Chap. XXIX. ON THE CONSTRUCTION OF MACHINERY.
1563
The cams are set out at the required distances on theturning wheel or cylinder, and are repeated as often asmotion is considered necessary; the three stampers shownare raised alternately, by attending to the several positionsin which the cams are placed.
M. Camus, to whose valuable treatise on the Teeth ofWheels we have so frequently referred, considered the bestform that could be given was that which placed themalways in such positions that they equally favoured theaction of each other; the smaller wheels of a machine aresometimes made out of a single piece of hard wood, withthe teeth cut out of the solid.
A crown wheel andpinion, construc-ted of timber, mustbe so framed, thatevery portion of itsrim or periphery isstrongly held andbraced together :this cannot be moreeffectually donethan by crossingtwo timbers at rightangles; through theopening in the mid-dle, the shaft maybe secured to theframe, and whenit revolves motionis conveyed to themachinery in aneasy and steadymanner.
Additional strengthmay be given to thearms on the underside of the large, andupper side of thesmallwheels; the cogsare formed of horn-beam, mortised andtenoned into the pe-riphery of bothwheels, the propor-
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Fig. 2919.
tion of which has already been described.
To “secure the wheel on the shaft which turns is easily effected bywedging: all these operations require attention to the strength of theseveral materials employed : they should be well seasoned, and not likelyto shrink from their original dimensions.
Where a spur-wheel is to work in a crown-wheel below, its spindle may pass into thesame timber that the gudgeon of the uprightshaft works in, if it be securely framed andbraced to resist any lateral movement. The' rims of these wheels may be further strength-ened by inner circles made fast to the outer,and the upright shaft leftsquare where it passesthrough the frame of thewheel.
Wheels which engageeach other should be bracedin proportion to the stressand action they are sub-jected to: where the dia-
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flip
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Fig. 2920.