "wattage" or thrust benchmark for the stock 680 motor. I'm looking at the ARF, not the RTF.

Thanks in advance. Need to order SOON. Your help is appreciated.

Tman,

The 2808 motor is not a good match for this size and weight plane. Even if you could squeeze out 300 watts from it, the lighter components would never balance it properly.

We test flew the AXI-fied Magister today and it was a total success! All three flight clips on the video were using the same 4000mAh battery charge for about 15 minutes of flying. After I returned home and recharged the pack, it put 1800mAh back in so it was about halfway depleted.

The plane flies 13oz lighter than stock, has twice the power, and flies for four times the duration.

[link=http://www.gregcovey.com/Reviews/MagisterAXIfied.wmv]Magister AXI-fied video[/link] (9meg)

Thanks for the advice Greg. I get your drift, balance is always a concern. However, I am confident I can manage that issue with servo locations and battery placement. I like the plane, and have ordered it. I have searched high-and-low for a 30-50 oz trainer with ailerons and foam construction. Just can't find anything even close. The small (sub-25 oz) birds are too squirrly, or don't have ailerons... or they are wood builds... or they are RTF's with all the gear (redundant and wasted). I like this bird too much to pass it up... it's perfect for Bill's (father-in-law) needs.

The lighter gear will help a lot. We can always upgrade to bigger stuff if necessary later. After reading your thread, and seeing the videos, it seems the 2808/24 will be plenty to make it fly with reasonable power. Granted, will be somewhat weak in hard acrobatics unless we push the hardware over limits a bit. No worries though, the quality stuff takes it in stride.

If you say the 2820/12 is twice the stock power, then we are golden with the 2808/24 for power. It should fly fine. If you say you are getting 15 minutes on 1800 mAH, then our 2100 mAH lipo's should get us similar flight times... not bad! With 2.7 oz's lighter in motor, and another ~4.5 oz's lighter on battery, we should be 7-8 oz's less than yours .

What is your current AUW now with the AXI aboard? I see lot's of notes about what you saved, but missed your starting AUW.