Motor KV and ESC combinations?

[thedubdude]

Hi Folks,

I was sold a 4200KV Chili Pepper CP20 motor in combination with a Phoenix-25 ESC. I don't know much about electrics so I'm not clear this combination will work. For instance, on Modefo's web site, http://www.modefosheli.com/combo_deals
he shows a Phoenix-35 in combination with a Chili Pepper 3600KV. So my questions are as follows:

1. What is the correct motor KV to use?
2. What is the difference between higher and lower KV performance?
3. What is the correct ESC to use....is it dependent on the motor KV?

Thanks in advance.

Regards, Don

[Hotshot Charlie]

I am using a HiMax 4100 kv motor (2025/4100) with the Phoenix 25 and it works perfectly. Yours should do the same.

What heli are you using it in?

[ErichF]

Your ESC should do fine in with that motor. There is no right or wrong kV rating for use in the T-Rex or any helicopter for that matter. kV rating is simply RPM per volt. It's kind of like a motor's internal "gearing" so to speak. Higher kV motors will spin up faster, and have a high rpm torque band. These usually need higher gear ratios to obtain the desired rotor head speed of around 2350. Lower kV motors are like fourstroke glow engines...making most of their torque in the lower RPM range. This is why you'll notice outrunner motors have lower kV ratings (Align 400S-2800kV). These motors require a larger pinion to make the lower gear ratio needed to get the right head speed. For example...your motor will need an 8 or 9 tooth pinion so it can spin up to it's ideal torque band, and the Align 400S-2800 needs a 13T pinion for the same head speed.

Here is an awesome tool you can use to "install" different motors and pinions and predict performance and current draws...

http://home.earthlink.net/~dr.electr...Comparison.xls

Enjoy and good luck!

Erich

Originally Posted by thedubdude

Hi Folks,

I was sold a 4200KV Chili Pepper CP20 motor in combination with a Phoenix-25 ESC. I don't know much about electrics so I'm not clear this combination will work. For instance, on Modefo's web site, http://www.modefosheli.com/combo_deals
he shows a Phoenix-35 in combination with a Chili Pepper 3600KV. So my questions are as follows:

1. What is the correct motor KV to use?
2. What is the difference between higher and lower KV performance?
3. What is the correct ESC to use....is it dependent on the motor KV?

Thanks in advance.

Regards, Don

[WillJames]

Sweet info Erich!! Thank you for sharing.

[mudbogger2]

Just a note that 4 servos and a gyro on the Phoenix 25 is over the bec's rated limit.
People do it all the time anyway witout problems. I am even guilty of it. A phoenix 35 would not have this problem so keep this in mind if you are buying new stuff. Only $20 more for the 35.

[thedubdude]

Originally Posted by Hotshot Charlie

I am using a HiMax 4100 kv motor (2025/4100) with the Phoenix 25 and it works perfectly. Yours should do the same.

What heli are you using it in?

This is for the T-Rex. I notice the smallest pinion the kit supplies is 11 tooth, though it is 2.3mm (vs. a 3.17mm 11 tooth pinon also supplied). Will this pinion be sufficiently small to work with the 4200KV motor?

Thanks.

[ErichF]

Unfortunately, from reports I have read, no. Try that spreadsheet and see what it comes up with tho. Most people are getting overheats and excess current draw with 11T.
Modefo's Helis has smaller pinions that will work. You can also check out the local RC car shop for pinions for just about anything.

Originally Posted by thedubdude

This is for the T-Rex. I notice the smallest pinion the kit supplies is 11 tooth, though it is 2.3mm (vs. a 3.17mm 11 tooth pinon also supplied). Will this pinion be sufficiently small to work with the 4200KV motor?

Thanks.

[thedubdude]

Thanks for the info. I'll have to wait until I get back to work to try the spread sheet as I don't have Excel on my home computer.

[thedubdude]

Here is an awesome tool you can use to "install" different motors and pinions and predict performance and current draws...

http://home.earthlink.net/~dr.electr...Comparison.xls

This spread sheet appears to be protected. I'm unable to enter any data into it. Can you un-protect it for us or post the password. Thanks.

[WillJames]

Or can you attach it to your post here so we can all download and use it please?

That would be

[ErichF]

Guys,

you need to change the security settings in your Excell.

Go to *Tools*

Then click *Options*

Then Click on the Security Tab

Then Click on Macro Security

Set to Medium or lower.

Close and re-start Excell....it should open up fine.

There is no password.

Erich

Originally Posted by thedubdude

This spread sheet appears to be protected. I'm unable to enter any data into it. Can you un-protect it for us or post the password. Thanks.

[thedubdude]

Go to *Tools*

Then click *Options*

FYI in my version of Excel (Excel 2000) the security is located at:

tools-->macro-->security

In any case changing the security level does work. Sadly the spread sheet requires inputting more information than I have available.

[ErichF]

Are you enabling component data on sheet one? It will automatically enter most of the info when you select a specific motor, battery, esc, etc...


Erich

[thedubdude]

Well I flew my T-Rex for the first time ever today. It was hovering fine (with training gear on) for about 6min and then the motor abruptly stopped.

No damage to the helicopter but I think I fried the motor.

I was using a Chili Pepper 4200KV motor with an 8 tooth pinion gear, a Pheonix 25 ESC and 3 cell LiPo Thunder power. The motor shaft seems pretty bound up and the ESC make feble sounds (is this normal?). In any case I'm pretty sure the motor is fried. So my questions:

1. Why did the motor fry....do I need more teeth on the pinion?
2. Is it normal for the ESC to sound weak after a motor frys....could I also have destroyed the ESC?

Looks like I need to by a heat sink. Coments welcome.

[ErichF]

You may have a shorted motor, in which case you probably did lose your ESC. Sounds like your motor came apart internally and shorted.

As to why? Couldn't tell ya. Depends on a ton of factors, such as current draw (what pitch/rpm relationship were you using), battery health, etc.

Erich

[thedubdude]

As to why? Couldn't tell ya. Depends on a ton of factors, such as current draw (what pitch/rpm relationship were you using), battery health, etc.

Any suggestions on how to trouble shoot this when I get the repaired motor back.

[Electro-Jeffro]

I am flying with a Neumotor MH3500 and 4s 1320 tp pack. I had to put my Jazz 40-6-18 in for a controller due to the BEC being able to handle 4s.

The thing leaps off the ground and the motor is only warm to the touch after a flight.

[thedubdude]

The thing leaps off the ground and the motor is only warm to the touch after a flight.

Is this the experience of others....that the motor only gets warm. My motor was very hot to the touch before it died.

[Hotshot Charlie]

My Hi-Max 2025-4100 only gets warm..... not hot at all. (This was on a Shogun)

[Electro-Jeffro]

The Chili motors are known to get hot. Hovering is tough on all of them. I am running 4s so my amperage is lower.