Servo - September 2007

valuable. I know a guy that collects vacuum tubes and builds custom vacuum tube amplifiers for people’s radios and musical instruments. He swears that the sound from vacuum tube amps is better than what you can get from modern digital equipment.

Q. Where is a good place to buy cheap electric gear motors?

— Mike Coleman

A. There are a lot of good places to buy cheap electric gear motors, like surplus houses and eBay. I generally don’t want to recommend these places since inventory changes without notice (i.e., the next time you want the same motor, you may never find it again), and quality is unknown until you have it. I’m not saying these are bad places to get parts (since many of the readers of SERVO Magazine buy from these resources and appear to be very happy with them). I prefer to recom-

mend places where you know you will always be able to get the same parts.

With that said, Lynxmotion ( www.lynxmotion.com), Jameco Electronics ( www.jameco.com), Solarbotics ( www.solarbotics.com), and the Robot Store ( www.robot store.com) are very good places to get low cost motors. If you want some really powerful motors, check out NPC Robotics ( www.npcrobotics.com).

Q. I am curious to hear your opinion on timing belt drives vs. sprockets and chains for a middleweight combat robot. Right now, I am in the information-gathering phase so I can build a winning robot.

— Lynn Hickman

A. Timing belts (or otherwise known as synchronous belts) and sprockets and chains will work just fine for your robot. Performance wise, you really are not going to notice a difference between the two systems,

unless you under-size them. Timing belt systems are lighter and quieter than sprockets and chains, are not as readily available as sprockets and chains and are usually a little more expensive. Finally, they usually require a little more precision in the overall robotdrive train construction. If you use a belt tensioning pulley, then the precision requirements are removed. Chain and sprocket systems can tolerate a looser fit and still function fully without slipping.

Choosing one drive system over another drive system is really more of a preference than anything else. Though in your area of design, where weight is paramount, the lightness of timing belts may be well warranted.

Sprockets and chains and timing belts and pulley components can be obtained at Stock Drive Products ( www.sdp-si.com). They have documents on their website that explain how to properly size your components and how to calculate the center-to-center distances between the different drive shafts. SV

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