Theatre Design & Technology - Summer 1993 - 41

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TECHNICAL
PRODUCTION

A
Shop-Built
Cable
Cylinder
GREGORY BELL

cable cylinder is a fluid
power device rhar convens
energy from a pressurized
fluid (compressed air,
pressurized hydraulic
fluid, pressurized warer,
erc.) inro back-and-fonh
morion. This reciprocaring morion can
perform many useful rasks on srage, such
as moving scenery wagons on and off
srage, remorely operaring a snow cradle,
pulling rracked panels or currains inro
playing posirion, opening and closing
elevaror doors, or sliding windows.
A major obsracle ro using cable cylinders in rhe rhearre is rheir high cose A
commercial cable cylinder wirh a 1-1/2inch bore and a four-foor
srroke cosrs more
rhan $300. Larger
bore cylinders wirh
longer srrokes cosr
much more. To grearly
reduce rhe cosr, a cable
cylinder can be builr in a
reasonably equipped rhearrical scene shop using
pam readily available from
mosr larger plumbing supply srores and hydraulic
repair srores. The parrs for
rhis cable cylinder, lisred on rhe nexr
page, cosr abour 550 plus abour 52 per
foor of srroke.
The load ro be moved by rhis shopbuilr cable cylinder is arrached ro rhe
flexible, vinyl-coared sreel cable above rhe
cylinder body. The load can be arrached
wirh a bolr rhrough a cable-rensioning
rurnbuckle. (See Figure I.) The cable
passes around sheaves ar each end of rhe
cylinder, enrers rhe cylinder body
rhrough cable seals (rhe reason for rhe
vinyl-coared cable), and is secured ro rhe
inside of rhe pisron wirh a nicopress srop
sleeve. (See Figure 2.) The pisron is
sealed ar borh ends againsr rhe inside wall
of rhe cylinder. Applying pressurized
fluid ro one side of rhe pisron pushes ir
roward rhe opposire end of rhe cylinder.
The pisron acrually pulls rhe cable wirh
ir, causing rhe load ro move in rhe direcrion opposire rhe pisron.

The pans for rhis cable cylinder are
joined roger her wirh PVC soh'enr
cemenr, held in posirion wirh nicopress
sleeves, or in mosr cases, simplY rhreaded
onro a maring parr. Always use Teflon
rhread seal rape when joining rhreaded
pans.
The holes drilled in rhe rhreaded end
caps (see Figure 3) and in rhe pisron cup
seals (see Figure 2) musr be exactl)'
enrered. Also, be very accurare in moun~-
ing rhe cable sheaves ro rhe axle suppon
blocks. (See Figure 4.) Any misalignmenr
berween rhe barrom of rhe cable sheave
and rhe poinr where rhe cable exirs rhe
cylinder could damage rhe
cable coaring or could cause
excessive wear on rhe inrernal cable seals.

Parts List for a
Shop-built Cable
Cylinder
Cylinder
2" Schedule (sch) SO
PVC pipe-minimum 2' long; maximum 20' long
2 @ 2" sch 40 PVC male adaprers
2 @ 2" sch SO PVC rhreaded (rhd) end
caps
2 @ male-rhd inler porr firrings-chose
fining comparible wirh rype of hosing or
rubing chosen ro supply pressurized fluid
ro rhis cylinder.
Pisron
1 @ I" sch SO PVC rhd coupling
2 @ l"x 3/4" sch SO PVC rhd bushings
2 @ 1-7/S" dia. x 112" high x liS" rhick
Buna I pisron cup seals
2 @ 3/4" x 112" sch SO PVC rhd
bushings
2 @ 1/2" long pieces of 114" o.d. copper
rubing
2 @ brass adaprer compression firrings114" o.d. rubing x 112" ~1[P (male pipe
rhreads)
2 @ 1IS" nicopress srop sleeves
Cable Seals
2 @ 3/4" x 3/S" sch SO PVC rhd bushTD&T

1993 SUMMER

39
Table of Contents for the Digital Edition of Theatre Design & Technology - Summer 1993
