Ford Escort ZX2 Aerodynamics

[BabyDiesel]

Originally Posted by freebeard

We talked about me again. I'm sorry.

So, '57 Mercury Turnpike Cruiser style rear skirts? Have you seen bubble skirts?
https://www.google.com/search?q=bubble+fender+skirts

What about the front? skirts or air curtain?
https://www.google.com/search?q=bmw+air+curtain

Edit: Just found this on http://ecomodder.com/forum/showthrea...rts-28821.html

We all talk about our projects, sir. No harm in that I'm actually picking ideas from all you posted earlier!

I did not know bubble skirts even existed till you posted this. I don't know about them... wouldn't you want to fill the frnders till they were flush with the body, instead of "bubbling" them out? It seems like a recipe for slightly increased frontal area, along with being not as aerodynamic. I'll wait for you to prove me wrong

Edit: I did some more reading and they appear to be pretty aero friendly.

About the front skirts: You're link is extremely interesting! I did not know about air curtains. They may be too hard for the average lay person to do correctly, as you would almost need a wind tunnel to see the effect. I have a plan on solid front skirts, similar to basjoos's. In fact, his Aerocivic is my inspiration for continuing aero refinement.

First thing I would have to do is obtain skinnier rims with a higher offset. I am wanting to run 14x4 spare wheels with my tires, which would set them in a good ways. I eventually will run 165/65r14 Potenzas. Then, I want to build an aluminum frame to match the body contours, and use coroplast for covering. This will be hinged at the top, and I will have rollers on the frame. Inside the fender well and on the frame, I want to place rare earth magnets so that there is no chance of a strong side wind pulling them out while driving.

Originally Posted by aerohead

When Walter Lay did his wind tunnel research,he found that the drag of an 'ideal' form could be duplicated with an 'optimized' windshield.Both gave Cd 0.12


-------------------------------------------------------------------------
With respect to 'reversed' bodies,there is zero wind tunnel studies performed with 'mutilated' forebodies.So we don't have any knowledge about what happens if we disturb the contour of a reversed body to create a 'working' windshield.
If it turns out that we can't,without raising drag,then Hucho would say 'fuggetaboutit', 'cause,the distortion of the radically-raked windshield would be too great to see through.
This Citroen Karen would be impossible to see out of

Crazy how they both have the same Cd.
This "optimized windshield" seems to have a steeper angle than my own. I wonder what penalties there are with a more layed back windshield like mine. Is there a certain way the windshield is shaped that is not shown in the drawing? It would make sense if the windshield pictured was pointed in the middle to redirect air to the sides.

I agree that the Citroen would be hard to see out of, and its rear aerodynamics leaves much to be desired. I am curious to know what benefits there are with a working windshield.

I have thought about building a platform, if you can imagine it, on top of my hood to relax the sharp angles from it to the windshield. I'll post a picture of what I mean to ease confusion

[BabyDiesel]

Here is a quick mock-up of front skirts and a complete rear boattail. The length will be 20-21 feet overall, not counting the extended front end.




FOr the front, I had the idea of adding a nose on. The length is a bit much, but I wanted to relax the angle going to the hood. The black on top of the hood is the "platform" to shorten my windshield. I do think it may cause visibility problems if the height is too much.



Here is a link to a new sheet of MPG calculations using the Aero & RR tool. I have adjusted it to theoretical numbers that will come to pass... one day I put in numbers that would reflect having lost weight, having Potenza's, lowering, complete aero mods, lean burn, turbocharger and a manual transmission. I would be ecstatic if I could really break 125 mpg between my usual 45-50 mph

Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com

[freebeard]

About the front skirts: You're link is extremely interesting! I did not know about air curtains. They may be too hard for the average lay person to do correctly, as you would almost need a wind tunnel to see the effect. I have a plan on solid front skirts, similar to basjoos's. In fact, his Aerocivic is my inspiration for continuing aero refinement.

The air curtain is a convergent nozzle. The inlet could be any shape, but the outlet is a tall narrow slot. It might be very narrow, a fraction of an inch. Here's a research picture of a Coanda nozzle—the profile may be similar:



You could get a low-tech peek at the performance on a freeway in the rain. I'm always watching other cars front wheelwells there, but I haven't seen one of these BMWs.

