HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Sep 12, 2012, 05:44 AM
Registered User
Ben D Wing's Avatar
The Peak District
Joined Dec 2006
3,002 Posts
As an addition to my last post: With the CG set at 220mm back, the left elevon has approx +0.5mm reflex and the right +1mm, but even so I think the balance point could benefit with going slightly further forward as the RJ is slightly pitch sensitive and does not pull out of a dive and this of course indicates a neutral CG.
After balancing the prop many times, my RJ has always displayed a resonance at full throttle with the dome prop nut looking very blurred. After trying many different props, I decided to swap the prop nut with a standard hex alloy nut from my spares box, and guess what, the vibration issue was cured! Now the motor is smooth through the whole rev range and this can only be good for the motor, Rx and servos as in my experience long term vibration usually causes some sort of failure. It seems that the supplied dome nut is not very accurately machined, but then I've also found this phenomenon with larger dome nuts of varying makes.
Finally, having never bothered to measure the motor's output before, I dropped my Wattmeter across it and at WOT it's drawing 3.1A with a power level of 23.5W (in). This may not sound much, but it does have a PWR of about 173W/lb and gives the RJ excellent vertical performance. And talking of performance, it's uncanny that this little RJ has almost identical flying properties to it's larger cousin, the original Multiplex Funjet. Well done HK!
Ben D Wing is online now Find More Posts by Ben D Wing
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 12, 2012, 06:16 AM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Quote:
Originally Posted by Ben D Wing View Post
As an addition to my last post: With the CG set at 220mm back, the left elevon has approx +0.5mm reflex and the right +1mm, but even so I think the balance point could benefit with going slightly further forward as the RJ is slightly pitch sensitive and does not pull out of a dive and this of course indicates a neutral CG.
After balancing the prop many times, my RJ has always displayed a resonance at full throttle with the dome prop nut looking very blurred. After trying many different props, I decided to swap the prop nut with a standard hex alloy nut from my spares box, and guess what, the vibration issue was cured! Now the motor is smooth through the whole rev range and this can only be good for the motor, Rx and servos as in my experience long term vibration usually causes some sort of failure. It seems that the supplied dome nut is not very accurately machined, but then I've also found this phenomenon with larger dome nuts of varying makes.
Finally, having never bothered to measure the motor's output before, I dropped my Wattmeter across it and at WOT it's drawing 3.1A with a power level of 23.5W (in). This may not sound much, but it does have a PWR of about 173W/lb and gives the RJ excellent vertical performance. And talking of performance, it's uncanny that this little RJ has almost identical flying properties to it's larger cousin, the original Multiplex Funjet. Well done HK!
It is looking to me that the 5g 2000kv motor on 3S is a better choice ... I'm flying with a 3S 180mAh ... and I have lot of power.

If you get vibration from your motor ... you better need to check the mount ... I did originally not glue the motor mount on the fuselage ... and I was having bad vibrations ... now with one side glue, and a line of transparent tape for reinforce & tight the foam around the mount ... it is better.

Stock propeller, as well ... it is not as good as a Graupner Cam Speed 4x3 that I had in my RC box since ages ...

Tchuss

e_lm_70

ps: I don't have the stock motor, I build my R420 from spare parts ... including the propeller and propeller adapter ... but possibly the propeller save adapter from my 5g motor is even better then stock adapter ... I will give a try with a normal nut if it will get better ...

pps: My 3S RadJet 420 , without removing the bottom decals (they really help me for orientation) ... in ready to fly configuration is 69g ... so ... still pretty light ... I get over 5min full power fly with my 180mAh 3S lipo. .... I can fly also with 2S 300mAh ... this is over 10min ... if I use the stock propeller , I can even fly longer ... but not sure I can have enough power with 2S set up


pps: Do you have an anemometer or a RPM meter ? ... I'm curios to know how many RPM or how much wind you can produce with stock power ... my guess it is that 3S 2000kv is more efficient then 2S and 3000kv ...
e_lm_70 is online now Find More Posts by e_lm_70
Reply With Quote
Old Sep 12, 2012, 06:50 AM
Registered User
Ben D Wing's Avatar
The Peak District
Joined Dec 2006
3,002 Posts
A quick check with an anemometer produced 31.6 MPH (50.8 KPH) using the stock set up.
Don't have a Tacho.
Ben D Wing is online now Find More Posts by Ben D Wing
Reply With Quote
Old Sep 12, 2012, 08:41 AM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Quote:
Originally Posted by Ben D Wing View Post
A quick check with an anemometer produced 31.6 MPH (50.8 KPH) using the stock set up.
Don't have a Tacho.
Strange value ...

It sound a bit too slow for real.

I'm sure my RadjJet fly over 70km/h.

And with my Turnigy Anemometer (that I just find by battery is dead, after many months of un-usage) .. it gave me always the impression was measuring more then the reality ...

Best things are the little optical tacho (it must cost 10$ in these days) .. the RPM reading is always accurate ... even better is the digital rpm ... but it is not practical if there is no access to the motor cables

Tchuss

e_lm_70
e_lm_70 is online now Find More Posts by e_lm_70
Reply With Quote
Old Sep 12, 2012, 10:43 AM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,853 Posts
Does anyone want a Radjet 420 kit (ARF) I have one still in the box, just never had time to get the electronics.

