Take a Load Off! Lightweighting for Engineers

I was fortunate enough to own a Lotus Elise for a number of years. I loved that car but had to give it up when I moved to the U.S. One of the reasons I liked it so much was the design philosophy it followed: “performance through lightweight.” The reduced mass of the car meant the relatively small engine could shove it along at a fair old rate, which is pretty obvious. But it also meant that the suspension didn’t have to be as beefy, and the amount of work the brakes had to do was also significantly reduced. Lightweighting has big benefits.

It’s a very virtuous cycle. Removing weight has a compound impact on pretty much all aspects of the car. Probably one of the least mentioned benefits (considering that this was a sports car) was the fuel economy. When I was driving at a steady speed on the motorway I could easily get better economy than a family sized diesel car.

lotus-elise lightweighting performance
Colin Chapman, the founder and brains behind the original Lotus racing team was known for saying that if something didn’t break, it weighed too much. This clearly isn’t a design philosophy that engineers would want to follow today.

While not every company is looking to build sports cars, weight reduction does have its advantages. Some are pretty obvious: less material equals less cost. Less material has other initial cost benefits also. Shipping and handling costs are reduced so sending goods to customers becomes easier.

We’ve been talking quite a bit about energy efficiency recently and lightweighting certainly has a part to play here. To move anything requires energy; in fact, to stop something or turn something requires energy too. The more mass something has, the more energy it requires.

As an extreme example, companies pay around $10,000 for every pound of weight sent in space. Although I don’t expect many of the readers of this blog to be massively concerned about how much it costs to put something into space, I have had the pleasure of working with some of those who do. A more down to earth example is that UPS will take your package from France to Tokyo for roughly 35 euros per kg. Pretty much any shipping price has some weight factor as part of it.

It’s clear that making lighter, better thought out products has many advantages, and in the quest for energy efficiency it’s an area that can’t be ignored. The reduction in material costs, shipping fees and knock-on effects are the cherry on the cake!
In order to build products with less mass it’s often useful to question the material composition of the products. Moving from the tried and tested metallic parts machined from bars or plates can be uncomfortable. The unknown factor often means that engineers will try using thinner plates or cut-outs to reduce weight. Swapping out materials entirely, or moving to a different manufacturing process — like composites layup — may seem too big a step.

ansys webinarsComposite materials are used extensively in aerospace to help with lightweighting. They have excellent strength-to-weight ratios, but they do pose design challenges. We’ll be talking about some of them in our webinar Composite Lightweighting with Confidence on November 11th at 1 pm ET.

The properties of each composite part depend heavily on the orientation and quantity of the layers of material used. Software can be used to help understand where, and how many, layers should be placed to get the desired performance.
There are additional challenges too when it comes to curing the part. The process of “baking” can result in spring-back and deviations from specified dimensions.
curing-processThis does sound like a lot of effort and work to get a lighter part. But, as I already discussed, the potential benefits of lightweighting are massive. As energy costs continue to rise I’m sure we’ll see lighter and lighter parts, and even sports cars, in the future.