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JWN
09-12-2005, 06:51 AM
I'm having questions about my motor choise for the Katana Mini kit I'm building. I was planning on running a Himax 2025-4200 in a gearbox with a CC 25 ESC and a 3s LiPo that will handle 20-25 amps current. Precision Aerobatics lists the empty weight at 13oz., but I'm seeing reports of 25-28oz flying weight. I'm not exactly sure how people are getting them that heavy as mine feels pretty light. I would like to be able to do some pretty serious 3D, or at least have the power to fly it that way. I would idealy like to be able to hover the model at less than 3/4 throttle yet still have enough top speed to have fun making low highspeed passes.

What would you folks recommend?

JWN
09-12-2005, 08:10 PM
I weighed all of the components of the model this morning. Though I did not have the receiver on the scale, and I used a 4015 motor instead of a 4025, the wheel pants were weighed (though I do not plan to use them) and all of the small parts were still in their bags. Give an take all of that and I'm confident my target weight of just under 25 oz. is accurate.What am I looking at for motor, geared inrunner or outrunner, and battery to make this model a 3D machine with moderate top end speed?

Dr Kiwi
09-12-2005, 10:46 PM
I don't think a 2025 will cut it - I am wondering if you could use a 2825-2300 - admittedly it is a hefty motor (169g with Cobri box) but I reckon you need at least 35-40oz thrust to be able to hover well - I bench tested a Himaxx 2825-4200 (23A) in a 2.5:1 Cobri box: with an 11x7 GWS HD it produced:

10.8v, 21.30A, 229W, 7470rpm, 49.5mph, 1203g (42.36oz), 5.25g/W

A Mega 600/20/8 (138g) is another possibility: 11x7 APC E

10.3v, 20.50A, 207W, 7020rpm, 46.5mph, 1124g (39.58oz), 5.43g/W

Cheers, Phil

JWN
09-13-2005, 02:07 PM
Phil,What is the prop speed reported for my Himax 2025-4200 w/ 6.61:1 gears spinning a 12X8 prop on a 3s battery? Maxx Products shows this setup in their charts with 42 oz. of thrust. It sounds promising, but then again it may only have a 29 mph speed which is way too slow.

The numbers on the 2825 do sound good, but you are right about it's weight. I've seen a few other motors in the 200w range which weigh considerably less.

Dr Kiwi
09-19-2005, 02:11 AM
Phil,What is the prop speed reported for my Himax 2025-4200 w/ 6.61:1 gears spinning a 12X8 prop on a 3s battery? Maxx Products shows this setup in their charts with 42 oz. of thrust. It sounds promising, but then again it may only have a 29 mph speed which is way too slow.

The numbers on the 2825 do sound good, but you are right about it's weight. I've seen a few other motors in the 200w range which weigh considerably less.

If you believe Motocalc:

Motor: HiMaxx HA2025-4200; 4200rpm/V; 0.75A no-load; 0.075 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: geared Himaxx; 12x8 (Pconst=1.31; Tconst=0.95) geared 6.6:1 (Eff=95%).
Motor Amps = 18.2
Motor Volts = 10.3
Input (W) = 188.3
Motor RPM = 36840
Prop RPM = 5582
Thrust (oz) = 35.3
PSpd (mph) = 42.3

*Interestingly, if you use our thrust calculator http://www.gobrushless.com/testing/thrust_calculator.php its not to far out: 33.2oz @ 5582rpm with a 12x8 APC E

Even if you change the prop constant to APC it doesn't make much difference

Motor Amps = 16.5
Motor Volts = 10.4
Input (W) = 171.2
Motor RPM = 37926
Prop RPM = 5746
Thrust (oz) = 34.7
PSpd (mph) = 43.5



Cheers, Phil

JWN
09-19-2005, 02:31 PM
Thank you Phil!

Even though the motor is rated at 175W, I'm seeing more and more people recommend it for the KM stating it really pulls the model around well. And these are people who are flying a lot of mixed 3D and pattern/IMAC type aerobatics. I'm going to give it a try and see how it does for me. I've already setup the stick motor mount and modified an MPI spinner to work with the HiMaxx gear box.

watt_the?!
09-22-2005, 11:58 PM
fwiw we tested and setup two setups for the fliton JJ.

himax 2025-4200 on 5.5:1 box and 12 x 6 prop was fantastic at 19A.

superior to the 6.6:1 setup in that it sucked more amps but not over the top.

actually the best gain- some 12-20% over this setup would be to get rid of the gearbox altogether and go for an outrunner.