SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Dec 24, 2012, 08:58 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Quote:
Originally Posted by TheCure View Post
I just measured my newer un-maidened parkjet. Its got a 4200kv 2627 outrunner motor, 50a esc, 4.1x4.1 prop, running on a 4s 1300 nano.
I read about 1100g pull, 58a max @836watts. I think it weighs around 350g.

Am i going go have problem hand launching it?? Can i get by without a bungie if i apply liberal throttle to launch?
Its not power that's the real problem ... its prop diameter + power that is ...

Think of it like this ... the prop is a flywheel. The bigger the diameter and rpm - the greater the flywheel effect ... Laws of motion dictate that for each action - there is an equal and opposite reaction.
This mean we reach a point where the force turning the prop also wants to turn the model. Usually called Torque Roll.

The trick is to find the limit of throttle that will allow model to launch without torquing into the ground. Some try to counter with offest aileron - forget it - torque roll occurs BEFORE model is flying, aileron offset only works when surfaces have airflow ... so yes ... reduced throttle on launch and power up as she flies ...

Better still get a catapult bungee !

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Sign up now
to remove ads between posts
Old Dec 24, 2012, 09:03 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Quote:
Originally Posted by headlessagain View Post
With that amount of power I would have thought she would have taken off vertically from your hand I once saw a Mugi Evo launched in a similar fashion and it only had half the power.
I used to let my WOT4 of vertically ....... trouble is the spin as she goes up ... you cannot stop it unless you have massive 3D controls ... the torque beats you. With a PKJ ... it's a small model and hard to orientate when rolling etc. - so not a good idea to vertically release IMHO

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 24, 2012, 11:28 AM
Registered User
ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
The parkjet reminds me of one of these. http://en.m.wikipedia.org/wiki/Vought_F7U_Cutlass
I have bought some sticker material from eBay. It's only 99p for an a4 sheet and comes in many colours. I have started cutting it up to fit the parkjet. Red and silver are my colours.
ledzep76 is offline Find More Posts by ledzep76
Reply With Quote
Old Dec 28, 2012, 11:42 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Parkjet Twin has now received replacement motors ....

Turnigy 2623 3000kv each.

Tests show a much better power set-up ..

3S draws 32A
4S draws 52A

Now only have to wait for suitable weather to give it the maiden ....



Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 28, 2012, 02:49 PM
Registered User
ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
I hope I am not trying to teach a grandmother to suck eggs but please do remember to put your props the right way round before you fly it. Numbers face forward and if the motor is spinning the wrong way just swap any two wires over between the motor and esc. This thing is going to be ballistic! I can't wait.
ledzep76 is offline Find More Posts by ledzep76
Reply With Quote
Old Dec 29, 2012, 05:24 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
Now that looks badass Nigel
love it.got my new kit.had it on the WATT meter and with 4.75x4.75 I was on 27A and 310W
a little much for the motor.it's rated at 20A,so will prop down to 4.1x4.1
its a 3900kv inrunner,I wont be close to you,but sure I should get a fairly decent speed.a mate of mine has offered to go radical on a pintjob and then going to cover with polyurethane so the paint doesn't peel so easily and will help with it being a little more "slippery" through the air
chop stiX is offline Find More Posts by chop stiX
Reply With Quote
Old Dec 29, 2012, 03:34 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Here's the test run on the new motors ....

PKJ(T) 2623 3000kv motors test (5 min 12 sec)


Had to swap out my wing servos ... stripped a gear while working on the model ...

Just have to wait for suitable day to maiden her now ..

