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-   -   Breakfast with Phil Knox (https://ecomodder.com/forum/showthread.php/breakfast-phil-knox-2540.html)

bondo 05-24-2008 11:34 PM

Breakfast with Phil Knox
 
1 Attachment(s)
I had the pleasure of having breakfast with Aerohead, aka Phil Knox, last Sunday, May 18. I had met Phil once before in 2005 and got to see his modified Toyota pickup in real life. Last Sunday I got to see the latest modifications on his truck. Some people have an intuitive sense of aerodynamics and Phil posesses this ability.

On his latest mods he has devised a simple effective air intake for the radiator which is just like the opening of a jet engine nacelle. An internal smooth plug is adjustible to increase or restrict airflow, whichever outside temperatures may reqiure. Both front wheels are skirted along with the rear wheel openings. Phil has also fabricated a component which sets upon the hood to streamline airflow over the front windshield. The rear aerocap is boatlike and has an extended surface rearward. The underchassis is smooth.

Phil has increased the fuel efficiency of his vehicle by over ten miles per gallon! My 4 miles per gallon increase pales in comparison. Phil has also been doing aerodynamic mods to pickups for years, long before it became so vouge. Fuel prices are making mpg modifications very vouge right now! We all owe Phil our gratitude for blazing the trail many, like myself, have followed.

Thank you Phil for the good conversation over breakfast. You're advise on modifying my lower airdam I am going to implement. I am looking forward to the road test when I head back to Denton from Little Rock.

The aero cap is on hold I am sorry to report. The untimely death of my business partners wife halted the work we on the verge of commencing. My business partner is also a dear friend and he has been devastated by the loss. I had to go ahead and take the position offered me in Denton, Texas with a major heavy truck manufacturer. It is fun because we are working on a new aerodynamic truck for the company. It is an irony that this company I am contracting with is located in Phil Knox's home town!

We plan to recommence work the aero cap as soon as possible. I am banking all the money I can now to ride out the rough times ahead when you don't get that weekly paycheck. But, to be working on the areo cap again will be priceless.

Thanks again to all here at ecomodder for your encouragement and support. Thanks again to you Phil, we all benefit from you sharing your knowledge and experience with us all.

I include a picture I took of Phil and myself that day. If any of you guys get down to Texas, stop on by!

Bondo

Johnny Mullet 05-24-2008 11:38 PM

So what did you guys have for breakfast?

bondo 05-24-2008 11:46 PM

Quote:

Originally Posted by Johnny Mullet (Post 28250)
So what did you guys have for breakfast?

Actually we both had an omlette at the IHOP. I think it is the International on the menu.

I'm envious of all that hair. Reminds me of my high school days when I had some.

Bondo

LUVMY02CREW 05-25-2008 12:01 AM

Quote:

Originally Posted by bondo (Post 28253)
I'm envious of all that hair. Reminds me of my high school days when I had some.

HAHAHAHA I fully understand!

Total head shave has been THE way to go for me. :D
I was aero/eco modding my hairstyle for a few months before I even found this forum. It has been great to find out that my slick skull helps lower my cd:D

But seriously, I bet that was pretty nice to see that ride of his in real life. Pictures can only do so much explaining sometimes....

Keep up the great work Phil!

Gone4 05-25-2008 12:31 AM

Quote:

Originally Posted by bondo (Post 28246)

If any of you guys get down to Texas, stop on by!

Bondo

I am down in Houston, Texas from Saturday until the start of August except for a wedding in NH and cave spelunking trip in NM. Where abouts in TX are you guys? It would be cool to meet some ecomodders doing real work. As a warning, I won't have a vehicle at all there.

MetroMPG 05-25-2008 09:06 AM

Thanks for the post, bondo.

I had arranged to meet up with Phil as well early this spring, and was really looking forward to it. My trip to Texas was cancelled, unfortunately. There's no doubt about the number of people he's inspired - you as well.

