Time for me to go brushless.... What size main motor do I get? I cant seem to understand the whole Kv to size relationship. Whats a good sized motor to get for just flying around? Im not doing any aerobatics yet either...

hey man, check this out.. I haven't watched the whole thing yet...

http://www.youtube.com/watch?v=s_UnWXkEGhA

What heli are you talking about?

Here's some good info on an earlier thread.

http://www.rcuniverse.com/forum/m_52...ushless/tm.htm

KV is the rpms the motor will want to turn at a given voltage. 1000 KV would turn 1000rpm at 1 volt and 10,000 rpm at 10 volts. The motor will try to turn that rpm no matter what is slowing it down. Say you have a big prop on a motor slowing it down, the motor will draw more amps to get it to turn faster. Take the prop off, and it draws less amps, even near none.

You need to balance the gear size, rotor size, motor size, and KV so you don't draw too many amps and cook your equipment.

In the above link there is a calculator to help you.

The AXE CP has a 180 tooth main gear. At 2500 rpm that's 450000 teeth per minute. With a 10 tooth pinion you would need a 4500 KV motor at 10 volts. Just as an example.

Seems like at least a 2200kv would suffice for non-aerobatic flying.
Now I found an Align 430L Brushless Motor - 4050KV on eBay for $30 is this motor overkill??
I would need an ESC that puts out as many amps as the motor can draw correct?

P.S. Im flying an Axe CP in case you didnt know....

ATB,
I'm running a [link=http://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idProduct=3849]KB20-40-17L 3400kv[/link] BL motor from United Hobbies. I'm working on a detailed BL conversion article based on my experience with the Axe, but it's gonna take a little while. Anyway with this motor the thing is a animal. It's fairly warm at the end of a run (160-170*F), but if it fails it's only $15.

I finally got fed-up trying to find info on this subject and ordered a tach to check RPM myself in addition to my meters for volts, amps, temp, and weight I should be able to nail this down. I basically used this set-up was a point of reference. At this point the head is really zipping along. I'm thinking of going to one of these two motors ([link=http://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idProduct=4875]Feigao 130-L (2040)Size 20T 2900kv[/link] and [link=http://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idproduct=4211]KB20-40L-20L 2900kv[/link]) to reduce headspeed, but I'll wait for the tach so I can take some readings to be sure. Being stuck with only the OE 14T pinion also adds to this challenge.

...for now to be continued...

Well I went ahead and bought an Eflight Hacker 3700kv brushless motor (model number E3-37) and a GWS 15amp continuous ESC (model number ICS-480Li).

Now I know that the Hacker may be a bit too powerful just for normal flight but that what having control is all about right? But at least when I start getting into aerobatics I'll already have a motor with punch to it. Another side benefit would be higher head speeds which will create more stability. If the headspeed is too much then I'll just switch to a smaller pinion.

Now on to the tail motor.... Can I run it off the OEM 3-in-1 board or do I have to get a separate ESC for that? Do they make brushless motors that small? If they do point me to where I can get one.

Have you found any pinions that will work? I haven't had any luck in that area. I've heard it's a weird pitch or something.

I'm running a BL tail motor. It's an [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWW3&P=0]Ammo 12-30-4110[/link], but I meant to actually get an [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWW2&P=0]Ammo 12-30-3850[/link]. The 4110 has alot of power. I'm sure they both do. I'm using it with a GY240 and as long as the T/R is going before the main blades she doesn't spin, but if the main motor starts first the surge from the gyro causes the tail to kick. I figured the kick would be a little less with the 3850. The tail now has a ridiculous amount of power though.

I've noticed with my 3400Kv BL the headspeed has increased quite a bit. Before with the OE motor the blades would stall at about 7/8 throttle, now with the increased headspeed it doesn't even stall. The problem is that drag increases exponentially so the head speed is drawing some amps, plus that extra torque has the T/R working harder. My run times decreased by about a minute or so with this set-up. I know a computerized radio would go a long way toward optimizing the Axe with a BL motor, but I know I still need to get the headspeed close.

Well I just tried out my new Glo-Bee tach. I actually took my reading from the paddles with the blades removed. It's a bit safer that way. As a light source I used my led flashlight. I think it worked well because the tach zeroed out right away when pointed at the flashlight.

Anyway with [link=https://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idProduct=3849]this[/link] motor my Axe's RPM's in a hover are 2880 and at full throttle 3120. [X(]TOOOO HIGH!!![X(]
I used DarkHorses BL calculator, but since the Axe isn't up there I'm thinking that to spite the fact I got the tooth-counts right I used the hornet set-up values so the gear circumferences were probably off. Anyway I'm going to try [link=https://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idProduct=4875]this[/link] motor next and see what happens. I wish there was a better method other than trial and error.

I would think that would be a perfect motor. If you could find a smaller pinion, it would slow down the head speed. Isn't a pinion easier to get than a whole new motor?

EDIT:

Here you go: http://www.allerc.com/product_info.php?products_id=1487

10 tooth, 2.3 mm, 64 pitch, brass pinion...
They're on backorder, but what the hey.

I agree, but I haven't found any that would work. I tried ordering pinions from Tower already. I found some that looked close and they were, but not close enough. Somebody posted that the gears are some kind of weird pitch like 55 or something. So far I've seen lots of suggestions, but I haven't found any post saying they found one that worked. I saw a video of a guy doing a BL main motor install and he used a E-Flite 370 4100Kv motor. He used the 10T that came with the motor. He said he also got a had a 12 tooth (I think it was 12?) with the motor, but it didn't mesh smoothly/properly. That comment alone makes wonder how well the 10T really worked. So with all that I ordered another motor. The one I ordered was only $15 so replacing it is no big deal. The [link=https://www.unitedhobbies.com/UNITEDHOBBIES/store/comersus_viewItem.asp?idProduct=4875]Feigao[/link] looks like it should work pretty good. A machinest once said to me that if it only takes two tries to get it right your doing pretty good. So we'll see. I probably just jinxed myself, but I'm keeping my fingers crossed.

Isnt a higher headspeed better (as in creating more gyroscopic effect/stability)? Now I don't mean going into insane speeds to where the parts come under undue stress from holding themselves togeher.

I hope I can get the stock pinion off the stock motor so I'll just use that.

The higher headspeed does help stability, but like anything else you can have too much of a good thing. It also makes the cyclic more sensitive. Now if I were an experienced 3D pilot who didn't crash then 3000 RPM might not be too bad, but I'm not. So if those blades hit something then they're hitting it with alot more force which results in more damage. And like you said the added stress on the parts isn't going to be helpful either. It also takes a while for it to spin down so even if I cut throttle before a crash it would still hit pretty hard.

My stock pinion was a little stubborn. Anticipating this I bought a GWS micro heli pinion puller from Helihobby, but they're out of stock right now. It worked really well.

Hey ATB I justed posted a spin-up vid of my Axe [link=http://www.rcuvideos.com/item/YLSJVQLWC72NR3BW]here[/link]. I just have to adjust the dragbolt tension so it doesn't vibrate on spin-up/down.

Sounds like you've got lots of head speed with that set up.

You'll have to get it outside and let it get some forward flight.

Wouldn't the pinion work that I linked you to in the above post?

You can say that again. That's what 3000 rpm sounds like. I'd rather have longer flights though as I said I'm no where near go enough to take advantage of that headspeed.

I'd love to. I had it outside the other day. I can't really do FF very well yet. I did goose the throttle though and it shot up like a rocket.

Honestly I don't know, I've tried several pinions already and none of them mesh properly. I haven't tried your suggestion yet so they might work.