SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Apr 29, 2008, 09:06 AM
www.rctodayshow.com
JustPlaneChris's Avatar
Austin, TX
Joined Sep 2005
11,509 Posts
Quote:
Originally Posted by dude_109
I'm a little confused with "KV" rating. I understand what it stands for but higher or lower doesn't really make sense to me. Seeing how 450 helis want to use around 3800 and lighter FPs need it in the 4000+, is higher better for a lighter heli? Reason I ask is I have a 4500kv motor (from cnchelicopter with 15A ESC combo) that I was going to use for the Compy. Will it be o.k. or will it drain my battery too fast?
KV simply is the rpm the motor turns per volt applied (in a no-load condition). You choose the Kv value of your motor based on the gear ratio of the heli and the desired head speed. Fixed pitch helis make that choice more difficult than CP, because you can't just choose a gear ratio that gives you a targeted head speed and run it wide open all the time. With a FP setup and a high Kv motor, you'll be spending a lot of time at very low throttle settings. That is inefficient and will make both the motor and ESC run hot. It's better to use a Kv that will put you in the desired rpm range (~1600 rpm for these guys) somewhere around mid-stick or slightly above.

Now, all that said I flew my FP with an ARC 130 / 8T combo (it's about the same KV as the motor you have). Give it a try, worst it can do is run too hot.

-Chris
JustPlaneChris is online now Find More Posts by JustPlaneChris
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 29, 2008, 09:53 AM
Registered User
dude_109's Avatar
Houston, TX
Joined Jan 2008
5,779 Posts
JPC,

Yeah, not being a CP murkys the KV situation. I listened to your ATTF episode but was still fuzzy on the concept.

I also watched the vid of your Compy FP with the 130. Your punch out power is much much higher than I think I would ever need. In that case, would I be able to fly on a 110 or even an 80 (probably to small) if all I'm after is smooth flying...like you usually see people flying with a scale fuselage. That way I can get the motor to higher rpm and nearing their efficiency range.

The variable I'm after is longer flight time and cooler running motor (shorter wait between packs).

Considering how I want to optimize everything, sounds like I need to invest in a data logger...
dude_109 is offline Find More Posts by dude_109
Reply With Quote
Old Apr 29, 2008, 10:51 AM
Registered User
USA, CA, San Diego
Joined Jun 2007
692 Posts
Quote:
Originally Posted by dude_109
That way I can get the motor to higher rpm and nearing their efficiency range.
It's not necessary to get too obsessed about running the motor at peak efficiency. It depends on the motor, but at least some brushless motors only lose a few percentage points of efficiency running at as low as half throttle.

FWIW, I'm flying my Compy with a 3100kV motor and 9T pinion at about 60% throttle, and my motor only started getting hot when the bearing started crapping out (probably from pinion dust, watch that gear mesh. You want it to be as tight as possible without dragging. As has been noted, the stock Compy main gear is usually too warped to be usable.)
ccdengr is offline Find More Posts by ccdengr
Reply With Quote
Old Apr 29, 2008, 11:07 AM
Registered User
USA, Eastern Ohio
Joined Jan 2005
976 Posts
As to gear mesh, if you take a strip of paper and pull your pinion up tight with the main gear with the strip between the two, your gear mesh should be good. That will give you app. .004" gear play. Hope this helps someone.
Thanks
Tag1260 is offline Find More Posts by Tag1260
Reply With Quote
Old Apr 29, 2008, 11:09 AM
Registered User
Joined Mar 2008
72 Posts
I know people have commented that the compy is a nice stable heli. Does the compy fly like a bigger heli, like a 400 series, instead of a twitchy 300 sized heli?

Thanks,

Dan
dhoff002 is offline Find More Posts by dhoff002
Reply With Quote
Old Apr 29, 2008, 11:36 AM
I can drift a heli
maarset's Avatar
USA, CA, Sacramento
Joined Mar 2005
2,366 Posts
I think mine flew like a bigger heli. But the compy is the biggest I have ever flown. The Compy flys very stable and percise. You can be very accurate with it. I can easily hover nose in with the Compy compared to the HBFP.
maarset is offline Find More Posts by maarset
Reply With Quote
Old Apr 29, 2008, 12:52 PM
Registered User
dude_109's Avatar
Houston, TX
Joined Jan 2008
5,779 Posts
Quote:
Originally Posted by ccdengr
It's not necessary to get too obsessed about running the motor at peak efficiency. It depends on the motor, but at least some brushless motors only lose a few percentage points of efficiency running at as low as half throttle.
Gee, I guess the efficiency curve is pretty flat around optimum then. If that's the case, playing with pinion size would have a much bigger effect.
dude_109 is offline Find More Posts by dude_109
Reply With Quote
Old Apr 29, 2008, 02:09 PM
Registered User
USA, CA, San Diego
Joined Jun 2007
692 Posts
Quote:
Originally Posted by dhoff002
I know people have commented that the compy is a nice stable heli. Does the compy fly like a bigger heli, like a 400 series, instead of a twitchy 300 sized heli?
This is so dependent on personal preference, setup, and skill level as to be really hard to answer. In my experience with HBFP, King 2, Compy, and Trex 450, the Trex is the most stable, followed by the Compy, the HBFP, and the K2 at the bottom. But indoors I would call the HBFP extremely stable; it's only hard for me to fly in FFF or in wind because it doesn't have much extra power or control authority, stock anyway.

