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aardvarcus · 01-25-2016, 07:46 AM

Don’t feel alone, I have wanted to build almost the exact same thing for a long time, and will if/when I start my next project vehicle. (Way too heavy for the Tacoma, plus crash/air bag issues.)

You mentioned a shock mounted covering; I assume you are emulating a crumple zone between your stainless cover and the rigidly mounted steel hitch. (Which I hope you meant as that is why I say your build is very similar to what I have been dreaming of.) I look forward to seeing what you come up with, as I have rolled that idea around in my head for some time. The best way I have been able to figure out how to accomplish that in a durable packaging is as follows.

First I would want the bumper to be able to slide forwards and backwards (aka crumple) without being damaged. I came up with either using a pipe in a pipe (like a hitch with no pin) to connect the two where the outer pipe is welded to the hitch base and the inner pipe is welded to the bumper; or alternatively welding coil springs to the hitch to hold the bumper, with them recessed back far enough so that coil bind isn’t the limiting factor.

The second thing I wanted was to provide energy dissipation as the bumper travels backwards. I took a note from racecars, and found they are using aluminum honeycomb or shaped extruded polystyrene for their crumple zones. You could make squares of extruded polystyrene foam (XPS, the blue/pink stuff) like a pyramid, progressively getting larger as you go back. Progressive absorption would reduce the shock wave transferred to the vehicle. Fit those squares between the two bumpers, with glue or something to hold them in place.

Then if (hopefully not but if) you needed to use your crumple zone, it would be there, and all you would have to replace would be the foam pyramids. Anyway that is how I dreamed up adding a crumple zone to a pre-1995 Chevy truck. Looking forward to seeing what you come up with.

Oh, and I would also suggest buying a piece of some stainless pipe and cutting it into quarters, and using those radiuses to help flow air into your ventilation openings.

01-25-2016, 07:46 AM	#5 (permalink)
aardvarcus Master EcoModder Join Date: Apr 2012 Location: Evensville, TN Posts: 676 Deep Blue - '94 GMC Suburban K2500 SLE 90 day: 23.75 mpg (US) Griffin (T4R) - '99 Toyota 4Runner SR5 90 day: 25.43 mpg (US) Thanks: 237 Thanked 580 Times in 322 Posts	Don’t feel alone, I have wanted to build almost the exact same thing for a long time, and will if/when I start my next project vehicle. (Way too heavy for the Tacoma, plus crash/air bag issues.) You mentioned a shock mounted covering; I assume you are emulating a crumple zone between your stainless cover and the rigidly mounted steel hitch. (Which I hope you meant as that is why I say your build is very similar to what I have been dreaming of.) I look forward to seeing what you come up with, as I have rolled that idea around in my head for some time. The best way I have been able to figure out how to accomplish that in a durable packaging is as follows. First I would want the bumper to be able to slide forwards and backwards (aka crumple) without being damaged. I came up with either using a pipe in a pipe (like a hitch with no pin) to connect the two where the outer pipe is welded to the hitch base and the inner pipe is welded to the bumper; or alternatively welding coil springs to the hitch to hold the bumper, with them recessed back far enough so that coil bind isn’t the limiting factor. The second thing I wanted was to provide energy dissipation as the bumper travels backwards. I took a note from racecars, and found they are using aluminum honeycomb or shaped extruded polystyrene for their crumple zones. You could make squares of extruded polystyrene foam (XPS, the blue/pink stuff) like a pyramid, progressively getting larger as you go back. Progressive absorption would reduce the shock wave transferred to the vehicle. Fit those squares between the two bumpers, with glue or something to hold them in place. Then if (hopefully not but if) you needed to use your crumple zone, it would be there, and all you would have to replace would be the foam pyramids. Anyway that is how I dreamed up adding a crumple zone to a pre-1995 Chevy truck. Looking forward to seeing what you come up with. Oh, and I would also suggest buying a piece of some stainless pipe and cutting it into quarters, and using those radiuses to help flow air into your ventilation openings.