HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 30, 2011, 08:21 PM
2.3 D Hack Bradenton FL
frankjp's Avatar
Joined Dec 2010
182 Posts
. Doc Rocks.[/QUOTE]

Yes! Doc Rocks!

OK. Eagle Tree is sending me the 140 Amp and the RPM pick ups, so we should be able to do some on-board testing this weekend weather permitting. Throttle position may also be a possibility.

Frankjp
frankjp is offline Find More Posts by frankjp
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 30, 2011, 09:06 PM
3D Hack
JC Spohr's Avatar
United States, IL, Glen Carbon
Joined Jul 2010
1,950 Posts
Quote:
Originally Posted by frankjp View Post
OK. Eagle Tree is sending me the 140 Amp and the RPM pick ups, so we should be able to do some on-board testing this weekend weather permitting. Throttle position may also be a possibility.

Frankjp
Did I mention that you guys rock!



JC
JC Spohr is online now Find More Posts by JC Spohr
RCG Plus Member
Latest blog entry: About Me
Reply With Quote
Old Dec 01, 2011, 12:41 PM
Registered User
leespaddock's Avatar
USA, WA, Redmond
Joined Aug 2010
231 Posts
Quote:
Originally Posted by frankjp View Post
. Doc Rocks.
Yes! Doc Rocks!

OK. Eagle Tree is sending me the 140 Amp and the RPM pick ups, so we should be able to do some on-board testing this weekend weather permitting. Throttle position may also be a possibility.

Frankjp[/QUOTE]

You Guys Rock +2
leespaddock is offline Find More Posts by leespaddock
Reply With Quote
Old Dec 03, 2011, 09:54 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
7,250 Posts
Thanks to Frank and Tom, I was able to put some raw data together today. From our preliminary discussion, I think it is safe to say that we all agree that what we saw has definitively put a few things to bed about the difference between the APC and the Xoar. The thing I can't wait to look at is the Vox 16x6 data. Some interesting stuff.

We did have a blast today... at dusk, a flying buddy came up with tickets to the Bradenton Motorsports Park next to where we were flying today. Watching and feeling the jet cars accelerating down the quarter mile really capped off the day for Tom and me. Thanks, guys (Frank, Ernie, and Troy).

We have the MCRC Christmas Party tomorrow, so I may not have the data charted until late Monday, so stay tuned.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Dec 03, 2011, 09:56 PM
Facts, Logic, 3D
Tom K.'s Avatar
Florida
Joined Nov 2010
3,585 Posts
Yeah.. jet cars, 6,000 lbs of thrust, 284mph, then the jet truck with that F-4 engine in it... definatel cool

--Tom K.
Tom K. is offline Find More Posts by Tom K.
RCG Plus Member
Latest blog entry: 12S on the 3DHS 74" Edge 540
Reply With Quote
Old Dec 03, 2011, 10:42 PM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by Tom K. View Post
Yeah.. jet cars, 6,000 lbs of thrust, 284mph, then the jet truck with that F-4 engine in it... definatel cool

--Tom K.
6,000 lbs is just a fraction of the engine on the 777.

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Dec 04, 2011, 12:20 AM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
7,250 Posts
Quote:
Originally Posted by vienquach View Post
6,000 lbs is just a fraction of the engine on the 777.

Vien
One vehicle had the same jet engine as was in both the F-104 Starfighter and the F-4 Phantom, which had two engines... between 15,000 and 18,000 lbs each. Quite a flame, smoke, and noise show.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Dec 04, 2011, 03:19 AM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by Aeroplayin View Post
One vehicle had the same jet engine as was in both the F-104 Starfighter and the F-4 Phantom, which had two engines... between 15,000 and 18,000 lbs each. Quite a flame, smoke, and noise show.
Yeah, jet engine is cool.

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Dec 04, 2011, 08:50 AM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
7,250 Posts
Okay, numbers has always been a major part of my professional life, but this venture has been a lot of fun, and this data has now become especially enlightening.