An FP is probably never going to be as twitchy as a comparably-sized CP.
ccdengr is offline Find More Posts by ccdengr
Reply With Quote
Old Apr 29, 2008, 02:15 PM
Registered User
USA, CA, San Diego
Joined Jun 2007
692 Posts
Quote:
Originally Posted by dude_109
Gee, I guess the efficiency curve is pretty flat around optimum then. If that's the case, playing with pinion size would have a much bigger effect.
Well, YMMV since the efficiency curve shape can be different for any particular motor and it's usually not provided by the manufacturer, so you have to figure it out with testing. And there are only so many pinion sizes available. I'm with JPC, give it a try and see what happens.

One thing that's nice about the Compy is that since practically any motor you can use is somewhat overpowered, if you hit the throttle you can nearly always get a good climb rate. On my stock HBFP I would frequently be at max throttle and be unable to avoid a crash.
ccdengr is offline Find More Posts by ccdengr
Reply With Quote
Old Apr 29, 2008, 02:58 PM
Registered User
jamesppp's Avatar
Georgia, USA
Joined Jan 2008
3,770 Posts
What blade lengths are readily available for the Compy? Does it use 235-250mm symetrical blades?
Another question, is there a domestic supplier for this heli yet? If not, where is the best place to pick one up?
Thanks,
Jimmy
jamesppp is offline Find More Posts by jamesppp
Reply With Quote
Old Apr 29, 2008, 03:37 PM
US Navy AT2 1987-1995
USNAviationjay's Avatar
Houston Texas
Joined Mar 2008
1,329 Posts
Sigh... My new toy still hasn't arrived..

7 shipping days from a fairly close state.. bah.. US Mail 4 teh lose.
USNAviationjay is offline Find More Posts by USNAviationjay
Reply With Quote
Old Apr 29, 2008, 04:14 PM
www.rctodayshow.com
JustPlaneChris's Avatar
Austin, TX
Joined Sep 2005
11,509 Posts
Quote:
Originally Posted by jamesppp
What blade lengths are readily available for the Compy? Does it use 235-250mm symetrical blades?
Another question, is there a domestic supplier for this heli yet? If not, where is the best place to pick one up?
Thanks,
Jimmy
Hey Jimmy! Tired of your Swift already? These little FP birds are fun, I really need to get one back in the air.

Most guys are either using the flat bottom woodies that come with the Compy kit, or the Kyosho M24 plastic blades. In theory you could use symmetrical blades with pitch washers to set some positive pitch, but they wouldn't make much lift and would require pretty high head speed.

-Chris
JustPlaneChris is online now Find More Posts by JustPlaneChris
Reply With Quote
Old Apr 29, 2008, 04:22 PM
Registered User
Joined Mar 2008
72 Posts
what about the compy compared to the blade 400? I was thinking about getting another heli. I either want to get the blade 400, mini titan, or a compy fp 300.

Not sure which is best, the blade 400 seems like a good deal though, for the price.

Thanks,

Dan
dhoff002 is offline Find More Posts by dhoff002
Reply With Quote
Old Apr 29, 2008, 05:02 PM
Registered User
USA, CA, San Diego
Joined Jun 2007
692 Posts
Quote:
Originally Posted by dhoff002
what about the compy compared to the blade 400? I was thinking about getting another heli. I either want to get the blade 400, mini titan, or a compy fp 300.
You can't really compare the Compy to the other two; I see the Compy as complimentary to a larger heli, not instead of. The Compy can probably be flown in a smaller area, but I end up flying all my helis in fairly large open fields anyway. I'm not sure when I prefer flying the Compy to my Trex; they're both fun, but at this point I'm probably a little more relaxed with the Compy.

If you don't have a good radio, the B400 is a good package to start with, but I haven't flown the B400.

You really need the Compy and a 400-class heli.
ccdengr is offline Find More Posts by ccdengr
Reply With Quote
Old Apr 29, 2008, 05:57 PM
Registered User
jamesppp's Avatar
Georgia, USA
Joined Jan 2008
3,770 Posts
Quote:
Originally Posted by JustPlaneChris
Hey Jimmy! Tired of your Swift already? These little FP birds are fun, I really need to get one back in the air.

Most guys are either using the flat bottom woodies that come with the Compy kit, or the Kyosho M24 plastic blades. In theory you could use symmetrical blades with pitch washers to set some positive pitch, but they wouldn't make much lift and would require pretty high head speed.

-Chris
Chris, im not tired of any of them yet..I am looking for some blade alternatives for the Parkmite. I bought a Parkmite kit yesterday to go with the RTF one I bought last week. Im an idiot.

Are there any M-24 type symmetrical blades available. Im going to get some 240mm woodies from Dan Rosella when he gets a new undercariage upgrade for my Parkmite ready.

I want to get a Compy too. I was wanting a V2 cp model but dont really know if they are available yet so I thought an FP would be more flyable for me at this stage of my ability. Right now the HBFP is the only single rotor heli I can really fly around.

The next pretty day off with light wind, the swift is going to do some FF or die trying.
jamesppp is offline Find More Posts by jamesppp
Last edited by jamesppp; Apr 29, 2008 at 06:37 PM.
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Motor/ESC combination for Compy 300 FP? generalbacardi Micro Helis 1 Oct 31, 2008 10:43 PM
Sold Excellent Compy 300 FP RTF with Lots of Extras!!! - Blowout Price - $170 SHIPPED cdbarnett Aircraft - Electric - Helis (FS/W) 14 Nov 16, 2007 06:16 PM
Discussion Compy 300 FP coming out? generalbacardi Micro Helis 2 Nov 09, 2007 12:50 AM
Video Compy 300 FP video testing the Esky beefed up paddle frame and Compy swash electric-flyer Electric Heli Talk 0 Oct 04, 2007 10:41 PM
Cool Compy 300 FP video electric-flyer Micro Helis 0 Jul 17, 2007 03:24 PM