motor a vapor (vapeur - vertical steam engine)

7/27/2019 Motor a Vapor (Vapeur - Vertical Steam Engine)

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has played a historic role in steam-powerdevelopment. The engine is a double-actingnoncondensing one that exhausts directlyinto the air with the familiar puff pup of adonkey engine or steam shovel.With its l?: cylinder bore and 1 pistonstroke and with 75 or 80 Ib. of steam inits boiler the little engine will turn overat 1 500 r.p.m. Actual power will dependmuch on the boiler used and on t h e work-.manship in the engine itself. The design isfor heavy duty however with main bear-ings and other working parts larger thanscale and the engine will stand up wellunder hard continuous runs at full workingload developing enough power to drive aquite large model boat a small dynamoan air fan or other light equipment ofFractional-horsepower rating.Much exacting work is required inbuilding an engine of this type espe-

Although it is not a-: tale reproduction ofany particular engine it has the same gen-eral appearance and eye-taking appeal ofthe picturesque old-timers so hard at workabout the turn of the centuiy.The model is equipped with the link-motion reverse gear perfected by George

which also provides a variable steam cutoff shaper, he work clamp=d t he faceplate.POPULAR19 S C I E N C E


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L n p i g - +IM I N B E A R

S TS RE9

H O L E O R. s ,

T P 5-40 . L -i: 1 6 - , , ,

B A S E Car on S A l O A R esr


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cially since the reverse gear and crankshaft,to be described in a later installment, andother small parts must be machined fromsteel. However, it is enjoyable work for themodelmaker, and it is of a kind well withinthe scope of anyone who h s becomeproficient in the use of a screw-cutting lathe.If you are experienced in ~voodworking,you can build the necessary patterns andhave iron or bronze castings made at yourlocal foundry for the base, standard, cylin-der, cylinder head, steam chest, and fly-wheel. Or you can even make up the sandmolds and pour bronze castings yourself.The pattern work, however, is by no meansa one-evening project, and castings can besupplied for those who want to get rightat the machining. Dimensions shown in thedrawings are for the finished parts. If pat-terns are made, an allo\vance of 3/32 must.be added to surfaces to be machined.Shrinkage allowance need not be considered.h4achining operations are possibly bestbegun on the base since many of the partscan be fitted on it and temporarily assembledas the work proceeds. The casting is easilyhandled in shaper, but if your shop boastsonly a lathe, the facing can be done withthe work clamped to the faceplate and themilling can be done with the lathe millingattachment. Since the casting is open at thecenter, only the bottom and top need befaced and slots milled for the bearings,after which the pin holes are drilled andthe piece cleaned up with a file. Drilling andtapping the screw holes should wait untilthe mating parts are fitted, when both canbe drilled at the same time.Two identical main bearings are made upfrom X by X brass bar stock cut to lengthand soldered together in pairs. Mountedin the four-jaw chuck, each bearing is drilledand reamed to size for th e crankshaft andthe ends faced smooth. The halves are thenmelted apart and the parts filed to shapeand to a good snug fit in the base. Savedrilling them and the base for screws untilthe crankshaft can be set in place.The standard or main column is held inthe three-jaw chuck, and the solid body isbored smoothly and accurately to take thecrosshead. With the piece on a mandrel,the head is faced square with the bore andturned to diameter; then the work is reversedon the mandrel and the feet are trued. Screwholes are next drilled in the head to holdthe cylinder in place and in the feet formounting on the base. The tapped holes in

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Slots are machined across the top of the baseto take the main bearings, which will be m ade asnug fit. If a shoper is not available, the workcan b e done on a lath e with a milling attac hment.

Since the top pa rt of the standard or main columnis cast solid, it must be drilled and bored out t otak e the crosshead. The opera tion i s performed inth e la the with he work in the three-jaw chuck.

the base are spotted from those drilled inthe feet.In making the crosshead, a short pieceof cold-rolled sreel or bronze is held in thethree-jaw chuck and turned to a nice slidingfit in the main-column bore. Next, the upperend is recessed hnd turned to shape, and itis also drilled and tapped for the piston rodwhile still chucked so the outer diameterand the piston-rod hole will be concentric.Th e part is then cut off and the oppositeend faced smooth.Grooves are cut on both sides in theshaper or with the milling ~~ttachment,env-ing a 96 thick web to take the forked end ofthc connecting rod. The hole for the con-necting-roc1 pin is then cross-drilled in thelower end. TO BE CONTINUED.


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Here the base cast ing s clamped to the faceplateof the lathe and the to p is machined smooth andto height. A heavy cemented carbide tool is used.Any roug h spots are cleaned up with a f i le.

