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E-Flite Mini Pulse XT

Old 03-16-2009, 09:53 PM
  #376  
MustangMan
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Originally Posted by rudderfeet View Post
That is fantastic info about the motors, thank you so much!

I'm new to reading motor specs (please don't tell anyone I graduated with an electronics degree 20 years ago), but I'm guessing that the (1st) motor you use is a little better than my Park 450 anyway. The 450 (http://www.horizonhobby.com/Products...rodID=EFLM1400) is 890 kv, whereas yours is 1050 kv. What ESC do you use, and why the 10x5 prop? My 450 comes with a 22A esc and a 10x7 prop, but they say a 10x8 is a recommended upgrade...?

Oy, SO many variables!
I'm using a 25 amp Castle Creations ESC with a separate UBEC to power the radio and servos.

Higher Kv doesn't mean a "better" motor. It simply means that the motor wants to ideally spin at Kv times input-volts = RPM. Thus an 890 Kv motor will try to spin at 890 * 11 = 9790 RPM on 11 volts and a 1050 Kv motor will try to spin at 1050 * 11 = 11550 RPM. For a given propeller power rises as the QUBE of the RPM. Under load neither motor spins at the theoretical value. The amount of RPM drop depends on the mechanical load, motor geometry, magnet strength and quality, stator material characteristics, and winding resistance (and probably a few other variables as well). The difference in Kv means that swapping out the motor from the Park 450 to the Turnigy 2217/16, without changing the propeller, would result in an approximate power increase of 64%. The Turnigy would likely be overheated by that much power so a step down in propeller is needed to protect it. I have flown my MPXT with both a 10x7 APC prop and an 11x5.5 APC. I didn't like the strain they put on the power system with marginal difference in performance so I went back to the 10x5.

Heat is the primary killer of our motors. Most of that heat comes from the I squared R losses due to the resistance of the copper wire in the windings. Thus heat generation rises as the square of the current. When pushing a motor close to its limits a small increase in current can mean a large increase in heat. That heat also means wasted energy since it doesn't contribute to the propulsion of your airplane.

I encourage anyone interested in experimenting with power setups to explore and use one of the numerous power system calculation programs available such as DriveCalc, MotoCalc, etc. These work from the device characterization parameters of motors, batteries, ESC's, propellers, and gear boxes (if used) to compute useful estimates for information like RPM, pitch speed, amps, watts, efficiency, etc. Often getting the parameters for a component you're interested in using is the hard part. The manufacturers and retailers aren't always forthcoming (and don't understand the need for) with this information. The programs aren't a substitute for direct measurements of your setups though. At a minimum you need a way to measure Amps.

Yeah, my Physics and EE education was more like 40 years ago and I don't remember anything about electromechanical theory from then, if we were exposed to any. My interest at the time was almost entirely digital logic and software anyway so I've had to learn about electric flight power systems from scratch. I've been playing with them for five years now and have never, knock on wood, smoked any components. I have puffed a couple of Lipo's though.
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Old 03-28-2009, 09:22 PM
  #377  
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I took the MPXT up for a dozen more flights this week and am now using a 10x8 prop with the same stock Park 450 motor. I'm definitely getting better performance with the new prop and plan to stay with the 450 until I spot a steal of a deal on a 480 or equivalent (let me know if you have one!).

I gotta say I'm REALLY liking the MPXT. It doesn't care a whit about winds up to 10 mph, and is still quite flyable up to 15 mph with 20 mph gusts. It's quiet, smooth and gives me a solid 8 minutes of flight on my FlightPower 2500mAh batteries, and that's consistently with 25% remaining!

The only thing I will say is that sometimes I wish I would have gone larger with the Pulse 25 or with Hangar 9's Funtana 40. But those don't fit in the car so easily, and I can't use the same batteries in them as I can my T-Rex, so maybe it's just the (RC) disease talking...
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Old 03-28-2009, 09:47 PM
  #378  
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Yep, the MPXT is a sweet airplane alright.

I too have the yearning for a bigger, though similar type, of airplane. It is the disease talking but we have GOOD REASONS to justify it!

Good to hear you're enjoying yours.
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Old 03-28-2009, 10:10 PM
  #379  
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Originally Posted by MustangMan View Post
I'm using a 25 amp Castle Creations ESC with a separate UBEC to power the radio and servos.

Higher Kv doesn't mean a "better" motor. It simply means that the motor wants to ideally spin at Kv times input-volts = RPM. Thus an 890 Kv motor will try to spin at 890 * 11 = 9790 RPM on 11 volts and a 1050 Kv motor will try to spin at 1050 * 11 = 11550 RPM. For a given propeller power rises as the QUBE of the RPM. Under load neither motor spins at the theoretical value. The amount of RPM drop depends on the mechanical load, motor geometry, magnet strength and quality, stator material characteristics, and winding resistance (and probably a few other variables as well). The difference in Kv means that swapping out the motor from the Park 450 to the Turnigy 2217/16, without changing the propeller, would result in an approximate power increase of 64%. The Turnigy would likely be overheated by that much power so a step down in propeller is needed to protect it. I have flown my MPXT with both a 10x7 APC prop and an 11x5.5 APC. I didn't like the strain they put on the power system with marginal difference in performance so I went back to the 10x5.

