Need For Speed Extreme Parkjet Twin !!

[solentlife]

For some time now I've been talking about the Hobby King Parkjet and possibly mounting twin motors .......... well finally it's coming together ...

Here's the donor PKJ2 ... my 4400kv Ultra speed machine :



Motors and mounts laid out ready to fit ...



The single motor mount and 4400kv motor to be removed and area infilled to stiffen it up ...





Pink closed cell foam used ....

Next is to mate up the motor mounts - plastic beam mounts from RCTimer - with hardwood beams. Because the elevons are almost to the vertical fins - I cannot set the motors and beam in the fins ... so opted for along inside. The motor can needs a square cut out of the fins.





Now epoxied into place ...



Screws in through bottom as security ...



Mounts in place and motors ..







Now its wire up and install the twin 50A ESC ... note one will have the red BEC wire pulled so that only one BEC is supplying required Rx voltage.

I have had to lengthen the battery wires of the ESC's into the combined single feed ... and now I've run out of bullets to plug in the motors !!



Balance - I bet you're wondering ... well with a 2200 3S 25-35C Turnigy at 194gr and a Zippy Compact 1600 4S 25C ... it balances out at front edge of finger holes.

She weighs in without battery at 442 grams ...

She aint no lightweight anymore ... but still she's flyable weight .. may just be a little hot on landing.

My one query is the vertical fins may now be undersized and with motors sitting in them ... wondering whether to add a V piece to each to fill in the front V edge ... so its a straight line top to fuselage ? Give a bit more vertical stability ?

Anyway ... there she is .... now I need the bullets to connect the motors and weather to fly.

Nigel

[solentlife]

Scrounged bullets of other gear .....

WOW what a sound ! You have to hear it to believe it ....

Needs serious battery though .... the 1300 3S 35C puffed in just secs literally !

Nigel

[road king 97]

That looks like 100 mph plus plane ,should get your blood a pumping good flying that. lol joe

[solentlife]

Originally Posted by road king 97

That looks like 100 mph plus plane ,should get your blood a pumping good flying that. lol joe

100 ?? My PKJ1 with single 3700kv did 222kph (138mph)

This is twin 3800's ......

The idea behind it is actually not for power - but to control the high levels input into the small frame. The 1.1Kw of the single 4400Kv was literally uncontrollable ..... The twin set-up is contra-rotating props so in essence all torque and associated effects should be cancelled out. The props also being more outboard should pull air better over the surfaces instead of the single that sat in the shadow of the canopy.

My concern though is that the vertical fins are reduced ....

Nigel

[solentlife]

Another requested proof of the twin and the sound ...

http://www.youtube.com/watch?v=DHn-ce8FUZM



Nigel

[stevecooper]

Originally Posted by solentlife

Another requested proof of the twin and the sound ...

http://www.youtube.com/watch?v=DHn-ce8FUZM



Nigel

YouTube says it's a private vid bubsteve

[solentlife]

Originally Posted by stevecooper

YouTube says it's a private vid bubsteve

Sorry about that - uploader auto set the Private ! Now changed to Public ... enjoy !

Nigel

[solentlife]

I have to now consider serious about how to fly this having just Wattmeter'd her ............

On a 3S 2200 she hit OVER 100A and 1.1KW ..... with LiPo showing distress literally seconds into the test ....

Trying to hold the machine was an exercise in itself !!

My thoughts are whether to swap out the motors to something less demanding ? keeping these for single power set-ups ?

I didn't even try the 4S on the meter ... the Wattmeter cables were warm and I don't want to risk damage to that and also my LiPo's !!

So Guys ... SUGGESTIONS please !! (I know some of you will want me to fly this set-up - but how ?? ) Only way would be to EPA the throttle back so low to control the amps ...

Nigel

[solentlife]

Wonder whether to swap out to these litttle babies ....

http://www.hobbyking.com/hobbyking/s...or_3000kv.html

Review shows :

But this little bastard really rocks on 3 cells! No warranty then of course, but so cheap it doesn't matter..
This setup is for WOT in short burst:
5x5 (electric, Not parkflyer type propeller)
3cells lipo
22,6 Amp
236,7 watt!

