Motor heat

[Darin Jordan]

And by the way the screwy launch start at 30 seconds and below is the NAMBA system. AKA - the bad influence I referenced.

Should I take offense to this, since I'm the one that described it??

[DPeterson]

Terry said...
[QUOTE]Then it turns out.......... your club was just doing it screwy.[/QUOTE

Darin - check with Terry. We were using the NAMBA start. He quoted it as screwy. Not sure what you described.

Here we go again.

[dan pralle]

Just curios why the p class can't just limit the kv motor you run. Why does it have to be brand specific. P is not a rtr class it refers to motor size right?


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[Darin Jordan]

Just curios why the p class can't just limit the kv motor you run. Why does it have to be brand specific. P is not a rtr class it refers to motor size right?


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There is a BIG difference in "mass" between a 2000KV 40mm motor, and a 2000KV 36mm motor, just to use one example. The same can be said for 2-Pole vs. 4-Pole vs. 6-Pole, 50mm long vs. 60mm long vs. 73mm long, etc...

KV is such a SMALL part of the overall picture...

[dan pralle]

But the rpms are the same correct?


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[dan pralle]

So with a bigger can motor could you spin a bigger prop


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[Darin Jordan]

But the rpms are the same correct?

RPMs are the same unloaded... The ability to turn the prop under load aren't. Think torque. The motor with more torque isn't going to be "bogged down" as much, so the loaded RPM will be considerably different, given the same prop. The larger/higher-torque motor, therefore, could be prop'd with more pitch/diameter and therefore, would be faster.

[dan pralle]

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque


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[photohoward1]

Yes..Just like my fuel motor analogy.

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque


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[Darin Jordan]

So as Doug referred to motor mass would a longer motor or bigger diameter create more torque.

Generally speaking, yes. Remember, by "longer" or "bigger diameter", we are referring to the internal windings. The outer can diameter or length can be misleading. It's the actual core that matters. More copper, more mass, better heat capacity, improved efficiency, etc. These are very high-level explanations, and someone like Tyler could certainly get into the really nitty-gritty details, but for the purposes of what we are discussing here, these will suffice.

[dan pralle]

This is good education. You bring up efficiency. A motor that is 85% vs 95%. Does that just give you longer run time


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[Darin Jordan]

This is good education. You bring up efficiency. A motor that is 85% vs 95%. Does that just give you longer run time

I don't want to sidetrack Doug's thread too much, but hopefully he finds this all relative to the general Motor discussion.

Higher efficiency does increase run-time (less energy lost as heat). That also means more of the power is getting through the motor to the prop. Probably better acceleration, etc.

The bottom line is that KV really is just a tiny measure of what you might expect out of a motor. You have to look at a lot of more complex factors.

You might be able to get away with specifying a can size or range of can sizes, and THEN limit the KV and maybe specify a pole count. That won't help in putting limits on efficiency or internal design (rotor design, magnet shape, wire size, etc.), but it would probably get you close enough to have a good, and relatively fair race of it.

[dan pralle]

Ok I see why you need to specify a list of motors. And if your motor is running too hot that means you have too big of prop on that hull right?


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[DPeterson]

Darin - I am all in for good quality, positive and unbiased contributions on threads!!

Dan is trying to figure out how to beat us Wisconsin guy's with electric. Might be why he has so many gas boats.

[dan pralle]

Doug it's all a big learning process to keep up. Sounds like your trying to make it easier by doing the testing AND SHARING your results. And trying to make it more economical to build a boat and put more drivers on the stand.


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