If this does not explain why meter-read Watts is such a useless variable to us in this application, nothing will. Anyone who looked at Watts in the past and immediately related it to performance will have an epiphany.

Frank, Tom and I spent a substantial amount of focused time on this, but yesterday's field test was by far the most productive. We worked as a team, at various points around the plane, to collect an accurate representation of Amps, Volts, Thrust, Watts, and RPMs.

The intended result was to establish a clear difference between the APC and the Xoar at the 16x8 size level. We also added an ad-hoc comparison of the 16x6 Vox, since there was the possibility that lowering the pitch may allow the motor to spin up a bit more while reducing the negative aspects of the Amps that we were seeing on this 16 inch prop size.

I just finished plotting the data and I personally feel that what I was looking for, from the data side, has been achieved. The remaining aspect of the project is to get Tom in the air with each prop so we can get some videos of some power maneuvers, and a subjective commentary on their flight performance and characteristics.

I may post the charts first so that the open conversation can begin here, but my own analysis will be available in PDF early next week if anyone is interested. This is good stuff and Iím anxious to get it to you, but we have a Christmas party that we have to leave for soon, so I may not get to it until after my typical Monday calms down. I have two projects deadlines coming up on Jan 1.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Dec 04, 2011, 09:14 AM
c/f
Registered User
Joined Jan 2004
3,315 Posts
"Anyone who looked at Watts in the past and immediately related it to performance will have an epiphany."

In the RCG powerplant section you will see a sticky of Dr Kiwi, who does many motor reviews, He constantly downgrades motor specs from factory specs based on your epiphany above, because increasing watts beyond a certain point of efficiency just turns into HEAT that is unproductive to the system as a whole.

What his static tests dont prove and your Eagle Tree will prove is that electric motors DO IN FACT UNLOAD in air,this may be an epiphany for you, The moral of the story is the less eff a motor is static, it will unload to greater degree in air to improve the eff.

This is what I am most interested in your findings as unloading in air for 3D may never occur unless flying high energy versus slow flight 3D. Please try to include this type of flying defined.
c/f is offline Find More Posts by c/f
Reply With Quote
Old Dec 04, 2011, 09:19 PM
Not as Good as The Kid
Aeroplayin's Avatar
South Pasadena, FL
Joined Sep 2009
7,250 Posts
Quote:
Originally Posted by c/f View Post
"Anyone who looked at Watts in the past and immediately related it to performance will have an epiphany."

In the RCG powerplant section you will see a sticky of Dr Kiwi, who does many motor reviews, He constantly downgrades motor specs from factory specs based on your epiphany above, because increasing watts beyond a certain point of efficiency just turns into HEAT that is unproductive to the system as a whole.
This brings up another good point. We have always addressed the internal resistance issue and how even the Amps reading can be way off. What I am talking about is how a noticeable voltage sag may flag the fact that some Amps are not being accurately displayed at the meter too. Here is a real experience:

We had a motor that was originally set up with a 3S blue Turnigy battery and generated 533 Watts and 48 Amps in the smaller plane. This means that since Watts = Amps x volts, my voltage was 11.10 volts total, or 3.70 volts per cell, under WOT load. My 4 cells setup was generating 680 Watts and 53 Amps. This means that my voltage was 12.8 volts total, or 3.20 volts per cell, under WOT load.

The difference between the 3.70 volts and the 3.20 volts is significant enough to raise a red flag. If I was getting 3.70 volts per cell on the first setup that ran fine, the drop in voltage could be the evidence of a problem. Any loss of current this significant could mean high internal resistance and a significant conversion to heat. To test this, I used Ohm’s Law.