The column is then mounted on a mandr el heldbetween centers for facing the head square withthe bore and turning t o d iameter. It is next reversedon the mandrel and the feet fac ed smooth and true.

Stock for the crosshead s turned to a sl id ing fitin the mai n-column bore; then one end is recessedan d turned to shape. The piece is also dri l led an dtapped for the piston rod while chucked.

Halves for the main bearings are dr i l led and reamedwhile soldered toget her then s p l t apart and eachhalf f i led t o shape. He re the lower halves arein thei r slots th e uppe r ones beside the base.

Dri l l ing the head for screws to hold the cyl inderin place and the feet fo r four mountin g screwsapiece completes the standard. Tapp ed holes inthe base are spotted from those dril led in the feet.

Grooves milled in opposite sides of the crossheadtake the forked end of the connecti ng rod. Thisopera t ion may e don e in a shaper as shown hereor with a lathe mil l ing at tachment.

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achining ylilldery C W WOODSON

P R T T W O

UCH of the per- roughing cut to get the bit under the hardM formance of a surface scale and bring the hole nearly tosteam engine depends size. Then, with a freshly ground bit in-on the accuracy and serted in the boring bar, take light finishingsmoothness of the cyl-inder bore. This is as true for the miniaturereyersing engine here described see PSMApril 47, p. 190) as for full-size engines.The casting for the cylinder is firstmounted in the the three-jaw chuck and aroughing cut taken across the bottom so itcan be reversed and held squarely for facingthe top. If you have available an expandingmandrel, the cylinder is best bored after therough facing and then mounted on themandrel, where its ends can be faced smoothand squared accurately with the bore.Lacking such a mandrel, face the topsmooth first, and then reverse the piece andface the bottom smooth and square beforeattempting to bore. Although the cylinder

may be held in the three- or four-jaw chuckfor these operations, there is less likelihoodof slipping if it is clamped to the lathe face-plate with lugs over its flange.Bore the cylinder first with heavy

cuts while using very fine- power feed.If care is taken in sharpening the bit andsetting it to eliminate chatter, an almostmirrorlike finish can be obtained.The steam-port face can be machined inthe shaper or, as shown in one of the photo-graphs, while mounted on an angle plate inthe lathe. Again take a heavy roughing cutfirst to get under the scale, and then, withthe bit freshly ground and honed to a keenedge, finish with light cuts and a fine feed.Remove the work to the drill press, clampin the vise, lay out the steam and exhaustports carefully, and drill a series of holes foreach. Chip out the intervening metal andfile the resulting slot to shape. Then mountthe work in the angle vise and drill fourholes for each of the two angle ports to meetthose in the face. Chip and file out as be-fore. chisel made from 3/32 drill rod andhardened may be used for chipping. Thecylinder is next remounted in the vise and


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In boring -th e cylinder take a heavy roughingcut to get under the surface scale. Finish thebore with light cuts and a freshly ground bit.

2 If an expanding mandrel i s available bore thecylinder before finish-facing the flanges; if not

machine-the flanges first and then bore.

Drill and tp one hole in the flange and thenbolt the cylinder head on before spotting the

others. Use a clamp a t the opposite side.

the exhaust port drilled in from the side tomeet that in the face. Don't drill the 4-48holes until the covers have been made.Mount the cylinder-head casting in thethree-jaw chuck and turn the chucking lugstraight so the casting will run true whenreversed. Machine the top and outer edge toshape, and then score a light 1% ircle onthe faee for locating the bolt holes. Againreverse the piece in the chuck, take off t hechucking lug, face smooth, turn the step togood snap fit in the cylinder bore, anddrill a 7/16 hole ?& deep to clear the nuton top of t he piston.The bolt holes are then stepped off ac-curately with dividers, centerpunched, anddrilled clearance size. Snap the head inplace, spot one of th e holes in the flangewith a clearance-size drill, drill tapping size,and tap. Next, insert the bolt and spot theremaining holes. Make a file mark on meet-

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Face the steam chest on both sides taking aheavy roughing cut on each first and finishing

with light cuts to assure a steamtight joint.

ing edges so that the head can be replacedin the %me position; then finish drilling andtapping the flange.In machining the lower cover, it is im-portant that the step fitting in the cylinderbore be concentric with the piston-rod holeso there will be no binding ,at tha t point.Equally important it is to turn the step onthe outer face, or bottom, concentric forfitting the shouldered bore in the standard.

