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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 12-18-2022, 03:14 PM   #1151 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
An interesting edge case. How do you handle 200MPH tail winds?

I thought it would have suction fans to hold it down, but it doesn't just lay frame, it can drive spikes into the ground!

The biggest development from Dominators 1 & 2 is the gable roof, presumably to kill lift compared to a flat roof. Cybertruck would be a good base vehicle for this, it would need just skirts and a bed-liner coating.

__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 12-19-2022, 06:31 PM   #1152 (permalink)
It's all about Diesel
 
cRiPpLe_rOoStEr's Avatar
 
Join Date: Oct 2012
Location: Porto Alegre, Rio Grande do Sul, Brazil
Posts: 12,548
Thanks: 0
Thanked 1,622 Times in 1,447 Posts


Now look at the rear section...
  Reply With Quote
Old 12-23-2022, 11:25 AM   #1153 (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
Post #198
Ducktail Critique from an Industrial Design Perspective - Page 10 - Pelican Parts Forums










If anyone ever finds some wind tunnel testing of this creation, please post it.
__________________
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
The Following User Says Thank You to kach22i For This Useful Post:
freebeard (12-23-2022)
Old 01-06-2023, 08:45 PM   #1154 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
https://www.mt-propeller.com: Another World’s First Takes First Flight – The 11-bladed Propeller!



Quote:
On a PA31T1 equipped with the P&W PT6A-135A turbines, the World’s first 11-bladed propeller took the sky with an impressive noise and sound signature.
The very promising results in static thrust, 15% increase over the standard certified 5-bladed propeller, and the jet-noise signature showed another time what could be possible in the propeller developments.
They've worked their way up through 7- and 9-blade versions.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Old 01-06-2023, 08:58 PM   #1155 (permalink)
EcoModding Apprentice
 
Bicycle Bob's Avatar
 
Join Date: May 2008
Location: N. Saskatchewan, CA
Posts: 1,803

Appliance White - '93 Geo Metro 4-Dr. Auto
Last 3: 42.35 mpg (US)

Stealth RV - '91 Chevy Sprint Base
Thanks: 91
Thanked 459 Times in 327 Posts
Multiple blades help with the very coarse pitch used to keep the tip speeds subsonic. On windmills, a single blade is sufficient to extract almost all the possible energy, but it needs a counterweight, and adding a second blade causes weird balance issues, so three are used.
__________________
There is no excuse for a land vehicle to weigh more than its average payload.
  Reply With Quote
Old 01-06-2023, 11:33 PM   #1156 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
I see a lot of Prandtl influence, with lots of pitch at the hub with washout to zero at the tips.

More blades allow slower rotation? They really sell the sound signature.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
Old 01-07-2023, 12:21 AM   #1157 (permalink)
EcoModding Apprentice
 
Bicycle Bob's Avatar
 
Join Date: May 2008
Location: N. Saskatchewan, CA
Posts: 1,803

Appliance White - '93 Geo Metro 4-Dr. Auto
Last 3: 42.35 mpg (US)

Stealth RV - '91 Chevy Sprint Base
Thanks: 91
Thanked 459 Times in 327 Posts
Quote:
Originally Posted by freebeard View Post
I see a lot of Prandtl influence, with lots of pitch at the hub with washout to zero at the tips.

More blades allow slower rotation? They really sell the sound signature.
Slower rotation keeps the tips subsonic and quiet, but it does not chop up the column of air passing through the prop disk finely enough to push on all of it with only two or three blades. Using such a coarse pitch puts a lot of totally wasted spin on the propwash - this would be a good place for contra-rotating props, if they don't have new sound issues.
Fan jets are basically multi-bladed turboprops with tip shrouds. Every time they brag about better mileage, the size goes up, and the wasted momentum in the exhaust is reduced.

Attached is a picture of a prop showing the correct pitch all the way across. The rate of change is highest at the hub, and it never goes flat at the tips.
Attached Thumbnails
Click image for larger version

Name:	PropFairing1.jpg
Views:	22
Size:	31.2 KB
ID:	33162  
__________________
There is no excuse for a land vehicle to weigh more than its average payload.
  Reply With Quote
Old 01-07-2023, 10:03 AM   #1158 (permalink)
Somewhat crazed
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 4,043
Thanks: 462
Thanked 1,103 Times in 973 Posts
Pitch is measured in distance per revolution>>>at the tips<<< As you progress towards the hub, in order to have the same thrust and prop load, pitch gets higher until its so high that part stalls. The insane pitch shown is what it takes to run that prop at the speed they want at the rpm the prop is operating at. According to Irv Culver, when the tips go sonic all that thrust is turned to noise and does not contribute to thrust. One of the multitude of reasons commercial aircraft don't fly supersonic.

Btw: on that non operating turbine, the prop is "feathered" or in low drag mode
__________________
casual notes from the underground:There are some "experts" out there that in reality don't have a clue as to what they are doing.
  Reply With Quote
Old 01-07-2023, 01:29 PM   #1159 (permalink)
EcoModding Apprentice
 
Bicycle Bob's Avatar
 
Join Date: May 2008
Location: N. Saskatchewan, CA
Posts: 1,803

Appliance White - '93 Geo Metro 4-Dr. Auto
Last 3: 42.35 mpg (US)

Stealth RV - '91 Chevy Sprint Base
Thanks: 91
Thanked 459 Times in 327 Posts
Quote:
Originally Posted by Piotrsko View Post
Pitch is measured in distance per revolution>>>at the tips<<< As you progress towards the hub, in order to have the same thrust and prop load, pitch gets higher until its so high that part stalls. The insane pitch shown is what it takes to run that prop at the speed they want at the rpm the prop is operating at. According to Irv Culver, when the tips go sonic all that thrust is turned to noise and does not contribute to thrust. One of the multitude of reasons commercial aircraft don't fly supersonic.

Btw: on that non operating turbine, the prop is "feathered" or in low drag mode
Pitch is the same at any diameter. The propeller blade can twist to match forward and rotational speed all the way to the hub and across, as illustrated. There is no stalled zone, but the high angle near the hub is just unable to do much work so it is often neglected, especially if it is not needed to cool the following motor, or needs more physical strength.
A variable-pitch propeller is only correct at one setting - the effective angle of attack will vary at different diameters at other settings.
It is quite common for prop tips to go supersonic during take-off, and they get loud, but they don't stall any more than supersonic aircraft fall out of the sky. That much power would create very destructive noise if it was all converted.
__________________
There is no excuse for a land vehicle to weigh more than its average payload.
  Reply With Quote
Old 01-07-2023, 09:47 PM   #1160 (permalink)
It's all about Diesel
 
cRiPpLe_rOoStEr's Avatar
 
Join Date: Oct 2012
Location: Porto Alegre, Rio Grande do Sul, Brazil
Posts: 12,548
Thanks: 0
Thanked 1,622 Times in 1,447 Posts
Most of the propellers I see are still no more than 3-blade, and that's not considering the fixed-pitch 2-blade propellers that I see more often on cropdusters.

  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