|Nov 05, 2004, 01:16 PM|
Joined Sep 2004
Souping-Up a T-Hawk
I have a T-Hawk "pusher", using the original 380 brushed motor with a 5"x3" prop and four 1100mA NiMH seven-cell packs. I prefer to stay with the T-Hawk, because it's durable, which my level of expertise requires. I need to take off from and land on a dirt strip that is half the length of a baseball diamond. The plane's nineteen ounces barely clear the grass, and it has flipped over a couple of times. I would like to replace the 380 with a GoBrushless out-runner because I want to build the motor.
I looked at their motor database to see what might work. Wow! Those numbers are all over the place. Just when I think I'm "getting it" I come up with a motor that doesn't.
All I want to do is come up with a brushless outrunner that will lift the T-Hawk quickly and allow it to climb with authority . . . probably around twenty to thirty ounces of thrust with a five inch prop (to clear the tailboom.)
I need to know what parts I should buy, number of turns, guage of wire, number of stators and poles, size of can, width and length of shaft, battery configuration, whether I need ball bearings, etc.
Is there anyone out there who can help.
|Nov 05, 2004, 01:32 PM|
If you have a 5" prop you'll need that prop to be spinning at 30,000rpm or more to get 30oz thrust! There are no outrunners that I know of which could do that and CERTAINLY there is no CD-ROM motor which can get anywhere near it.
|Nov 05, 2004, 01:35 PM|
>>"Is there anyone out there who can help."<<
Well, I am no expert, but I have had experience with the T-Hawk. I bought it at the urging of one of our club's teen hot shots. He has since buried his T-Hawk, I continue on with mine, enjoying it, having made some notable modifications to it.
1.) Forget about taking it off from the ground. This plane was built to be handlaunched. The landing gear is a joke, so remove it and learn to land without benefit of wheels. It is better training in the long run.
2.) Battery packs available from the supplier were either 600 mAh or 900 mAh 7 cell packs. The 900's are by far the best to work with. However, you could use a stronger pack. Consider the GP 1100 packs, Firebird configuration, from www.maxamps.com A good pack, best price around, I paid $16.95 or a pack, complete with 16 gage wire and Deans Ultra female plug. You will pay $24 and up for 900's elsewhere.
3.) Get rid of the Tamaya type battery connections that come stock with this plane. Consider Deans Ultra's.
4.) For a cheap but effective boost in power, consider the special speed 400 motor from www.trickRC.com These are motors that are specially reverse wound for pusher operation, and also have some advance built into them for more power. They cost $9.95, alot cheaper than looking at brushless motors.
5.) I continue to use the original prop design, supplied with the plane. I feel they are the best for this plane, thrust-wise and clearance wise.
6.) I have never had a problem gaining altitude with the plane, even in stock configuration. My neighbor had it up and soaring in a thermal, for a total of around 18 minutes. I fly it WOT, burning up as much sky as possible, to include snap rolls, loops. 8-9 minutes under those conditions.
Please note the following warnings:
A.) If you go with a special Speed 400 as described above, you may have to change out the speed controller, as this motor will pull more amps than the 380 OEM motor.
B.) If you go with a brushless motor, you will be REQUIRED to change out the speed controller, one built specifically for brushless motors. These controllers, in the amp range you would need, are expensive, starting at around $65 and going UP!
Attached are some photo's of my T-Hawk. Over 100 flights on it, only one really serious lawn-darting event. Also, go into the Parkflyer forum and search for T-Hawk. There is or was a good thread on this plane.
Oh yes, almost forgot, there are ways to make the T-Hawk much more responsive, but that is not your goal at this time. Learn the basics first.
Good luck, keep in touch
|Nov 05, 2004, 01:37 PM|
Try this for a ridiculous scenario - a 2T Mega motor could get you 30oz thrust, but on 3s it requires 520 Watts-in @ 61A!!!!!
Motor: Mega ACn 16-15-2; 4600rpm/V; 2.97A no-load; 0.012 Ohms.
Battery: Thunder Power 1900 (G2); 3 cells; 1900mAh @ 3.7V; 0.012 Ohms/cell.
Speed Control: Castle Creations Phoenix 25; 0.0065 Ohms; High rate.
Drive System: Himaxx; 5x4 (Pconst=1.11; Tconst=0.95) direct drive.
Airframe: Anything you want.
Conditions: Sea Level, 29.92inHg, 59°F
Batt Amps = 61.4
Motor Amps = 61.4
Motor Volts = 8.5
Input (W) = 521.2
Loss (W) = 83.8
MGbOut (W) = 437.4
MotGb Ef(%) = 83.9
Shaft Ef(%) = 64.2
Prop RPM = 34444
Thrust (oz) = 30.2
PSpd (mph) = 130.5
|Nov 05, 2004, 01:48 PM|
>>"Try this for a ridiculous scenario "<<
Definitely.....no disrespect intended. Your statistical analysis on this and other setups is both impressive and very much appreciated.
However, I would question the direction of plowing more $$$$ into the plane than what you paid for it. There is one fellow who installed a Mega 16/15/3 with outstanding results, using a LiPoly pack. There was a video of it that I have on file. There is only so much power you can channel thru the stock prop. I have tried some alternate Cam Speed props, but the original wide 2 blade prop has given best performance.
Cooling of the motor in this model is not good, I have run into the problem of overheated motors. Otherwise, lots of fun, a good trainer but it can bite you if you turn too sharp, at low altitudes.
|Nov 05, 2004, 03:08 PM|
Why 30 ounces of thrust?!? Heck, if you could get half of that it would be a pretty good boost in performance, and with that prop clearance limit (I think, if it were a bit further aft you could go to 6 inches - the stocker is more like 5.7 than 5) even that's a challenge. Besides, think of the awful shriek that would make!
Anyway, I think Doug's suggestions are good ones, and taken together will yield quite a boost in performance. I also concur on his comment that motor cooling is not great in the plane.
I LIKE being able to take off from the ground and so made a new gear for my T-Hawk from 1/16 music wire. It took some fussing to get it in, and it's still not strong enough, really, but it's way better than the stock one. I plan to make one from .078 music wire, but I'll have to pull the servo tray out and widen the gear slot before that will work.
If you really want to wind your own motor there's a new kit just released at Aircraft-world.com that might yield a 100-140W motor that would be a big boost in performance. The trick would be choosing a wind that works best turning at, say, about 14000 RPM. At just over 24mm in diameter it may fit with adequate clearance from the indentations that attempt to support the stock motor. http://www.aircraft-world.com/shopexd.asp?id=2746
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