Motor gets warm, but 20+ flights so far, all good

Battery? I used Flightmax 3s1p 800 Mah (20-30C)


So 2 of those with 30a ESC's to cut back on weight ..... ??

Nigel

[stuart]

Nigel.....your a sick pup!! i just watched your video,and love the pkjt[parkjet twin]. i'm supprised you didn't blow stuff and the heli off the window sill.

i dont think your going to have any issues with launching the pkjt on bungee. after my last group of launches i learned the feel for throttle up. i get the feeling you'll hit the release and off you'll go. it also sounds like your battery didn't suffer from drain during your vids wot bench test which is promising for those wot runs to get dopplered.

any way,i just got my laptop back from the repair shop and now it's working perfectly! i ditched the new one cause i have o desire to learn windows 8.looking forward to the pkjt maiden and a vid!!!very cool lil bird ya got there.

[solentlife]

Was going to hit the buy button for some other motors today - but then got hit for big car repairs ... it's annual technical and she has a few issues ! Volvo work aint cheap !! Especially when its the XC.

I might have to just EPA the throttle back to save my lipo's and ESC's ... until I can get more acceptable motors fitted ....

When I did the 3S test - she actually powered up HIGHER than the vid above .. I think the 3S 2200 LiPo allowed the motors to draw what they wanted .. the 4S 1600 was well overtaxed ... luckily it survived !
As the throttle was opened for the test - loads of stuff flew out the door !! into the upstairs lounge !! Holding the PKJT actually was not so easy ... the nose pushed into my ribs. She has some awesome thrust ... pity I cannot do a thrust test - it's just too risky.

The result I think is that with a twin set-up - we need to look for efficiency rather than brute force as in a single. So better lower amp demand motors, better props etc.

Previously I was using the black TGS Sport props as advised by HK on the PKJ ...

http://www.hobbyking.com/hobbyking/s...propeller.html

but later changed to the wider blade APC style from HK :

http://www.hobbyking.com/hobbyking/s...tion_2pc_.html

because they were available in left and right hand config. I have a feeling that they draw a higher load than the TGS. I know when I swapped out the TGS to APC style on the F15 - the sound changed and speed I think went up slightly.

Brings me to think motors change - but I'll still need APC style as I need the contra props.

Even with the 2623 at 24 odd amps each on 3S ... that's still pushing the LiPo to 50 odd amps ....

Oh sod it ... I've hit the buy button .... 2 x 2623 3000kv motors on their way ...........

Nigel

[road king 97]

Originally Posted by solentlife

Was going to hit the buy button for some other motors today - but then got hit for big car repairs ... it's annual technical and she has a few issues ! Volvo work aint cheap !! Especially when its the XC.

I might have to just EPA the throttle back to save my lipo's and ESC's ... until I can get more acceptable motors fitted ....

When I did the 3S test - she actually powered up HIGHER than the vid above .. I think the 3S 2200 LiPo allowed the motors to draw what they wanted .. the 4S 1600 was well overtaxed ... luckily it survived !
As the throttle was opened for the test - loads of stuff flew out the door !! into the upstairs lounge !! Holding the PKJT actually was not so easy ... the nose pushed into my ribs. She has some awesome thrust ... pity I cannot do a thrust test - it's just too risky.

The result I think is that with a twin set-up - we need to look for efficiency rather than brute force as in a single. So better lower amp demand motors, better props etc.

Previously I was using the black TGS Sport props as advised by HK on the PKJ ...

http://www.hobbyking.com/hobbyking/s...propeller.html

but later changed to the wider blade APC style from HK :

http://www.hobbyking.com/hobbyking/s...tion_2pc_.html

because they were available in left and right hand config. I have a feeling that they draw a higher load than the TGS. I know when I swapped out the TGS to APC style on the F15 - the sound changed and speed I think went up slightly.

Brings me to think motors change - but I'll still need APC style as I need the contra props.

Even with the 2623 at 24 odd amps each on 3S ... that's still pushing the LiPo to 50 odd amps ....

Oh sod it ... I've hit the buy button .... 2 x 2623 3000kv motors on their way ...........

