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Hobbyking parkjet...need for speed!!!!!!!!!!!!!

Old 08-03-2012, 12:39 PM
  #476  
solentlife
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I have been working t9oo much, the little time at home has had bad weather etc. - been flying ion big meetings etc. - so the PKJ has been very quiet apart from the shattered prop incident at the fly-in on 22nd July.

Now I am sitting in Mozambique waiting for job to actually start. Dahawk in the 50mm EDF listings here has linked to a 50mm EDF that looks remarkably similar to our PKJ's ... and an idea I had for my old 222 PKJ.

My mind is coming round to taking PKJ1 and doing an EDF conversion -I have a high power 50mm EDF set-up spare with a 5000kv motor in it.

So ideas please on mounts and where on the frame to put ? On TOP of rear fuselage like the pusher ? Set into the rear ? maybe UNDER the fuse ?

Second - PKJ2 which is yet to prove herself ... having shattered one motor, broke a shaft, shattered props, .. all seems against getting this baby in the air ( she has 1.1KW power !! ) ... I am coming to the idea that I should use this one for my twin prop attempts. I have various props in matching contra versions. I have the two 2800kv motors .. I have the ESC's ... maybe she's just trying to tell me something ?

The twin prop design - I reckon should have each motor set into the vertical tail fins at base . I plan to glue 10mm beams along the fin to wing joint on the inside ... then use beam mounts to fit the motors ... the fins cut to allow the motors to set into them. I have two strong plastic beam mounts from RCTimer spot on for this job. I did think about using the composite mounts that come with the kit, maybe cut ply discs and glue into the fins - but they are very thin ... and I think the beam mount is stronger ...

I'm really interested in ideas on this .. and if anyone else looking to try this route ? The bungee launcher will have to be looked at to make sure the twin props can clear the rails etc. Maybe create a dolly to sit on the rails to lift props clear ?

Nigel
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Old 08-04-2012, 02:49 PM
  #477  
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Default The launcher design that i went with

Originally Posted by solentlife View Post
When you have her on the rails ... power up to about 1/3rd ... enough to just fly but not so much to scream her .. you want the bungee to work its trick of getting speed into those wings before hit the throttle.
It's difficult to explain in typed words .. but as she goes fwd - you ease up the throttle ... she comes of the rails and should be in slight shallow climb ... as you ease on more power she will likely bank slightly and curve to the left .. let her go but control that bank ... easy easy .. within a few secs - you can let her rip !

This is what happens if you hit that throttle TOO quick ... this was 4S and about 800W power .... (video says 550W ... but on rechecking on Wattmeter .. was nearer 800 !)

http://www.youtube.com/watch?v=UfpL-...7&feature=plcp

Believe me - the adrenaline rush once you get something like 700W up this little baby ... I have to sit down and have a drink after .. I have a Cessna 182 that I fly inbetween ... first flights etc. to calm me down ... get me ready.
You'll understand once you hit those speeds !

Here's a compilation vid showing the launcher in slow motion as well ... this shows just how much force is in that - watch those rails flex !!

http://www.youtube.com/watch?v=7XLX9A2vNkc

I'm actually considering building same frame but next size up in pipe diameter + add the insulation to be kinder on the wings ...

Nigel

Here is the the rc groups link to the catapult launcher that i built.http://www.rcgroups.com/forums/showthread.php?t=190617 I think that it is a great design, I put 1/to3/4 adapters where the rail uprights meet the cross beams that are the stand for adjusting so that it will accommodate different size models and to keep it from wobbling.

Thanks for every thing.

Last edited by FLOATN; 08-04-2012 at 02:53 PM. Reason: forgot to put link
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Old 08-14-2012, 06:41 PM
  #478  
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One of the major items of my launcher is the actual bungee line to model is not the release line. I looked at designs where there was only 1 line - but didn't like the change of angle of the trigger pin.

Second - I wanted the trigger to be well back from the launcher and not have to put my leg / foot near the prop.
My trigger base is held by 4 tent pegs and can accept up to 20kg pull.
The bungee anchor has 3 pegs in a V and that holds 10kg easily.

As others have said - once you have one - you wonder why you didn't make one before !!

Nigel
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Old 08-17-2012, 01:10 AM
  #479  
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Old 08-17-2012, 06:34 PM
  #480  
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Hi Stu ....

Yep - we need a T Shirt / Cap .....

