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What was this 1969 bumper made of, and how was it made?

Hi all-so, for reasons I am not going to go into now(unless you really want to hear it!), I have a vested interest in “cloning” the bumper from the 1969 Lamborghini Marzal. You can google it, or see images of it here:

I am mainly interested in what the likely manufacturing techniques were in that period of 1968-1980 ish, in regards to auto bumpers. It appears to be some kind of either fiberglass, plastic over composite foam, or ??? To the wise folk here, if you were tasked with cloning a functioning bumper that would look as close to this as possible, what manufacturing techniques would you pursue? the car itself is a concept car. i will never be able to get into the same room with this actual car, but surely there is some universality in manufacturing techniques with this bumper and others of the era? thanks!!!

Are you interested in the black bumper part?

It can’t be fiberglass since it would shatter in a hit.

Likely a urethane sheet pressed into shape in a mold. The foam may be injected while the sheet is still in the mold with a cap to shape the back side.

Bumpers of this type are just starting to appear in this era… 69 Pontiac LeMans or 71 Camaro.

Duplicating the look would be easier in fiberglass filled with a 2 part foam.

Mustangman-AWESOME info!!! thanks so much. yes, the black singular molded bumper, that lives below the headlights, is the item in question i want to clone.

ok, if i were looking at duplicating it in fiberglass and 2 part foam, how would i go about this? i’m assuming that first, i need to generate a mold? thanks so much for the help on my hair brained scheme!

As a one off, hand built, concept car, never intended to be “manufactured” in the traditional sense the nonfunctional “bumper” could have been made out of literally anything but my guess agrees with yours. fiberglass or coated foam backed by steel for rigidity.

As far as universal manufacturing techniques for bumpers in 1969, the applicable US crash regulations didn’t go into effect until 1974 so bumpers on most production cars were chrome plated stamped steel bolted onto the chassis although on some cars it was whatever you could get away with or none at all.
Wiki MGB or the Lotus Elan/Europa for examples .

Unless people are going to be scrutinizing this car for authenticity, which is unlikely since it is stated to be a clone, why care how it was originally fabricated? Are people going to disassemble it to see the back side? As long as it looks like the end product you envision, why do you care so much how it is fabricated? I would use modern techniques over what was available back in the day unless I was going to pebble beach with this ride… :wink:

Oh, oh… I would like to hear the short version, hoping that that I can overcome feeling that you are a candidate for a tin-foil hat.

Is it for looks? Can you make one from wood? Are you going to be doing any time travel?

Have you posted this on a Lamborghini forum?

Yep, you need a mold. If you make a bumper that has the right shape out of wood, you can create a mold from that and them lay the fiberglass inside. Once cured and removed, pour 2 - part foam inside.

OR, make your bumper from fiberglass laid over a foam core. Shave the foam to the bumper shape minus 0.2 inches or so. Lay fiberglass over, let cure and finish with fiberglass resin filled with micro-beads to act as body filler. Or you can use body filler (Bondo) to fill and smooth. Probably the easiest way to make only one.

There are YouTube videos showing how to do this.

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The important question is whether or not you have the original bumper, because if you do your life will be a whole lot easier being able to take measurements from it, etc.

beancounter-you are exactly right. i do NOT care how they did it in 1969 for the purpose of recreating the process. I only want the closest, easiest, cheapest path to the final result-as close to an exact clone of the bumper as possible.

for the record, my usage for this would likely get me stoned to death on pebble beach(da dum, crash-here all week folks!). but it could be of benefit for me to be able to repeat the process, depending on results. i stumbled across a 2 part polyurethane foam system, that you mix together and it cures. I’m considering maybe a wooden mold that i pour the foam into, and embed it in a steel bar to attach to the car frame? thoughts?

it will be impossible to get access to the original bumper. it’s a one off concept car that traded hands for 700k the last time it sold. the closest i’ll be able to get is to recreate it using photos and measurements. the good news is this: i will have access to the exact same dimensioned grill area, so i CAN get the height and width very close.

That is the technique used for the reproduction of rare parts when one is not at hand. That is how this car got an entire new body formed from aluminum sheet. A fiberglass replica was made using photographs and the new body made the fiberglass mockup.

Yeah, I thought you might have a replica of it and were trying to fix something, but it sounds more like you’re trying to make a replica of it, yes?

yes, i want to replicate it as a functioning bumper.

anyone know what kind of foam do people use to shave down, that comes in a 4’ long block?

Me, I’d make a duplicate in wood, then use it to make a mold. That is a very complex shape!

Would this be a time when a 3D printer could be used to help make the mold?

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Sure, if those bumps are a repeating shape you could make them on a 3D printer, then attach them to a wood base shape. Good idea.

Unless it’s a really high-res 3d printer you’ll end up with stripey lines from the deposit layers.

When people 3d print stuff at home and need it to be smooth, they often build an acetone fog chamber. Put the part in there, fog it with acetone, which melts the outside just enough to smooth it out, and you’re good to go. For precision fitting the parts together you might need to glue them up and then fog them, which would require a large fog chamber. but you could probably build one fairly easily -the main trick would be to have the actual fogger - the part that turns acetone into mist - capable of sufficient volume to fill the whole chamber evenly.

A lot of those foggers use ultrasonic vibrations to turn liquid acetone into mist, but I’m not sure that’d work well for the volume necessary to do a whole bumper.

my thinking for a “soup to nuts” process would be to maybe carve or form the basic shape of the bumper WITHOUT the ridges. then, find a way to duplicate a bunch of those ridge pieces. then adhere them with rubber cement or something, get the cracks/seams tight, and spray paint it.

this isn’t gonna be a daily driver, so aesthetics over “impactability” is a trade i’m willing to make.

i was wondering if that foam insulation board, cut into strips and glued together, might be the best way to start the basis of it? what is going to cut easiest?

Assuming that you can produce a template of the planned bumper, the traditional way would be to carve it out of an appropriate wood or a dense structural foam and if you make a minor error on the ridges or elsewhere you can use the kneadable epoxy to fill. When you’ve got the shape right, then apply an epoxy sealer to seal and add some strength.

Google “wood boat building” and “fiberglass boat building” for some tips

It won’t be automotive grade strong, waterproof or warp proof but then you don’t have automotive builder facilities or budget.