This document provides instructions for building a wooden-wheel clock. It describes constructing the frame from quarter-sawed hardwood and includes diagrams of the frame assembly. It also details making the wheels, shafts, gear teeth and escapement mechanism. Fine adjustments are needed to properly match the gears and calibrate the escapement for accurate timekeeping. When completed, the clock will run for 24 hours on a single winding and provide a view of its 15th century mechanical workings.

1. ,,*sr
Builda wooden-
wheelclock
ffi ONrv roun wooden wheels, a rocker arm
(foliot escapement)instead of a pendulum, and
full visibility of its operation, make this 15th-
century clock a fascinatingconversationpiece. It
will run for about 24 hrs. on aD ll.ft. rveight
cord beforeshifting the weighu, andis adjustable
for timing. In making it, usequarter+awed hard-
wood, well seasone{,Black cherry is especially
recommended.Quarter-sawed wood swells and
shrinksleastin width.
Frame: Start with the frame, top left ptge 673,
Fig. 1. To get correspondingholesof both plates
in alignment, clamp the plates together and drill
both at the sametime. Use sharp drills asd feed
them slowly so that the grain won't divert their
true course. The brass bushings are short to
minimizefriction andarea pressfit. Removethe
burrinsidebothends.
Two dowelsproject from the back plate to
holdtheweightcord.Oneonthefrontplateholds
thehourwheelandhand.A brassbearingbracket
clearsthe rocker-armshaftandsuppofisthe es-
capementwheel. The lower end of the shaft
etrgagesa brass-screweyebearing.The frame
crosspiecesare detailedin Fig, 2 at'the upper
right of page673.This drawingalsoshowsthe
w.heelassembly.Gluethecrosspiecesto theback
plateonlyandatperfectrightanglesto it.
IVheeIsandshafts:In makingthe threewheel
shafts,Fip. 3, 7 and8,first drill thebearing-pin
holesat the endsof the blocksin perfectaligrr-
mentbeforeyou do thetunring.Slightmisalign-
mentcan causebindingof pins in bearingand
wobblingof shaftsandwheels.The drive-wheel
shaft,Fig. 3, hasa bearingpin at oneendonly.
Theotherendrotatesin aholein thefront plate.
You drill four pilot holesin this endfor brads
thatserveasapinlontoturnthehourhand.
All the wheelsand the ratchet pulley have

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673

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CENTERtrHEEL
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ffe"tou
STEEVEGLUED
TO WfIEEL
Yz-in. center holes drilled before turning, and
theseare usedto mount the work on a threaded
arbor. One side of eachwheelthat can be seen
in the assembledclock is turned to a pleasing
contour. The shafts are turned so the wheels fit
them snugly. The hole in the rachet pawl is
pivoted on the side of the drive wheel and is
kept in firm contact wlth the rachet by a music-
wire springsecuredby staples,Figs. 4 and 5.
Cutting the teethl The gear teeth can be cut
in different ways.One metbodconsistsof laying
off the teeth according to dimensionsin Figs. 5
and 6, using a sharply pointed hardJead pencil,
or by tracing them from thesedrawings.Remove
the wastewith a fine+oothbandsawasshownin
the photo, a jigsaw,or evena hand fretsaw,and
674
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dressdown to the marked lines with a small flat
file or manicure sandingstick. Another method
involves the useof a router that slideson a track
above the lathe, and an indexing plate on the
lathe spirdle having the required number of in-
dexingholes.
ltfate;hingwheelsto pinions: Check eachshaft
separatelyfor easyrotation in the frame sothere
is no traceof binding in the bearings.Match the
drive wheel to the 7-tooth pinion on &e c€nter-
wheel shaft before gluing on the center wheel.
The fit betweenwheelandpinion may turn out.to
be so close that the wheel cannot turn freely.
Free the teeth by very delicate dressing,but first
blacken with ink the tip of one pinion tooth and
the tips of two wheel teeth that straddle it when
meshing.This assuressubsequentreassembling
?/a"
SIDT FACING
FRONTlURNEO
ro coNTouRAs
IN FIG.9
r1
ya"
3/t"
TAPERED-HOLE,?4;TO y2"