Nigel

After years of building fast motorcycles and street rods i can tell you for sure that speed costs more $$$$$ . My harley started out stock ,then i needed SPEED so new ,cam ,crank shaft ,bigger injecters , new valves ,reprogramming its brain. lol it never ends but it does throw me back in the seat now when i hit the throttle . My next one i will leave alone i hope . naaaaaa joe

[solentlife]

Originally Posted by road king 97

After years of building fast motorcycles and street rods i can tell you for sure that speed costs more $$$$$ . My harley started out stock ,then i needed SPEED so new ,cam ,crank shaft ,bigger injecters , new valves ,reprogramming its brain. lol it never ends but it does throw me back in the seat now when i hit the throttle . My next one i will leave alone i hope . naaaaaa joe

I used to Club Race a Ford RS Capri .... so tell me about costs for speed ! By the time Manx Racing had finished with her - I was seriously short of cash !! But WOW - you could drop the clutch on her and near lift the front wheels literally of the deck ....

275 valves and cams
machined ports and head
smooth flow exhaust and tuned
forced air draught carbs
special high heat brakes and discs

the list went on and on and on and on ........

Nigel

[dahawk]

Wow ! This should be good. Seperate Ubec? I do have one suggestion though. Share the prescription they gave you in the hospital ! This plane is wild !

-Hawk

[solentlife]

Originally Posted by dahawk

Wow ! This should be good. Seperate Ubec? I do have one suggestion though. Share the prescription they gave you in the hospital ! This plane is wild !

-Hawk

Yep - separate BEC ... I know that the LVC is going to cut in and I know that I am going to have battery problems ... the ESC's are optos as well ...

First I'll be EPA'g the throttle back to 50A total ... then trying to decide what to do next ....

As you know I'm pushing limits on my EDF's and also now have the Edge racer ... all are having issues with LiPo's ...

Nanotechs failed me ... I cook batterys regularly ... luckily the batterys can be relegated to sport models like the Cessna ...

Nigel

[solentlife]

Hey Stu ... over on RCGroups - we have another jockey pushing the 190kph !!

Nigel

[solentlife]

I'm a total idiot !!
There's me - gone and fitted two overpowered heli motors to the PKJ(T) ... when in fact all I needed to do was to fit two lesser motors that took bigger props !
There would be no worries about torque from a big prop as they would have been contra-rotating .... I could fit 2 7x6 props no problem.
Consider the speed of the Rarebear ... the Edge 540 racer ... both are reckoned around the 100mph range when sorted ... and that's WITHOUT 100A overloads.
I was so far down the road of high kv .... immense power with the single - I lost sight of the twin advantage ...

Nigel

[solentlife]

Motors arrived ..... just have to find moment when Xmas festivities are not occupying my time !

She's finally coming ....

Nigel

[solentlife]

Will be starting on the refit today ... once I get "wife" sorted ... still expected to be taxi-driver ... but hopefully that is over today and I can get back to important job !!

When fitting new motors - will correct an error I made before ... one motor has an out of true thrust line... the beam mount moved when epoxy set. I'm hoping I can correct by washers behind the motor bolts.

Hopefully all will be sorted today or tmrw ... then it's test and then wait for suitable day ..

Tried getting to flight field yesterday - I have a Volvo XC70 .... it got stuck in deep snow, the snow piled up under the car and basically lifted her so light on the wheels ... finally came to stop and that was it. We dug away at it but finally had to call a tractor to pull her out !
I need a Range Rover !!

Nigel

[stuart]

Nigel my friend,post plenty of pictures. the pkj"t" is really going to be cool to see flying. your a true pkj test pilot...lol.where the few dare to go.

best news,i heard again from Shawn at hitec,my tx arriving Friday will work for my 2.4 module. I'll post more on the thread i started regarding it demise.

[solentlife]

You all remember this ...



When tested - the 450 motors ran up over 100A ... destroyed my LiPo .. caused a hurricane in my room !

Ordered two replacement motors ... they arrived and now I have them fitted ... Turnigy 2623 3000kv each one.

General view ...



Back end ..



