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aerohead 10-16-2010 04:21 PM

Pickup Truck Streamlining
 
7 Attachment(s)
I remembered to bring the camera and hope Al will be able to post images before the store closes at 4:00 PM.
I'll go ahead and briefly explain the latest mods to the T-100 which went on the last trip:
(1) The nose was re-configured more like the half-zeppelin profile of the 'Template',kicking the air over and around rather than allowing to flow underneath.
(2) Both front wheel arches received for the first time,a rear radius which integrates into rocker panel fairings.Short of full skirts,this is an attempt to clean up the flow here a bit.
(3) As mentioned above,the truck received rocker panel fairings to integrate flow coming from the new wheel arch radii.
(4) The hood blister finally got the plex wing fairing for the driver' side.The T-100 has a fairly mediocre windshield and the blister with wings attempts to 'soften' the pressure gradients present before,around,and over the windshield.The proper solution would be a $3,000 GTP compound-curve laminated safety glass windshield and re-engineering of the cabin,both outside the scope of the project.
(5) Driver-side cab/Poco-Loco integration fairing.Finally,after 5-years waiting,I finally have a fairing to eliminate the locked-vortex which occupied this area adjacent to the back of the cab and forward section of the aero-shell "Poco-loco" named from the sailboat from which it is derived.
(6) Passenger side Poco-Loco side window.No aerodynamic benefit but a great safety addition while backing out of parallel parking spaces into traffic.
(7) Rear windshield for Poco-Loco.Again,no aero benefit however I get rear vision for the lane I'm in and vision while backing.The dimensions of the fenestration are the bare minimum for vision,while minimizing the volume of the locked-vortex created by the new void.
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OBSERVATIONS:
Without the 24-inch boattail, missing 2-sections of the bellypan,and missing the diffuser section entirely,over the recent 4,100-mile trip the truck performed close to the 2005 performance which included the tail,full belly and 1st-gen trashcan nose.
At a trip average of 31.3 mpg and mileage ranging from 28-36 mpg it appears that the new mods are allowing 'long' truck mpg from the 'short' truck.
It should only get better from here.
On a velocity-weighted basis,using the MPG data through the 'back door' of GM Lab's Cd/MPG relationship,the truck's mpg would indicate approximately Cd 0.20 compared with the original Cd 0.44.
If things fall together over this next year we may finally know if the trailer can push the Cd even lower.

Varn 10-17-2010 11:19 AM

Excellent! You might try putting some radius on the front of the bed wedge. Or install some filler between the bed and and the cab.

Keep sharing.

darcane 10-18-2010 03:52 PM

Did you make any runs with it at Bonneville?

Any details on how you made the hood blister and nose modifications? They appear to be sheetmetal that was formed and riveted in place?

Mike

max_frontal_area 10-19-2010 02:37 AM

venturi
 
Hey Phil,
does your hood tilt forward like a vette? is there a practical purpose to the gap between the rearmost top of the cab and the bed fairing?
on the air/cooling intake which is frenched into the bumper i see a cone, is it part of a fixed venturi? if so what temp drop do you get on the interstate?

i have been thinking on ram air setup on my 80's 300TD wagon, removing the ugly DOT imposed "sealed beam headlights" which displaced the most powerful lights on the road in those days with barely functional candles. intead i will source the smallest (frontal area) high low beam lights i can find, place a huge ram air scoop (exclusively to feed the turbo) on one side of the radiator
and an intercooler on the other side. i feel strongly about feeding turbos and keeping the compressor side cool, therefore the desire to use a venturi.
however, as air velocities change i feel a venturi of that size needs to be variable much like the cones in the SR71, if only they could have found a way to syncronise them, in the time they took to actuate pilots fopund themselves 11 miles off course. back on the ground, do you have any ideas on making one variable, and, a way of acuating it:eek:
oops, forgot to mention i also want to do pre turbo misting (h2o) i can make tiny drops which wont hurt the compressor vanes, so its placement will either complicate this design or could possibly create symbiosis - if the misting head can be placed within the cone of the venturi...