Any chance you can feed us the occasional tidbit about the new truck design elements? (I realize you may be tied by non-disclosure.)

bondo 05-26-2008 09:07 PM

Phil,

I did the modification to the front spoiler you suggested. I went from 21.5 to 22.6 on the trip back from Little Rock to Denton, Texas today. Thank you!

It is amazing what a slight change to a certian area will get you aerodynamically.

Bondo

aerohead 05-27-2008 01:19 PM

Theres an omelette waiting for you
 
Quote:

Originally Posted by GenKreton (Post 28261)
I am down in Houston, Texas from Saturday until the start of August except for a wedding in NH and cave spelunking trip in NM. Where abouts in TX are you guys? It would be cool to meet some ecomodders doing real work. As a warning, I won't have a vehicle at all there.

GenKreton,I live a little north of Denton,and when Brett is over from Arkansas,he's working his magic near the Denton airport.If you can get this way,let me know.If Brett's in town,maybe we can all get away for some cholesterol.

aerohead 05-27-2008 01:31 PM

airdam mpg
 
Quote:

Originally Posted by bondo (Post 28717)
Phil,

I did the modification to the front spoiler you suggested. I went from 21.5 to 22.6 on the trip back from Little Rock to Denton, Texas today. Thank you!

It is amazing what a slight change to a certian area will get you aerodynamically.

Bondo

Hey Brett,thanks for the kind words,for sharing your library with me,and am glad reduced frontal area worked out.P.S.,I looked at my big-rig stuff,and certain numbers looks real doable.Renault hit Below Cd0.35 with an 18-wheeler and there are bus designs with Cds below 0.25. At 56-mph,some of the rigs return over 10-mpg.Tasty! We'll all be waiting to hear more about the cap.Best to ya,Phil.

ebacherville 05-28-2008 01:17 PM

your tell me you met and saw this truck and owner and only got one pic with no details!!!

You got to be holding out?!

aerohead 05-28-2008 02:21 PM

holding out
 
Quote:

Originally Posted by ebacherville (Post 29116)
your tell me you met and saw this truck and owner and only got one pic with no details!!!

You got to be holding out?!

Brett's real busy,it was his day off, had errands to run,and we'd burned a lot of his day at breakfast.I've posted more current photos of the T-100 over at maxmpg in the photos section,including the tuft-testing photos captured by my road-warrior friends.I apologize if I haven't mentioned that.Metrompg is going to help move some of these images over as time permits,however,he has a real life too,and spare time can become a rare commodity.We got 3-inches of rain in about ten minutes yesterday and my jobsite is drying out,and is only reason I'm free to look at internet today.Anyway,there's no big conspiracy over the T-100.If anyone wants to look over at maxmpg,I have a lot of posts about the truck and most current mods.The last two testing runs were foiled by high winds and I've suspended activity on the T-100 until I can prepare more shop space.The weather is trying to reclaim what I.ve done,and I need "inside" space to bring things to completion.

Chris D. 06-02-2008 05:11 AM

www.maxmpg.com?

didn't work if thats the address..

what were the mods made to the airdam? any pictures of that?

MetroMPG 06-02-2008 08:05 AM

Chris - MaxMPG is a Yahoo group:
http://autos.groups.yahoo.com/group/maxmpg/
You need to register to view the gallery.

Phil - I haven't forgotten about importing your photo gallery to EcoModder. The latest upgrade in our forum software was supposed to have a photo gallery feature, but it never materialized. I'll have to look at alternatives.

aerohead 06-03-2008 03:58 PM

T-100 latest photos
 
Quote:

Originally Posted by Chris D. (Post 30410)
www.maxmpg.com?

didn't work if thats the address..

what were the mods made to the airdam? any pictures of that?

