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My search for the perfect brushelss upgrade - 7/21/2009 11:29 PM   
Krusher_r


 

Posts: 24
Score: 100
Joined: 7/21/2009
Last Login: 7/16/2012
From: Loudon, TN, USA
Status: offline 		Hello everyone; this is my first post here.  The last few days, I have been on a quest to find the perfect brushless motor upgrade for my LMH 120.  It seems that for the last few years, most people went with the Mega 16-15-3 motor and that appears to be a good replacement motor with better power and it works with the newest 3S LiPo batteries.  The problem is that this motor is apparently discontinued, although you can still find it on the 'net if you look for it.

My goal was a bit different, I wanted:
- A current-generation motor with internal fan that could be re-used in a new heli (the LMH has parts available, but they won't be available forever...)
- An easy-to-program heavy-duty ESC
- The motor and ESC need to be at least 2X bigger than necessary, but not overkill.  I don't want to wait for the motor to cool down in-between flights.
- Works with my current 7-cell 3,000 mAH NiMH AND future 3S 5,000 mAH LIPo batteries (~$150 each!)
- Reasonably priced
- Uses the remaining stock parts, i.e. no gear replacements necessary

I started out with the Castle Creations ESC and NeuMotors, which quickly became very expensive.

Then, on Tower Hobby's web site, I came across the Miniature Aircraft X-Cell Furion 450.  This has approximately the same size main blades as the LMH, and they sell a 60A fully programmable ESC (with a "remote control") and a 474W brushless motor.  Ok, a bit overkill for this fixed-pitch heli, but the ESC is programmable so I can limit the motor from 50-100% throttle.  The motor, ESC, and most of the servos should be re-useable in the Furion, which is made in the USA just like the LHM was.

The X-Cell (Miniature Aircraft) motor is actually a Scorpion 2221-8 re-labeled motor, which is widely available.  (See the link below for model numbers.)  This motor is a 3595Kv motor, so at 3595 RPM/Volt, it's a bit faster than the Mega 16-15-3 motor at 3000Kv.  (The Scorpion 2221-10 is the RPM equivalent if you already have a 3S LiPo and Mega 16-15-3 motor setup.)  But, remember that I still have the 7 cell battery pack yet, so my motor will only get 8.4V instead of 11.1V on a 3S LiPo.
http://www.scorpionsystem.com/catalog/motors/hk22/compare/?p12=143&p13=72&p14=70&p15=71

Anyone doing a search on Tower's web site will find the 4400Kv motor, and it's listed above as the -6 motor.  I won't bore you with the calculations, but the end result is that I feel the 4400Kv motor in the LMH is dangerous.  The manual's maximum head speed is 2,000 RPM and with only my 7 cell battery pack, that equals 3,261 RPM.  I know, that is the unloaded speed (no rotors attached), but remember that's a 525W motor.  Compared to the stock 150W brushed motor, the LMH's rotor will not present much of a load and you could easily break off the rotors in flight!  An 11.1V LiPo battery could produce 4,309 unloaded RPM...oh my!!!  (The 4400Kv motor also has a higher no-load current draw; so it will suck your batteries down faster even though you'll never use 525W.)

So, here is a list of the parts I found for this little project.  I will provide an update after I get this put together in ~2 weeks.  These are Tower Hobby part numbers.  If you also order this from Tower, check the home page as they have coupon codes.

LXWDJ4 - Miniature Aircraft 3595Kv motor, $59.99
LXWFK2 - Miniature Aircraft 60A programmable ESC, $99.99
LXSDG6 - Integy motor spacer, $11.99 *** see note below
LXWDJ3 - Miniature Aircraft 4400Kv motor, $59.99 *** see note below

*** The shaft on the X-Cell/Scorpion motor is ~6mm longer than the stock LMH brushed motor; I was lucky and found this 6mm motor spacer so I would not have to modify the shaft or gear.  Hopefully it fits; it will also double as a nice heat sink.
*** I listed the 4400Kv motor here for comparison purposes; the 4400Kv motor is dangerous on the LMH in my option.