- dig your stuff. dont ever stop!

miket 10-19-2010 05:16 AM

How much difference is there between the radiused wheel arch and a full wheel fairing? If you extend the middle of the wheel fairing down to cover the the rim would you still need moon covers?

I also want to know how you made the airdam/nose.

d0sitmatr 10-19-2010 09:55 AM

well aerohead, I have to say, you are a huge inspiration to me.
looking at the mileage your getting with that tank (;)) makes me believe Im going to achieve my 30+mpg mark with relative ease :)

I wanted to ask, have you considered a basic wind tunnel for the engine bay ?

Im working up a plan for directing the air flow through the bay area and out 2 side ports that I will engineer in the upper fenders of my ranger. slotted on 1 side to pull the heated air from the engine itself, while also streamlining the airflow through the engine bay.
I also have a couple of ideas rolling around through my head for smoothing my front end, (like most vehicles, its horrible with little nook and crannies) while still giving it some air flow (about 33%) as well as dropping my front wind guard down several inches. and most importantly, an aerolid and belly pan.
I'll be putting a work log up when I start any of my projects, and I would like if you stopped by the threads when I do for any advice you might have.

(ps, I also love the nose, but from reading other posts of yours, its too bad its such a pita to find that piece.)

aerohead 10-20-2010 06:39 PM

radius
 
Quote:

Originally Posted by Varn (Post 199311)
Excellent! You might try putting some radius on the front of the bed wedge. Or install some filler between the bed and and the cab.

Keep sharing.

Varn,I taped some tufts just behind the gap where I could watch in the mirrors.They laid flat against the aeroshell and basically straight back until higher up,where they started pointing into the lower pressure coming down off the roof portion.
It appears that the air just skips over the gap and keeps on going.The guys at tech inspection at Bonneville recommended the leading edge radii also.I'll do it but I don't anticipate any measurable gain.

aerohead 10-20-2010 07:05 PM

runs
 
Quote:

Originally Posted by darcane (Post 199492)
Did you make any runs with it at Bonneville?

Any details on how you made the hood blister and nose modifications? They appear to be sheetmetal that was formed and riveted in place?

Mike

I run next year,with and without the trailer.
Some of the guys really wanted me to run,I knew I was a year away from being ready ( close though ).
The big thing was to get approval for the trailer runs and we got that sorted out at tech inspection thanks to USFRA President Jim Burkdoll,who's given me the okay as long as I don't exceed 130-mph.
I have a laundry list of safety equipment to come up with over the next year and I've begun the search for tire options for the trailer.
--------------------------------------------------------------------------
The blister was built on the truck using a polyisocyanurate foam board skeleton and skins that were glassed over using Bondo cloth and polyester resin from Home Depot.The wings are scaps of plexiglass attached to aluminum sheet with panel screws.There is a beam near the windshield for rigidity and I riveted an aluminum ramp to relax the angle of attack there.
--------------------------------------------------------------------------
The nose is a cedar wood skeleton of formers and stringers glued and screwed and attached with steel angle brackets.The grille-block inlet is a stainless steel trashcan lid.The interior ogival valve is a commercial outdoor aluminum light fixture housing.Headlight and turn signals covers are heat-gun formed plexiglass.The new skin is aluminum sheet,screwed at the top to the original nose,the lower section to a 1/2-inch EMT bow which was bent with a tubing bender at 2-inch increments and through-bolted to the steel bumper sides.There is no 'bottom' to the new nose skin .There are only simple 2-dimensional curvature,nothing complex.
The flexible foam rubber chin spoiler is made from inter-locking foam cushion material for concrete floors sold locally at BIG LOTS.

aerohead 10-20-2010 07:38 PM

hood/gap/cooling
 
Quote:

Originally Posted by max_frontal_area (Post 199622)
Hey Phil,
does your hood tilt forward like a vette? is there a practical purpose to the gap between the rearmost top of the cab and the bed fairing?
on the air/cooling intake which is frenched into the bumper i see a cone, is it part of a fixed venturi? if so what temp drop do you get on the interstate?

