If you’re shopping for a scooter, you’ve probably noticed the term “pressed steel monocoque” in the specification sheet for modern Vespas. The picture above is of a Vespa LX’s monocoque, which is also referred to as a unibody or unit body.
Now that the Ford Crown Victoria and Lincoln Town Car have motored off into the sunset, all passenger cars built and sold in the U.S. are of unibody construction. The individual pieces are stamped out of sheet steel and welded together by robots, which can assemble such parts far more consistently and accurately than any human can. Vespa has a great video that shows exactly how this happens.
This method of construction goes all the way back to the original Vespas from 1946. Why? Well, before Piaggio made scooters, the company made airplanes. Airplanes constructed of metal stampings (usually aluminum, it being lighter than steel) welded or riveted together. The Vespa 98 was made of pressed steel stampings because that’s what Piaggio knew how to do. Of course, a lot of the Vespa 98’s components were leftover airplane parts because, well, they were left over.
The advantages of monocoque construction include solidity and heft, which translates to a smooth, stable ride, among other things. The minuses include higher cost and greater weight, and in the case of the Vespas, a need to have body damage repaired by a body shop or others with the equipment to straighten and return damaged body panels to their original shape, which is rather expensive.
It is the considerably lower cost of a tubular frame as shown in the picture on the right that makes such construction the preferred method for inexpensive scooters.
Lambrettas employed a tubular frame because Innocenti was a manufacturer of seamless steel tubing before taking up scooter production in the aftermath of World War II. Like Piaggio, the company went with what it knew.
The advantage of a tubular frame aside from lower cost is the ability to attach body panels of pretty much any shape. Or none at all; back in the day, you could get a naked Lambretta, just like you can now get a naked Honda Metropolitan, aka Ruckus.
These days, such body panels are made of some kind of plastic. Making a mold for a plastic part is whole lot easier than making a die for a 10-ton press; an injection-molding machine, which is how most plastics are formed, takes up considerably less space than that 10-ton press. In addition, plastics can be molded in color, which means you don’t have to paint the body parts. A paint booth takes up a lot of space, too.
More importantly, plastic body parts are far more resistant to damage than metal ones. And should a plastic body part get damaged, it can be easily replaced, usually by undoing screws or bolts, at far less cost than an equivalent metal part.
At the risk of having a fatwa declared on me, I will point out yet again that had plastics as we know them today existed in the mid-1940s, Vespas and Lambrettas would most definitely have had some plastic body panels. Europeans were poor back then, and anything that aided in lowering the price of the finished products was very important… the original Vespa plan called for a 4-stroke engine, a drive belt and other features that would have made the Vespa 98 too expensive for its intended market. It sold for the equivalent of $40 U.S., though lots of buyers still needed an E-Z payment plan. In 1946 Italians were poor.
While it’s curious that what some people refer to as “plastic scooters” employ body panels made of materials that are likely to last thousands of years, a scooter’s longevity has nothing to do with what the body panels are made of. It’s the frame/monocoque and the engine that will most determine how much useful life your scooter will give you. Which is why I always say, get a scooter made by a quality manufacturer, at a well-established, reputable dealer. You get what you pay for, for sure.