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 29, 2012, 04:22 PM
Registered User
gchrisgo34's Avatar
United States, GA, Jonesboro
Joined Nov 2010
1,659 Posts
you need to turn your props around solentlife! they're on backwards. have the numbers face the front of the plane.
gchrisgo34 is offline Find More Posts by gchrisgo34
Reply With Quote
Old Dec 29, 2012, 04:25 PM
Registered User
gchrisgo34's Avatar
United States, GA, Jonesboro
Joined Nov 2010
1,659 Posts
i just read the post above about the backwards props, sorry.
gchrisgo34 is offline Find More Posts by gchrisgo34
Reply With Quote
Old Dec 30, 2012, 03:18 AM
Registered User
ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts

Did a little more last night. Adding sticker material to the elevons makes them much stiffer.
Made a new motor mount too as the original one fell apart in my hands!

ledzep76 is offline Find More Posts by ledzep76
Reply With Quote
Old Dec 30, 2012, 03:19 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Quote:
Originally Posted by gchrisgo34 View Post
you need to turn your props around solentlife! they're on backwards. have the numbers face the front of the plane.
There are NO numbers on these props and I am fully aware of face / back of props ...

These grey props are strange ... the shaft adaptors are loose in the boss, the blades have a strange twist ... I use them because of the extra blade area compared to other same size.

I agree they were back to front - but that was due to my rush to get it tested ... with these you have to carefully check the blade profile.

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 30, 2012, 03:27 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Quote:
Originally Posted by ledzep76 View Post
[IMG].............
Did a little more last night. Adding sticker material to the elevons makes them much stiffer.
Made a new motor mount too as the original one fell apart in my hands!
.................
The stock motor mount is rubbish ... and the alloy mount over counter is too brittle at the 90 deg joint.

The best I have used so far is the metal furniture L bracket. YES - common DIY shop L bracket.... it is inserted into the foam hard up under the wood beam ... epoxy it in .... self-tapper screw up into the wood beam ...
Before fitting - motor mount holes are drilled in the upright of the L ...

That DIY mount will NEVER fail !!







That mount has carried my 4400kv 1.1Kw .... my 3700kv 550W ... and the 2200kv 200w motors. The other beauty of it - you can bend to alter thrust line without fear of breaking it.

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 31, 2012, 02:54 AM
how'd I do that....oh
chop stiX's Avatar
South Africa, GP, Pretoria
Joined May 2011
2,260 Posts
My PJ1 uses the original mount that I just beefed up abit and 2 years and a few crashes she's still holding up
chop stiX is offline Find More Posts by chop stiX
Reply With Quote
Old Dec 31, 2012, 04:00 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,570 Posts
Quote:
Originally Posted by chop stiX View Post
My PJ1 uses the original mount that I just beefed up abit and 2 years and a few crashes she's still holding up
Beefed up a bit ?

Seriously anyone going down similar road to Stu and myself with high power - you reallly need a better mount.

Nigel
solentlife is online now Find More Posts by solentlife
Reply With Quote
Old Dec 31, 2012, 01:50 PM
Registered User
ledzep76's Avatar
United Kingdom, England, Bisley
Joined Oct 2010
87 Posts
Servos centralised and linked up fins fitted and pod fitted over the engine mount. This should help with the aerodynamics. Just waiting for my prop adapter to arrive. The stock one does not hold the prop central very well and at these high rpm the prop needs to be held central otherwise it could go out of balance and vibrate the thing to pieces!



I can't wait to get her in the air! All up weight with a 2s 1300 is 240 grams.
ledzep76 is offline Find More Posts by ledzep76
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Hobby lobby F9F Panther EPO Jet Receiver Ready ARF smasher41 Foamy EDFs 1014 Nov 19, 2014 01:48 AM
Discussion HK AT-6 Texan EPO Plug-n-Fly 29.5" w/s stuart warne Electric Warbirds 12 Jun 14, 2011 03:47 AM
For Sale HK Mini-PITTS -- EPO, Brushless, Plug 'n Fly WRXronald Aircraft - Electric - Airplanes (FS/W) 3 Aug 04, 2010 11:03 PM
New Product New HK Mini F-16 EDF Fighter Jet / EPO Plug-n-Fly CrashingDutchman Foamy EDFs 13 Jul 02, 2010 12:15 AM
Discussion HK's EPO F-16 WRXronald Foamy EDFs 5 Apr 11, 2010 03:47 PM