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Old Dec 14, 2008, 09:52 PM
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brati4's Avatar
Wichita,Ks
Joined Feb 2007
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Quote:
Originally Posted by gotboostedvr6
From experience using a 4s lipo

this motor with a 4.7 x 4.2

http://www.hobbycity.com/hobbycity/s...hless_Inrunner

This motor on a 6 x 5.5: 105 mph 450 watts 6 x 6 graupner 470 watts and 108 mph
http://www.hobbycity.com/hobbycity/s...hless_Inrunner
Thanks, you mentioned experience, Have you used these motors? What kind of amps are we talking and how did you get the numbers for watts and mph?
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Old Dec 14, 2008, 11:08 PM
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gotboostedvr6's Avatar
USA, NJ, Mt Laurel
Joined Oct 2007
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The first motor is a personal favorite of mine. It also responds well to the multiplex black 5 x 4 on 4s.

The second is in a fellow fliers Stryker at my field that I built and test flew. It had vertical like you would not believe.... it really liked 5s and a 5.5 x 4.5 out of a slight dive(funjet is WAY more areo so this would be unnecessary).

The second motor is heavy but uses a much longer magnet to help swing a larger prop under load.. Plus it has less teeth/pole count so it has a low IO value and is efficient for the KV due to larger gauge windings.. it will run 4s and 5s very well if your lipos are at least 2500 mah 4s, and 2200 5s, to help CG>
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Old Dec 14, 2008, 11:23 PM
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Thanks for the inputs, I'm trying to avoid trial and error and get thing in the 110mph area.

Quote:
Originally Posted by gotboostedvr6
The first motor is a personal favorite of mine. It also responds well to the multiplex black 5 x 4 on 4s.

The second is in a fellow fliers Stryker at my field that I built and test flew. It had vertical like you would not believe.... it really liked 5s and a 5.5 x 4.5 out of a slight dive(funjet is WAY more areo so this would be unnecessary).

The second motor is heavy but uses a much longer magnet to help swing a larger prop under load.. Plus it has less teeth/pole count so it has a low IO value and is efficient for the KV due to larger gauge windings.. it will run 4s and 5s very well if your lipos are at least 2500 mah 4s, and 2200 5s, to help CG>
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Old Dec 14, 2008, 11:40 PM
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gotboostedvr6's Avatar
USA, NJ, Mt Laurel
Joined Oct 2007
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Second motor and 5s would be the ticket on the cheap.

cheap Hobby king setup:
Super simple 70 map esc, HXT D9 G2 4100mAh 5S 15-25C Lipoly Pack for $80 or Rhino 4900mAh 5S1P 20C Lipoly Pack for $60 or Rhino 3700mAh 5S1P 20C Lipoly Pack for $65 and a 5.5 x 4 APC sport prop and you will be on your merry way.

more costly:
Buy a ARC 1.5 and a 100amp speed controller from lightflightrc.com, a 4000-5000 4s lipo from hobbyking 60-$80, and a 6x4 gas prop and you will see 130-140 + for around $180
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Old Dec 15, 2008, 08:13 AM
I buy, I fly, I buy....
Wingwrecker's Avatar
United States, OH, Toledo
Joined Feb 2008
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Looks like lightflightrc is having some stock issues. The 1.5 and 2T are out as well as the 100a esc's.
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Old Dec 15, 2008, 08:24 AM
Annoying people since 1970 :)
United Kingdom, England, Taunton
Joined Nov 2005
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Quote:
Originally Posted by brati4
Thanks for the inputs, I'm trying to avoid trial and error and get thing in the 110mph area.
Why not run a $50 HET 4W on 4 cell with a 6x5.5 APC. It's cheap and will get you to 110mph.
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Old Dec 15, 2008, 09:01 AM
Xtreme Nut
Kuala Lumpur, Malaysia
Joined Oct 2005
2,046 Posts
Brati ... I used the Hobby City KB28-47 2,100 on 4S with a 4.75 x 4.75 with a 4S pack, I vaguely remember it was pulling about 50A max. That was ok. She was fast but maybe about 100 mph max. I do have the KB28-47 2,300 but have not used it, I think that is better.

Frankly, the FJ is flying at its optimum with a 4S 2,500 mAh pack, anything more is really pointless, I have gone 6S and its really a waste of time, I pulled about 1KW to gain maybe 15-20 mph over the 4S set up, that is almost twice the power for another 20 mph.

Not to forget the handling, it was a real pig to fly. If you can, stick to 4S. If you really want to go fast, look for something else ... hey a real hotliner. Something like the VIP Racer and Sokol etc will leave the FJ far behind on a mere 3S set up.

The answer to speed is in the fuse not the power system.
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Old Dec 15, 2008, 10:21 AM
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Quote:
Originally Posted by wastegate
Why not run a $50 HET 4W on 4 cell with a 6x5.5 APC. It's cheap and will get you to 110mph.
I was thinking about that one. Trying to do the coin toss between the 3W or 4W
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Old Dec 15, 2008, 10:30 AM
Annoying people since 1970 :)
United Kingdom, England, Taunton
Joined Nov 2005
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If your using 4 cell then I'd go with the 4W. You'd have to use a small prop with the 3W on 4 cell for it to last.
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Old Dec 15, 2008, 11:31 AM
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Bay Area, CA
Joined Sep 2007
1,162 Posts
Quote:
Originally Posted by Eagle50
Wow first slowflyers, then pusher props, then EDF's and now I can easily see moving forward into the small turbine$! There is something about that sound that can just catalyze one's need for speed!