Heat is the primary killer of our motors. Most of that heat comes from the I squared R losses due to the resistance of the copper wire in the windings. Thus heat generation rises as the square of the current. When pushing a motor close to its limits a small increase in current can mean a large increase in heat. That heat also means wasted energy since it doesn't contribute to the propulsion of your airplane.

I encourage anyone interested in experimenting with power setups to explore and use one of the numerous power system calculation programs available such as DriveCalc, MotoCalc, etc. These work from the device characterization parameters of motors, batteries, ESC's, propellers, and gear boxes (if used) to compute useful estimates for information like RPM, pitch speed, amps, watts, efficiency, etc. Often getting the parameters for a component you're interested in using is the hard part. The manufacturers and retailers aren't always forthcoming (and don't understand the need for) with this information. The programs aren't a substitute for direct measurements of your setups though. At a minimum you need a way to measure Amps.

Yeah, my Physics and EE education was more like 40 years ago and I don't remember anything about electromechanical theory from then, if we were exposed to any. My interest at the time was almost entirely digital logic and software anyway so I've had to learn about electric flight power systems from scratch. I've been playing with them for five years now and have never, knock on wood, smoked any components. I have puffed a couple of Lipo's though.
MustangMan' a

bub, steve
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Old 03-28-2009, 10:17 PM
  #380  
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Originally Posted by rudderfeet View Post
I took the MPXT up for a dozen more flights this week and am now using a 10x8 prop with the same stock Park 450 motor. I'm definitely getting better performance with the new prop and plan to stay with the 450 until I spot a steal of a deal on a 480 or equivalent (let me know if you have one!).

I gotta say I'm REALLY liking the MPXT. It doesn't care a whit about winds up to 10 mph, and is still quite flyable up to 15 mph with 20 mph gusts. It's quiet, smooth and gives me a solid 8 minutes of flight on my FlightPower 2500mAh batteries, and that's consistently with 25% remaining!

The only thing I will say is that sometimes I wish I would have gone larger with the Pulse 25 or with Hangar 9's Funtana 40. But those don't fit in the car so easily, and I can't use the same batteries in them as I can my T-Rex, so maybe it's just the (RC) disease talking...
RudderFoot::This is a good one for after you Mini-Pee get's older,,, Brio-10,, bub, steve
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Old 03-29-2009, 02:45 PM
  #381  
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Thanks for the idea Steve!

BTW here's a quick vid of me flying my MPXT yesterday:

[media]http://www.youtube.com/watch?v=eNS7tk468Ao[/media]
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Old 03-29-2009, 03:07 PM
  #382  
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Originally Posted by rudderfeet View Post
I took the MPXT up for a dozen more flights this week and am now using a 10x8 prop with the same stock Park 450 motor. I'm definitely getting better performance with the new prop and plan to stay with the 450 until I spot a steal of a deal on a 480 or equivalent (let me know if you have one!).
What about this motor from Heads Up RC?

Power Up 480 Plus
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Old 03-29-2009, 11:40 PM
  #383  
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Originally Posted by gfdengine204 View Post
What about this motor from Heads Up RC?

Power Up 480 Plus
VERY interesting! Have you used this one?
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Old 03-30-2009, 01:39 AM
  #384  
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Originally Posted by rudderfeet View Post
VERY interesting! Have you used this one?
No not yet. I'm told it is a re-branded Suppo motor. You can't go wrong ordering from Jeff at HeadsUpRC. He has the best service anywhere.
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Old 03-30-2009, 03:14 AM
  #385  
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Originally Posted by stevecooper View Post
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bub, steve
Gee Steve, thanks for pointing that out. Otherwise no one would have noticed!
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Old 04-28-2009, 08:50 PM
  #386  
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Pre newbie here...
Have an MPXT ARF but it's still in the box. Went ahead and got the reccommended completion parts; E Flite 450 BL motor, E Flite 25 amp ESC, 4 S75 servos and the other stuff. Now I'm wondering if the 25 amp ESC will be OK. Initially I had read that the 25 was reccommended but there were other sites that reccommended a 30 amp ESC. I got the 25 and now can't fond my way to the sites that said 25 was OK. Any suggestions? Don't want to get that plane flying, just to take home a handful of toothpicks. Read somewhere " When you're 100% confident with the T-28, then you're redy for the MPXT" Gettin' there...
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Old 04-28-2009, 08:53 PM
  #387  
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Hi Pat; if you can fly, you can fly the MPXT. It's smooth, predictable and just down right fun to fly. It was my 2nd plane and as easy as the trainer I started with. Not sure about the ESC as I bought the PNP version and just fly the wings off it. Best luck to ya!
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Old 04-28-2009, 09:02 PM
  #388  
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I've heard of issues with the T-28's ESC not quite being up to the task, but not the MPXT. I also have the PNP version, which comes with a 25 amp ESC and a 450 motor (not the E-F Park 450, but very similar). Never a problem, though I've never been impressed with the throttle response. I have $15 TowerPro ESC's that work better, IMHO.