Wiring needs tidying ! ..



Test?
On 3S she ran at 32A ... split across the 2 ESC - that's a more sensible 16A each ... and for a normal lIPo - much better !
On 4S she ran 52A ... again a much better result that will allow me to run my normal LiPo's ...........

Thrust ? WOW ! is all I can say ... holding her she is making me hold hard !

I envisage a similar situation as with power boats where two motors give better than a single of same power. Efficiency may be crap - but two props give better thrust. With contra props as well - I hope that all torque problems will be cancelled out. I have not coupled motors to turn copntrol as I dont want such power complicating matters ....

I see when I tested - she has a definite nose-down thrust - so I think a decent amount of UP reflex will be needed. Once I get her to fly ... I will adjust motor thrust line - to allow reflex to be taken out and maximum clean airflow on surfaces to give good speed run.

Nigel

[stuart]

VERY NICE NIGEL!!!man i do wish i could be there to see the pkjt tear up the sky. it must sound awesome. just curious,do the motors have a sound of balance when running or is there a pulsating sound when motors are out of sync?

as far as my future pkj runs..........new transmitter is here and works great with the module thats already binded to all my planes. weather isn't looking good for this weekend,snow/rain mix. Sunday is church,then a funeral of one of our church members who's been ill for some time.

so the next flight day may be 1/1/13,I've got nothing but smiles for the dopplering of the pkjs and funjet on new years day. i believe there also a frost fly day at the club field that day so hopefully I'll get flight time alone with the gang quite to get these doppler readings.

I'll reinstall all planes into the new TX Saturday.

enough about my stupid TX,hows the weather been in Russia,glad you got your car free from the snow.

[solentlife]

The motors hum together nicely ... seems well matched through throttle range. At top-end it's like a an alley of cats all screaming !!

Trouble at moment is to rig the catapult on such hard ground - frozen ... and with deep snow.

I would never allow anyone to try hand-launch her - as those twin props are just waiting to bite !

So maiden is a problem ... we plan to go flying tmrw 30/12/12 .... but lets see ...

Nigel

[stuart]

you can always do the weighted method. it works really well but i have a 25 l/b weight and the eye bolt i use sticks into the ground 5" just by dropping it down where ever i need it to stay.

one thing comes to mind with flying anything in the snow and certainly the small pkjs.....if it goes down into any minor depth of snow could disappear till spring. our club field is on top of an old refuse dump covered in tall 6" grass and when a bird goes down it usually goes out of sight. a friend at the field found my downed pkj once that was lost for days. it was in the grass off to the right of where i searched for hr's....he went looking for a lost landing gear and came back with both. i can just picture the pkj's nose diving into even a little depth of snow and leave little to no trace to find it...lol..

do a vid of the pkjt running up in your workshop shop at wot so we can get the rush of this lil screamer thats possibly going to make speed records tougher to beat than the already 222kph.

[solentlife]

Originally Posted by stuart

you can always do the weighted method. it works really well but i have a 25 l/b weight and the eye bolt i use sticks into the ground 5" just by dropping it down where ever i need it to stay.

one thing comes to mind with flying anything in the snow and certainly the small pkjs.....if it goes down into any minor depth of snow could disappear till spring. our club field is on top of an old refuse dump covered in tall 6" grass and when a bird goes down it usually goes out of sight. a friend at the field found my downed pkj once that was lost for days. it was in the grass off to the right of where i searched for hr's....he went looking for a lost landing gear and came back with both. i can just picture the pkj's nose diving into even a little depth of snow and leave little to no trace to find it...lol..

do a vid of the pkjt running up in your workshop shop at wot so we can get the rush of this lil screamer thats possibly going to make speed records tougher to beat than the already 222kph.

Snow makes it easier to find actually ... the holes are the give away ... grass tends to close back in again behind the article. I have front nose leg and wheel missing at our site ... spent hours doing search pattern EXACTLY where we all saw it fall ... never did find it in the grass.

The run up as you requested :

http://youtu.be/g2jKy0Dxthc

Just please allow a bit for upload to complete ... (I have new digital radio Internet link ... its much better than my last ...)

Nigel