And yes, for the first flight I will be limiting the throttle to 50% and will slowly ramp up the limit as I test what the motor can do.  (Saftey glasses on!)


< Message edited by Krusher_r -- 7/22/2009 1:57 AM >

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RE: My search for the perfect brushelss upgrade - 7/30/2009 8:05 AM   
Krusher_r


 

Posts: 24
Score: 100
Joined: 7/21/2009
Last Login: 7/16/2012
From: Loudon, TN, USA
Status: offline 		My parts came tonight and I mounted the motor.  The Integy motor spacer mentioned above, Tower part number LXSDG6 is not needed and doesn't have holes which line up with the motor's holes.  The new motor shaft's extra length fits better on the old gear, although it does not have a flat spot (key) on one side of the shaft.  No problem, just tighten down the hex nut good by holding onto the gear itself (not the motor) while you crank it down good.

The only modification I had to make was to the washers as the old screws were the perfect length (for my wood Lite Machines 120.)  The washers had to be ground on one side so the thickness was around 1.5mm.  I used a Dremel and just held the washer on the grinding bit until it was a "D" instead of round.  (It will tend to rotate when you tighten the screw; I wedged a small knife in one side to stop the washer from rotating into the gear's bushing.)  You could use a very small washer instead, but then it will dig into the wood too easily.  If you have one of the newer aluminum frame LMH's, you might just need the screws included with the motor, which are much shorter.  Check it carefully because you don't want to bottom out on the brand new motor windings!

This is an outrunner motor that I haven't seen before, and it works differently than I am used to.  Instead of just the shaft rotating inside the motor, the whole outer can rotates and only the base stays put.  This motor is a bit longer than the Mega motor, but it looks small compared to the original.  Parts will need to be tied down good, because with that outrunner type motor, nothing can come in contact with the motor's can at anytime...it would act like a sander!

Tomorrow I will hook up the new ESC.  This new ESC is quite a bit larger than the original Castle Creations model; I guess it has to be because it's 60A and has that "remote control" feature in it.  No problem, the motor is a lot lighter by comparison.  It also puts out 5.5V to the servos instead of 4.8V, so it'll have faster response time but a little more current draw from on batteries.

I will try to take some pics for the next posting as well.


< Message edited by Krusher_r -- 7/30/2009 8:33 AM >

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RE: My search for the perfect brushelss upgrade - 8/1/2009 2:59 AM   
Krusher_r


 

Posts: 24
Score: 100
Joined: 7/21/2009
Last Login: 7/16/2012
From: Loudon, TN, USA
Status: offline 		I finished assembly and wire routing a few hours ago.  It rained here today so I won't be flying it, but thought it would be a good time to take some pictures.  It's a little crowded on the "left side" pictures because I had to leave lots of space for that motor.  I hope to get this flying tomorrow and will leave one final post in case someone else wants to do this and wondered how it turned out...

ADDED:  The LMH manual says that "The Corona files best with an Electro-Fusion 6 motor and six-cell battery at a weight of about 42 ounces (1190 g)."  I weighed mine on the scale with the 7-cell 3,000 mAH battery and it came out to 1142 g, or 40.2 ounces.  So, it's pretty close to the book's ideal weight.


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< Message edited by Krusher_r -- 8/1/2009 3:52 AM >

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RE: My search for the perfect brushelss upgrade - 8/2/2009 12:05 AM   
Krusher_r


 

Posts: 24
Score: 100
Joined: 7/21/2009
Last Login: 7/16/2012
From: Loudon, TN, USA
Status: offline 		I just finished flying three batteries on this combo, and figured out a few things.  Run time was quite a bit longer, but I didn't measure it.  There's a reason why it flew quite a bit longer than I expected, however.

If you use the 7-cell NiMH or NiCD batteries and never plan to change, the 4400kV motor would be a better choice.  That's because in order to hover, I had to put the stick "one line" above center.  Acceleration was about equal to the original brushed motor.  I think what's going on here is that the load on the motor is higher than expected, and there is some voltage drop in the battery under full load.  So you'd need a bit more "oomph" from that motor with the stock cell configuration.  With a 5.6V cutoff I could run the heli until it wouldn't hover any more.  There was no sharp cutoff where the heli drops from the sky.