i have been thinking on ram air setup on my 80's 300TD wagon, removing the ugly DOT imposed "sealed beam headlights" which displaced the most powerful lights on the road in those days with barely functional candles. intead i will source the smallest (frontal area) high low beam lights i can find, place a huge ram air scoop (exclusively to feed the turbo) on one side of the radiator
and an intercooler on the other side. i feel strongly about feeding turbos and keeping the compressor side cool, therefore the desire to use a venturi.
however, as air velocities change i feel a venturi of that size needs to be variable much like the cones in the SR71, if only they could have found a way to syncronise them, in the time they took to actuate pilots fopund themselves 11 miles off course. back on the ground, do you have any ideas on making one variable, and, a way of acuating it:eek:
oops, forgot to mention i also want to do pre turbo misting (h2o) i can make tiny drops which wont hurt the compressor vanes, so its placement will either complicate this design or could possibly create symbiosis - if the misting head can be placed within the cone of the venturi...

- dig your stuff. dont ever stop!

The forward tilting hood is the ultimate objective.Right now I have to remove two handfuls of screws and the blister just to open the hood.Prototypes are like that.No convenience whatsoever!
-------------------------------------------------------------------------
The cab/aeroshell gap allows clearance for frame flex inherent in the non-unibody trucks.I'll soften the leading edge of Poco-Loco at some point to help in yaw conditions but I've got bigger fish to fry first.
-------------------------------------------------------------------------
The 'cone' inside the grille-block inlet is actually a 'valve' to help regulate airflow volume especially in the winter,when it will actually fully close when the truck is parked.I thought it might help conserve some engine heat,reducing 'cold-start' issues.The inlet to the radiator is air-tight and the engine runs at normal temp,although at lower load do to the reduced drag of the grille-block.So far the computer appears to be smart enough to keep the BSFC fairly constant,where a carburetored truck might suffer.
-------------------------------------------------------------------------
I'm not going to be much help to you on the turbo.I'd be looking at serious race cars on that one.You almost need to get a static pressure probe and a good manometer and locate your highest pressure,whether at the forward stagnation point,or maybe even inside a wheel well.Don't know.
I think the bigger issue is rejecting the heat of compression from the compressor section.Does anyone mist the inter-cooler itself? De-ionized/de-mineralized water so zero salt buildup on the core? And no risk to the turbo if there is a plumbing problem?

aerohead 10-20-2010 07:47 PM

Moons
 
Quote:

Originally Posted by miket (Post 199637)
How much difference is there between the radiused wheel arch and a full wheel fairing? If you extend the middle of the wheel fairing down to cover the the rim would you still need moon covers?

I also want to know how you made the airdam/nose.

The Moons eliminate any windage of the wheel so basically having them ( on both sides of the wheel ) would offer the lowest drag.Or something like Ford did with Probe-IV.
I don't have any specific data on the wheel arch radii other than they have been used in racing since the 1960s and on amphibious cars since 1915.Short of full skirts I think they offer a modicum of drag reduction.But I will run full front skirts at Bonneville in 2011.You get a 1/4-mile to turn there.
-----------------------------------------------------------------------------
I covered the nose construction in an above post,see if that works for ya.I did get some photos of some of the build which I could post at the DIY forum sometime.

Varn 10-20-2010 09:46 PM

Impressive effort!

miket 10-21-2010 01:42 AM

Interesting, i never thought about aerodynamically covering the inside of the tire too. Im concerned about brake cooling, i wouldn't want to deal with alot more more warped rotors. Brake fade wouldn't be good either.

How about slots on the covers that slide open when the wheel is decelerating? Shouldnt be that hard. Drag and cooling would be beneficial when braking. Alternatively they could be held open by NiTi shape memory springs that actuate above a certain temperature.

miket 10-21-2010 01:06 PM

Is there a name or another thread already for that idea it seem so simple. 2 slotted moon covers together, the outer one partially rotates when the wheel decelerates or when a NiTi spring heats and the slots in the covers line up. When the wheel accelerates or niti spring cools it rotates the other way so the slots dont line up.

