Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 05-14-2017, 08:32 PM   #1 (permalink)
Master EcoModder
 
JRMichler's Avatar
 
Join Date: Feb 2011
Location: Phillips, WI
Posts: 1,013

Nameless - '06 GMC Canyon
90 day: 37.45 mpg (US)

22 Maverick - '22 Ford Maverick XL
90 day: 41.9 mpg (US)
Thanks: 188
Thanked 466 Times in 287 Posts
Radio Antenna Drag

I have not removed my radio antenna, which was commented on in at least one thread. Now I know why because I finally did the calculation for drag from my radio antenna. Here's the calculation:

INPUTS
Antenna diameter 5/32"
Antenna length 29"
Air density 0.075 lb/ft3
Viscosity of air 3.8E-7 lb-sec/ft2
Speed 80 ft/sec (just under 55 MPH)

CALCULATIONS
Reynolds number = 0.156" / 12 in/ft X 0.075 lbs/ft3 / 32.2 ft/sec2 / X 80 ft/sec / 3.8E-7 lb-sec/ft2 = 6400

Cd for a cylinder at Re 6400 = 1.0

Drag = 0.5 X Cd X A X rho X V2 =
= 0.5 X 1.0 X 0.156" / 12 in/ft X 29" / 12 in/ft X 0.075 lb/ft3 / 32.2 ft/sec2 X 80^2 ft2/sec2 = 0.234 lbs drag from the radio antenna

At 80 ft/sec, this is 0.234 lbs X 80 ft/sec = 19 ft-lbs/sec = 0.034 hp (1 hp = 550 ft-lbs/second). The radio antenna air drag requires 0.034 hp (0.025 kw)

I averaged 35 MPG last year. If we simplify by assuming all driving was at that speed, then fuel flow was 55 MPH / 35 MPG = 1.57 gallons/hour = 9.4 lbs/hour. Power is estimated by assuming 0.5 lbs/hp-hr, so 9.4 lbs/hour / 0.5 lbs/hp-hr = 18.857 hp. Removing the radio antenna would reduce this to 18.857 - 0.034 = 18.823 hp. The resulting estimated gas mileage would be 35 MPG X 18.857 / 18.823 = 35.06 MPG.

I would gain an estimated 0.06 MPG. I drove 10,588.6 miles last year. That would be 302.53 gallons at 35 MPG, and 302.01 gallons at 35.06 MPG. The radio antenna cost me 0.52 gallons of fuel last year. The actual savings would be less because part of my driving is at slower speeds. I will pay that cost in order to listen to the radio once in a while.

__________________
06 Canyon: The vacuum gauge plus wheel covers helped increase summer 2015 mileage to 38.5 MPG, while summer 2016 mileage was 38.6 MPG without the wheel covers. Drove 33,021 miles 2016-2018 at 35.00 MPG.

22 Maverick: Summer 2022 burned 62.74 gallons in 3145.1 miles for 50.1 MPG. Winter 2023-2024 - 2416.7 miles, 58.66 gallons for 41 MPG.
  Reply With Quote
The Following 8 Users Say Thank You to JRMichler For This Useful Post:
ajohn7211 (06-18-2017), BabyDiesel (05-15-2017), BamZipPow (05-16-2017), ChopStix (05-15-2017), Ecky (05-16-2017), mcrews (05-16-2017), oldtamiyaphile (05-14-2017), SoobieOut (05-15-2017)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 05-14-2017, 10:20 PM   #2 (permalink)
Master EcoModder
 
Join Date: May 2012
Location: Tampa, FL
Posts: 1,745

Volt, gas only - '12 Chevrolet Volt Premium
90 day: 38.02 mpg (US)

Volt, electric only - '12 Chevrolet Volt Premium
90 day: 132.26 mpg (US)

Yukon Denali Hybrid - '12 GMC Yukon Denali Hybrid
90 day: 21.48 mpg (US)
Thanks: 206
Thanked 420 Times in 302 Posts
Im actually surprised it was that much.
__________________




  Reply With Quote
The Following User Says Thank You to ksa8907 For This Useful Post:
mcrews (05-16-2017)
Old 05-15-2017, 12:07 AM   #3 (permalink)
Primer is still paint!
 