$40 shipped
johnnyrocco123 is offline Find More Posts by johnnyrocco123
Reply With Quote
Old Sep 12, 2012, 12:47 PM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Quote:
Originally Posted by johnnyrocco123 View Post
Does anyone want a Radjet 420 kit (ARF) I have one still in the box, just never had time to get the electronics.

$40 shipped
RadJet Kit does not exist

Either you have the full set of spare parts ... or you the the PNF version ...

Tchuss

e_lm_70
e_lm_70 is online now Find More Posts by e_lm_70
Reply With Quote
Old Sep 12, 2012, 01:09 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,853 Posts
Quote:
Originally Posted by e_lm_70 View Post
RadJet Kit does not exist

Either you have the full set of spare parts ... or you the the PNF version ...

Tchuss

e_lm_70
Oh yeah, I have the full set of spare parts to make an ARF.

Canopy, fuse, motor mount, wings, fins.
johnnyrocco123 is offline Find More Posts by johnnyrocco123
Reply With Quote
Old Sep 12, 2012, 01:40 PM
Registered User
United States, TN, Jackson
Joined Mar 2007
4,022 Posts
Quote:
Originally Posted by johnnyrocco123 View Post
Oh yeah, I have the full set of spare parts to make an ARF.

Canopy, fuse, motor mount, wings, fins.
Interrested.... Decals???

Kevin
Kevin Greene is offline Find More Posts by Kevin Greene
Reply With Quote
Old Sep 12, 2012, 02:20 PM
Registered User
Austria
Joined Jan 2004
8,069 Posts
Quote:
Originally Posted by Kevin Greene View Post
Interrested.... Decals???

Kevin
Decals are included in the official spare part from HK ...I mean the wing has the decals for wing ... the fuse has the decals for the body ... the two tail stabilizer come with decals already applied

The fuse come with motor mount and little screw as well

Some post above you find the complete list that I did edit (and I did used for order mine) of the needed parts for build your RadJet 420 from spare parts.

Tchuss

e_lm_70
e_lm_70 is online now Find More Posts by e_lm_70
Reply With Quote
Old Sep 12, 2012, 02:26 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,853 Posts
Quote:
Originally Posted by Kevin Greene View Post
Interrested.... Decals???

Kevin
Yes, they have the decals applied
johnnyrocco123 is offline Find More Posts by johnnyrocco123
Reply With Quote
Old Oct 03, 2012, 04:40 PM
Crashomatic
CrashMeUp's Avatar
United States, CA, SF
Joined May 2010
2,072 Posts
are you still selling the parts?
CrashMeUp is offline Find More Posts by CrashMeUp
Reply With Quote
Old Oct 04, 2012, 12:38 PM
You down with EPP?
johnnyrocco123's Avatar
Houston, Tx
Joined May 2009
6,853 Posts
Anyone want the kit? I still have it.

If interested, I can take a picture. Just pm me.
johnnyrocco123 is offline Find More Posts by johnnyrocco123
Reply With Quote
Old Nov 07, 2012, 07:36 PM
Crashomatic
CrashMeUp's Avatar
United States, CA, SF
Joined May 2010
2,072 Posts
pmed you a while ago (well, 1 month), zero reply, just sayin'
going to get it from HK
CrashMeUp is offline Find More Posts by CrashMeUp
Reply With Quote
Old Nov 12, 2012, 04:32 PM
Registered User
Joined Nov 2012
1 Posts
Quote:
Originally Posted by everydayflyer View Post
SOP is to place the battery where it needs to be so the CG is correct. If you had the aircraft I could tell you and you would understandt but. LiPoly goes in vertical (laying on narrow edge ,not flat) and about half and half in the vertical slot near rear of cavity area.

Balance point is in the area of the launch grip area. Specified CG is way to far back. This thing needs very little elevator. On my DX7 Elevator is set at 15% and it is still way more than needed.

Charles
The battery goes right where you say and mine flies perfectly with no issues at all. Low rates at 50% and 50% expo and its perfect.
andy.b55 is offline Find More Posts by andy.b55
Reply With Quote
Old Nov 15, 2012, 07:49 AM
Registered User
BadBert's Avatar
Nederland, Noord-Brabant, Hoogerheide
Joined Mar 2007
620 Posts
Could i fit in a 2s 460 mah nanotech lipo in it? could i get the cg right?
BadBert is offline Find More Posts by BadBert
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion RadJet from the KING! vettster Foamy EDFs 1 Jun 01, 2014 07:00 PM
Discussion HK Skyfun or Radjet?? nogas Pusher Prop Jet Models 5 Feb 17, 2014 02:51 AM
Wanted Wtb wtb hk radjet lectroglide Aircraft - Electric - Jets (FS/W) 0 Feb 27, 2012 10:49 PM
Help! Turnigy 420 Charger Problem LukeSkywalker Batteries and Chargers 6 Feb 26, 2012 10:35 PM
New Product New Funjet clone- HobbyKing Radjet Kmart FPV Talk 7 Oct 20, 2011 11:33 AM