Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Hi-Performance and Sailplanes
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Hi-Performance and Sailplanes RC hotliners, electric pylon racers, F5B, F5D, sailplanes and gliders

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 07-23-2011, 11:00 PM   #1
twinbrother2010
Member
 
Join Date: Nov 2010
Posts: 45
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (0)
Default 160 mph Setup Question


Watch the above video. The guy who is flying this 160 mph Revolver claims to have the following setup:

12S lipos
Spin 99 Jeti ESC
5330/18 AXI motor 259kv
16x16 APC gas prop

The Jeti power box reports a top amp draw of only 80amps. I don't see how that's possible. My setup on my plane:

10S lipos
Hobbywing HV 12S 100amp ESC
E-flite 160 size brushless motor
16x15 APC E-prop (cut down 20x15)
80 amps full throttle

I don't see how this guy is only drawing 80 amps on a heavier gas prop with more cells on that Axi with a similar kv rating. With that many cells, he has to be drawing at least 120 amps. And he's overloading that Axi which is rated 10S max. Do I need to push my E-flite motor to get 160mph because I'm only getting 110mph with my setup.

And I even tried that same 16x16 gas prop, which I trimmed down to 14x16, and on 10 cells, it was drawing 106 amps on 10S for another motor rated at 270kv. On 12S, it would have blown the motor. How did the guy flying that Revolver achieve that? The setup doesn't add up.
twinbrother2010 is offline  
  Reply With Quote
Old 07-23-2011, 11:27 PM   #2
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,160
View rcers's Gallery57
Thanked 501 Times in 491 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

I would be skeptical too. Has someone Dopplered his video?

Mike
rcers is offline  
  Reply With Quote
Old 07-24-2011, 12:04 AM   #3
twinbrother2010
Member
 
Join Date: Nov 2010
Posts: 45
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (0)
Default 160 mph Revolver setup

The guy who filmed the video had his partner with the radar gun and it showed 160 mph. My plane goes 110 mph and it's not even close to how fast that Revolver is. My passes look way slow compared to that plane.

I guess it is possible if you fly for 1 min 30 sec. My flights typically last about 4-5 minutes aggressive flying. So if you cut down the flight time significantly, the motor won't have enough time to build up that much heat and you'll be sparing the motor from a meltdown.


The above video, the guy is pushing his Alekto setup with 12S and after the flight, everything is running HOT!!! One ESC was nearly 200 F. Insane!!! Appears the only way for large electrics to get that kind of speed is to push the components and reduce the flight times. I researched his components and the motors should only be running 7-8s max. He's putting in 12S on those motors.
twinbrother2010 is offline  
  Reply With Quote
Old 07-24-2011, 12:28 AM   #4
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,160
View rcers's Gallery57
Thanked 501 Times in 491 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

3600W 80amps 45V with a plane likely around 10lbs. 360w/lb. I guess it is doable. It does seem like he would be drawing more amps.

259kv x 45v (assumed) = 11,655 RPMs (at 100% efficiency). Pitch speed on a 16" pitch for that is 11655rpm x 16" x (.0009469) = 176.5mph.

I we take 80% 9324 rpms x 16" X .0009469 = 141mph.

90% efficiency is 10490 x 16 x .0009469 = 159mph.

Certainly in the realm of possibility.

Mike
rcers is offline  
  Reply With Quote
Old 07-24-2011, 12:36 AM   #5
CHELLIE
Super Contributor
 
CHELLIE's Avatar
 
Join Date: Oct 2006
Location: Hesperia, So. Calif
Posts: 18,282
View CHELLIE's Gallery13
Thanked 2,116 Times in 2,026 Posts
Club: Chino Renegades RC Flying Club
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Ambassador Award  100mph Speed Demon 
iTrader: (4)
Friends: (306)
Default

Originally Posted by twinbrother2010 View Post

Watch the above video. The guy who is flying this 160 mph Revolver claims to have the following setup:

12S lipos
Spin 99 Jeti ESC
5330/18 AXI motor 259kv
16x16 APC gas prop

The Jeti power box reports a top amp draw of only 80amps. I don't see how that's possible. My setup on my plane:

10S lipos
Hobbywing HV 12S 100amp ESC
E-flite 160 size brushless motor
16x15 APC E-prop (cut down 20x15)
80 amps full throttle

I don't see how this guy is only drawing 80 amps on a heavier gas prop with more cells on that Axi with a similar kv rating. With that many cells, he has to be drawing at least 120 amps. And he's overloading that Axi which is rated 10S max. Do I need to push my E-flite motor to get 160mph because I'm only getting 110mph with my setup.

And I even tried that same 16x16 gas prop, which I trimmed down to 14x16, and on 10 cells, it was drawing 106 amps on 10S for another motor rated at 270kv. On 12S, it would have blown the motor. How did the guy flying that Revolver achieve that? The setup doesn't add up.
Elevation, thinner air I think he is flying his plane in a higher elevation with thinner air, so there will be less draw on the motor and less Air drag on the plane.

