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Old Mar 28, 2012, 06:41 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia / UK visits
Joined Jan 2010
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Quote:
Originally Posted by morris.hans View Post
thanks solentlife/aeromaniac,

i ordered two of the 4800's because i plan to melt the first one on my test bench (200a capable) seeing how far i can push it and then have one to put on the plane, If i cant fry it on 3s then i will try to on 4s......this should get interesting
It's fine on 4S ... but then you'll need a very high amps ESC ... it gets way over 50A ... I never took it higher than 54A on 3S and 4S ......... but 4S was clearly much higher ...
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Old Mar 28, 2012, 06:46 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia / UK visits
Joined Jan 2010
8,335 Posts
Quote:
Originally Posted by Jpette View Post
Thanks for the canopy tips guys . Now I am using a simple rubber band and it won't move an inch .

Morris

Better melt the foam than your motor man

4800 kv motor seems far to high for any propeller and most of all on 4 cells !!

Will be interesting to see if only pitch without diameter will move the plane or just make holes in the atmosphere

Sorry for opening the debate again . Can't help it !!!
No problem .... its a Forum !

As we all know the big problem as we increase rpm is the sheer torque we develop. It's generally accepted that torque is diameter and speed is pitch.

Good example is a Tugboats propeller and the racing speedboat. Tugboat with fine pitch and large diameter ....... the speedboat with small diameter but high pitch.
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Old Mar 28, 2012, 06:54 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia / UK visits
Joined Jan 2010
8,335 Posts
Quote:
Originally Posted by Jpette View Post
I really have no experience with so high KV motors and such a tiny prop .

I just know that prop efficiency will drop drastically when it becomes to tiny to overcome the drag .

What about this motor :

http://www.hobbyking.com/hobbycity/s...ner_Motor.html

On a 4 cells battery, one could use a 5,25x6,25 so the pitch should be almost as high than with your 4800 kV motor but the prop diameter would stay large enough for better efficiency .

I don't own that motor but I would bet more on it to give insane speed than on thoses high kV motors .

Anyway , continue testing guys in all directions and we"ll together find the best way on how to convert a Parkjet in a cruise missile .
Just make sure you get reliable speed measures by repeating them a significant number of times . I don't really trust the one time measures that can be totally falses .

Solentlife

I know I "ll be a pain in your a. but how many times did you get that 222 km/h reading ?
One of the problems that I believe is against the large diameter prop is the small wingspan we have ... it cannot resist the torque roll of the more efficient props.

Speed run ? Once - basically because we had serious trouble launching and also after the run - the battery pack hold-down separated from the fuselage ... in the freezing cold we had that day - no way I could fix it on-field.
I fully accept that the speed achieved could have been affected by some influence or whatever ... as you say it needs multiple runs to be sure. But as far as we all could tell .... there were 5 people there involved - we could not find anything to doubt the speed recorded.

We all knew it was fast .......... the comments behind me while flying were testament to it ...
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Old Mar 28, 2012, 06:57 PM
222 km/hr Parkjet flyer
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Latvia / UK visits
Joined Jan 2010
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Quote:
Originally Posted by morris.hans View Post
right!

not to take away from solentlife but i pulled 143mph on radar gun but didnt bother to post it cause it was down wind and could'nt repeat it. i agree there must be atleast 2-3 repeats before its worth mentioning.
Nice one ... at last !!

Good luck and hope you get runs in .... and with wind - just do one way and then reverse the other way ... average the two.

You've now given me even more reason to push harder !
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Old Mar 28, 2012, 07:03 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,646 Posts
With only 1.8 posts aday lol you seem to be posting here most, mate go do some flying, as us pommies would say less talking more action lol.
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Old Mar 28, 2012, 08:59 PM
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United States, LA, Shreveport
Joined Jun 2011
331 Posts
Quote:
Originally Posted by solentlife View Post
Nice one ... at last !!

Good luck and hope you get runs in .... and with wind - just do one way and then reverse the other way ... average the two.

You've now given me even more reason to push harder !
naa u still have it, i pull 130 mph consistent, i had a 10-15mph wind that day, all my planes were running fast
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Old Mar 28, 2012, 09:29 PM
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Joined Aug 2005
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Thanks for the gear recommendation guys, Ill look up those links from hobbyking. I guess ill just have to reuse those 800mahs on another foamie. Thanks again!
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Old Mar 29, 2012, 01:52 AM
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Australia, New South Wales, Sydney
Joined Jan 2011
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Quote:
Originally Posted by solentlife View Post
No No No ... canopy hold down is simple and can be much cleaner ............
very secure looking system Solentlife but mine works well for me. The rear is fine with the rare earth magnets on mine, but I know you push the upper speed boundaries and that sucker has to really stay put front and rear!
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Old Mar 29, 2012, 08:30 AM
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United States, LA, Shreveport
Joined Jun 2011
331 Posts
"rcfoamfighters style" hk parkjet

gonna hold off on buying a esc to see how many amps the 4800kv pulls on 4s, i did get my 100A to fit with the canopy on so if its close to that then ille run it.

starting on the top side, almost time for colored tape, the color scheme will be Orange and Blue, with a little Black and White, schemed after RCGROUPS.COM :

sooooo. thus far i think its going to be the 4800kv with ~100A esc, 4s 1300 45C-90C, and a 4.1x4.1 prop and the setup will continue to change as i find out more info/burn stuff up/get additional info from you guys....thanks in advanced
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Old Mar 29, 2012, 02:08 PM
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Joined Mar 2012
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Hi I am lokking for a stick motor mount for my parkjet! The stock one completly explode on my bench test. Those HXT Alloy Composite Stick Mount 20mm from hobby king seems to be the best for my purpose, however they are in backorder since one month now!!!!! Have you got guys any idea where can i buy them online. Thank you very much, and I will unpload soon some pictures of my baby!

