Monday, June 02, 2008

Respect the System

One of the most important things to think about in engineering is how the different components you design will interact in the system for which they are designed. Here's an example: your car is the system and lets say the engine, transmission, and axles are all components of the system. Any component alone won't even get you to 7-11, and you usually have to have them all to get anywhere. Not only do you have to design the components to perform well individually, but you have to design them to play nice with the other components.

Today's blog is about how I didn't respect the system.

In this case the system is my 1/10th scale RC racer, and the components are the motor system, transmission, and differential. As indicated in my last blog, I have recently taken the step up to a brushless motor system. The power is fantastic, but there is one little problem--the power can't quite get to the road. I installed this new motor without any regard to the condition of the rest of the drivetrain and it was too powerfull for the differntial in the car. Actually, I shouldn't say that it's too powerful, but that the differential was not in good enough repair to accept the torque. A little running in the yard, and a couple dozen laps on the track spelled the demise.

The problem is there wasn't enough tension in the diff to keep it from slipping. Slipping is bad. In order to correct the slipping I tried to tighten the screw and after only about 30 degrees of turn I heard a snap. Snaps are usually also bad. The snap turned out to be the first three threads of the diff nut stipping out. This equals toasted diff. So now, the car is sadly stationary until the parts come in. This works out well because this Wednesday I won't be able to make it to the races, so it's the perfect week for techinical difficulties. Fortunately, this service isn't that expensive. All the parts came to only $17. We'll be up and going in no time.


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