Brett had the airdam pretty low.CAR and DRIVER got away with 3-inches of ground clearance with "Crisis-Fighter-Pinto",however we think Brett's airdam was low enough that the added sectional area was canceling out any benefits.Anyway,he cut it back some,even with the bottom of the suspension,and the mpg came back.As to maxmpg,just go to GOOGLE and type it in.When the page comes up,click on the very first entry.That should get you in.The photos of the trashcan nose and tuft-testing may be under "phrekna" at the PHOTOS section.

miket 06-13-2010 01:47 PM

the max mpg yahoo group is dead. Where are the pictures of the aero t100 now?

aerohead 06-19-2010 03:34 PM

now
 
Quote:

Originally Posted by miket (Post 178810)
the max mpg yahoo group is dead. Where are the pictures of the aero t100 now?

miket,there is a fairly recent truck in the Aerodynamic-Streamlining-Template:Part-C,page 4.
I'll attempt a link to it:
http://ecomodder.com/forum/showthrea...-c-9287-4.html
the photo is at second bottom post on page 4

miket 06-19-2010 05:46 PM

wow thats quite an extension. How can you turn with the fairing covering the front wheels?

Do you have any pics of the undertray?

I bought Huchos book but havent had time to read it yet.

I cant use a cap that slopes down because of storgage space. Maybe an inflatable kamm back for highway speeds.

KamperBob 06-20-2010 07:58 AM

Quote:

Originally Posted by aerohead (Post 179758)
miket,there is a fairly recent truck in the Aerodynamic-Streamlining-Template:Part-C,page 4.
I'll attempt a link to it:
http://ecomodder.com/forum/showthrea...-c-9287-4.html
the photo is at second bottom post on page 4

The forum does crazy things with content. Here's a stab at the actual pic.

http://ecomodder.com/forum/attachmen...3&d=1249762201

Cheers
KB

aerohead 06-21-2010 05:28 PM

turning
 
Quote:

Originally Posted by miket (Post 179771)
wow thats quite an extension. How can you turn with the fairing covering the front wheels?

Do you have any pics of the undertray?

I bought Huchos book but havent had time to read it yet.

I cant use a cap that slopes down because of storgage space. Maybe an inflatable kamm back for highway speeds.

miket,the full skirt was for proof of concept.It was 'fixed' and did limit the wheels range of motion,although not much of a problem.
The 'final' skirts will attach to pantograph/hinged parallelogram mechanism which allows the tire sidewall to engage inline skate rollers attached to the mechanism,swinging it out and up to clear the 'steering' wheel,then stow flush against the fender when centered.
As to the belly,if you'll GOOGLE Phil Knox,it should get you to Jessica Savage' EV World article back in 2005.I think the bellypan photos are there.
The inflatable tail will work for you.Mine uses a 12-VDC fan from a Westfalia VW Campmobile.The fabric used on inflatable advertising would be ideal.Ripstop nylon from a fabric store will do.Seam sealer for tents to seal stitching.Do not use expandable Naughehyde,it will not hold a shape under pressure.I learned that one the hard way!
It's nice to mock up something at full-scale from which you can lay out and tailor the fabric sections.Top-stitch is good,a French seam better.
Interior lacing may be necessary to 'hold' the envelope form.You'll just have to see.
If everything is attached to an airtight shallow box,the box can be attached in any number of ways.
My prototype was made with a discarded bean-bag chair.
In HUCHO's book you should find a great inflatable design by Fachsenfeld,done for Omnibus at FKFS around 1936.

The Toecutter 06-22-2010 03:05 AM

Phil, had I known your location when I lived in Texas, I'd have tried to arrange a meeting with you on the drive back to St. Louis...


Oh well.

That T100 is a piece of work. I can't wait to see what you do with the Ghia...

miket 06-22-2010 05:26 AM

http://www.evworld.com/images/pknox_bellypan.jpg
I can't really see what you did around the axles and wheels.

I would love to have an inflatable airplane.

Document sans titre

Woopy-Fly Inflatable Wing Aircraft

Im imagining some sort of shape memory alloy springs that when heated shrinks the inflatable truck tail like accordion or roll up the tail like a sleeping bag. Or a rope that pulls the tail up and over the vehicle. Realistically i would probably get out and fold it up on the street before i entered a parking lot lol.

