Machine Design

Arrows fly true with acetal cable guide

To improve accuracy, bow designers at New Archery Products devised a mechanism that drops the arrowrest from the flight path of the arrow's fletching (feathers).

PTFE and silicone-lubricated acetal help ensure high-tension cables that position the Quicktune drop-away arrowrests don't abrade as the bowstring is drawn and released.

To improve accuracy, bow designers at New Archery Products, Forest Park, Ill. ( www.newarchery.com), devised a mechanism that drops the arrowrest from the flight path of the arrow's fletching (feathers). This eliminates contact between the fletching and the bow that would knock the arrow off course.

Key to the design is a polytetrafluoroethylene (PTFE) and silicone-lubricated acetal that makes up the CarbonGlide cable guide. When drawn, two bowstring cables pass through the guide in opposite directions; a third cable activates the arrowrest. Upon release, the cables travel back through the guide to their stops, moving 3 in. in 8 msec. The third cable deactivates and moves the arrowrest safely out of the fletching's path.

To ensure the guides don't abrade the high-tension cables, the company selected an RTP 800 Series PTFE and silicone-lubricated acetal from RTP Co., Winona, Minn. (www.rtpcompany.com). According to New Archery Products spokesman Bob Mizek, the RTP compound is three times stronger than PTFE-loaded nylon 6/6 the company initially tried. "Early field trials showed high humidity combined with nylon 6/6's hygroscopic nature noticeably reduced its wear properties," says Mizek. "In contrast, the RTP acetal has seen thousands of cycles in all kinds of weather without sacrificing its low friction."

-- Jean M. Hoffman

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