BamZipPow 10-21-2010 04:11 PM

I think those would be called spinner wheel covers? ;)

miket 10-21-2010 10:33 PM

Quote:

Originally Posted by BamZipPow (Post 200149)
I think those would be called spinner wheel covers? ;)

No, spinner wheels dont stop after 1/5 or 1/8 of a revolution they keep going and going etc. Wouldnt be very good. If there was a cheap spinner with slots that line up good i could probably easily modify it.

BamZipPow 10-22-2010 03:05 AM

Quote:

Originally Posted by miket (Post 200223)
No, spinner wheels dont stop after 1/5 or 1/8 of a revolution they keep going and going etc. Wouldnt be very good. If there was a cheap spinner with slots that line up good i could probably easily modify it.

They would if you put a stop tab on there. ;)

miket 10-22-2010 06:30 AM

Quote:

Originally Posted by BamZipPow (Post 200263)
They would if you put a stop tab on there. ;)

Which is how i would modify it.

d0sitmatr 10-22-2010 02:40 PM

Ive been thinking of a way to cover almost the entire wheel, sort of using the same method as a roadster ?
a full cover, that would actually exclude the brake within its fold :)

darcane 10-22-2010 04:19 PM

Why the great concern over brake cooling? Most of the people here try to limit their brake usage enough that cooling shouldn't be an issue.

orange4boy 10-22-2010 05:29 PM

Nice work Phil,

I love how you covered the headlights/grille. I did the same for my grille but never got around to doing the headlights.

Any thoughts on smaller mirrors? I'm still hoping to do that myself sometime.

What do you think about the idea of A-pillar "fillers" I had the idea of creating plexi bubbles like those rain drip guards but they would fill the area where the vortex forms instead of stopping drips. Thoughts?

d0sitmatr 10-22-2010 05:34 PM

how about using those door ding guards ?
the kind that slips over the very edge ?

Ive been toying with that idea for a while and as soon as I can afford too, I am going to buy a 100' roll and then proceed to do every crevice on my truck.
to completely surround my doors will take 17' for one side

aerohead 10-22-2010 05:57 PM

mirrors/A-pillars
 
Quote:

Originally Posted by orange4boy (Post 200352)
Nice work Phil,

I love how you covered the headlights/grille. I did the same for my grille but never got around to doing the headlights.

Any thoughts on smaller mirrors? I'm still hoping to do that myself sometime.

What do you think about the idea of A-pillar "fillers" I had the idea of creating plexi bubbles like those rain drip guards but they would fill the area where the vortex forms instead of stopping drips. Thoughts?

Commuting is pretty scary and I'm going to stay with the bigger glass.Eliminating the mirrors altogether on the CRX made no difference at 100 mph,I don't think modern mirrors are the liability they once were for the good they do.
As to the A-pillar vortex,it seems like the 'bubble' would have to extend so far out to the sides,that the increase in frontal area would cancel out the benefit of the vortex elimination.
An EV-1 windshield would solve all this but they've gone the way of the Easter Island Lumber Co..

miket 10-22-2010 07:55 PM

Quote:

Originally Posted by darcane (Post 200335)
Why the great concern over brake cooling? Most of the people here try to limit their brake usage enough that cooling shouldn't be an issue.

I've had problems with warped rotors and I just upgraded the calipers per technical service bulletin. Also the truck will sometimes be fully loaded which will put more stress on the brakes. Cant forget steep hills too. It just seems a bit odd to me that the rotors have vanes inside specifically for moving air and then seallng the tires up tight.

darcane 10-22-2010 08:42 PM

Well, hills and towing certainly put you in the exception category. Carry on.

Varn 10-22-2010 09:06 PM

I have no interest in sealing up the brakes on any of my vehicles. You can't coast that long on some hills around here before you get over the top of what is controllable. We have steep hills some of which if you hit at 25 mph you will be at 65 at the bottom and there are some tight curves at the bottom.

