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Old Dec 10, 2011, 06:52 PM
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Whats Hobbypartz closest motor to a E-flite 400 and 450?

I was wondering what is the Hobbypartz closest equivalent to an E-flite 400 and 450. Thanks!
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Old Dec 10, 2011, 07:17 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Originally Posted by E-reevo View Post
I was wondering what is the Hobbypartz closest equivalent to an E-flite 400 and 450. Thanks!
The best way to choose alternate motors is to look at the specs and note the weight and Kv of the motor you want to replace. Then simply buy a cheaper motor of approximately the same weight and Kv.

Park 400, 56 grams, 920 Kv - http://www.horizonhobby.com/products...920kv-EFLM1305

Park 480, 87 grams, 910 Kv - http://www.horizonhobby.com/products...910kv-EFLM1500

If you want to add a little more power to the equation buy a motor that is a little heavier. Most motors produce about 3 Watts of power for each gram of motor weight so if you mutltiply the weight in grams by 3 you will get about that much power. Note that the 87 gram Park 480 is described as a 250 Watt motor, multiply 3 x 87, that is 251 Watts.

Many of the other numbers in the specs are presented out of context, may be presented in a confusing or even dishonest manner, and are prone to mistakes or exaggeration. The 3 watts per gram rule is easy to apply and seldom very far off of the mark.

You don't mention what Kv you want, that is an important consideration if you did not know that. If you don't buy a motor of the right Kv for the propeller you intend to use the motor will not work for you. Kv selections do not need to be precisely the same from one motor to another, but should be similar, like withing a few hundred RPM or less.

Jack
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Old Dec 10, 2011, 07:49 PM
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Originally Posted by jackerbes View Post
The best way to choose alternate motors is to look at the specs and note the weight and Kv of the motor you want to replace. Then simply buy a cheaper motor of approximately the same weight and Kv.

Park 400, 56 grams, 920 Kv - http://www.horizonhobby.com/products...920kv-EFLM1305

Park 480, 87 grams, 910 Kv - http://www.horizonhobby.com/products...910kv-EFLM1500

If you want to add a little more power to the equation buy a motor that is a little heavier. Most motors produce about 3 Watts of power for each gram of motor weight so if you mutltiply the weight in grams by 3 you will get about that much power. Note that the 87 gram Park 480 is described as a 250 Watt motor, multiply 3 x 87, that is 251 Watts.

Many of the other numbers in the specs are presented out of context, may be presented in a confusing or even dishonest manner, and are prone to mistakes or exaggeration. The 3 watts per gram rule is easy to apply and seldom very far off of the mark.

You don't mention what Kv you want, that is an important consideration if you did not know that. If you don't buy a motor of the right Kv for the propeller you intend to use the motor will not work for you. Kv selections do not need to be precisely the same from one motor to another, but should be similar, like withing a few hundred RPM or less.

Jack
Thank you for the advice, that will definetely help me in the future.
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Old Dec 10, 2011, 08:20 PM
Jack
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What a coincidence, Rick and I replied at almost the same moment in time with me beating him by seconds or nanoseconds. And when I chased the links in his answers, the suggestions were pretty much right on the money with the 3 Watts per gram rule too.

The big difference between Optima and Hobby Zone Park motors is the fact that you can buy about three Optimas for the cost of one HZ Park motor.

Jack
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Old Dec 10, 2011, 10:03 PM
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Some good reading. Its funny to me how the weight of the motor will give a representation of power. Would think the higher end manufactures would use lighter, more expensive materials to reduce weight while keeping the same amount of power. The opposite for the lesser priced motors.

In terms of the 3 gram rule....thats not really the amount of watts the motor can make. But more the amount of watts that is safe to run? Still get confused with this.

For instance i know of a 26 gram motor that gets over 110 watts pulled though it all the time. Is it safer to cheat and pull more power through a smaller 26 gram motor than a 87 gram motor?
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Old Dec 10, 2011, 10:37 PM
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In terms of the 3 gram rule....thats not really the amount of watts the motor can make. But more the amount of watts that is safe to run? Still get confused with this.

Motors don't "make" watts... they consume them.

Most run-of-the-mill motors can cope with 3W/g safely (without over-heating)... higher end motors can possibly manage a bit more...also, with very good cooling the limit can be a fraction higher... but your example of 5W/g means the motor is probably living on the edge.
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Old Dec 11, 2011, 07:58 AM
Jack
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Joined May 2008
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Originally Posted by wopachop View Post
Some good reading. Its funny to me how the weight of the motor will give a representation of power. Would think the higher end manufactures would use lighter, more expensive materials to reduce weight while keeping the same amount of power. The opposite for the lesser priced motors.
If you go to the web pages for the better quality (more expensive too) motors you'll find motors that are rated for more than three watts. But not a huge amount more. Look at some of the MicroDan motors and the Scorpion and Motrolfly motrolfly motors on this page and you'll see the specs and details on some better motors.

http://www.gobrushless.com/shop/inde...how&ref=motors

Quote:
In terms of the 3 gram rule....thats not really the amount of watts the motor can make. But more the amount of watts that is safe to run? Still get confused with this.

For instance i know of a 26 gram motor that gets over 110 watts pulled though it all the time. Is it safer to cheat and pull more power through a smaller 26 gram motor than a 87 gram motor?
It is not necessarily so. You are talking about in flight and with better cooling, we may be talking about static testing power measurements. It is safe to do it if the motor does not get too hot and burn up. The thing that really remains constant is that 1A at 1V = 1 Watt. The voltage and current will go up and down, the heat will vary with that, and the heat will be dissipated at different rates.

It is easy to misuse or misapply the term "watts" as far as where they are or come from. Especially so if you are not the most technically minded person in a crowd that includes a lot of more technical minds.

I always say motors "are good for" or "produce" or "crank out" their power and it is measured in watts. That works for me and the meaning is generally understood I think.

Jack
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Old Dec 13, 2011, 01:30 PM
Ignint McNugget
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FWIW, I had the same interpretation of your words as Dr. Kiwi. You said "motors produce watts" which to me means watts out - but I think you meant watts in - the difference between them being related through the efficiency.
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