First thing I would have to do is obtain skinnier rims with a higher offset. I am wanting to run 14x4 spare wheels with my tires, which would set them in a good ways. I eventually will run 165/65r14 Potenzas. Then, I want to build an aluminum frame to match the body contours, and use coroplast for covering. This will be hinged at the top, and I will have rollers on the frame. Inside the fender well and on the frame, I want to place rare earth magnets so that there is no chance of a strong side wind pulling them out while driving.

If you increase the offset of the front wheels, you're working against yourself when it comes to making the front skirts. Lowering will compensate for the reduced track in cornering.

Magnet hold and then let go completely. Bungee cords will release and then increase tension.

I propose a four-bar arrangement for the front skirt. Nobodies made one yet.



You have to imagine the pivots into place, until I make a better drawing. They could be done in 1/4" steel rod and follow the contour of the wheelwell. The two top bars are connected together so that any tendency to rock front to back is damped. Or it could be clamped in the center and be a torsion springs to hold it closed.

You want the front skirts to be bubbles, so you can turn the wheels a bit without invoking the skirt. But it's there for sharp low-speed turns and parking.
_________

Your side view looks reasonable. Extending the nose isn't really necessary unless you are going 250 mph and entering tunnels.Keep in mind the 3D view. Here's a VW Beetle in the aeroform:



There are thing that don't show up in side-view.

[aerohead]

Originally Posted by BabyDiesel

We all talk about our projects, sir. No harm in that I'm actually picking ideas from all you posted earlier!

I did not know bubble skirts even existed till you posted this. I don't know about them... wouldn't you want to fill the frnders till they were flush with the body, instead of "bubbling" them out? It seems like a recipe for slightly increased frontal area, along with being not as aerodynamic. I'll wait for you to prove me wrong

Edit: I did some more reading and they appear to be pretty aero friendly.

About the front skirts: You're link is extremely interesting! I did not know about air curtains. They may be too hard for the average lay person to do correctly, as you would almost need a wind tunnel to see the effect. I have a plan on solid front skirts, similar to basjoos's. In fact, his Aerocivic is my inspiration for continuing aero refinement.

First thing I would have to do is obtain skinnier rims with a higher offset. I am wanting to run 14x4 spare wheels with my tires, which would set them in a good ways. I eventually will run 165/65r14 Potenzas. Then, I want to build an aluminum frame to match the body contours, and use coroplast for covering. This will be hinged at the top, and I will have rollers on the frame. Inside the fender well and on the frame, I want to place rare earth magnets so that there is no chance of a strong side wind pulling them out while driving.



Crazy how they both have the same Cd.
This "optimized windshield" seems to have a steeper angle than my own. I wonder what penalties there are with a more layed back windshield like mine. Is there a certain way the windshield is shaped that is not shown in the drawing? It would make sense if the windshield pictured was pointed in the middle to redirect air to the sides.

I agree that the Citroen would be hard to see out of, and its rear aerodynamics leaves much to be desired. I am curious to know what benefits there are with a working windshield.

I have thought about building a platform, if you can imagine it, on top of my hood to relax the sharp angles from it to the windshield. I'll post a picture of what I mean to ease confusion

Here are some of the wind tunnel model configurations Lay tested.


Once the windshield header/A-pillar radius is 'enough' to get attached flow,no amount of further rounding will produce a drag reduction.It has reached 'saturation.' As to the angle,of course,the steeper the better up to the point where internal reflections interfere with outward vision.
Your windshield should be okay as it is.
------------------------------------------------------------------------
I built blisters for the hoods of the Dodge and Toyota trucks.I don't know if they do anything to lower drag,but I don't think they increase drag.Since I couldn't lay the glass back at a steeper angle,the blisters helped to relax the angle of the flow coming at them.Here is the Toyota

It flowed very well in the wind tunnel although I intend to widen it out to the edge of the fenders in hopes of slowing the flow a bit which will impact the side-view mirrors.

