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Old Jul 24, 2012, 12:09 PM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Awesome!
Even finding new music.
Thanks
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Last edited by IFlyRCs; Jul 24, 2012 at 12:40 PM.
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Old Jul 26, 2012, 04:29 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,854 Posts
Just bought a Radjet 420 ARF. Actually, I pieced it together.

I didnt think I wanted to build it anytime soon but turns out I do.

What servos, battery, motor, and ESC is good for a fast setup? Not looking to hog out foam or make any structural mods, just want something similar or a a little faster than the micro stryker.
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Old Jul 26, 2012, 05:33 PM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Did you watch the video on the previous page?
Stock on 3s is considerably faster.
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Old Jul 26, 2012, 05:36 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,854 Posts
Quote:
Originally Posted by IFlyRCs View Post
Did you watch the video on the previous page?
Stock on 3s is considerably faster.
So what are the stock components? I have no electronics, I pieced together an ARF.
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Old Jul 27, 2012, 02:24 AM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
not sure about esc

hk 5320 1.7 servos
http://www.hobbyking.com/hobbyking/s...dProduct=17540
ap05 motor
http://www.hobbyking.com/hobbyking/s...idProduct=9662
plush 6a
out of stock and not sure it has molex 1.25 connector
prop
http://www.hobbyking.com/hobbyking/s...dProduct=21276
prop adapter
http://www.hobbyking.com/hobbyking/s...dProduct=23227
Rx
http://www.hobbyking.com/hobbyking/s...dProduct=18827
stock battery size 180 2s
http://www.hobbyking.com/hobbyking/s...dProduct=23135
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Old Aug 20, 2012, 03:34 AM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Hi,

I did maiden my cheap Radjet 420 ARF.

Build up from spare parts, that save lot of money as total but mainly in shipping cost.

I was having a micro 5g brushless motor : http://www.hobbyking.com/hobbyking/s...er_2000kv.html

That is much cheaper the the stock motor ~8$ instead of 16$

But it has "only" 2000kV

Interesting, with 300mAh 2S my ready to fly was 70g ... less then the 75g as advertised by HK.

I did maiden with a GWS 4x2.5 propeller ... and power was really modest ... so modest that first hand launch was not strong enough for avoid a crash ... plus the twim was out and I had too much control ... so I did over controlled.

Little crash, relative big damage on the nose ... fixed with some transparent tape.

I did change the hole of the control horns ... put in a 4x3 GM propeller that I was having around since ages ... and this little bird did come alive

Still power was not enough for much aerobatics ... loops only from a dive.
Fly time ... over 10 minutes with a 300mAh 2S ... but 10 booring minutes

So ... final step ... I had some 180mAh single cell ... still never used ..

So I made my own 180mAh 3S ... rated only 15C ... but who cares ...

So ... the bird with 3S did come alive ...

Just checking the price from HK ... order all part cost only 43$ ... and it is less then 200 gram ... so shipping is only 6$

Order it from the PNF version cost 57$ ... and due to over 600g ... it require a 20$ shipping ... and this bigger size and higher cost will also activate the custom 30% taxes.

So .. for me order in parts was a win win

I have made a video of my RadJet 420 with 3S lipo ... I will post on youtube soon ... unluckily I did discover after the flight that 1 horn was louse ... and this did cause some boring trimming on the first part of video ... and then the confidence on the bird was not so high for pull nice aerobatics ... anyhow ... it can be see the vertical capability and the roll rate.

Unluckily I have not unlimited vertical ... even if it go up vertical for 40 meters from level flight before stall ... looping is unlimited

Tchuss

e_lm_70
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Old Aug 20, 2012, 08:30 AM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,854 Posts
What servos and ESC did you use?
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Old Aug 20, 2012, 10:02 AM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Quote:
Originally Posted by johnnyrocco123 View Post
What servos and ESC did you use?
Same as PNP vrsion: tunigy plush 6amp, and digital servo 1.7gram

Only motor and propeller is different then PNP

As Rx I'm using the 5ch FrSky micro 2g receiver

Which weight has the stock pnp? Mine is 51g without battery

Tchuss

E_lm_70
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Old Aug 20, 2012, 12:05 PM
Registered User
Austria
Joined Jan 2004
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Here is a video of my RadJet 420
Hobbyking Radjet 420 Micro Pusher Jet - Custom Cheap Set-Up - 3S 180mAh (5 min 8 sec)


I just finish to replace the 4x3 propeller for a plastic folding propeller ... and going to go back to 2S 300mAh ... it should be a better glider.