The current cap is a foot taller than the cab, im going to try and buy a used utility cap, i would like to have the flip up sides and not have the equipment so visible though big glass windows. Some of those utilty caps dont have a radius on the rear and top corners. Sharp edges are bad right? A shorter cap level with the cab would reduce rear area by 4sq feet.

a 2"f/4"r lowering kit would be very pricey but i could lower the rear 2" with a $60 pair of drop shackles if that would be a good idea. I'd probably have the clearance above the diffuser to do it.

I wish the truck had one of those engines that shuts off half of the 8 cylinders while cruising.

Yes i could attach the tail to the trailer hitch or flip up cap door, roof racks etc. I wonder how much a 5ft long tail would reduce cd and improve mpg at 65mph?

aerohead 06-23-2010 06:03 PM

belly tail
 
Quote:

Originally Posted by miket (Post 180214)
http://www.evworld.com/images/pknox_bellypan.jpg
I can't really see what you did around the axles and wheels.

I would love to have an inflatable airplane.

Document sans titre

Woopy-Fly Inflatable Wing Aircraft

Im imagining some sort of shape memory alloy springs that when heated shrinks the inflatable truck tail like accordion or roll up the tail like a sleeping bag. Or a rope that pulls the tail up and over the vehicle. Realistically i would probably get out and fold it up on the street before i entered a parking lot lol.

The current cap is a foot taller than the cab, im going to try and buy a used utility cap, i would like to have the flip up sides and not have the equipment so visible though big glass windows. Some of those utilty caps dont have a radius on the rear and top corners. Sharp edges are bad right? A shorter cap level with the cab would reduce rear area by 4sq feet.

a 2"f/4"r lowering kit would be very pricey but i could lower the rear 2" with a $60 pair of drop shackles if that would be a good idea. I'd probably have the clearance above the diffuser to do it.

I wish the truck had one of those engines that shuts off half of the 8 cylinders while cruising.

Yes i could attach the tail to the trailer hitch or flip up cap door, roof racks etc. I wonder how much a 5ft long tail would reduce cd and improve mpg at 65mph?

miket,the area around the front wheels is just open for all the area of wheel flop.I've made no effort to dial in all the little nuances.
The area at the rear axle is open allowing full extension of the axle.There's nothing remarkable about any of it.
My tail rolled up like a sleeping bag with a couple cinch straps to hold when stowed.
Next phase has a hinged,rigid 2-pc bottom which folds down,exposing the envelope which inflates also with fan.
A mechanical reversing valve switches action to evacuate the bag and a simple cable/pulley system folds the bottom panels and draws it to the stowed and locked position.
With respect to your cap,my friend switched a 10-inch taller than cab height box for a cab height box and picked up 3.6 mpg hwy.
Jeeps have a swing-away spare tire holder which might serve you for a tail mount.Parked at the curb you just unlatch and swing to access the utility bed.A 12-VDC umbilical 'hinges' with it to power the tail.
I would recommend you not drop the rear unless you can match it at the front.A negative rake,I believe,would work against you.
18-inches of structure worked out to about 24-inches of tail on my VW Bus,due to the radius at the back of VW's body.That got me 4-mpg.5-feet would be pretty remarkable considering what 44-inches did on the Chrysler Airflow.

miket 06-24-2010 05:29 PM

I love that idea!!!

All the 1gen tundra drops i've seen are lowered 2" more in the back than the front. I've seen 1" rear drops sold as leveling kits. IF i find a budget way to drop the front 2" or maybe 3" Then im looking at droping the rear 2"-5" for about $55parts.

Why would a neutral or negative rake work against me???

If the inflated tail could work with the tailgate extender out then i wouldnt have to worry about rain or snow on the tailgate outside of loading/unloading. I wish my father bought a truck with an extended cab + long bed. Doubt 2' makes much of a driving difference on an 18' truck, heck we will be carrying a 20' long ladders sometimes. But he didnt. Im hoping with bedslides and a shelf we'll be able to cram everything under the cap most of the time and that we''ll need the tailgate extender rarely.

What would i do about the taillights? some sort of trailer light setup?

aerohead 06-24-2010 05:53 PM

rake
 
Quote:

Originally Posted by miket (Post 180639)
I love that idea!!!