Nigel
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Old 08-18-2012, 07:52 PM
  #481  
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+1
I would purchase one if for no reason but to be a good wannabe LOL
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Old 08-18-2012, 10:24 PM
  #482  
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Deleted. Wrong thread.
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Old 08-25-2012, 01:16 AM
  #483  
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been a while since i'v posted anything new with pkj's. so here is a few pictures of pkj#3. i still have pkj#2 ready and hoping to get a successful flight on 4cells.

this pkj is a step down in power and weight from pkj2 with dons wicked rc 3000kv.i'm using the TP 4850 kv motor,60 amp mystery esc,using a 1300mah 30c lipo with a 4.5x4.5 prop. the motivation to putting the pkj together is to clean up the workshop for building balsa models. the next job will be installing a castle creation 100amp ice and an eflite power 60 in the gp edge 300s. motor should arrive monday. i can't wait to get the edge in the air. i 'll post the motor swap on a seperate thread.

will post finish pictures later on the pkj and hopefully maiden next weekend. weather is looking good for saturday so charging batts now for the pig and slick.
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Old 08-25-2012, 09:06 AM
  #484  
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This weekend looks not too bad ... bit grey but wind has died down.

May have a try at my speed record today or tmrw ...

Twin is still waiting a couple of bits ... so that's shelved for a while.

Great to hear you are still at it Stu ...

Have to admit that work and EDF's have taken up my time recently and I apologise to PKJ fans !!

Nigel
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Old 08-25-2012, 01:24 PM
  #485  
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always good to hear from you nigel,and like you i'm to busy 5 days a week working and prefer to fly on the weekends ...just like today. i was going to make today a date with my wife to the jersey shore but this is the second weekend where the weather isn't inviting to be sitting on the beach...so it's off to the field ......thats like going from a beach day to the country club...lol..

i can't wait to see how you load the gear for the twin pkj,i can barely fit a 4 cell in....

have a great day and good flying,stu
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Old 08-25-2012, 04:37 PM
  #486  
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the plan is to mount the motors at the fins ... so they are reasonably separated. The ESC's can sit just fwd of the motors on inside of fins. The leads will then Y in to the main battery pack - haven't decided what's best packs yet .. The pack will be pushed right fwd and Rx sit at rear.

The Rx power will be via a 250mAh small pack, with the ESC's red 'servo' leads disconnected. The ESC's Y lead into the Rx for throttle.

I have various sizes of contra props ... 4.1 up to 5 ... so will be trialing each to see what gives best.

Nigel
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Old 08-27-2012, 02:58 AM
  #487  
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here it is! pkj3 and no decals other than duct tape and fiber tape to help protect and discern the top from bottom. it's dialed in on pkj2's channel in the tx which means i'll be trimming both plans in the air and will have to record the trim #'s for each pkj.

now at least i can attempt 2 flights on each pkj and 2 flights on the funjet...this makes setting up the bungee launcher worth while. i haven't been flying the funjet mostly for that reason. i have 2 batteries for each of these birds,so if no crashes I'll gain lots of speed adreilin.... i just this moment decided to ask my daughter to accompany me to the field to be my photographer and the second person required as the club rules requires. so maiden may be this week.
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Old 08-27-2012, 08:00 AM
  #488  
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Nice to see ideas come up ... the two bolts canopy hold-down. Mine are a little fwd of yours .. but they really stiffen that area up.

Weather here is up and down and haven't been able to get my PKJ2 up again .. (4400kv single motor version)

I've now removed the gyro and reverted to straight control. I had no end of trouble trying to get it to stop wobbling the wings. It's just way too sensitive.

I may remove the 280mAh Rx pack and fit a UBEC ... that will save some weight from the back end.

I have to admit that the 3800kv was nerve wracking, but this 4400kv job is frightening ... I really have to psych myself up for it !!

Nigel
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Old 08-27-2012, 04:40 PM
  #489  
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Today re-arranged installation in the 4400 PKJ2 ..

Previously with the gyro, mixer etc. in there - the Rx was at the front and LiPo between Rx and ESC.
Now with Gyro / mixer removed - the LiPo is now at front with Rx behind.

The V3 Pitot tube is now through the foam nose with small amount taken out of canopy front to sit over it.

With 1600 4S LiPo this now balances at front of finger holes.

Just looked out window !! Blowing a hoolie and rain !

Nigel
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Old 08-30-2012, 07:50 PM
  #490  
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PKJ2 went to field for flight today ............ wind was direct onto the cars .. so no way was I launching her towards the cars !.

Really frustrating ...

Nigel
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Old 10-02-2012, 02:27 AM
  #491  
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I'm on the Kerosine Chicken tonight going home .... so should arrive home tmrw afternoon.

I'm checking weather reports to see when I can get the PKJ out and have a go at beating my old record ... Yep - Nigels back itching to go FASTTTTTTT !

It's been a while since the PKJ got her airing ... so it's about time to dust of and carve up the air.

