Snail Cam: Difference between revisions

Revision as of 17:27, 27 August 2016

Description

A Snail Cam (aka Drop Cam), so-called because of the snail-like appearance, has a slow rise and then a sudden drop. This is a one-event-per-turn cam with a slow build-up to the peak and a rapidly decreasing edge. These cams can rotate in one direction only, which in the case of the illustration shown, is counter-clockwise.

Features and Applications

Snail Cams are a particular type of Radial Cam and can be used to drive punches, hammers, automata, or drum sticks in mechanical fairground organs - or any circumstance when a sudden drop is required.

Animation

Examples from Nguyen Duc Thang's YouTube Channel 2100 Animated Mechanical Mechanisms

Disc Cam - the cam profile is an Archimedian spiral so the follower’s speed is constant. Gravity maintains permanent contact between follower and cam.

Disc Cam - the pink Input cam is driven by a motor and the orange weight maintains contact between the cam and red pin of the yellow follower. The blue cable should be wound more than one revolution on green pulleys to increase friction torques.

DT Online Buyers' Guide

Cam profiles (i.e. the shape of the outer edge of the cam against which the Follower engages) can be drawn as a Displacement Diagram using Drawing Instruments or CAD software.

Cams for models can be made simply by drilling an MDF or Ply Disc off-centre to make an Eccentric Cam or by mounting a disc at an angle to a dowel axle to make a Swashplate.

The use of Cams can most easily be explored using Contruction Kits such as those listed below.

Click top left to enlarge


Engino "STEM Mechanics" Cams and Cranks Set	Engino "STEM Mechanics" Levers and Linkages Set	Fischertechnik 536622 - Mechanic & Static 2	Engino Mechanisms Set	Engino Gears Set

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 | [https://youtu.be/F3scqTa1CDw '''Disc Cam'''] - the cam profile is an '''[[Spiral|Archimedian spiral]]''' so the follower’s speed is constant. Gravity maintains permanent contact between follower and cam.
 | {{#ev:youtube|F3scqTa1CDw|200x200|right||frame|loop=1&autoplay=1&playlist=F3scqTa1CDw}}
+| [https://youtu.be/fe8pu1bo8mA '''Disc Cam'''] - the pink Input cam is driven by a motor and the orange weight maintains contact between the cam and red pin of the yellow follower. The blue cable should be wound more than one revolution on green pulleys to increase friction torques.
+| {{#ev:youtube|fe8pu1bo8mA|200x200|right||frame|loop=1&autoplay=1&playlist=fe8pu1bo8mA}}
 |}