All the 1gen tundra drops i've seen are lowered 2" more in the back than the front. I've seen 1" rear drops sold as leveling kits. IF i find a budget way to drop the front 2" or maybe 3" Then im looking at droping the rear 2"-5" for about $55parts.

Why would a neutral or negative rake work against me???

If the inflated tail could work with the tailgate extender out then i wouldnt have to worry about rain or snow on the tailgate outside of loading/unloading. I wish my father bought a truck with an extended cab + long bed. Doubt 2' makes much of a driving difference on an 18' truck, heck we will be carrying a 20' long ladders sometimes. But he didnt. Im hoping with bedslides and a shelf we'll be able to cram everything under the cap most of the time and that we''ll need the tailgate extender rarely.

What would i do about the taillights? some sort of trailer light setup?

miket,the nose down rake ensures that the fore-body of the truck is in a positive pressure regime,especially the roof.
If you drop the rear only,you run the risk of moving the separation point forwards,at a point of larger cross-section,resulting in a larger wake of lower base pressure ( higher delta-P,bad,never good ).
If you plan to run with a tailgate extender you'll have to configure the tail to capture that extra volume.
Reflector/taillight kits for a utility trailer are perfect for these applications however require some rigid structure,not necessarily a problem,but extra imagineering and fabrication.
Refective material as highway workers employ with their safety vests can also be sewn to the envelope.Biking/jogging gear ditto.

miket 06-24-2010 06:58 PM

Im confused by that because i thought the roof sloping down was a good thing??? The top of the cap is flat. edit1: and the cab is close to flat.

I dont think the nose would raise noticably and the undertray angle could deal with lift.

Hmm your right i would have to make the inflatable tail hollow to do that and that would be more complicated.edit1: Maybe the second version lol.edit2: Id ither need alot of strings inside to make the tail a hollow cone or use a series of connected poles on the inside that unfold to make a tent of sorts around the tailgate.

miket 06-25-2010 03:20 PM

If the bottom is going to be rigid folding panel i could make the sides top and back rigid folding panels too and not mess with the inflationary stuff??. If i connect a rope and pulleys to the ends of the panels they'll pull together and unfold/extend. How advantageous is it to have 5 of the sides smoothly curved from inflation instead of more flat?(cap has 2 sides too) Of course theres the hybrid version with folding panels inside the base of the tail and an inflatable piece for the tip. That could give me the tailgate storage space if i desire it.

aerohead 06-26-2010 02:18 PM

how advantageous
 
Quote:

Originally Posted by miket (Post 180831)
If the bottom is going to be rigid folding panel i could make the sides top and back rigid folding panels too and not mess with the inflationary stuff??. If i connect a rope and pulleys to the ends of the panels they'll pull together and unfold/extend. How advantageous is it to have 5 of the sides smoothly curved from inflation instead of more flat?(cap has 2 sides too) Of course theres the hybrid version with folding panels inside the base of the tail and an inflatable piece for the tip. That could give me the tailgate storage space if i desire it.

miket,the panels could be flat and just perform with less efficiency than a perfect organic form.
Flow might separate and re-attach creating locked vortices which are known to provide some drag mitigation.Even "bad" boat-tails appear to provide some benefit through a process I call 'stuffing the wake,'whereas the act of filling the turbulent wake with 'anything' seems to displace some of the physical void,pushing the 'base' out closer towards the more energetic flow field.
There is no hard and fast rule as to 'how' to do the tail but it should be air-tight,and they work best with a back on them.
I think of mine like a segmented ironing-board which drops out of a wall,hinged at half-length,with an additional section which flips up to form the 'end.'
Everything else is the envelope which is inflated during deployment,and evacuated during the stowing operation,triggered by a cruise-control,automatic ,speed-sensor/logic/enable-dis-enable-slaved servo-motor,fan set,and reversing valve.
Normally-open/normally-closed momentary micro-switches provide 'proof' to system.

miket 06-27-2010 05:01 AM

The truck/cap is 6 flat sides so i'd have to transition from flat to round some how.