I bet that warped rotors and increased pad wear cost more than the gas it saves.

max_frontal_area 10-23-2010 03:41 AM

Quote:

Originally Posted by aerohead (Post 199964)
The forward tilting hood is the ultimate objective.Right now I have to remove two handfuls of screws and the blister just to open the hood.Prototypes are like that.No convenience whatsoever!
-------------------------------------------------------------------------
The cab/aeroshell gap allows clearance for frame flex inherent in the non-unibody trucks.I'll soften the leading edge of Poco-Loco at some point to help in yaw conditions but I've got bigger fish to fry first.
-------------------------------------------------------------------------
The 'cone' inside the grille-block inlet is actually a 'valve' to help regulate airflow volume especially in the winter,when it will actually fully close when the truck is parked.I thought it might help conserve some engine heat,reducing 'cold-start' issues.The inlet to the radiator is air-tight and the engine runs at normal temp,although at lower load do to the reduced drag of the grille-block.So far the computer appears to be smart enough to keep the BSFC fairly constant,where a carburetored truck might suffer.
-------------------------------------------------------------------------
I'm not going to be much help to you on the turbo.I'd be looking at serious race cars on that one.You almost need to get a static pressure probe and a good manometer and locate your highest pressure,whether at the forward stagnation point,or maybe even inside a wheel well.Don't know.
I think the bigger issue is rejecting the heat of compression from the compressor section.Does anyone mist the inter-cooler itself? De-ionized/de-mineralized water so zero salt buildup on the core? And no risk to the turbo if there is a plumbing problem?


10-4 on the hood, for me that would be a pita, sompin is always being tweaked under there...

cab/aeroshell gap, yes the flex was ovious, but with your clever sourcing of materials i recon you could have come up with something there as well!?

the grille-block inlet valve is manually adjustable from the driver seat?
you might find that at just the right setting it will cool your intake air
like a carburetors venturi.

on my turbo... it seems most streamliner designers haphazardly place engine air inlets figuring at over 200 mph there will be plenty of air for the engine
only to find they are starving it. some of the brighter teams look into tuning their scoops to work like venturies, effectively cooling their intake charge
and packing more air in the engine.

and that is what i am hoping to achieve but with a vehicle that is not quite as sexy.
yes, i intend to mildly dimple (golf ball) the compressor involute of my turbo
with a small ball nose end mill to introduce xtra mass, and fit it with a housing and duct which will supply cool air from the stagnation point.
i have read that pre turbo water injection is supposed to be quite effective,
however too much water won't flow well through intercoolers!!
yes ppl spray their intercoolers with water although i doubt they are using distilled h2o.
the hip way for racers is to blast it with bottled co2 - much more effective.
but no chance of gettin into green heaven with that method.
traditionally, the additional cooling of the IC is only needed during continued
boost.
i have a slightly different twist in mind, the idea is to supply a the max cool air to the turbo and keep it cooled along the way to the combustion chamber thus maxing out volumetric efficiency (on a 30some yo engine design) so that the turbo is always producing boost. secretly hopin for 5 psi.
the idea is to significantly lower rpm's therefore increase mpg by buring fuel more completely as well as reducing recipocating and parasitc losses - all the while extending engine life. best of all i can go to work without having to fool
computers or sensors :thumbup:

forgot to ask, on your grille-block inlet are you using airflow straightners
between the inlet and the radiator or is the air wild? takes lots of energy
forcing dirty air through lil fins. main reason why i dislike pusher fans.
also is your radiator sealed on its outer periphery, lots of cooling air is wasted
flowing around it, if you adress that you could effectively close your "valve" a bit more.
never cared for the looks of the t-100. i do now!

bondo 10-23-2010 08:25 AM

Gap Fill between cab and aerocap.
 
1 Attachment(s)
I have read alot of discussion here and in other threads about the importance of filling or covering the gap between the cab of a pickup and the aerocap.

