SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Apr 01, 2012, 10:02 PM
Registered User
tobydogs's Avatar
Joined Mar 2012
78 Posts
it is both a good and beat rule to have ,but a lot of the members are older and have cautious ways.

i heard of accidents that happen over the many years and that would put the club at risk with the town who owns the refuse dump thats been closed and buried with grass on top. cuts from prop bites that required surgery and diving yourself to the hosp wouldn't have been good for one guy recently. if i go to parks to fly,i have less fun then when hanging with the gang. a great bunch of guys who love RC flying.

just received the shipping notice from the foilz company,after work flying will be next week[I'm wondering why it just emailed tonight,Sunday at 10:51,thats strange.]

the parks i fly in are to small for the funjet and pkj,as well as most of my kit builds. i ordered the Bushnell speedster radar gun for measuring speed along with the V3 speed pitot tube from hk. if the gun says 140mph,i Will expect the V3 to be a few mph more. the gun has a rep to recording less than the actual speed. still will be fun to use during the speed runs with pkj#2 .....and when we all figure out the very best setup is when I'll build the the pkj#3 thats sitting on the side waiting
tobydogs is offline Find More Posts by tobydogs
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 02, 2012, 03:00 AM
Registered User
Finlande
Joined Dec 2007
422 Posts
Tobydogs

Better throwing straight forward or very little up angle so that the plane get on speed quickly .

The only time I thought I would crash was when I launched once with a steep angle . Don't do that man cause you see on the video the plane crashing because of that .
Also, better not to move forward at the same time cause this will only increase the chances you don't throw straight .

Good luck and have fun
Jpette is offline Find More Posts by Jpette
Reply With Quote
Old Apr 02, 2012, 07:42 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,458 Posts
Quote:
Originally Posted by Jpette View Post
My motor is :

http://www.giantcod.co.uk/2217-2700k...-p-402979.html

With a 40A mystery ESC

My best recorded speed with APC 4,75x4,75 :

3S-Rhino-1050-30C : 162 km/h : 247W
3S Rhino -1550-30C : 169 km/h

4S Turnigy 1000-30C : 178 km/h : 380 W
4S nano-tech 1300-45C : 186 km/h


My recorded speed vary only 1-3 km from thoses max values.

Speed difference isn't that big between 3 or 4 cells :

Added power is hitting a "wall" because of the excess drag at thoses speeds .

I agree with you Solentlife that I could convert some of this power in speed by increasing the pitch . I"ll give it a try next time with a 4,75 x5,5 but my Turnigy packs won't cope wit it cause they already got pretty warm .

Let's go back flying guys cause this is such a fun plane !!
See the speed is there ..... we just have to get you up a bit and you'll be ;passing my mark. Given your kv ... it's very good. Mine was 3700kv and a heavy motor which counters the battery pack.

Pitch I still say is the key ... along with kv. But diameter is a killer .........

I reckon to try a 4 x 6 or higher pitch sometime ... ONCE I get bas*** to launch .. but I'm still away on assignment and don't get home till 2 days from now.
When going up in pitch - we have problems sourcing ... so I suggest cutting back larger props which also gives a stronger blade to take the thrust / stress.

I have loads of 8x6 elctro props that as a 8x6 are pretty flimsy ... but cut back are stiffer than the stock 5x5 I have ...
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Apr 02, 2012, 02:34 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,804 Posts
Anyone tried rc speedo on the iPhone, it recorded my fastest pass at 155kph, I'm not trying to beat you guys, it came as a total surprise it was moving the quick,
aeromaniac is online now Find More Posts by aeromaniac
Reply With Quote
Old Apr 02, 2012, 09:55 PM
Registered User
Finlande
Joined Dec 2007
422 Posts
Can you recal what is your setup ? Do you have any watt readings ?
Jpette is offline Find More Posts by Jpette
Reply With Quote
Old Apr 03, 2012, 03:34 AM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,804 Posts
Quote:
Originally Posted by Jpette View Post
Can you recal what is your setup ? Do you have any watt readings ?
I am using 3s1800mah 20c batteries, this kda 3500 kv motor http://www.hobbyking.com/hobbyking/s...i%5FMotor.html , tgs 4.1x4.1prop with a 25amps static. Motor comes down cold and esc has a hint of warmth.
aeromaniac is online now Find More Posts by aeromaniac
Reply With Quote
Old Apr 03, 2012, 09:22 AM
Registered User
Finlande
Joined Dec 2007
422 Posts
So it seems that pitch isn't all in the search for speed

Your motor draws about 262 W ( 25 A x10,5 V ) and you have a 3500 kV motor on 3 S with a 4,1x4,1 and you get 155 kph

My motor with less power (247 W on 3S) and less pitch with a 2700 kV and a 4,75x4,75 gets me to 162 kmh.
.
I think That this proves that in our search for speed , pitch isn't all and if you don't have enough diameter , you don't get as much speed .

