Friday, May 23, 2008

Engineering Essentials - Segment One

Some time ago I alluded to an upcoming series of posts regarding all things engineering. This will be the first post in that series and sure, it would make sense to start with a "first" in engineering such as Newton's First Law, but since our vision at LM is to educate our community about as many of the details of vehicle engineering small and large and the vehicle as a whole, I thought I'd start with explaining a simple little part on every car that is hugely critical. One of the things that always bugged me about my engineering education was that so much time was spent on how formulas such as Newton's First Law (and countless others) were derived, and less on the application and its actual impact. I constantly found myself thinking, "Yes, give me an understanding of the principle behind the theory, but spend more time on showing me how it applies, or more importantly in some cases how it doesn't apply to certain situations." This is the type of education I envision providing our community - applications focus. In the radio biz, this would be summed up by the phrase, "Less talk, more rock!"

I'll start with a question...

Ever wonder what allows air into your tires and keeps it there?

It's a simple piece of equipment called a Schrader valve. It is also commonly used in the fuel rails of fuel injected engines, for the same reason as in the tires it's used for - to keep the fluid in the pressurized vessel that contains it.

Below is a simple illustration of how it works:


Schrader valves consists of a valve stem which has a core threaded into it. The valve is a type of valve called a poppet valve. There is also a spring inside the core which assists the valve in staying shut.

Now, to keep true to my belief, there is actually a decent level of detail that I could go into on what makes the valve work (like the theory behind spring coefficients etc), but the important thing to know is that the spring must keep the right amount of pressure on the valve to keep it closed, and for obvious reasons, shouldn't be too stiff so that you can open it with only a slight bit of pressure. It's also important to note that the cap although not generally thought to be all that critical is actually a very key component. It will keep dirt out of the tip and prevent such dirt from lodging in the core and possibly causing the valve to stay open, creating a leak. Also commonly overlooked is the importance on tire pressure. Tire pressure is so critical to the way your car brakes and accelerates, and hugely impacts how your car handles. The valve in your tires is a bit more forgiving, but imagine how critical keeping the cap on your fuel rail is in that case!

All of this is controlled by a very small, simple valve that most people don't know has an actual name...it's called the Schrader valve.

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