RV Chassis Design – Look Maw, It's A UFO!

Chassis design is one of those things that draws a lot of opinions, some educated and others… well you get the idea. Chassis design under a motorhome, for the most part, depends what is available from a vehicle maker like Ford or Chevy, and it shares its engineering for a variety of purposes.

The class C is a van that was produced by the factory as a cut off, meaning that the back of the van was left off at the factory. The super C is a cut off heavy-duty pick up truck or light duty box truck. Class A’s were basically school bus chassis. And there was very little done to make a motorhome different from a UPS truck.

But that is changing, as we see some makers supplying chassis that are different such as the UFO Workhorse. And there is more to a UFO than just the option of a rear engine with either a gasoline engine or a diesel engine. Lets look at the suspension to begin with. It has coil springs on the rear suspension. So what you ask?

Well in a conventional suspension that uses leaf springs, the springs locate the rear driving axle in the chassis fore and aft as well as side to side. It also carries the power of propelling the rig. The problem is that the springs are springs and will allow the axle to move side to side adding rear steer to the rig in a cross wind, cornering maneuver, or other things that will cause rear tail wag. A rear Panhard rod or better known as track bar will help solve this problem. The coil sprung and air bag suspension have this device built in and as a result handle better. The front suspension on the UFO chassis runs a solid axle and a single leaf spring.

There has been some chat in the forums recently that gas engines are difficult to cool when mounted in the rear. The truth of the matter is that a diesel gives off more heat than a gas engine because diesel fuel has more BTU’s per gallon than gasoline. The one thing that a rear mounted engine has to overcome is the heat given off by the engine block. In a front engine rig the engineers get rid of about a third of the heat of combustion through the liquid cooled radiator, a third through the oil pan and block, and a third through the exhaust system. Moving the engine to the rear changes the air flow pattern and means a higher power fan and as we see on rear engine rigs a bigger radiator is added to get rid of the heat. This is the same for gas and diesel alike.

Well that is about all for this week but stay tuned for next weeks ramblin’s.