My motor weight 70 g while yours is 43 g . Does it changes something in my reasoning ?
Jpette is offline Find More Posts by Jpette
Reply With Quote
Old Apr 03, 2012, 12:37 PM
Registered User
Finlande
Joined Dec 2007
422 Posts
I just got today some results with a higher pitch of 5,5.


------------------------ APC 4,75 x 4,75 / 4,75 x 5,5
Rhino 3S -1050 -30 C ---- 159 km/h -------152 km/h
Rhino 3S -1350 -30C ------ 162 -------- 162
Rhino 3S - 1550 -30C ----- 169 --------- 164

Turnigy 4S - 1000 -30C ----- 178 --------- 172
nano-tech 4S 1300 -45C ---- 186 --------- 183

I had a higher pitch today and even if there is a margin for errors , we see that speeds were lower than before .
I had noticeably much less acceleration , batteries were pushed harder and quite warm , flight time was reduced and all that for no benefit in top end speed .

By increasing the pitch, I lost power to overcome the drag and if I want to go faster , I should rather increase the diameter first but not the pitch alone .
My 4,75x5,5 which is oversquared has a terribly lower efficiency than the 4,75x4,75 .

In conclusion , I Idon't believe that searching the high kV motors with a very small prop is the way to go fast and by now , we don't yet have any proven results that would show otherwise .

Impressions aren't accurate and my 186 km/h Parkjet feels because of it's small size much faster than my over 200 km/h larger Funjet . I could easily estimate my Parkjet going over 220 km/h .

I am waiting for evidences guys with your own setups and the purpose isn't to bragg to know who has the fastest but just searching which setup will give max fun and speed so we can all benefit from it . That's part of the fun
Jpette is offline Find More Posts by Jpette
Last edited by Jpette; Apr 03, 2012 at 01:06 PM.
Reply With Quote
Old Apr 03, 2012, 04:26 PM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
So pop a 6x4 sport on it and let's get on with it! lol
IFlyRCs is offline Find More Posts by IFlyRCs
Reply With Quote
Old Apr 03, 2012, 09:32 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,804 Posts
My 1800's are a couple of years old And i have got a new turnigy 1800 to compare the difference, I believe my motor is settling back around 19amps in flight but can not prove it.
aeromaniac is online now Find More Posts by aeromaniac
Last edited by aeromaniac; Apr 03, 2012 at 10:37 PM.
Reply With Quote
Old Apr 03, 2012, 10:36 PM
Glow 😡 no no no
Australia, SA, Evanston Park
Joined Mar 2010
4,804 Posts
Back in the good old 80's I was racing 1/10 scale electric off road buggies, a friend and had 2 cars the same, so the performance on the race was, yes u guessed the same apart from driving style.
One day he said to me that he had gone to a 3 tooth smaller pinion the give him more acceleration but lower top speed, to our surprise his car was faster down the straight that my taller gearing.
It worked out hat his motor was spinning more freely and generating greater rpm under load, this was enough to make his car faster down the straight even with the lower gearing. I later found out it is related to back emf, if you look on YouTube you can find videos explaining back emf. Which will also effect duration but we already know that.
The trick is to load a motor to allow it to spin as hard as it can but still produce usable power by means of prop size and pitch, to much either way will reduce performance, it is often referred to as "the sweet spot" lol.
My sweet spot might be the same as yours but that's life, in this case I want a fast park jet but also want a reasonable duration, other are willing except a short duration for a couple of frenzy minutes of speed.
aeromaniac is online now Find More Posts by aeromaniac
Reply With Quote
Old Apr 04, 2012, 01:40 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,458 Posts
Quote:
Originally Posted by Jpette View Post
So it seems that pitch isn't all in the search for speed

Your motor draws about 262 W ( 25 A x10,5 V ) and you have a 3500 kV motor on 3 S with a 4,1x4,1 and you get 155 kph

My motor with less power (247 W on 3S) and less pitch with a 2700 kV and a 4,75x4,75 gets me to 162 kmh.
.
I think That this proves that in our search for speed , pitch isn't all and if you don't have enough diameter , you don't get as much speed .

My motor weight 70 g while yours is 43 g . Does it changes something in my reasoning ?
Of course diamter has to be accounted for - but not as much as Pitch ... you show immedaitely with your 4.75 vs his 4.1 an immediate gain ... The 4.1 is revving it's guts out and reaches max speed way before yours.
You have less KV not pitch ....... in fact a sig. increase in pitch and diameter.

No need for fancy maths ... just pitch x diameter x kv x volts ....

