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Old May 18, 2011, 03:47 PM
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Originally Posted by SandHog View Post
It'll probably be a little faster, but don't expect a night-and-day difference.

The stock motor is an 870kV, and your new Power-Up-25 is a 950kV. Higher, but not dramatically higher. The difference is only 80kV, and 80kV X 11.1V = about 900 RPM's higher. That won't equate to much additional speed.

Depending on the new motor's efficiency, you may see a little longer flight times. The big difference will come when you decide to try 4s. THAT will give you significantly more speed. Just remember, though, the Apprentice is a trainer, not a pylon racer. Its huge wing provides a lot of lift, but also creates a lot of drag.
Isn't the stock motor a 15 size vs. his new 25 size ??? I would think it should be somewhat faster
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Old May 18, 2011, 03:57 PM
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i dont know if its a true 15 size i know its no power 15. Thats what alot of people are upgrading to is a power 15. Not sure on the exact scaling of the stock motor. May be some sort of 15 size
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Old May 18, 2011, 03:59 PM
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Originally Posted by FTA_FTW View Post
Noooo, not the news I wanted to hear hehe jk.

I don't plan on making it a wild racer, as you said it is a high wing trainer. But I just don't trust that stock plastic housing motor, which is mainly why I wanted to replace it. And of course to get a bit more speed.

I can also experiment with different sized props with my 3s batteries?
Yeah, different sized props will help get some more speed as well. Since your new Power-Up-25 has a higher watt rating --note that this is only an assumption; I have never seen an actual watt rating for the Apprentice plastic BL15 motor, I am basing my assumption on the fact that the Eflite Power 15 has a watt rating of 425w, and the Power-Up-25 has a watt rating of 620w--, you can prop it more aggressively and get more out of the new motor than the older 870kV.

MAKE SURE YOU HAVE A WATT METER before changing the prop size, though, so you can take readings and don't burn up your new motor (or smoke your 30A ESC).
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Old May 18, 2011, 04:03 PM
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Originally Posted by robtest View Post
Isn't the stock motor a 15 size vs. his new 25 size ??? I would think it should be somewhat faster
The stock motor is what they call a "15-sized brushless" I think they're basing it on the size of the motor housing and a close approximation to the Power 15 kV and watt rating. However, that aside, "size" doesn't matter (no juvenile snickering, please!) The kV (RPM per volt) of the motor and it's watt rating is what matters in terms of speed.

If you could make it fit, the Eflite Power 32 motor with the stock battery and prop would actually make the Apprentice go SLOWER than the stock motor, because the Power 32 is only 770kV vs the 870kV of the stock plastic motor.
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Old May 18, 2011, 05:52 PM
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SandHog you are so helpful! I owe you lots of beers lol

I'm not using the stock 30A ESC with the Power Up 25, I purchased an EMAX 50A ESC. I'll be comparing the stock prop (11x8) to the 11x5.5E prop I bought for the new motor. Than in a few weeks I will pickup a 12x6 to see if the increase in thrust is noticeable and worth it... because I will sacrifice some speed with that 12x6 right?

WATT Meter is a good idea, will look into it.

Quote:
Originally Posted by SandHog View Post
Yeah, different sized props will help get some more speed as well. Since your new Power-Up-25 has a higher watt rating --note that this is only an assumption; I have never seen an actual watt rating for the Apprentice plastic BL15 motor, I am basing my assumption on the fact that the Eflite Power 15 has a watt rating of 425w, and the Power-Up-25 has a watt rating of 620w--, you can prop it more aggressively and get more out of the new motor than the older 870kV.

MAKE SURE YOU HAVE A WATT METER before changing the prop size, though, so you can take readings and don't burn up your new motor (or smoke your 30A ESC).
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Old May 18, 2011, 06:40 PM
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Originally Posted by SandHog View Post
The stock motor is what they call a "15-sized brushless" I think they're basing it on the size of the motor housing and a close approximation to the Power 15 kV and watt rating. However, that aside, "size" doesn't matter (no juvenile snickering, please!) The kV (RPM per volt) of the motor and it's watt rating is what matters in terms of speed.

If you could make it fit, the Eflite Power 32 motor with the stock battery and prop would actually make the Apprentice go SLOWER than the stock motor, because the Power 32 is only 770kV vs the 870kV of the stock plastic motor.
I guess my over simplification was that the bigger size motor typically has more wattage, which is where the power comes from.