On a 3S LiPo battery setup, I'd bet this 3595kV combo would be humming along really well!  The 4400kV motor would likely be 'too much' on a 3S LiPo setup.

So at this point, I either get the 4400Kv motor on my next Tower Hobbies order, or try to exchange this one.  The motor is now "used" so I am probably better off running this one for awhile, and once I make that next order, get the 4400kV motor at that time.  For now, here's what I've come up with on this project:

- Use the 4400kV motor if you have the 7-cell NiMH battery configuration on your LMH and don't plan to use LiPo batteries in the near future.

- Use the 3595kV motor on your LMH if you have 3S LiPo batteries now or plan to get them as an upgrade at the same time.

- The Fuiron 450 controller works well; I had to reverse the direction with a program change.  I thought about swapping some motor leads, but swapping it in the software would alert me if the program ever gets lost.  The rotors would run backwards and I'd know something is wrong.  This controller is a bit heavier than I wanted, but it does put the heli into its ideal weight range.

If I put that 4400kV motor in there eventually I will post an update; otherwise, let me know if you have made the swap out as well and how it works.  Good flying!

UPDATE:  Yep, Tower's policy is that they exchange only new, unopened merchandise.  Makes sense; a lot of places do that.  So, I will save the 4400kV motor order for the future...stay tuned! 


< Message edited by Krusher_r -- 8/2/2009 8:51 AM >

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RE: My search for the perfect brushelss upgrade - 9/26/2009 6:44 AM   
Krusher_r


 

Posts: 24
Score: 100
Joined: 7/21/2009
Last Login: 7/16/2012
From: Loudon, TN, USA
Status: offline 		Last update for now...

I ended up getting two 11.1V Flightpower EON Lite 2550 LiPo batteries because my previous 7 cell NiCd batteries that were being used on Dad's R/C boat died.  The 3,000 mAH NiMH batteries were nice replacements for that application.  I could have bought that 4400kV motor to try it out, but this 3595kV motor / LiPo battery combo will make a better beginner setup on the Miniature Aircraft someday.

I did some surfing on the original brushed Corona 120 motor, and another guy figured out that it was a 4500kV motor.  So, if you have lots of those 7 cell battery packs laying around yet, the 4400kV brushless from the Miniature Aircraft heli should work well.  Just keep in mind that I would not use the 4400kV motor with the 11.1V batteries for safety reasons.

Those Flightpower batteries make the heli about 237 grams "too light" according to the manual.  It's amazing how much more power these LiPo batteries hold.  You can certainly buy heavier/higher capacity LiPo batteries to add weight, but they are really expensive and require more expensive LiPo charger balancer setups.  The new LiPo batteries only get about half as hot as the NiMH batteries did.

It hovers one line below center now instead of one line above center like the heavier 7-cell NiMH batteries did.  As a result of the low weight and rotor speed, it's a little twitchy in the wind.  I have two choices now; either add weight or increase the blade RPM.  All LMH's come with 4 and 6 dot grips; combining the two per assembly instructions will give you 5 degrees of pitch.  If I replace the 6 dot grip with a 4, I'll drop one degree of pitch and the RPM should go back up to what it was before without adding extra weight.  If I don't respond again, you can assume that worked.  If that makes things worse, I will reply to myself one more time. 

I did try 'punching it' briefly and it's a little scary.  There's so much torque that the heli spun 90 degrees before I knew what happened; I will have to adjust the REVO mixing to see if I can compensate.  If that alone isn't enough, then I'll have to reduce the maximum throttle through the ESC.  I also changed the low battery cutout to 7.6V (because the LiPo batteries say 7.5V is the minimum.)

Happy flying!

EDIT: My REVO mixing was set from my other model; resetting it to the default values with the 4-dot grip made it much easier to fly.  The only down side now is if I run the batteries down very low, it does drop out of the sky quickly.  It's time for a monitoring circuit I suppose.  I'm still a little apprehensive to apply full throttle but when I can handle flying well over my head I'll give it a try then.


< Message edited by Krusher_r -- 9/28/2009 9:12 AM >

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