Yours : 4.75 x 4.75 x 2700 x 11.1 = 676,198.12 lets call it speed factor
His : 4.1 x 4.1 x 3500 x 11.1 = 653,068.5

% diff = 3.42% .... speed diff = 4.3%

Seems to agree in my book .............
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Apr 04, 2012, 01:50 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,458 Posts
Quote:
Originally Posted by aeromaniac View Post
Back in the good old 80's I was racing 1/10 scale electric off road buggies, a friend and had 2 cars the same, so the performance on the race was, yes u guessed the same apart from driving style.
One day he said to me that he had gone to a 3 tooth smaller pinion the give him more acceleration but lower top speed, to our surprise his car was faster down the straight that my taller gearing.
It worked out hat his motor was spinning more freely and generating greater rpm under load, this was enough to make his car faster down the straight even with the lower gearing. I later found out it is related to back emf, if you look on YouTube you can find videos explaining back emf. Which will also effect duration but we already know that.
The trick is to load a motor to allow it to spin as hard as it can but still produce usable power by means of prop size and pitch, to much either way will reduce performance, it is often referred to as "the sweet spot" lol.
My sweet spot might be the same as yours but that's life, in this case I want a fast park jet but also want a reasonable duration, other are willing except a short duration for a couple of frenzy minutes of speed.
I too raced electric cars ...... 1/12th indoor jobs ... remember all that silicon'g of tyres etc. Agree totally - I found same when I geared up ... accelleration was sluggish, top-speed needed far more straight length than available and batterys were pushed over the limits.

But on this PKJ I have ... we have another factor that comes in. Having had this proven to me in pylon racing and slope soraing - light is not always best. A ballasted model can perform faster due to gravity .......... a light floater can reach max speed far earlier against drag. My PKJ is heavy ... there is no doubt about that and now I have a lighter motor that is abouit 1/2 the weight .......... it will be interesting to see the difference. I expect with this motor - a 3800kv and will be fitted with 4.6 x 5 prop ... to get to about 180kph max. I do not expect to repeat my 222kph. In fact I do not want to ... I want to build back up to that as it was too difficult to launch. I want to sort it up in stages to keep stability in launching as much as possible.
solentlife is offline Find More Posts by solentlife
Reply With Quote
Old Apr 04, 2012, 03:11 AM
Registered User
Finlande
Joined Dec 2007
422 Posts
Quote:
Originally Posted by solentlife View Post
Of course diamter has to be accounted for - but not as much as Pitch ... you show immedaitely with your 4.75 vs his 4.1 an immediate gain ... The 4.1 is revving it's guts out and reaches max speed way before yours.
You have less KV not pitch ....... in fact a sig. increase in pitch and diameter.

No need for fancy maths ... just pitch x diameter x kv x volts ....

Yours : 4.75 x 4.75 x 2700 x 11.1 = 676,198.12 lets call it speed factor
His : 4.1 x 4.1 x 3500 x 11.1 = 653,068.5

% diff = 3.42% .... speed diff = 4.3%

Seems to agree in my book .............
You are right . I didn't take my calculator and thought it was opposite .

My previous point was only to show that with my specific motor, no 4,75 diameter prop would push faster no matter the pitch .
I think I" ll keep my 4,75x4,75 for a while cause 185 km/h is fast enough on that small airframe .

It could also be that the 4,75x5,5 prop doesn't accelerate fast enough and I have to turn before I can reach max speed . with the 4,75x4,75 , it accelerates like a dragster and it's much more fun .


IFlyRCs

Man , I enjoy more when we stay in physic than entering the ironic mode .
Your own setup and datas would be of more interest for the thread .
Jpette is offline Find More Posts by Jpette
Reply With Quote
Old Apr 04, 2012, 10:33 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
8,458 Posts
Ok ... if thats case that you can't get the straight run ...... go high, do a fighter wing over turn to come down to low height getting speed in that downward part ... level out ............ the excess will clear quite quickly and should not spoil a speed run. But you should be at max speed per prop.

Or if you are using a V3 as I am .......... then try to do wide circles so momentum builds up ........... instead of straight then yank and bank. With the speed we are doing - the wide circles is much easier and smoother.
solentlife is offline Find More Posts by solentlife
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 1004 Oct 18, 2014 11:01 PM
Discussion HK AT-6 Texan EPO Plug-n-Fly 29.5" w/s stuart warne Electric Warbirds 12 Jun 14, 2011 02:47 AM
For Sale HK Mini-PITTS -- EPO, Brushless, Plug 'n Fly WRXronald Aircraft - Electric - Airplanes (FS/W) 3 Aug 04, 2010 10:03 PM
New Product New HK Mini F-16 EDF Fighter Jet / EPO Plug-n-Fly CrashingDutchman Foamy EDFs 13 Jul 01, 2010 11:15 PM
Discussion HK's EPO F-16 WRXronald Foamy EDFs 5 Apr 11, 2010 02:47 PM