ChopStix's Avatar
 
Join Date: Aug 2015
Location: box by the river
Posts: 547

85 Chevy Pickup C10 - '85 Chevy C10
Thanks: 89
Thanked 120 Times in 94 Posts
I think some older cars would be worse as they had brick shaped antenna bases. But I would not remove it either, gotta have my tunes!
  Reply With Quote
Old 05-15-2017, 01:30 AM   #4 (permalink)
Polymorphic Modder
 
SoobieOut's Avatar
 
Join Date: Aug 2010
Location: Utah
Posts: 307

2006 DaCivic Hybrid - '06 Honda Civic Hybrid
90 day: 45.16 mpg (US)
Thanks: 188
Thanked 40 Times in 25 Posts
Wonder what the flags and Mascots add to the drag. Also here in Utah when the FANatics go to athletic events they have two flags fluttering on both sides of the car.
  Reply With Quote
Old 05-15-2017, 01:43 AM   #5 (permalink)
Primer is still paint!
 
ChopStix's Avatar
 
Join Date: Aug 2015
Location: box by the river
Posts: 547

85 Chevy Pickup C10 - '85 Chevy C10
Thanks: 89
Thanked 120 Times in 94 Posts
Quote:
Originally Posted by MorphDaCivic View Post
Wonder what the flags and Mascots add to the drag. Also here in Utah when the FANatics go to athletic events they have two flags fluttering on both sides of the car.
Or the Jack Balls! -lol

  Reply With Quote
Old 05-15-2017, 12:44 PM   #6 (permalink)
Master EcoModder
 
kach22i's Avatar
 
Join Date: Jul 2011
Location: Ann Arbor, Michigan
Posts: 4,158
Thanks: 120
Thanked 2,790 Times in 1,959 Posts
Just think of all the gas that radio can save you when avoiding traffic jambs and road construction.
__________________
George
Architect, Artist and Designer of Objects

1977 Porsche 911s Targa
1998 Chevy S-10 Pick-Up truck
1989 Scat II HP Hovercraft

Chin Spoiler:
http://forums.pelicanparts.com/off-t...effective.html

Rear Spoiler Pick Up Truck
http://forums.pelicanparts.com/off-t...xperiment.html

Roof Wing
http://ecomodder.com/forum/showthrea...1-a-19525.html
  Reply With Quote
Old 05-16-2017, 01:51 AM   #7 (permalink)
EcoModding Lurker
 
Join Date: May 2016
Location: Virginia
Posts: 44
Thanks: 1
Thanked 20 Times in 15 Posts
Thanks for doing the calculations.....now I won't feel too bad about adding my wilson 5000 CR antenna to the roof..... .06 MPG is hardly anything! (graned the wilson 5000 is taller but even double the mpg loss is still not too much).

As an aside, with your great mathematical skills, would it be possible to calculate how many MPG's one would gain by removal of side mirrors or conversely how much one would lose if one were to add vent visors (to allow one to keep the side windows open without fear of rain getting in).

Thanks in advance for any and all help.

Andrew
__________________
2003 Jetta TDI Wagon, 5 sp, 210K miles, Stock.....for now!
  Reply With Quote
Old 05-16-2017, 12:24 PM   #8 (permalink)
EcoModding Lurker
 
Join Date: Apr 2017
Location: da U.P.
Posts: 36
Thanks: 2
Thanked 5 Times in 4 Posts
You donut always have to remove the antenna. A more efficient design might be possible, otherwise on my saturn I was able to move the antenna inside the a pillar or fender. You just need to get creative
  Reply With Quote
Old 05-16-2017, 12:53 PM   #9 (permalink)
Master EcoModder
 
Ecky's Avatar
 
Join Date: Dec 2011
Location: New Zealand
Posts: 5,005

ND Miata - '15 Mazda MX-5 Special Package
90 day: 42.54 mpg (US)
Thanks: 2,866
Thanked 2,501 Times in 1,547 Posts
1600 ways to save an ounce.

Plus, not everything I do needs to have a positive ROI.







EDIT: Only problem now is, I'm going 3-4 months between tanks of gas.
  Reply With Quote
Old 05-16-2017, 01:06 PM   #10 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,562
Thanks: 7,738
Thanked 8,554 Times in 7,041 Posts
Quote:
As an aside, with your great mathematical skills, would it be possible to calculate how many MPG's one would gain by removal of side mirrors or conversely how much one would lose if one were to add vent visors (to allow one to keep the side windows open without fear of rain getting in).
Not saying he shouldn't give it a shot, but mirrors and visors ride within the turbulent boundary layer, while the antenna stands out. The situation is much more complex. That's why the Nissan Leaf has little glass fins on the headlight, to set up airflow across the rear-view mirrors a foot or two further back.

One might solder a 1/8" by 1/4" Isosceles triangle on the back side and hand file a Template profile.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com