Again why would it be back to have the flat roof slope down slightly, i would think that would be a positive benifit of slightly negative rake.

aerohead 06-30-2010 05:51 PM

rake
 
Quote:

Originally Posted by miket (Post 181057)
The truck/cap is 6 flat sides so i'd have to transition from flat to round some how.

Again why would it be back to have the flat roof slope down slightly, i would think that would be a positive benifit of slightly negative rake.

miket,if the roof is raked backwards,so too will be the grille/bumper (maybe not so bad a thing),the hood ( maybe not a good thing ),windshield ( not bad ),how the airstream is divided at the nose/windshield ( potentially harmful ),also,how the undercarriage is 'presented' to the air.
During development of the truck,it's Cd may be totally dependent upon the factory rake and could be degraded if tilted back as this would impact flow penetration.In addition,the weight bias can be altered which will affect braking and handling.
Concept cars and supercars with active suspension typically drop the nose for better performance,I've never seen an instance where the tail was dropped,unless the nose went with it.
The forward rake maximizes the amount of car within a positive pressure regime,maximizes the available energy aft of the point of max cross-section,providing the most energetic boundary layer from which further streamlining can benefit.

miket 06-30-2010 08:56 PM

Given the vehicle lengths dropping the rear bumper 2" would raise the front bumper 0.4" and change the rake less than a single degree. Honestly a 4" drop would make it easier to load/unload the bed and definitely the ladder racks and a 2" drop is really all I can get out of the front. The hood would stay in positive pressure, might have to check the wipers. Its hard to tell if the roof of the cab peaks in the front or middle, its relatively flat. I think the undercarriage would be presented with the undertray. I think even with the body dropped the axles are still the lowest point.

I just realized that the back is always sagging down bad from the constant load lol. Its already lowered. I think i should add a leaf or a helper spring, especially since i plan on adding a few hundred more pounds. I think supercars are raked for downforce more than anything.

Do you ever have problems with snow or dirt flying up through the gaps around the wheel wells or in front of the axles and filling up the cavity above and weighing down on the undertray? Ever have any problem with vertical undertray components when they'r pushing through deepish snow either driving forward reverse or turning?

aerohead 07-01-2010 04:59 PM

drop
 
Quote:

Originally Posted by miket (Post 181687)
Given the vehicle lengths dropping the rear bumper 2" would raise the front bumper 0.4" and change the rake less than a single degree. Honestly a 4" drop would make it easier to load/unload the bed and definitely the ladder racks and a 2" drop is really all I can get out of the front. The hood would stay in positive pressure, might have to check the wipers. Its hard to tell if the roof of the cab peaks in the front or middle, its relatively flat. I think the undercarriage would be presented with the undertray. I think even with the body dropped the axles are still the lowest point.

I just realized that the back is always sagging down bad from the constant load lol. Its already lowered. I think i should add a leaf or a helper spring, especially since i plan on adding a few hundred more pounds. I think supercars are raked for downforce more than anything.

Do you ever have problems with snow or dirt flying up through the gaps around the wheel wells or in front of the axles and filling up the cavity above and weighing down on the undertray? Ever have any problem with vertical undertray components when they'r pushing through deepish snow either driving forward reverse or turning?

If you do the drop,you might consider some time to familiarize yourself with anything new and quirky which might show up in handling.
I had air-shocks on an El Camino and they were great for load leveling.Something like that,or air springs might help with load stabilization when she's buried in pipe or tubing.
--------------------------------------------------------------------------
I have experienced material buildup on top of the pan,as I've never invested the extra time to detail out the wheel wells.After a good rain,I can usually chase everything out with a blast from the garden hose.
I've never had a clearance issue with the pan until the floodwater,when I struck a submerged hazard and it rip the diffuser off.And it struck me that the racing tires were partly responsible for that,as the truck rides a little lower.
The times I've driven in snow,traffic had already knocked down significant accumulations so it wasn't an issue.My pan is pretty strong and could support quite a 'load' and doesn't deform.The leading section is the fiberglass skin from a Mustang trunklid and is radiused well,not a 'snagger.'
If you're 'trail-blazing' on un-plowed streets or roads in heavy snow,you'll have to be mindfull of clearance.