With normal propeller ... it really activate an air brake without applying power ...

Tchuss

e_lm_70

ps: Aerobatics stuff are more on the end of video ... I was trimming at start ... I should make a shorter video version, without all the boring video part ..
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Old Aug 20, 2012, 02:44 PM
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Austria
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Experiment with folding propeller was not so good ...

Going back to 3S and 4x3 propeller.

Tchuss

e_lm_70
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Old Aug 20, 2012, 06:13 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,854 Posts
Quote:
Originally Posted by e_lm_70 View Post
Same as PNP vrsion: tunigy plush 6amp, and digital servo 1.7gram

Only motor and propeller is different then PNP

As Rx I'm using the 5ch FrSky micro 2g receiver

Which weight has the stock pnp? Mine is 51g without battery

Tchuss

E_lm_70
Judging the weight and the look of the airframe, I am thinking you are going to want to pull 15-18a on 3S to get this thing moving to a good speed.

I have been sitting on the ARF for a while, just trying t ofind the time to piece together a good setup.
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Old Aug 21, 2012, 03:29 AM
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Austria
Joined Jan 2004
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Quote:
Originally Posted by johnnyrocco123 View Post
Judging the weight and the look of the airframe, I am thinking you are going to want to pull 15-18a on 3S to get this thing moving to a good speed.

I have been sitting on the ARF for a while, just trying t ofind the time to piece together a good setup.
15-18 amperes

Man these little motor are at best rated 3amps

15amps ... there is no little battery that can hold it.

Anyhow 3amp x 10volt is already 30watt ... that for 70gram bird it is already a lot.

Anyhow ... I did change the ESC setting ... now I did activate the brake, and put the middle timing (normal is soft timing)

WOW

What a difference ... I can fell much more power ... I think I have unlimited vertical capability now ... speed is very nice ... and now ... the propeller even if it does not really stop .... it does not active anymore as a air brake.

Nice .... I just change timing to hard now ... tested with a propeller RPM meter ... and I can see a little increase of RPM, using a 2S test battery ... now on a half discharged 2S, I get over 10.500 rpm on the Graupner Sport 4x3 propeller.

In the morning flight ... after 4m30 sec, I have still 3.77volt per cell on my battery ... and motor was not really warm

So ... really happy with my final cheap set up

Going to post a better video soon, for show how is doing my RadJet 420 ... and I guess it is doing better then the stock RadJet .... using 3S lipo and 5g 2000kv motor I think it is a better match then 2S lipo and 5g 3000kv motor

Tchuss

e_lm_70
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Old Aug 21, 2012, 05:07 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,854 Posts
Looking at a different motor of course.


......3S 500mah, more like 10-12amps
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Old Aug 21, 2012, 05:18 PM
Registered User
Austria
Joined Jan 2004
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Quote:
Originally Posted by johnnyrocco123 View Post
Looking at a different motor of course.


......3S 500mah, more like 10-12amps


A 3s 500mah ... is 42g, a 10amp motor is at least 15g more heavy ... so you end up with a bird that is twice more heavy, so almost a flying brick

Tchuss

E_lm_70
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Old Sep 11, 2012, 02:53 PM
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Ben D Wing's Avatar
The Peak District
Joined Dec 2006
3,009 Posts
Having looked back through this thread I've noticed some mention of various CG positions. I would concur that the recommended CG in the manual is too far rearwards (as previously mentioned) and should be at about 220mm back from the nose which brings it on the wing joint line (see pic). Coincidentally, this falls in line with the Mutiplex Funjet's CG position (of which the Radjet 420 is a near perfect miniature, check the wing outline and sweep angles etc). In order to achieve this CG position, the 180mAh Nano-Tech battery has to fit in the rear of the cockpit (see pic) so I've glued a small bit of foam across the fuz to stop it moving about.
To save some weight (every little helps with a small model like this), I took the liberty of removing 3.7g worth (!!!) of decals off the lower surface and as a result the AUW is down to 62g, of which 12.6g is the LiPo (I wonder how much the upper decals weigh?).
I haven't used dual rates, but using the max suggested throws I have 50% expo on the ailerons and 40% on the elevators to assist in smoothing out the flight envelope.
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Last edited by Ben D Wing; Sep 11, 2012 at 03:00 PM.
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