In the wind tunnel testing of my Aerolid, I was told by the Engineers, at the American pickup truck manufacturer whose wind tunnel I was in, that the air flowing around the top and sides of the cab never gets sucked into the gap between the cab and a camper shell/aerocap. This is due to there being higher pressure air being forced out the gap from underneath the truck, so the air actually travels backward from what one would intuitively think.

The smoke tests showed this to be true also.

Bondo

d0sitmatr 10-23-2010 10:06 AM

Quote:

Originally Posted by bondo (Post 200437)
I have read alot of discussion here and in other threads about the importance of filling or covering the gap between the cab of a pickup and the aerocap.

In the wind tunnel testing of my Aerolid, I was told by the Engineers, at the American pickup truck manufacturer whose wind tunnel I was in, that the air flowing around the top and sides of the cab never gets sucked into the gap between the cab and a camper shell/aerocap. This is due to there being higher pressure air being forced out the gap from underneath the truck, so the air actually travels backward from what one would intuitively think.

The smoke tests showed this to be true also.

Bondo

but would that not change if your using a full belly pan ?

euromodder 10-23-2010 12:30 PM

Quote:

Originally Posted by bondo (Post 200437)
In the wind tunnel testing of my Aerolid, I was told by the Engineers, at the American pickup truck manufacturer whose wind tunnel I was in, that the air flowing around the top and sides of the cab never gets sucked into the gap between the cab and a camper shell/aerocap. This is due to there being higher pressure air being forced out the gap from underneath the truck, so the air actually travels backward from what one would intuitively think.

The smoke tests showed this to be true also.

In the pic, the smoke seems to be detaching from the aerolid rather than following it :confused:

Regardless of what direction the actual flow goes, it'll create more drag being there than when it wasn't there.

aerohead 10-23-2010 04:17 PM

straighteners/sealing
 
Quote:

Originally Posted by max_frontal_area (Post 200426)
10-4 on the hood, for me that would be a pita, sompin is always being tweaked under there...

cab/aeroshell gap, yes the flex was ovious, but with your clever sourcing of materials i recon you could have come up with something there as well!?

the grille-block inlet valve is manually adjustable from the driver seat?
you might find that at just the right setting it will cool your intake air
like a carburetors venturi.

on my turbo... it seems most streamliner designers haphazardly place engine air inlets figuring at over 200 mph there will be plenty of air for the engine
only to find they are starving it. some of the brighter teams look into tuning their scoops to work like venturies, effectively cooling their intake charge
and packing more air in the engine.

and that is what i am hoping to achieve but with a vehicle that is not quite as sexy.
yes, i intend to mildly dimple (golf ball) the compressor involute of my turbo
with a small ball nose end mill to introduce xtra mass, and fit it with a housing and duct which will supply cool air from the stagnation point.
i have read that pre turbo water injection is supposed to be quite effective,
however too much water won't flow well through intercoolers!!
yes ppl spray their intercoolers with water although i doubt they are using distilled h2o.
the hip way for racers is to blast it with bottled co2 - much more effective.
but no chance of gettin into green heaven with that method.
traditionally, the additional cooling of the IC is only needed during continued
boost.
i have a slightly different twist in mind, the idea is to supply a the max cool air to the turbo and keep it cooled along the way to the combustion chamber thus maxing out volumetric efficiency (on a 30some yo engine design) so that the turbo is always producing boost. secretly hopin for 5 psi.
the idea is to significantly lower rpm's therefore increase mpg by buring fuel more completely as well as reducing recipocating and parasitc losses - all the while extending engine life. best of all i can go to work without having to fool
computers or sensors :thumbup:

forgot to ask, on your grille-block inlet are you using airflow straightners
between the inlet and the radiator or is the air wild? takes lots of energy
forcing dirty air through lil fins. main reason why i dislike pusher fans.
also is your radiator sealed on its outer periphery, lots of cooling air is wasted
flowing around it, if you adress that you could effectively close your "valve" a bit more.
never cared for the looks of the t-100. i do now!

