Unibody Versus Frame Construction

Monster TruckMy business is auto body repair Salt Lake City. Last week a customer brought in a car that was making an odd noise when he drove it. I put the car up on the lift and saw that the lower rail on his unibody constructed vehicle was cracked at the lower control arm and the crossmember mount. Of course I knew that in order to repair the vehicle I had to replace the lower unibody rail. I understand that to a non-Greek speaking person who is unfamiliar with a mechanic’s jargon this probably sounds like Greek to them. I will attempt to clarify what I mean.

In 2016, a vehicle typically has one of two basic types of structure; frame and unibody. A frame structure is comprised of different pieces which connect at different locations. Upon this frame is mounted the suspension, axels and the engine. On top of all this is mounted the actual body of the car. By contrast, a unibody type structure does not employ a separate frame from the vehicle’s body. Unibody structures are typically constructed from aluminum or steel which is then stamped with cross members upon which the other components are mounted. Most vehicles these days are constructed using a unibody structure. The two main advantages of unibody construction is that it keeps the vehicle’s over all weight lower compared to frame structure and it also redirects the force of a crash away from the passengers inside the car.

As I said, my business is auto body Salt Lake City and I know cars. When you are my customer there is no need for you to know the difference between unibody and frame construction. That is my job. That is how I knew that to repair the vehicle I had to replace the lower unibody rail.

To Disc Grind or Tack Weld? That Apparently is the Question

Monster TruckWhen it comes to auto body repair I am not an expert. That is why if I need an auto body repair in Salt Lake City I do not try to fix the problem myself. I would not know the first thing to do and this is why I would take my car to a professional. At the same time I am interested in the field of auto mechanics. This is why I started looking at sample questions on a mechanic certification exam. I quickly found most of the jargon to be foreign to me. So I decided to take one of the questions and look up the terms I was not familiar with.

The question I selected happened to be, “A damaged steel door outer panel (skin) is being replaced. Technician A says that the damaged panel could be removed by grinding away the outer edge with a disc grinder. Technician B says that the new panel could be attached by tack welding. Who is right?” The answer (according to the author of the question) is that both technicians are correct.

A “disc grinder” also known as an “angle grinder” or a “side grinder,” I discovered is (not surprisingly) a hand held power tool that is commonly used for polishing and grinding. The tool employs an abrasive rotating disk to accomplish these tasks.

“Tack welding” (I discovered) is a temporary weld that is used to initially weld two pieces of metal together. The tack weld is commonly employed to hold the two pieces of metal in position so that the seam between them can be filled in to create a stronger bond.

I have to be honest and admit that looking up these two definitions has done little to edify me as to the finer points of this particular question and auto mechanics in general. I suppose the lesson here is that the field of auto mechanics is a field that really cannot be properly explored by five minutes of casual on line research but is probably best learned through practical, hands on experience. Fortunately, I can always take my car to an auto body shop in Salt Lake City and not rely on the definitions I looked up on line to guide me in making my own repairs.

Daddy, What are Cars Made Out Of?

Custom ChevyThe other day I was sitting in an auto body repair shop in Salt Lake City with my son when he asked me what cars are made of. Of course I had a vague idea of what materials are used to build a car I did not have a ready answer. I told him I would get back to him on that question. I then fished my phone out of my pocket and did some quick research.


It turns out that the material which accounts for most of the weight in modern cars is steel. This material is used to make the chassis, door beams, roofs and body. Steel is also used to make the engine and other parts in the car. Interestingly, the auto industry employs both rigid steel and steel designed to crumple so as to absorb the force of impact in an accident.


Another commonly used material in car manufacturing is plastic. Plastic is an extremely versatile material because it is durable, cheap and light weight. As such, it is used to make a wide variety of parts including the dashboard, dials, gauges, air conditioner vents, switches, door handles and airbags for example.


Light weight, yet durable aluminum is also used quite a bit in modern car manufacturing for various parts including wheel rims, engine and other car parts.


Rubber is another important material used primarily for tires but also wiper blades, engine mounts, hoses, seals, and engine belts. As with plastic, rubber is extremely durable, flexible and cheap.


The last major material employed in car manufacturing my quick research revealed is glass which is used to make windshields, mirrors, navigation screens camera  lenses and other parts.

As I related this information to my son I noticed his eyes began to glaze over and I suspected he regretted asking me the question that originally prompted this research. So I put my phone back in my pocket grateful I was able to kill some time waiting for our car in that auto body repair shop in Salt Lake City.