I put a power 25 and it's esc from a crashed e-flite T-34 into my apprentice, and it flies a bit quicker than the stock motor... The power25 runs good on 3s battery, now that Power32 you mentioned, that screams for 4s batteries! LOL
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Old May 18, 2011, 09:19 PM
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Originally Posted by SandHog View Post
Yeah, different sized props will help get some more speed as well. Since your new Power-Up-25 has a higher watt rating --note that this is only an assumption; I have never seen an actual watt rating for the Apprentice plastic BL15 motor, I am basing my assumption on the fact that the Eflite Power 15 has a watt rating of 425w, and the Power-Up-25 has a watt rating of 620w--, you can prop it more aggressively and get more out of the new motor than the older 870kV.

MAKE SURE YOU HAVE A WATT METER before changing the prop size, though, so you can take readings and don't burn up your new motor (or smoke your 30A ESC).
You refer to the plastic motor - the new ones come with metal - is it the same power and everything, just with a metal cover instead of the plastic?
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Old May 19, 2011, 10:04 AM
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yes correct same motor just with metal endbell not plastic
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Old May 19, 2011, 02:32 PM
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Originally Posted by FTA_FTW View Post
SandHog you are so helpful! I owe you lots of beers lol

I'm not using the stock 30A ESC with the Power Up 25, I purchased an EMAX 50A ESC. I'll be comparing the stock prop (11x8) to the 11x5.5E prop I bought for the new motor. Than in a few weeks I will pickup a 12x6 to see if the increase in thrust is noticeable and worth it... because I will sacrifice some speed with that 12x6 right?

WATT Meter is a good idea, will look into it.
Root Beers, please! I need a clear head when I fly!

Good man; glad to hear that you upgraded your ESC as well as the motor. You'll actually lose speed with the 11x5.5 prop. Less pitch = lower speed, more thrust. When you try the 12x6 (with larger wheels on the Apprentice, the 11x8 prop swings close enough to the ground) you'll find that you do have an increase in thrust, but again less speed.

Larger diameter smaller pitch = more thrust, less speed (like low gear in a car)
Smaller diameter larger pitch = more speed, less thrust (like high gear in a car)

A 10x10 prop would give you more speed at pretty close to the same watt consumption. Rule is "one up, one down" for diameter and pitch.
Thus an 11x7 prop would draw about the same watts as a 12x6 prop, for example. Up one in diameter, down one in pitch. So ideally, you'd get a 10x9 prop to replace the 11x8, but I've never seen a 10x9 electric prop.
Just check with your watt meter to make sure you're not exceeding max burst current. You'll also find that you draw LESS current with the 11x5.5 prop. To little current draw, and your airplane is under powered.
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Old May 19, 2011, 02:38 PM
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Originally Posted by robtest View Post
I guess my over simplification was that the bigger size motor typically has more wattage, which is where the power comes from.

I put a power 25 and it's esc from a crashed e-flite T-34 into my apprentice, and it flies a bit quicker than the stock motor... The power25 runs good on 3s battery, now that Power32 you mentioned, that screams for 4s batteries! LOL
I'm guessing the Eflite Power 25 was slightly faster (even though it has the same kV rating as the stock motor) because it is a more efficient motor with likely stronger magnets. More efficiency + stronger magnets means that the motor will spin closer to its rated kV with a load on it. Remember that a motor's kV rating is with no load. Put a prop on it, and that causes drag, but the motor will still TRY to spin at its rated kV. But less efficient windings and weaker magnets mean it won't have the muscle to do it.

And yes, the Power 32 with 4s batteries and an appropriate prop would probably pull the poor Apprentice apart by the seams! (or at least tear the firewall away from the silicone caulk that holds it to the foam!)
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Old May 25, 2011, 06:52 AM
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At the Dam (6 min 46 sec)
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Old May 25, 2011, 07:13 AM
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Nice video Lucyf-18!
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Old May 25, 2011, 11:49 AM
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Nice shots lucyf-18, what onboard cam did u use/
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Old May 25, 2011, 09:42 PM
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Awesome video man! Looks great with floats, actually suits the plane more IMO.

My Power Up 25 Sport 900kv motor arrived today along with a 50amp ESC. Will mount it tomorrow and hopefully do a flight test on Friday (weather permitting). Also bought the 808 keychain camera #11 (HD) but hasn't arrived yet.
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Old May 26, 2011, 07:43 AM
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Nice shots lucyf-18, what onboard cam did u use/
The Camera is the inside of a pocket cam with just the circuit board and wires hanging out the side. It sucks bc it sticks straight up and acts like a giant air-brake. I would get a Sony Bloggie to replace bc it mounts flat with a lower profile.

thanks!
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