Romy
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Old Mar 29, 2012, 03:49 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
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Quote:
Originally Posted by romy View Post
Hi I am lokking for a stick motor mount for my parkjet! The stock one completly explode on my bench test. Those HXT Alloy Composite Stick Mount 20mm from hobby king seems to be the best for my purpose, however they are in backorder since one month now!!!!! Have you got guys any idea where can i buy them online. Thank you very much, and I will unpload soon some pictures of my baby!

Romy
I'm using these and so far been great.

http://www.hobbyking.com/hobbyking/s...in%5FPack.html
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Old Mar 29, 2012, 08:47 PM
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United States, GA, Jonesboro
Joined Nov 2010
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HEADSUPRC.COM, its were i ordered mine. its the mount thats places the motor directly behind the jet 15/16" is the size. will be at your door in a couple 2-4 days. great place to order from. i also ordered some of their magnets, plan to use them to help hold the canopy down. im getting ready to start finshing my parkjet. looking forward to buiding this one
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Old Mar 29, 2012, 09:04 PM
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Joined Mar 2012
78 Posts
hey there don,after i get used to using a pvc launcherwith pkj#1,i'll be using the 3000kv wicked,60 amp plush,and 4cell in pkj#2. a 4.1x4.1 like your site suggests.

to power up the wicked 3000 on the field turns heads from all the other flight tables. to bad i got a bad toss on a hand launch and needed repaires so she looks pretty.....pretty ugly that is.

a lot of beautiful pkj's here! nice paint jobs. also congards on the 140+ flight.
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Old Mar 30, 2012, 12:50 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia / UK visits
Joined Jan 2010
8,335 Posts
GUYS .... PLEASE .....

We are all now seeming to get into launchers ............ we need to consolidate the good and bad info that we have ...

What works .......... what sometimes works ............ what sometimes doesn't work ... what doesn't work ............

Our work can help all to achieve the ideal set-up ...

If a certain pull or combo of bungee / angle / length of rails fails or is better ... all is very important info for all.

We don't want to repeat others mistakes if the info is out there ...

Cheers
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Old Mar 30, 2012, 11:06 AM
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United States, LA, Shreveport
Joined Jun 2011
331 Posts
Hans' Launch Notes:

every launch successful since COG has been on.

1 - (Launch from Rails) rails are 6 feet, I can launch at the back of the rails and get the full 6 feel of wing support or at the end of the rails and get the exact same result as long as COG is right on. !COG must be on or else it will flip all over the place once it leaves the rails!

2 - (Launching from the Grass) gets the exact same results as rails. Just hold or step on the cable then pin the jet, once you let go or lift you foot it takes off just like from rails except wings stay straight cause grass/ground is level (my favorite easiest way cause it has less potential of hurting your plane from smacking the ground from the rails but only works if servos on top) !COG must be on or else it will flip all over the place once it gets airborne!

3 - (Launch Cord/Bungee Pull Length) I think that the safest way to determine this since its different on every plane cause of weight is to remove the prop and start with a pull length that you know is too little, let the park-jet slide across the grass, then add a few feet......keep launching and adding a few feet until it starts holding itself airborne, Once you can get it to hold a solid glide, put the prop back on and add throttle on next glide and it should keep going, if not add a few more feet. Different sized bungees are definitely gonna have different pull strengths, mines is the HK 10Meter Bungee so a few feet to me is like 7 feet !COG must be on or else it will flip all over the place once it gets airborne!

4 - (Rail Angle) I tried with 0-35 rails. All other things equal it didn't matter as long as CG was right.

5 - (Rail Friction & Pull String Friction) This is where i ran into most of my trouble at first. My rails didn't have an equal amount of friction so one wing would drag more than the other causing it to come off the rails unevenly and roll to the side of more drag. Fixed with wrapping rails with slippery packaging tape (anything slippery will work). I had the same issue with the key-ring that i would hook to the bottom of the plane. The Key-ring would get cocked unevenly under the plane and pull to one side, fixed with a new smaller key-ring. (probably not an issue with others as my key-ring was big and warped haha)

6 - (Hand Launch) Throw plane with even amount of pressure between fingers. 45 upward angle just to be safe. 50%+ throttle (low thrust setups) 50%- throttle (high thrust setups) I always get someone to throw it for me so i can control it immediately and i've never tried hand launching then jumping to controller sorry (US Mode 2).

All my Parkjets are 400+ grams

COG COG COG

Start slow and take the path of least resistance.
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Last edited by morris.hans; Mar 30, 2012 at 11:20 AM.
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