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
CHELLIE is offline  
  Reply With Quote
Old 07-24-2011, 12:54 AM   #6
twinbrother2010
Member
 
Join Date: Nov 2010
Posts: 45
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (0)
Default

Originally Posted by rcers View Post
3600W 80amps 45V with a plane likely around 10lbs. 360w/lb. I guess it is doable. It does seem like he would be drawing more amps.

259kv x 45v (assumed) = 11,655 RPMs (at 100% efficiency). Pitch speed on a 16" pitch for that is 11655rpm x 16" x (.0009469) = 176.5mph.

I we take 80% 9324 rpms x 16" X .0009469 = 141mph.

90% efficiency is 10490 x 16 x .0009469 = 159mph.

Certainly in the realm of possibility.

Mike
90% efficiency? That's pretty unreal. I've had a few AXI motors and none of them have really impressed me all that much. Maybe it's the elevation as I'm just slightly above sea level. But even with the increased drag at lower elevations, I can't see the amp draw being that low. If the guy says he's running 12S, I believe him. I may just have to run 12S on my motor with a 16x16 prop for a 1 min flight and see what happens. If the motor blows, at least I'll know.
twinbrother2010 is offline  
  Reply With Quote
Old 07-24-2011, 01:01 AM   #7
CHELLIE
Super Contributor
 
CHELLIE's Avatar
 
Join Date: Oct 2006
Location: Hesperia, So. Calif
Posts: 18,282
View CHELLIE's Gallery13
Thanked 2,116 Times in 2,026 Posts
Club: Chino Renegades RC Flying Club
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Ambassador Award  100mph Speed Demon 
iTrader: (4)
Friends: (306)
Default

Originally Posted by twinbrother2010 View Post
90% efficiency? That's pretty unreal. I've had a few AXI motors and none of them have really impressed me all that much. Maybe it's the elevation as I'm just slightly above sea level. But even with the increased drag at lower elevations, I can't see the amp draw being that low. If the guy says he's running 12S, I believe him. I may just have to run 12S on my motor with a 16x16 prop for a 1 min flight and see what happens. If the motor blows, at least I'll know.
normally with more cells the amps will go down and the watts will go up, depending on the prop used, if you cut down a 20" prop, it will be wider than a 16" standard APC prop, that may be giving you the high amp reading. and the wrong airfoil for the prop, 4" off a prop is alot.

http://www.apcprop.com/ProductDetail...ctCode=LP16016

http://www.apcprop.com/v/Engineering...n.html#airfoil

I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
CHELLIE is offline  
  Reply With Quote
Old 07-24-2011, 01:20 AM   #8
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,946
Thanked 685 Times in 667 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by twinbrother2010 View Post

Watch the above video. The guy who is flying this 160 mph Revolver claims to have the following setup:
.
Word to the wise, my Revolver model airplane came apart at 90 MPH, flying straight and level. The cause of the failure is noted in this thread:
http://www.wattflyer.com/forums/showthread.php?t=48819
http://www.wattflyer.com/forums/showthread.php?t=46876

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 07-24-2011, 02:33 AM   #9
twinbrother2010
Member
 
Join Date: Nov 2010
Posts: 45
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (0)
Default Hold on here.

Originally Posted by CHELLIE View Post
normally with more cells the amps will go down and the watts will go up, depending on the prop used, if you cut down a 20" prop, it will be wider than a 16" standard APC prop, that may be giving you the high amp reading. and the wrong airfoil for the prop, 4" off a prop is alot.

http://www.apcprop.com/ProductDetail...ctCode=LP16016

http://www.apcprop.com/v/Engineering...n.html#airfoil
Let's not start confusing people here. If you use the same prop, increasing the number of cells will also increase the amp draw. An 11S on a 16x16 prop will draw more amps than a 10S on a 16x16 prop. And I understand cutting 4" off a 20x15 prop is a lot. I've done the tests though. The amp draw on a 16x15(cut down 20x15 e-prop) is about the same amp draw as a 16x14 gas prop. There is only about a 5 amp difference when running 10S.
twinbrother2010 is offline  
  Reply With Quote
Old 07-24-2011, 03:00 AM   #10
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,160
View rcers's Gallery57
Thanked 501 Times in 491 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

Originally Posted by twinbrother2010 View Post
90% efficiency? That's pretty unreal. I've had a few AXI motors and none of them have really impressed me all that much. Maybe it's the elevation as I'm just slightly above sea level. But even with the increased drag at lower elevations, I can't see the amp draw being that low. If the guy says he's running 12S, I believe him. I may just have to run 12S on my motor with a 16x16 prop for a 1 min flight and see what happens. If the motor blows, at least I'll know.
So couple of weird things on square and over-square props. I have actually seen them exceed their theoretical limit on pitch. Couple of things happen I think.

As you get in the air and the props unload the motor can actually spin faster and this the pitch speed increases. I think this is less common with electric motors, but it does occur. In flight measuring of RPM, amps, watts and speed would be really valuable here.

While I agree 90% motor efficiency is not likely 90% efficiency overall is - with that prop unloading once the static load is lifted. The propeller becomes MUCH more efficient so that helps raise you higher in overall efficiency.