The original grille is still inside there for turbulence and distribution to the heat exchangers.
The inlet is sealed to ensure that the air is delivered only to the heat exchangers.
The valve is fixed at 'wide-open.' After the pick and shovel work is done,and if the truck survives that long,I'll get around to some of the 'fun' stuff,doing the 'active' aerodynamics.
I recall carburetor icing issues with my 1st VW after deleting the heat-riser on the intake manifold,so the venturi effect is certainly real.

max_frontal_area 10-24-2010 01:02 AM

phil, the "grates" :) that channel airflow to the radiator or a/c cooler
are for the birds. in all the vehicles i worked on, import or domestic there was always a huge gap between them and the radiators, lots of possibility for air to go errand and irrevocably attempting to hit the fins at an angle instead of just flowing through. when u put the gardening tools away think of fashioning
some tighter airflow straigteners and be amazed how lil cooling air your engine acutally needs.
out of pure experimentation i removed the only, thermostatically controlled electric fan on my 82 IDI Jetta wondering if it was possible to go without.
that was 4 years ago. the only time it gets hot is in traffic when i use the heater and simlpy open the windows :=) the aperture is about 2/3 the size of yours, and i left the air snorkle to fend for itself.
b.t.w. i live near the desert in central california.

Bondo:
there is no perceptible gap in the picture of your cab/aerolid, how wide is it actually? the airflow does seem to be seperating but at least it is not going turbulent. the dip generated by the fitup of the aerolid to the cab, and the channel on the top of the aerolid is causing a very interesting swell which is forced to flow over the prevailing airflow going over the top.
very interesting. wonder what would have happened if and exact fitup (more difficult to suit all truck shapes) had been done?

regardless great work!

bondo 10-25-2010 10:31 PM

2 Attachment(s)
Hello Max,

The gap is about three quarters of an inch. I think the smoke is behaving like it is in the picture in my earlier post because the attached air on top is meeting the attached air along the side of the Aerolid at the intersection of the two planes. Since the lid slopes back, the attached air runs out of surface to attach to on the sides and mixes with the air flowing over the roof.

The earlier Aerolid I built, the silver one, had a front surface which angles in and meets the angled surface of the rear of the cab. In the later version I built, the white one, I extended the forward surface of the Aerolid to cover the angled rear surface of the cab.

Both versions deliver about a 15% increase in fuel efficiency at freeway speeds. I do like the later version better as far as style goes.

Bondo

aerohead 10-26-2010 06:59 PM

cooling
 
Quote:

Originally Posted by max_frontal_area (Post 200528)
phil, the "grates" :) that channel airflow to the radiator or a/c cooler
are for the birds. in all the vehicles i worked on, import or domestic there was always a huge gap between them and the radiators, lots of possibility for air to go errand and irrevocably attempting to hit the fins at an angle instead of just flowing through. when u put the gardening tools away think of fashioning
some tighter airflow straigteners and be amazed how lil cooling air your engine acutally needs.
out of pure experimentation i removed the only, thermostatically controlled electric fan on my 82 IDI Jetta wondering if it was possible to go without.
that was 4 years ago. the only time it gets hot is in traffic when i use the heater and simlpy open the windows :=) the aperture is about 2/3 the size of yours, and i left the air snorkle to fend for itself.
b.t.w. i live near the desert in central california.

Bondo:
there is no perceptible gap in the picture of your cab/aerolid, how wide is it actually? the airflow does seem to be seperating but at least it is not going turbulent. the dip generated by the fitup of the aerolid to the cab, and the channel on the top of the aerolid is causing a very interesting swell which is forced to flow over the prevailing airflow going over the top.
very interesting. wonder what would have happened if and exact fitup (more difficult to suit all truck shapes) had been done?

regardless great work!

Max,the inlet opening was sized according to Walter Korff's recommendations for low-drag cooling system design and the inlet duct is airtight,so I'm reluctant to go any smaller for fear of zorching something.
On some mountain ascents I could hear the clutch-fan lockup and start pumping air at the low air speeds.I think I'm near the ragged edge.


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