[aerohead]

Originally Posted by BabyDiesel

Here is a quick mock-up of front skirts and a complete rear boattail. The length will be 20-21 feet overall, not counting the extended front end.




FOr the front, I had the idea of adding a nose on. The length is a bit much, but I wanted to relax the angle going to the hood. The black on top of the hood is the "platform" to shorten my windshield. I do think it may cause visibility problems if the height is too much.



Here is a link to a new sheet of MPG calculations using the Aero & RR tool. I have adjusted it to theoretical numbers that will come to pass... one day I put in numbers that would reflect having lost weight, having Potenza's, lowering, complete aero mods, lean burn, turbocharger and a manual transmission. I would be ecstatic if I could really break 125 mpg between my usual 45-50 mph

Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com

When Hucho was at Volkswagen,he tried different noses on the Golf/Rabbit.


The upper 'ideal' nose had no lower drag than the lower 'optimized' nose.Again,once the rounding is enough,you're done.
Consider these two cars with identical drag coefficients

[freebeard]

Originally Posted by BabyDiesel

Here is a quick mock-up of front skirts and a complete rear boattail. The length will be 20-21 feet overall, not counting the extended front end.

My motorhome is 18 1/2ft long, and it fills a parking space.

[mwilliamshs]

Originally Posted by BabyDiesel

...The length will be 20-21 feet overall, not counting the extended front end...

Originally Posted by freebeard

My motorhome is 18 1/2ft long, and it fills a parking space.

My van is 18' 9" without its rear-door-mounted spare tire and yep, it's as big as you want to try parking like a "normal" vehicle. The very "snub" nose of the van (< 18") is a huge asset. A long vehicle with a sizeable overhang at both ends would be a monstrosity. Consider the dimensions adopted by nearly all large vehicles from 18 wheeled Class 8 OTR trucks to bread vans to fullsize vans to minivans...short noses are the way to go, especially if the back's gonna be lengthy. Having driven a number of Corvettes, a GT40, etc trust me when I say long frontends belong on expensive cars that aren't driven on every errand because they get damaged easily and only the owner of supercar is going to pay for the repair over and over, not to mention the hassle and neck-pains of re-parking and craning out the window for an improved vantage point. Likewise, backing-in to parking spaces in a vette is a breeze since you can see everything up close and personal from that angle. A GT40...not so much LOL

[BabyDiesel]

Originally Posted by freebeard

The air curtain is a convergent nozzle. The inlet could be any shape, but the outlet is a tall narrow slot. It might be very narrow, a fraction of an inch. Here's a research picture of a Coanda nozzle—the profile may be similar:



You could get a low-tech peek at the performance on a freeway in the rain. I'm always watching other cars front wheelwells there, but I haven't seen one of these BMWs.

I'm glad I'm not the only one who watches wheelwells in the rain

I had to look up what exactly is the Coanda nozzle and the Coanda effect. From what I can glean, the air coming in would be trapped inside the wheelwell similar to a parachute. Having the narrow slot for the incoming air to escape would allow it to "reattach" smoothly to the body of the car, thereby decreasing drag. Correct?

I will design the Coanda effect to work in conjunction with front skirts.

If you increase the offset of the front wheels, you're working against yourself when it comes to making the front skirts. Lowering will compensate for the reduced track in cornering.

Magnet hold and then let go completely. Bungee cords will release and then increase tension.

I propose a four-bar arrangement for the front skirt. Nobodies made one yet.



You have to imagine the pivots into place, until I make a better drawing. They could be done in 1/4" steel rod and follow the contour of the wheelwell. The two top bars are connected together so that any tendency to rock front to back is damped. Or it could be clamped in the center and be a torsion springs to hold it closed.

You want the front skirts to be bubbles, so you can turn the wheels a bit without invoking the skirt. But it's there for sharp low-speed turns and parking.
_________

Increasing offset means that the wheels are tucked closer to the body. +25 mm offset would tuck the tire assembly closer inside, -25 would stick waayyy out! The spare rims have the "tuck" needed, and are thin enough for a 165 width tire.