From my original setup’s readings, I can calculate that 11.1v divided by 48 Amps equals 0.23125 Ohms. This is the representative value of internal resistance. 3.7 volts per cell minus 3.2 volts per cell equals 0.5 volts per cell, which means that my 4 cell setup can be losing 2 volts somewhere. If voltage = Amps x Ohms, then Amps equals volts divided by Ohms:

Amp = 2.0 volts / 0.23125 Ohms

The problem was that I was also running the motor on a 60A max ESC. The 53 Amps that the meter told me I was drawing was probably more like 62 Amps. We did cook the ESC and when we went to an ESC that had a max rating of 80A, the meter then suddenly register 62 Amps. Imagine that.

This is just another reason why I have always been asking guy who post stats what the prop size and RPMs are. Every prop spinning at specific RPMs requires a specific amount of Watts to achieve that RPM. The prop simply will not spin that fast unless the motor is generating the required power, and power is Watts or HP and 749W equals 1 HP.
Aeroplayin is offline Find More Posts by Aeroplayin
RCG Plus Member
Reply With Quote
Old Dec 04, 2011, 10:17 PM
They Call him Dead!
YellowJacketsRC's Avatar
United States, SC, Pawleys Island
Joined Jul 2003
7,063 Posts
Man, the suspense is killing me!
YellowJacketsRC is offline Find More Posts by YellowJacketsRC
Reply With Quote
Old Dec 04, 2011, 10:20 PM
Registered User
vienquach's Avatar
Chicago, IL
Joined Nov 2009
3,039 Posts
Quote:
Originally Posted by dead View Post
Man, the suspense is killing me!
Dead,
How do you like the Motrolfly 2815 700 kv that you purchased a while ago ?

Vien
vienquach is offline Find More Posts by vienquach
Reply With Quote
Old Dec 04, 2011, 10:23 PM
VOLTS > AMPS
stgdz's Avatar
United States, MN, Buffalo
Joined Jul 2011
3,867 Posts
Quote:
Originally Posted by dead View Post
Man, the suspense is killing me!
yeah I saw AP's post and I got all excitted. Will have to check out the results tomorrow at lunch.
stgdz is offline Find More Posts by stgdz
Reply With Quote
Old Dec 04, 2011, 10:39 PM
They Call him Dead!
YellowJacketsRC's Avatar
United States, SC, Pawleys Island
Joined Jul 2003
7,063 Posts
Quote:
Originally Posted by vienquach View Post
Dead,
How do you like the Motrolfly 2815 700 kv that you purchased a while ago ?

Vien
I like it better than the Torque I had. I am using a 14 x 7 APC and ind that it gives more stability in post stall, especially hover; has really powerful pull out of hover and really rockets to the sky; also, the 14 x 7 does not stall on me when trying to get out of trouble. I found that on the 12 x 6 with the torque I would often get very slow response from the motor when I was low and hovering and needed to get a quick burst of power. The motor would spool up very fast, but there would be a lag between spool up and actual torque. I can only assume this was related to the prop spinning without moving much air or "stalling". The new set up completely nullifies this problem!

I can not compare it to the 2820 that Tom is flying cause I have not flown or seen it in person. My thought was that the 2815 was about the same weight as the torque so.... I did not feel that I needed a lot more power per se. I just wanted instant torque out of hover and more stability in 3D flight. I got both with the larger prop and am very happy.
YellowJacketsRC is offline Find More Posts by YellowJacketsRC
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question RC kits for experimenting with flight control systems SubZer0 DIY Electronics 11 Oct 12, 2011 09:58 AM
Wanted left wing for extreme flight yellow and black 74 yak hondaboy92hatch Aircraft - Fuel - Airplanes (FS/W) 0 Sep 29, 2011 11:18 AM
Discussion Extreme power systems & Royal Evo 12 rbehrends Radios 5 Oct 11, 2007 06:55 PM
Discussion Battery for Logo 10 - Thunder Power "eXtreme" 5S 4600 or Flight Power 5S 3700? WeatherB Electric Heli Talk 6 Jan 25, 2007 11:29 PM