Aerodynamic Truck Front Bumper Options

[aardvarcus]

Hello everyone,

For those who didn’t see my other thread, I have a good gas mileage car as my daily driver, but I need a rough and tough truck for construction, bad weather, etcetera. Well I purchased a welder and I am trying to get ideas for an aerodynamic front truck bumper. Here are my requirements and what I hope to accomplish.

1. Improve aerodynamics while still accomplishing the other items as best as possible.
2. Improve utility of truck by being able to push/pull with bumper.
3. Improve light impact ability of truck by providing for small impacts to be contained within the bumper with no damage. (I.E. hit a deer, push through brush)
4. Improve hard impact (car wreck) survivability of truck and passengers by providing alternative crumple zone in the front bumper. (I.E. Bumper destroyed, but truck can drive away, everyone is ok.) Also bumper will go down lower to “mesh” with lower bumpers on cars.
5. Not overly increase weight of vehicle
6. Look cool. (Well, more like just not look too dumb.)

My basic idea for how to accomplish this is as follows. Remove existing bumper. Create light steel back plate to protect truck. Cover this plane with extruded polystyrene foam to provide aerodynamic shape and crumple zone. Mount new light steel front bumper also in an aerodynamic shape. Mount it semi rigidly (Hard Springs?) such that for small impacts it will act rigid (not activate crumple zone) and for large impacts it will allow bumper to compress right into the foam, limiting the peak deceleration experienced by the vehicle and passengers.

My two ideas for the front outer bumper are as follows. Aerodynamic “Bull Bars” roughly 4-6” in front of complete fiberglass/foam front shell. Bars would be probably 3” in width and shaped like the truncated teardrop. Alternatively a semi flush “normal bumper” covering the lower half of the front, with just the fiberglass/foam front covering the top. Crumple Zone foam will be behind this bumper, and there would be a 2-3” step from bumper to top part.

Other details are as follows. Incorporate operable grill opening. Put aero cover around existing headlights or provide new headlights. Also I will be doing a belly pan, side steps, and rear bumper in a similar manner to complement the front bumper, but I am holding off on their design until I get this design semi-finalized as I want them to complement each other. I don’t know how bad it is to slope up the belly pan from the lowest point in the middle up towards the sides to maintain side ground clearance. Overall ground clearance wouldn’t change, as belly pan would be at the height of lowest cross member. I will eventually be doing tire fairings either way.

I attached some sketches I made to give you a rough idea of what I am discussing. I know you have ideas or comments, so through them out there. Thank you in advance.

[oil pan 4]

I don't know how you are going to make a bumper that is made of a push capable thickness material and bend it to that convex shape you want.
Push bumpers I have priced are very expensive and very heavy (300lb of 1/4 inch steel).

[oil pan 4]

I got the idea a while ago that I should build a front bumper.
Originally I thought I would build it from scratch, then realized I could save a ton of time, weight and looks if I chopped up a semi bumper.
So this is where I am now:
http://ecomodder.com/forum/showthrea...ant-22160.html

[aardvarcus]

Oil Pan,

Thank you for the reply. I have been reading your thread and am anxious to see your pictures when you get it welded up.

I have not ruled out the idea of modifying an existing bumper. My idea for the complex shape of the bumper shown in the sketch and making it “push rated” was to start with a tube frame, and then skin it with “thin” 1/8” or so steel plate that could be torch bent into the right shape and then welded on. Yes, it will still be 200lbs or so.

I would really like to use steel (as I am not set up to weld aluminum) so maybe I can find a steel semi bumper. I could add reinforcement to the back if necessary.

[Otto]

Why not make a removable nose cap fairing out of very light weight foam and fiberglass? Use polyurethane expanding foam as do custom body work designers and contour as you wish. Use Dzus fasteners or similar and remove the cap as needed on the rare occasions you need to push something.

