aluminum undertray advice wanted

[lunarhighway]

these Dzus things look pretty handy but as you say they don't really do ways with the need for welding.

today i tried to fit a piece or corrugateded plastic underneath the car. it's alost exactly the width of the subframe. i might hang it from the frame with zipties if i can find some big enough aroudn the house. i can't make it go all the way back as the exhoust would probably mely it (or set it on fire wich is the last thing you want)

it seems i could get aways with one or two attachement points under the bumper.

and some "hooks" to suspend it from the subframe at the rear.

i'll see if i can safely put this together in the next few days and what the effect on FE will be, depending on the results i might choose to get some sheet aluminum and build an upgraded version, but than again, if this version works well enough i might keep it as it is.

does anyone know how hard sheet aluminum is to work with and how one would go about bending and cutting it to shapes? would some metal shears work? i wouldn't mind invesing a little money in a need mod that has proven to work; but i wouldn't like mess up to much of the aluminum

[adrive7]

These are nice. They make nice cuts and its like a hot knife through butter with sheet aluminum.

http://www.toolbarn.com/product/kett/KD-442/

Hand shears would work, it would just be harder, and more annoying/painful. For bending a table with a sharp edge and a mallet works.

[lunarhighway]

@adrive7 looks like a fine tool, but it's a bit expensive... it would sort of cancle out any financial saveings the undertray could have. if this thing delivers an actual 1% improvement in overall FE it might pay for itself 1 or two years... of course the higher fuel prises go the sooner it'll pay off, and i hope i'll save more gas, but it's not that big an area so i try to be realistic.


for the construction apparently sometimes it also pays of to look at a problem from the other side... i always envisioned the tray had to be removable from below, but when i opened the hood i saw there was plenty of room to reach down so i might suspend the undertray by just slideing it underneath the back of the bumper, suspend the other side from an alluminum L beam that rests on top of the subframes at the back and than use a conveniently located screw in the middle to hold a bracket that the whole assembly from shifting backwards and detaching.

to attach everything i'll drill holes trought the undertray, put some bolts trought it from below, and secure these to the tray with nuts from the top and than run these trough the L beam and the bracket and finally secure them with wing nuts.

to detach the undertray i would simply have to undo a couple of wingnuts and the whole thing would fall off with all the bolts staying in the undertray. i'll use some rubber wachers to dampen the vibrations a little to keep things from shakeing loose.

since te aluminum sheet might be a little floppy (i'll go for the things i can get as thats cheapest and lightest!) i might need to rivet some L beams along the edges.

anyway that's the plan.

i think i'll construct the frame and than cover it with some corrugated plastic. if that gives some measurable gains i might build a more solid version.

[lunarhighway]

ok enough said, here's my first attempt.


i used a piece of gorrugated plastic from a sign and some metal brackets made form these little things that back off unused card slots at the back of a computer.

there whas a single bolt sticking out the botton of the radiator frame (it holds a bracket for the power steering line...edit: looks more like a water hose in the picture...that'll probably be it...whatever) it stuck out just far enough to accept my own bracket and another nut.

next i slid the coroplast sign underneath the bumper and folded the bracket down so it toughed the plastic. i'd already drilled two holes in the bracket so this location was marked and than a bolt was ran trough the plastic attached with a nut and than through bracket and secured with a wingnut. basically that made sure things would stay in place but the fairing was still a little floppy at the back so i bolted two more brackets on top of the plastic that squeeze it against the subframe. undo the wingnuts and it all falls clean off.

the faring isn't as long as i'd like but the exhaust would interfere, and while i could cut a hole for it, it would still represent a fire/meling hazard.

also the sign only covers the center section and not the sides, because, well that was the size of the sign. on the final aluminum version (if this one shows it's worth persuing the idea) i'd make it both wider and longer with a cutout for the exhause.

at the front there where some holes in the radiator support. i cut out two holes in teh fairing that match up with these. they seem to evacuate air before the radiator, wich is a little odd, but i suppose they're there for a good reason so i don't want to mess with them.


it's still a little floppy at the front but so far i'm rather happy with it. lets hope it does something good!

as a final note, i'd initially planned to use done headed bolds for a little extra aero, but than i realized these had a little square extention below the dome that was taller than the thickness of the aluminum so the nut would never work.. so i went with standard screw heads. i did align the slit for the screwdriver with the airflow... that a few mm less frontal area im a bit perfectionistic sometimes.

[aerohead]

Lots of good suggestions by members and I'll add what I did to the soup.Fortunately for me,the Toyota had all kinds of frame rail penetrations already in strategic locations.The holes were large,however by filling the big holes with suitable flat-washers,then capturing those from both sides with even larger flat-washers,I was able to attach hangers for my belly-pan by through-bolting, without drilling or welding.And a note of caution: the frame is hardened steel and if heated,can loose strength,and yield at a lower load.If you simply have to weld,use TIG or MIG to localize the heat and keep some wetted heat sinks surrounding the area to conduct heat away to the environment.Remember too that you have the potential for fire and explosion if any part of the fuel system is compromised.Angle metal can be attached to the hangers with bolts.I recommend nylon-insert nuts,as they cannot inadvertedly come loose.The angle metal can be drilled for skin attachment,and speed-nuts,from auto parts or auto refinishing supply provides an anchoring point in lieu of Dzus fastener weld-on backing plates.Also,light metal angle can be pop-riveted to the aluminum sheet to create modular panels which can be attached as a unit.I've used this since the 1970s and never had a failure.Aluminum is prone to fatigue fracture and needs to be securely fastened.Big fender-washers are handy at attach points,as they distribute fastening force over a broad surface area.Whatever method you use,just make it tough and strong and avoid some of the stupid moments I've encountered over the years.

[nwbabybronco]

Have you had any problems with the ladder frame flexing against the tray and fasteners? Are bushings needed?

[lunarhighway]

i'm wondering about that too, not the tray is plastic so it'll flew pretty easy, but on the final version, it'll be an aluminum sheet framed by small aluminum L beams...that'll be pretty stiff.

i'm also wondering if i might need to design an radiator air exit duct in...i might just get away with a top grill block, but the grills are pretty exactly sized, and it doesn't make sence to try and smooth out the airflow under the car and at the same time obstruct the flow trough the car, wich already had a hard time.... or would that needlessly complicate things?

[lunarhighway]

here's what i've made so far

it's a 0.5mm 100x50 cm aluminum sheet, cut and folded, the folds really give it much more strength and rigidety than i expected.

[COMP]

Nice,,,you have a brake ???

[zjrog]

I like that skid... I need to find some coroplast political signs to hack for the Neon...