Note specs :

4400kv motor
70A ESC with separate BEC (note this ESC is right on its limits !)
1600 4S
5x5 prop


Nigel
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Old 10-02-2012, 03:00 AM
  #492  
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Dr Frankenstein said it best for this ol need for speed thread.....

it's alive!!!!!...lol i really need to load up the car with all my parkjets and take the risk of coming home with foam chips.... will be tossing the stinger in the air next so i might as well put a hook on it and bungee it even though many folks make it look like an easy underhand toss at a steep angle.

welcome home Nigel,i think the thing thats holding me back the most from flying the pkjs and the funjet is the inability to get verification of top level speed.[or any accurate speed measurement]and the realization that till i figure on how to record the speed i don't want to wreck em. i know the funjet is toping 100mph but the highest a phone app dopplered it was 99mph out of a dive and the owner said it was faster than 100. his funjet can do 145mph and i got a really nice video of it here on the forums.
funjet 145+mph video



i may as well just fly em for the fun.....but man,i really do want to know how fast i'm flying them.
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Old 10-02-2012, 04:14 AM
  #493  
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For me ... the ET V3 sensor for on-board ... plus a good video to doppler ...

I have a pal that is very good at video'ing with my 8mm Sony. I now also have sorted my 808 keycam on the peak of my basebal cap ... so covering it as many ways as possible.

As I understand it Stu ... your problem is having another to be with you to video ?

I see HK are selling a radar gun ... $99 ... mmmmmmmmmm as you found - not the easiest to use .. at the speeds we are pushing - getting that low and close is HARD !! and makes the knees tremble !

I'm looking fwd to getting home and out on the field.

OH - nearly forgot. I tried pipe insulation on the catapult rails .. thinking it would be kinder on the models. Forget it ... it increases friction and actually causes model to dig in. I had to remove for the F15 which the tail feathers are lower than main wing. I straight away noticed the difference and back to better launches.
I still use 5kg tension for all models regardless of their weight ... works fine.

Cheers
Nigel
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Old 10-02-2012, 04:27 AM
  #494  
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lol on the radar gun and knees...,i have a bud at the field who was willing to walk out a bit to point and shoot the radar gun but i wouldn't dare allow it. then the thought of making a 3/4inch thick plywood shield came to that would be easy to carry and hide behind came to mind...but can you picture one of the old timers who fly there seeing that,they'd have a heart attack and i'd be looking for a new club.[still,it would work]

i also wish i had a bud to video flights. the keychain camera works great on my hats visor but getting sound recorded is a problem. lastly,i still want the mini gps logger,but i can't justify the $80 shipped by hk.
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Old 10-02-2012, 07:12 AM
  #495  
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Problems with any mini cam vid ....

a) Keeping it on subject. We tend to lead the plane when doing low passes and video ends up with plane out of shot one way ... near edge on other .. only when not doing low passes is it centred ! One guy I fly with added a wide angle lense onto his key-cam ... it works.
b) Wind noise, we can't stand still and so we get the wind across the mic hole. I've heard of people putting small thin tape over that hole ... but when I tried - it blocked sound significantly. I wonder if accoustic foam as used on newsmans microphone would work ?
c) other model noise that upsets doppler .... bit unfair to tell them not to fly just for your own use !!

If I go GPS - then I want a proper logger for whole flight - not the max speed single result of HK ... that't expensive for a single number logger. I'll stick with ET V3 .....

Nigel
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Old 10-05-2012, 01:36 PM
  #496  
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I am really annoyed ..... I get home ... weather turns absolute crap !

I have just a few days before I scoot of again to Singapore for another assignment ......... hoping that at least 1 day will give me a chance at breaking my record !! At least let me FLY !!

Nigel
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Old 10-05-2012, 01:48 PM
  #497  
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Hmmmm. Let's see. Singapore is usually pretty warm right? Do you have a box you can ship to your hotel with a couple of small planes? Might help the appetite for flying ! Just a thought...
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Old 10-05-2012, 02:41 PM
  #498  
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Originally Posted by dahawk View Post
Hmmmm. Let's see. Singapore is usually pretty warm right? Do you have a box you can ship to your hotel with a couple of small planes? Might help the appetite for flying ! Just a thought...
As I understand it - RC Flying is strictly controlled in Singers ... and Licenced. I plan to search out RC'rs there if I get some spare time ... but usually I'm tired out working all hours etc. I don't have a 9 - 5 job ... I can be out all night and next day catching naps in quiet spells ...

Nigel
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Old 10-20-2012, 10:55 PM
  #499  
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i hope the utube vid downloads . i was at the field from 9:30am to 4pm.i do have a smile on my face still.
flew the towershobby uproar 3times,the 3dhs slick 3 times,the funjet ultra twice,and best of all the hk pkj with the 4850kv TP motor 40amp mystery esc,3cell bluelipo from valuehobby 1300 30c. got around 4mins flight and battery came down hot and slightly puffed. it cooled and returned to its normal unpuffed shape.

bungee launch went perfect,flew very high for the first minute of the flight to get it trimed. had some nice speed runs videoed by a fellow club member who couldn't use the view screen as the camera i have stinks. he did a great job of tracking the pkj and even though the vid is poor quality i still wanted to post it here....

so if youtubes ready...here it is

1300mah 30c


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Old 10-20-2012, 10:56 PM
  #500  
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grrrrrrr,try again



uploaded a video 26 minutes ago
3:52 WATCHED

hobbyking parkjet 4850kv with 3 cell 1300mah 30c
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