Addiction:

"The compulsive need for and use of a habit-forming substance, characterized by tolerance and by well-defined physiological symptoms upon withdrawl"
Wow, Glad to know I'm not alone
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Old Dec 15, 2008, 11:59 AM
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Bay Area, CA
Joined Sep 2007
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Quote:
Originally Posted by Lostlad
he like most that take a running start to throw there plane almost always stop just before they throw it..... lol I think it's funny.
Actually there is a lot of physics behind it.

Conservation of momentum and energy.
Newton's Pendulum (0 min 16 sec)

I simple terms, when you run and then stop abruptly, the intertia / momentum is transfered to your arm (and then to your plane) which is beginning to launch and you get that extra boost when your plane leaves your hand.

If have look at javelin throwing, same laws of physics are in action.
WR Javelin Throw 104.80m (0 min 24 sec)

Usually this technique works better with heavier planes. With lighter planes I haven't experienced any extra benefit.

Happy flying !!!
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Old Dec 15, 2008, 12:03 PM
What smoke?
Lostlad's Avatar
SoCal
Joined Feb 2008
279 Posts
Quote:
Originally Posted by numb_thumb
Actually there is a lot of physics behind it.

Conservation of momentum and energy.
Newton's Pendulum (0 min 16 sec)

I simple terms, when you run and then stop abruptly, the intertia / momentum is transfered to your arm (and then to your plane) which is beginning to launch and you get that extra boost when your plane leaves your hand.

If have look at javelin throwing, same laws of physics are in action.
WR Javelin Throw 104.80m (0 min 24 sec)

Usually this technique works better with heavier planes. With lighter planes I haven't experienced any extra benefit.

Happy flying !!!
LOL well I never said it didn't work I just think it looks funny!
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Old Dec 15, 2008, 01:32 PM
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United States, CA, SF
Joined Mar 2008
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Lostlad,

, the video clearly showed the guy doing a horrible job by losing 95.73% of any momentum he had built....he didn't look graceful either.

_______________________

numb_thumb,

I agree that there was a remote resemblance of some physics being used by the guy launching his plane.......(Rolling on the floor laughing)

He could have done much better with a half step.

Seriously though:
How is your bad boy Funjet coming along?

There is a guy who posted a 158 MPH Funjet Eagle Tree chart (GPS sensor) on the Stryker thread (RCG) yesterday...grossly over propped the 28mm MEGA. I think a smaller prop on same motor could hit the same speeds.
158 MPH was not full watts so must be a dive, but 4th and 5th wide open throttle runs show 155, 154 MPH...pretty good for hobby city pack.
I wonder what speed he could achieve on his first full throttle pass if he was not climbing or diving.

Your efficiency on the 36mm motor at same 1900+W 5S should be a lot better.


Gryphon
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Last edited by GryphonRCU; Dec 15, 2008 at 01:47 PM.
Old Dec 15, 2008, 02:20 PM
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United States, CA, SF
Joined Mar 2008
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This following chart was made by me from a friend's data.
I do not know the accuracy of data expect that it was from a new data logger.
I had some difficulty trying to make it a picture file; I hope it looks clear enough with stretch skew etc....

The power figures seem a lot more than some of you posted with same motor, and I guess it has to do with the size of cells (larger versus smaller cells). Assuming no one had any issues.

Medusa 28-56-2800 V2
TP 3S-3850 25C V2
CC Phoenix 125A ESC

Not sure if one of the middle size props was a cutdown prop or not.
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Old Dec 15, 2008, 11:22 PM
CERTIFIED LIPO PUFFER
United States, CA, Cypress
Joined Jan 2008
276 Posts
running lauch, pendulum thingy, and javelin throws

running launch: i've always thought that the purpose of a running launch is to combine arm speed and foot speed to induce a greater speed when the plane leaves the hand. i've seen quite a few people do a running start, only to slow down or almost stop just before the throw. I think this is a case of them not being used to doing running launches causing them to slow down to get in proper form to throw, or else they'll end up w/ a bad throw. This, i think, defeats the purpose of the running. This one guy used to fly 5 or 6 pylon ships at my field, all on nicads (he's old school), so they're all underpowered. He always used the running launch method and he never stop or even slow down as he throw his planes.

pendulum thingy: i notice that the first ball comes to a stop as it hits the next ball when it goes at full speed. this will transfer all of its energy to the next ball, therefore conserve energy. Don't quote me but i always thought inertia/moment/work thingymajigatey is a function of mass and velocity. If the pilot stops/slows down just before the throw, then inertia is gone/ lower. I don't think anything is transfered to his arm.

javelin throws: i know nothing about this particular sport but i would assume that ultimate speed as the javelin leaves the hand is not as important as how much cajones is put into it, therefore, i don't think it's all that important for the thrower to be still running as he releases the javelin.

i don't even know what i'm sayin' i never did finish that physics class.
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