miket 07-02-2010 11:10 PM

How much difference is there between a boat tail or kamm back with the back end closed or open?

miket 07-06-2010 04:08 PM

Quote:

Originally Posted by aerohead (Post 180077)
miket,the full skirt was for proof of concept.It was 'fixed' and did limit the wheels range of motion,although not much of a problem.
The 'final' skirts will attach to pantograph/hinged parallelogram mechanism which allows the tire sidewall to engage inline skate rollers attached to the mechanism,swinging it out and up to clear the 'steering' wheel,then stow flush against the fender when centered.
....
In HUCHO's book you should find a great inflatable design by Fachsenfeld,done for Omnibus at FKFS around 1936.

I dont quite understand. I would think that a pantagraph would be used if you wanted the skirt to pivot at the front edge or the back edge when the wheel turns outward but if the skirt swings upwards instead then a simple hinge at the top would do.

I find it interesting in huchos book p184 he dismisses eliminating the rear wheel arches because of it only having less than .01cd improvment even on a streamlined vehicle.

The inflatable boatail on p456 has an underside that is rounded with much steeper angles than 4deg?

Is 6959958 the patent you were refering earlier to on semis?

aerohead 07-06-2010 04:53 PM

closed/open
 
Quote:

Originally Posted by miket (Post 182098)
How much difference is there between a boat tail or kamm back with the back end closed or open?

miket,Sepp,(I believe he lives in Belgium) reported that closing the back on his Nissan Frontier aeroshell made a definite improvement compared to an open tail.
My neighbor Bob ran an open boat-tail on his VW Vanagon and it returned less MPG than what I experienced with my VW Transporter.
Bob never enclosed his,so I have no comparative data to share.
I've never run an open tail,so I have no data to offer.
Perhaps others will come forward with some supporting data.Good question!

aerohead 07-06-2010 05:20 PM

pantagraph
 
Quote:

Originally Posted by miket (Post 182487)
I dont quite understand. I would think that a pantagraph would be used if you wanted the skirt to pivot at the front edge or the back edge when the wheel turns outward but if the skirt swings upwards instead then a simple hinge at the top would do.

I find it interesting in huchos book p184 he dismisses eliminating the rear wheel arches because of it only having less than .01cd improvment even on a streamlined vehicle.

The inflatable boatail on p456 has an underside that is rounded with much steeper angles than 4deg?

Is 6959958 the patent you were refering earlier to on semis?

miket,my setup provides for the skirt to remain always parallel to the side of the vehicle,moving away and up as the steering tire/wheel moves off center.
There are 4-links,to which 8-pivots,4 at the attachment to the wheel arch,high and low,and also 4 at the carrier framework,high and low ,to which the molded skirt attaches.
A roller,fore and aft on the inside frame is what is contacted by the turning wheel,displacing the frame/skirt until re-centered.
I don't have any materials with me,so I'll have to wait to respond to Hucho's comment on wheel arches.A casual thought would be that for any 'low-drag' car,the arch would be superflous,as it would be hidden behind a streamlining skirt.
I'll have to re-visit Hucho to look at the inflated tail.I hope we have the same book!
The one I like best,I'm pretty sure is from Baron R.von Fachsenfeld around 1936,that he did for Omnibus at FKFS.I have a U.S.Patent which is similar to it,I'll have to ferret that out.

miket 07-06-2010 07:06 PM

I would need to see a picture to understand exactly what you described. I do see the advantage of going up like that instead of a simple hinge on top because the bottom edge of the fairing wouldn"t swing out much farther than the wheel. As a practical matter how do you make the pivots?

I was interpreting what hucho meant by elimination of the rear wheel arches he meant no arch around the wheel well just a flat across fairing? I have the fourth edition of aerodynamics of road vehicles. The Fachsenfeld is what i was refering to, the bottom of the boat tail curved almost as much as the top curved down.