4. *$1"
,r,."r Xt" x2t/t" ROD INTO
a,
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W KERF
THREAD
GROUND& SHAFTBEARING
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RODINTO
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,: DOWEL
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TO TOP& BOTTOMPINS
of pinion andwheelin thesamerelationship.
To match wheel and pinion teeth, hold the
frame in a padded vise and gently apply a little
pressureon the wheelin the samedirection that
it will rotatein the clock,at the sametime putting
a slight drag on the pinion to simulate aqfiral
working tension.Carefully determinejust where
binding occurs,both when a pinion tooth starts
to engagethe wheelteeth and when it disengages
from them. A small piece of carbon paper fed
betweenthe meshingteethwill locatethe points
of excessiverubbing.
Dress only the slopes of the wheel teeth but
not the tips as this reducesthe wheel diameter.
Too much dressingruins a wheelbecauseit pro-
ducesexcessiveclearanceandallowspinion teeth
to strike the tips of wheelteeth.Removeall high
SCREW
EYE
s-HooK
Irl4 wtRE
DIAI,
CENTERPART
OPEN
%,' DOWEL TAPEREDBRASSPINS
THROUGHFRONTPTATE ENGAGENOTCHESIN DIAI.
spots from the wheel teeth that tend to slow
rotation of the wheel when it is barely touched
with your finger and the pinion is kept under a
slight drag. The tips of pinion teeth should be
semicircularin cross section and must not be
dresseddown on the top. If the tips of the wheel
teethbind on the bottom of pinion gullets,deepen
the gulletsa trifle. After matchingthe drive wheel
to the pinion on th€ center-wheelshaft, glue the
center wheel to its shaft aod proceed to match
it to the pinion on the escapement-wheelshaft.
This is done while the drive wheel is removed.
Escapementmechanismand tinain$ Drill pilot
holesfor the equidistantbrads of the escapement
wheel, Fig. 8, using $ue on fhe brads for extra
holding power. Uniform height is obtained by
grinding. Fig. 11 shows the rocker-arm foliot
HANAMERED
TO WIDEN
ROCKERARM
1A"x 6" V1 o
TIGHT
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(APPROX.t
ABOUT,f6"
ENDVIEWOF
SHAFT& SHEET.
METALRETENTS
Pultfft&H00rs
67s

5. .i,1
.a
Wastebstwegnlhe te€th ls tlrst
removedwith a bandor a jig-
8aw then th€ tEethshouldb6
filed with a small,tlat filo. Bo
careful not to take matorial
otf the tips ot lhe te€th
tII
fu
tl
ft
m
t
t i l
shiftedto adjusttiming. If this is not enough,the
rocker-arm weights are made lighter for faster
movementand slowerfor slower movement.Fig.
12 detailsthe weightpulleysandcord. The latter
goesthrough theanchorpostandis knotted above
each.If the cord slips on the ratchet pulley, ap-
ply somerosin. The pulleys must not bind in the
sheaves,which may be enough to stop clock
movement.The 3-oz. weigbt keepsthe cord taut.
Ilour wheeland diah The hour wheelis identi-
cal to the center wheel but is $ued to a sleeve,
Fig. 9,'which fits the dowel on thc front plate.
Fig. 10 showsthe hand which is easyto loosen
and tighten for changingits position. A tapered
brasspin slipsthroughthe dowel.The dial, also
shownin Fig. 12, surroundsthe hour wheeland
is held by tapered brasspins which also hold
the front plate on the crosspieces.Numeralson
thedial canbedonewith India ink.
The clock pictured here is a replica of one of
the first handmade,weight-operatedclocks.Mak-
ing a copy of it will increaseyour admiration of
bygone craftsmen. The closeup view minus the
dial, hour wheel and hand, shows the relation-
ship of the three time-keeping.wheelsand the
escapementmechanism.
tf
and associatedparts. Sheet-metalretents on the
shaft alternatelystop the escapementwheelmo-
mentarily. Just beforean obstructedpin.is freed
from one retent the opposite one swings in to
obstruct the pin moving toward it. Bend the
retentsseparatelyto proper shapeon a nail of
the samediameterasthe shaft,then slip themon
theshaftandsolderin place.
After pressing the rocker arrn on the shaft,
you can "snake" the latter into position down
through the hole in the upper crosspiece.When
the shaftis setin its bearingsand hangsfrom the
top pin by thread, the retentsshould swing about
halfway over the pins when engagingthem. Ad-
just for this dictanceby moving the bearings.
Avoid contactof thesha{tagainstthebearingpin
of the escapementwheel.
The escapementmechanismwill require deli
cateadjusting,mostlyby bendingthe retentsin or
out. If spreadapart too far, they won,t stopwheel
rotation. If a retent lands and stopson the tip of
a pin, the spread must be decreasedslightly.
When thp retents are too close, tlre pins caunot
passeitherof them.
Two %-oz. weights on the rocker arm can be
676