Correction: 20 amp ESC, not 25 in the PNP MPXT.
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Old 04-28-2009, 09:05 PM
  #389  
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Pat.
Eflite recommend 20a so no problem. Take a look at the ''tech&spec''
http://www.e-fliterc.com/Products/Te...rodID=EFLM1400

I agree with toomanyhobbies. The MP is one of the nicest and well behaved planes to fly. You will love it.
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Old 04-28-2009, 09:20 PM
  #390  
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Originally Posted by patmatgal View Post
Pre newbie here...
Have an MPXT ARF but it's still in the box. Went ahead and got the reccommended completion parts; E Flite 450 BL motor, E Flite 25 amp ESC, 4 S75 servos and the other stuff. Now I'm wondering if the 25 amp ESC will be OK. Initially I had read that the 25 was reccommended but there were other sites that reccommended a 30 amp ESC. I got the 25 and now can't fond my way to the sites that said 25 was OK. Any suggestions? Don't want to get that plane flying, just to take home a handful of toothpicks. Read somewhere " When you're 100% confident with the T-28, then you're redy for the MPXT" Gettin' there...
You self-identified as a pre newbie. If you don't have plenty of experience with a "trainer" airplane I'll urge you to start with one before going to the MPXT. As others have said, the MPXT is a great, well behaved, sport plane. It is not, however, a first time beginner plane. It's too fast (not that it's a particularly FAST airplane), neutral, and too agile for a first timer. The only exception to that would be if you have MANY hours of simulator experience.

I LOVE my MPXT and you'll likely love yours too if you're ready for it. Good luck.
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Old 04-28-2009, 09:25 PM
  #391  
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Another endorsement of the MPXT's flying habits. It's easily my favorite plane (vs. my Typhoon2 3D and Synapse) and it'll be with me for a quite a while, especially now that a friend gave me a bunch of spare parts and I just ordered a Park 480 and ESC equivalent set for it.

Just set up the low throws like the manual says and you'll be fine. It won't be long until you're landing on high rates because you forgot - it's that nice as stable. Like the others said, if you can fly an aileron plane, you'll very much enjoy the MPXT.

Would be nicer to have a brighter color scheme though. On clear days the blue can merge into the sky if you get too far out.
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Old 04-29-2009, 01:16 AM
  #392  
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Alright! Thanks much! Will use the 25 amp ESC and not worry. After all the glowing reports I'm really looking forward to getting this plane in the air.
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Old 07-04-2009, 07:32 PM
  #393  
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I put 3 packs thru my MPXT yesterday evening, and this is becoming my favorite plane. First two flights were with a Thunder Power Lipo, but the third flight was where she really shined. A Turnigy 3S 2200mAh 20-30C lipo from the last Wattflyer Buyers Club bulk battery buy, she fit a little different in the bay but still had plenty of room. Wow what a difference, flew as if on rails, took off at 50% throttle in 15-20 feet and was just a treat. With the one exception of me adding right aileron when I meant left (whoops), which did no harm as I had plenty of altitude to correct my dumb-thumb, the flight was non-eventful. Greased in all three landings, which is something I don't normally do. Soon I will start working on touch-n-go's. Between this plane and my Parkzone T-28 & Corsair, there will be a lot of flying time done this season!
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Old 07-04-2009, 09:54 PM
  #394  
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Glad you're enjoying yours gfdengine204. The Heads Up RC Park 480 and 40A ESC are proving to be an excellent pair for my MPXT (I'm running a 10x8 prop BTW). I think I paid $60 for both of them and am getting quick climbouts, unlimited vertical and 7+ minutes of spirited flight time on FlightPower 3S2500 batteries.
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Old 07-05-2009, 02:53 AM
  #395  
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Mine rebuilt from several MiniP's
She somewhat reskined an stiff'in up some too (carbon fiber's)
I only fly a 2409-18 & 30ESC in her which is better than I'd thought It would be
She'll do all the the aerobatics's you could wish for in a sport plane and then some
Fly's effortlessly inverted with only a tad-o-down'sy to keep her happy
A good bub of mine had her but no time to rebuild her an passed her on, I named it after his daughter who's a Mullet Marouder Member too
Mustangman got himself another Mini now, bubsteve
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