I do know a super clean airframe is a must. Remember our fastest RC models BY FAR are ones without motors, engines or turbines.

Also - he is not getting that speed in straight and level flight - he is diving to do that that is a BIG factor for overall speed and just how the DS guys do it.

Straight and level if his amp draw truly is 80amps would be around ~140mph I would guess.

Not sure thinner air is much of an helping issue but perhaps a small bit.

Mike
rcers is offline  
  Reply With Quote
Old 07-24-2011, 03:14 AM   #11
Larry3215
Look out for that tree!!!
 
Larry3215's Avatar
 
Join Date: Mar 2006
Location: Gig Harbor, Wa USA
Posts: 6,797
View Larry3215's Gallery63
Thanked 691 Times in 670 Posts
Club: Kitsap ARCS & E-FLAPS
Awards Showcase

90 Minute Thermal Duration  60 Minute Thermal Duration  30 Minute Thermal Duration  4kW 
iTrader: (6)
Friends: (21)
Default

Part of the problem is they are using the Jeti esc to report amp draw. They are known to be way off at times.

Id doubt the amp draw as reported. It could be a lot higher - or lower

I think I need a signature.
Larry
Larry3215 is offline  
  Reply With Quote
Old 07-24-2011, 03:47 AM   #12
kyleservicetech
Dennis V
 
kyleservicetech's Avatar
 
Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 7,946
Thanked 685 Times in 667 Posts
Club: www.racinercclub.com (I'm the newsletter editor)
Awards Showcase

Outstanding Contributor Award  3kW  2kW  100mph Speed Demon 
iTrader: (1)
Friends: (20)
Default

Originally Posted by twinbrother2010 View Post
90% efficiency? That's pretty unreal.

The problem with all of our electric motors, if you really push them way beyond their ratings for a few seconds, the motor efficiency tends to drop like a rock.

Motocalc suggests the motor efficiency for the AXI motor is only around 60% or so at those high power levels. That represents some 1100 watts being dissipated in the motor windings.

DennyV
Retired and the days are just too short, busier than ever!
kyleservicetech is offline  
  Reply With Quote
Old 07-24-2011, 12:38 PM   #13
rcers
Community Moderator
 
rcers's Avatar
 
Join Date: Jul 2005
Location: Trophy Club TX
Posts: 6,160
View rcers's Gallery57
Thanked 501 Times in 491 Posts
Awards Showcase

WAA-08 Pilot 
iTrader: (4)
Friends: (9)
Default

There are a number of things in question. I am not sure how he is getting 3600w of power in a 2000w motor. AXI motors are good but not that good.

There is no way that 23 ounce motor is capable of dissipating 1100 watts of power. Since he is going fast - you know cooling is an issue since that is so draggy.

I agree that he is pulling more than 80 amps. He is diving to get that speed (that is "cheating") and suspect just like Larry his "reported" amp draw is much higher.

I think if it were a Nue motor he would be in the 90% efficiency range but again this is not that.

So I think we are drawing more amps and I too wonder how that motor is not getting mighty warm. Something like the OP said just does not add up here.

Mike
rcers is offline  
  Reply With Quote
Old 07-25-2011, 05:15 AM   #14
twinbrother2010
Member
 
Join Date: Nov 2010
Posts: 45
Thanked 2 Times in 2 Posts
iTrader: (0)
Friends: (0)
Default Absolutely right!!!

Originally Posted by rcers View Post
There are a number of things in question. I am not sure how he is getting 3600w of power in a 2000w motor. AXI motors are good but not that good.

There is no way that 23 ounce motor is capable of dissipating 1100 watts of power. Since he is going fast - you know cooling is an issue since that is so draggy.

I agree that he is pulling more than 80 amps. He is diving to get that speed (that is "cheating") and suspect just like Larry his "reported" amp draw is much higher.

I think if it were a Nue motor he would be in the 90% efficiency range but again this is not that.

So I think we are drawing more amps and I too wonder how that motor is not getting mighty warm. Something like the OP said just does not add up here.

Mike
This is why I started the post. I've been flying electrics for 6+ years. I don't see how that 16x16 apc gas prop can spin a 12S Axi 5330/18 and get that speed. My experience with Axi is if the prop is too big, the motor just won't spin. I may just try to run my 245kv motor on 12S and try spinning a 16x16 apc prop just to see how many amps I'll be drawing. I actually purchased a 16x16 to see how big the prop is and it is big and heavy.
twinbrother2010 is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > Hi-Performance and Sailplanes

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
100+ MPH Club CHELLIE Hi-Performance and Sailplanes 1955 08-20-2014 02:55 AM
Its On, Start Building, 100 Mph Under $100.00 Foamie Contest CHELLIE Scratch and Kit Built Aircraft 151 09-12-2011 06:14 AM
Prop Selection Hose Man Beginners 7 03-23-2011 01:57 PM
Tri-Motor setup question KnowAceHere General Electric Discussions 9 02-08-2011 08:39 PM
Need help with complete setup. KenSue Power Systems 9 01-29-2011 01:36 AM


All times are GMT +1. The time now is 03:38 AM.


Powered by: vBulletin
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.34969 seconds with 49 queries