I have concerns with a totally solid hub cap concerning brake cooling and snow buildup. Obviously not at the same time lol. Tundras have been know to warp rotors. Solid hubcaps might prevent snow from getting in from the outside but all the snow that gets in from the inside might not be able to get out.

aerohead 07-08-2010 05:28 PM

pivots/etc.
 
Quote:

Originally Posted by miket (Post 182526)
I would need to see a picture to understand exactly what you described. I do see the advantage of going up like that instead of a simple hinge on top because the bottom edge of the fairing wouldn"t swing out much farther than the wheel. As a practical matter how do you make the pivots?

I was interpreting what hucho meant by elimination of the rear wheel arches he meant no arch around the wheel well just a flat across fairing? I have the fourth edition of aerodynamics of road vehicles. The Fachsenfeld is what i was refering to, the bottom of the boat tail curved almost as much as the top curved down.

I have concerns with a totally solid hub cap concerning brake cooling and snow buildup. Obviously not at the same time lol. Tundras have been know to warp rotors. Solid hubcaps might prevent snow from getting in from the outside but all the snow that gets in from the inside might not be able to get out.

miket,I almost had your questions addressed yesterday,then computer crashed before I could enter.( we think Verizon FIOS is the new term for FECES ).I'll take your questions one at a time in case the computer is looking for a repeat performance.
The pivot point 'outers' are created from steel C-channel welded to the outside of the fixed-frame and inside of the floating-frame.
The frames are joined by 4-steel tube double-T-bone links,through which hinge- pins are inserted and secured,creating the pivot articulation.
The floating-frame simply dangles from the 4 links,and it is in this position that the skirt is fitted and secured by Zeus fasteners

aerohead 07-08-2010 05:30 PM

wheel arches
 
miket,our books are different vintage so I'm going to need some help on the wheel arch issue.

aerohead 07-08-2010 05:51 PM

Fachsenfeld's tail
 
With respect to diffuser angle limits beyond a cars original rear bumper I have no data.
Hucho,in his section on racing cars shows some long-tail configurations along with lift/drag comparisons.
Hucho also has a full-boat-tail drag tabulation for the Daimler',M-B C-111 record car,and you'll notice that this car also has the upsweep.
Ditto,EV-1/Impact LSR car at Ft. Stockton,Tx.
The only thing that I would throw out,is that a 'track' car would require special considerations that a 'road' car would not.And I believe an upswept tail is a concession to cornering downforce ( say 257 mph around a curve in the Olds AEROTECH ).
The other 'clue',is from GM's display at EPCOT Center in the 1980s,where they displayed an 'active' diffuser which went 'flat' at highway speeds.No upsweep!
On the road,there would be no concern for approach/ramp/break-over clearance,so a 'flat',or 2.5-4.0 degree diffuser wouldn't pose an issue.
My streamlining template reflects a 'flat' diffuser as used by Jaray,Klemperer,Lay,Kamm,GM,etc. which would require the 'active' approach,something I don't feel to be a big deal.
Why Fachsenfeld did what he did died with the man.I would not,and will not design as he did,however,what he did remains a very high bar,better than anything I've seen to date.

aerohead 07-08-2010 06:29 PM

"solid" wheelcovers
 
No doubt your concerns have been shared by many over brake-related issues.
The 'answer' was to provide some 'minimum' aspiration to the wheelcover.
Renault,for it's Vesta-II,provided one streamlined opening in the disk which coincided with the valve stem position.
On Ultralite,GM had very small penetrations near the outer extremity of the wheel.
GM's Pontiac Div. used larger ones on Trans Am Firebird.
There's a long list of concessions to 'practicality.'
As to snow issues,I have little to bring to the table.I've driven in white -out conditions over Raton Pass into Colorado,with snow all the way to Colorado Springs without event.And plowing County Line road,east out of Palmer Lake.
I would let safety be the over-arching priority.High mpg is kinda meaningless when you're dead amidst the twisted remains of your car at the bottom of a ravine.


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