I wanted to use magnets because they were different. Springs and bungee cords would work better, and they have been proven.

I personally think your 4-bar arrangement with a torsion spring is great! I will figure out someway to implement it onto my car. I wish I had access to your software, I only have Paint. I would like to avoid bubble skirts as much as possible. I will have them if the tire is not as inset as I am planning. Avoiding an increase in frontal area is a concern of mine.

Your side view looks reasonable. Extending the nose isn't really necessary unless you are going 250 mph and entering tunnels.Keep in mind the 3D view. Here's a VW Beetle in the aeroform:



There are thing that don't show up in side-view.

Like I said earlier, I would LOVE to have your software. The real world plan is to minimize sharp angles and to make the boattail as close to a semicircle shape as possible while coming to a point, as in your Bug schematic.

Would having a shorter nose with a steeper angle encourage more air up and over the car? That is what I am after. Basjoos said that he added the nose so less air would flow underneath his car. Is he right, or no?

[BabyDiesel]

Originally Posted by aerohead

When Hucho was at Volkswagen,he tried different noses on the Golf/Rabbit.


The upper 'ideal' nose had no lower drag than the lower 'optimized' nose.Again,once the rounding is enough,you're done.
Consider these two cars with identical drag coefficients

Originally Posted by aerohead

Here are some of the wind tunnel model configurations Lay tested.


Once the windshield header/A-pillar radius is 'enough' to get attached flow,no amount of further rounding will produce a drag reduction.It has reached 'saturation.' As to the angle,of course,the steeper the better up to the point where internal reflections interfere with outward vision.
Your windshield should be okay as it is.
------------------------------------------------------------------------
I built blisters for the hoods of the Dodge and Toyota trucks.I don't know if they do anything to lower drag,but I don't think they increase drag.Since I couldn't lay the glass back at a steeper angle,the blisters helped to relax the angle of the flow coming at them.Here is the Toyota

It flowed very well in the wind tunnel although I intend to widen it out to the edge of the fenders in hopes of slowing the flow a bit which will impact the side-view mirrors.

If no one has ever told you, you are indispensable to Ecomodder and a treasure trove of pure, truthful information Aerohead! Simply incredible

The nose did not help front aerodynamics, but did it change the final Cd by diverting air towards a less dirty part of the vehicle? If I am beating a dead horse with this nose business, then by all means tell me to stop! I have a problem with getting caught up on non-critical aspects at times

It is hard to believe those 2 cars have to same drag coefficient! The top photo's uncovered tires likely played a big roll in that.

On your word, I'll leave the windshield alone. So the name of what I want to do with the hood is a blister... I would like to design on of those if possible. It can't hurt, like you said.

[BabyDiesel]

Originally Posted by mwilliamshs

My van is 18' 9" without its rear-door-mounted spare tire and yep, it's as big as you want to try parking like a "normal" vehicle. The very "snub" nose of the van (< 18") is a huge asset. A long vehicle with a sizeable overhang at both ends would be a monstrosity. Consider the dimensions adopted by nearly all large vehicles from 18 wheeled Class 8 OTR trucks to bread vans to fullsize vans to minivans...short noses are the way to go, especially if the back's gonna be lengthy. Having driven a number of Corvettes, a GT40, etc trust me when I say long frontends belong on expensive cars that aren't driven on every errand because they get damaged easily and only the owner of supercar is going to pay for the repair over and over, not to mention the hassle and neck-pains of re-parking and craning out the window for an improved vantage point. Likewise, backing-in to parking spaces in a vette is a breeze since you can see everything up close and personal from that angle. A GT40...not so much LOL

Yikes! Making my car longer than a full size van was not planned. I agree with you that my car would be painful to park practically anywhere. I have driven a Corvette, and I can attest to the long nose problems. While I can not change the length from where I sit to the front bumper, There may be something I can do about the rear boat tail.

The bottom angle is 2.5*, and this gives the best angle for... I can't remember the name, but the angle is ideal I do remember from a post by Aerohead that the angle can go to 4-5* and still provide improvements. After that, there was a regression. Increasing the angle may be the only way to shorten this beast.