Anyone know how many RPM's the Axe CP head is spinning at full throttle?

Heck with it. After a lot of googling, I've decided I'm going to order a brushless motor/pinion shooting for 2000 rpm head speed. I counted 45 teeth over 1/4 of the spur gear (counting from the center of one spoke to the center of the second spoke I got to), making the spur gear 180T by my count.

So what BL/Battery combo are you going to?

Do not know head speed but my new 11.1v LiPo runs heli at higher head speed and heli is more stable. Keep us posted as to what you come up with. Do you need to get a brushless ESC to go with that brushless motor? If you do need a new ESC then will you need to replace the 3 in 1 board with all new electronics?

I'm probably going to keep on using Thunder Power 1320's.

The 3-in-1 occupies a 3-pin connection on channel 3, and on channel 4 a single pin connects to the signal wire for rudder control. By unplugging the 3-in-1 from channel 3, you remove the power source of the receiver and servos. Plug a brushless ESC into channel 3 and the ESC's BEC will power the receiver and servos. The 3-in-1 will just have one pin plugged into channel 4 and will act as the gyro/speed control for the tail motor. If the 3-in-1 needs the throttle input to function correctly (they call it a mixer/esc/gyro, but I'm not at all sure what it actually mixes), then I'll try a using a 'Y' on channel 3. Or I may get rid of the 3-in-1 and buy a small 2-amp or 5-amp brushed ESC and use it along with a Telebee HH gyro I have laying around. Not sure what motor I'll be going with yet, just aiming for 2000 rpms head speed and about 150 watts of power.

Can anyone tell me what the advantages/disadvantages of using [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHHM6&P=ML]this motor[/link] as a direct drive tail might be? Other than being really inexpensive, I believe it will be a drop-in replacement.

***EDIT: retyped to clarify something inadvertently deleted.

What battery do you use? If its the one from tower can you get me the sku number on the package? Im not sure i got the right one. Thanks!!

Thunder Power 11.1v 1320mA 3 cell LiPo. Very happy with this battery. Going to limit my time to 10 minute flights so I do not discharge battery too much and damage it. I did fly 12 minutes and battery was still going strong but I will play it safe and stop at 10.

The 3-in-1 probably does need the throttle input to function correctly: it mixes the throttle with the gyro to get the output for the rudder motor.

As for that direct drive tail motor, the wording on the web page seems to imply that it was only designed for 6 to 7.2V (also, BPHobbies has a lot of documentation on these types of motors).
The 10.8V NiMH or 11.1V Lipo battery will probably fry it unless
you do something like install some resisters/diodes in series with that tail motor to drop the voltage.

How about the motor from [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXHHP5&P=7]this fan[/link]? It's rated for 9.6 to 10.8V. A guy put this on a Blade CP Pro and has a crazy video on rcgroups. Search for the thread over on rcgroups called '3D Video of BCPPro.'

As far as brushed motors go, is their voltage rating related to their kV?

I think the fan sounds okay.
One thing to keep in mind is that some of those ratings are propeller/rotor dependent: it may be okay with one propeller,
but another propeller may cause it to draw too much current.

As far as the kV, as far as I know, that just gives you an indication of how fast the motor will spin per volt applied when under no load.

What I meant about the kV: You never see a kV rating given to brushed motors. So does the voltage rating of a brushed motor have something to do with the motor's speed?

I think I'll use the motor from that fan with a GWS 3x2 or 2.5x2 propeller.

I agree, the kV rating is hard to come-by on brushed motors.
I found some data to estimate the kV for GWS brushed motors at:

http://www.bphobbies.com/view.asp?id=A0320095

http://www.bphobbies.com (under motors) in general has a lot of data on
Feigao brushless motors and GWS brushed motors.

http://www.gwsus.com/english/product/product.htm
also has data on GWS brushed motors.

One thing about the voltage rating on a brushed motor:
it often seems to be not a single absolute number.
It seems to be more of:
"if you run at this voltage with this propeller, it will draw this current (which if too much, will overheat the motor)"
So each propeller/motor combination will probably have a certain maximum allowed voltage
(which may depend in part on how much air flow the motor gets)

So it is not obvious to me what the relationship is between the voltage rating and the brushed motor's speed.

One detail on the voltages in these charts:
these seem to refer to the actual voltages that the motor sees,
as opposed to the rated voltage on the battery, which as you may already know, can be quite different
(for example, I have seen my 9.6V NiMH batteries produce ~8.5V under load).

I put in a brushless motor. I used a go brushless motor 14 turns connected Y. It seems to spin about the same RPM as stock. For the tail to work I had to use a servo Y adapter for the 3 in 1 also needed to use a Y to supply power to it. So far it is working great. I may drop it down to 13 turns for a little higher head speed when I get better at flying it.