[aardvarcus]

Otto,

I had considered just making a foam/fiberglass cover, though I hadn’t thought of making it removable. Honestly that is the best option when you are only considering fuel efficiency. The issues with this option are that my current bumper isn’t anywhere near push rated (chrome and plastic) and while that option would increase the safety of the passengers for crashes above the current level, it wouldn’t do much to help the vehicle survive impacts.

I want a "push rated" bumper not just for pushing things, but also for hitting a deer or something like that. A guy in town has a similar truck with a fancy push bumper (not aerodynamic) that he has hit two deer with, and the truck was not damaged at all. If I hit a deer with my current setup, the truck would be very badly damaged. The problem with the normal bolt it right to frame push bumper is that you have no crumple zone, so if you hit something bigger than a deer, like a oak tree, your vehicle is significantly less safe.

I want a vehicle that is safe for me, safe for others, durable, and fuel efficient. I am looking for the best option to balance all these factors.

[oil pan 4]

I am willing to compromise on the push rating. 1/4 inch thick aluminum is pretty tough but its not the ultimate push rated bumper option.
I like it because its pretty light and fairly strong.
If I do need to push something I think I will keep a square of 3/4 inch thick plywood handy that I can hook on to the bumber as needed for occasional use.

I would like to polish it up and clear coat it. I'm trying to stick with the 80's styling some what with the big shinny bumpers. I also have a chrome step bumper to put on the back, should be direct fit bolt in place and drive kind of mod, but I haven't gotten to it yet.

A while ago I ran some calculations and for a 6000lb truck, every 100lb you add or subtract will effect the fuel economy by about 0.1MPG at 65mph.
Thats why I went light on the bumper, but didn't go as far as making it out of fiberglass or carbon fiber, just to save weight.

[Neen]

Keep the stock bumper for safety.
Drive cautiously and Don't hit deers.
Add the temp bumper for MPGs.

[oil pan 4]

My stock bumper is about 1mm or less of stamped steel.
1/4 inch aluminum will be a big improvement.

[aardvarcus]

Here is the rough design I have come up with so far for the bumper. Many parts of this design are rendered as simple curves, but in reality would be complex curves. Note a few design features that may not be apparent through the sketch:

The “bumper” (bottom part) will be angled back slightly; to direct airflow both up and to the sides of the vehicle. The flat section between the curve of the lower bumper and the base of the grill/light covers will be rubber or other material.

The “grill cover” (top middle) bent tube part will install in front of the existing grill, and the vertical bars will be tracks, allowing panels to come out of the bottom part of the bumper and block off the grill. I am thinking this part will be pneumatically actuated from inside the truck, and will have two sections, each independently controlled. That way I can have open, halfway, and closed settings.

The light covers (top outside) sections are not rendered well on this drawing, but will be smaller bent tube, except covered in Plexiglas or similar to direct airflow around the truck. They will basically be a cover for the existing lights and fit very close to the bodywork.

For all of the parts on the upper half, I will use rubber or similar material to have a smooth transition between the bumper and existing bodywork.
Imperfections I know exist in the design:

There is the step between the lower bumper and the upper grill and light covers. This is part of my crumple zone system. I put a radius on the top of the bumper. Would it help to radius (Concave) between the flat bottom and the grill/light covers?

The grill cover is currently rendered as a flat piece. I would like this piece to be slightly curved, however since I am making this part actuated, I am not yet sure if I can curve it and make it operate well and still recess into the lower bumper section. The grill cover is rendered as a 100% grill block, however I wouldn’t want to cover the entire thing, so I don’t know if it would be better to try to make it fit flush with the sides and cut in vent holes, or just make the grill block stay away from the sides and let that be the gaps. I am figuring on roughly 15% free area as compared to the radiator when the grill block is fully closed. My understanding is that the best design on this would be to have the opening as a thin slit running horizontally across the base of the grill block, as compared to the vertical openings that would be present if I leave a gap on the sides.

So, anyone have any thoughts or ideas?