Vacuum Forming Splitter

[Z3_GoCar]

I had a combination of carriage head bolts and screws to the ABS bumper cover and the aluminum under tray. It wound up breaking into three parts. The center peeled the aluminum undertray into a ball under the car and moving the oil cooler line into the alternator pully. The two corner stayed some what bolted on, except the drivers side finder liner was part of the aluminum ball, along with my unharmed wired transponder. Since I have to install a new bumper cover, I could bolt some mounts with break-away points onto the aluminum bumper bar, but was thinking of swiss cheesing the bar for nose weight reduction. What I want is something that's easy to replace, and doesn't take anything else (bumper cover, under-tray, or finder liners) out when it goes away.

[Chip42]

plywood, attached from the top up to something like I showed will allow the splitter plank to break/break off without taking the bumper and other bits with it.

treat the splitter plate as disposable / expendable and you are halfway there.

[Eagle7]

Conceptually, that's exactly what I've got now, except I've got the front slot facing forward - which of course eliminates the possibility of a clean break. It took a big hit last summer and didn't fare well.

Do you have ideas for a rear pin that will shear when you want but not when you don't? Maybe something non-metalic and brittle? Or plastic?

[Chip42]

Whatever you choose it has to be strong enough to support the aero load and light dings but break free at a somewhat limitted contact force.

Pins dont really cover those criteria if you are making good aero use of the thing, ive been thinking about T6 aluminum flat stock, notched. But i have to run the math to see how much to notch and what cross section does best. Its not as easy to use as a bolt, but should give the desired results.

[Greg Amy]

What about shear bolts from a snowthrower? Made to shear under sharp force and you can buy them in six-packs at Lowe's. Just gotta design it so the shear plane is in the right location. - GA

[Chip42]

my thinking is that you need to have the aero-loading capability and the breakaway, so a pin, being equal strength in both rearward and downward loads (loaded in shear, mounted laterally) would need to be stronger than you might want for impact in order to be strong enough for use in general. but then there's the notion of orienting the bolt vertically...

[Greg Amy]

Understand, your vertical idea might work...but I think you're overstating just how much "downforce" these things provide, versus just reducing underbody lift. I'd be shocked if there's more than 50-75 pounds vertical force total on that plane...time for a fish scale, string, and GoPro camera?