One way is to turn the gland stem andshoulder on the outer face first, bore andcounterbore the iN hole, and then mount thepiece on a stub arbor or in a step chuck toface and step the inner side for a snap fit inthe cylinder bore. In counterboring for th'egland, be sure to start carefully in the piston-rod hole to assure concentricity.Snap the lower cover on the column,clamp, and spot the bolt holes through thecolumn flange. Then snap the cover on the


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3 Machine the steam-port face wi th the cyl indermounted on an angle plate finishing with very

light cuts. A shaper will also d o the iob.4 Ports are bor ed a t an angle from both ends of

the cyl inder t o connect with the steam portsin the face. Chi p and f i le them t o shape.

Chucked gland end out the steam chest can bedr i l led and reamed fo r the valve stem and thehole then opened out t o take the gland.

cylinder and repeat as for the head. Putwitness marks on the .column, cover, andcylinder flange, making certain that thevalve face is at 90 deg. to the crankshaftcenterline of the base.

Face the steam-chest casting on bothsides, holding it in the four-jaw chuck, andbring it to proper thickness. heavy rough-ing cut followed y several light finishingcuts will assure a steamtight joint.

Some difficulty may be encountered indrilling for the valve stem, since the innersurfaces of t he steam-chest casting will havea slope. If you have a hand grinder, a smallflat can be ground inside the stem-guideend for a drilling surface f ter which thesteam chest can be chucked and the holedrilled all the way through from the glandend. Otherwise it may be best to lay out theholes as accurately as possible on the outersurfaces, drill each from the outside with

8 Corner holes are completed first in the steamchest and cyl inder steam-port face ; then theparts are bolted and the remaining holes dri l led.

an undersize drill, and then ream from thegland end. In this case, drill the gland endfirst, counterbore, and support it with thetailstock center when drilling from the stern-guide end. Finish y enlarging the upperhole with a No. : drill and tapping % -28.

Lay out the 14 bolt holes, drill the fourin the corners clearance size, and spot, drill,a n d tap the corner holes in the cylindersteam-port face. Bolt through the four holes,and drill the remaining 10 tappinq sizethrough the steam chest into the cylinder.Separate the parts, tap the cylinder holes,and open up those jn the steam chest.

Face the steam-chest cover in the lathe,mill the recess, clamp the steam chest to itin the drill press, and drill the bolt holes.Th e valve-rod and piston-rod glands,

valve-stem guide, and steam-pipe flangeare turned from bronze bar stock to dimen-sions on page 193. TO BE CC)NTINUED

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Alignment of the two ends of the shaft is assuredif t is made as one piece and cut when pinnedin place. The flywheel is turned from a casting.

l king thN ACCURATE, true-running crankshaftis necessary if the model steam engine

is to work freely and use steam with maxi-mum efficiency. This par t is assembledfrom a shaft, two webs, each with an inte-gral counterbalance, and a crankpin. All aremade up from solid steel stock, the webscut with a hacksaw and filed to shape fromtwo 5/16 disks and the shaft and pin cutfrom drill rod.Clamp the webs together and drill them atthe same time for a drive fit on the shaft andpin. Because the shaft is cut as one piece416 long and must be driven a considerabledistance, it may be necessary to ream the.% holes for it slightly. Press both webs onthe crankpin first. Next, with a block be-tween the webs to prevent bending the pin,drive the crankshaft through. Then drillan d pin all parts. Pieces of bicycle spokemake good pins.The assembled crankshaft is next mount-ed between centers in the lathe and withthe block still between the webs. Face theouter web sides smooth, form the 1/32collars, and turn the outer rim of the bal-ance weights and the ends of the webssmooth and to exact diameter. Finally cutout the part of the crankshaft between thewebs and file the inner faces smooth. Key-

Moun ted between centers the crankshaft is faced Holes for the bearing bol ts are dri l led throughsmooth on the webs and the col lar turned. A block th e bear ing caps while the crankshaft i s in placebetween the webs prevents distortion. t o assure al ignment of t he bear ing halves.19 POPUL R SCIENCE


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u ~ n i n g ear

ll dimensions for the crankshaft flywheel connecting rod piston.an d piston rod are shown in the dr awin g. The reverse-lever ring isalso shown and may well e made at this time.


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ways or setscrew flats are optional, depend-ing on the use the engine is meant for.Fit the finished crankshaft into the bear-

ings next, clamp on the bearing caps, androtate the shaft to make sure it turns freely.There should be no binding, since shaftalignment is insured when the webs arepinned before cutting out the center portion.With the shaft in place, drill and tap thebearing holes and bolt both caps down.The connecting rod is rough-turned toshape from X by R steel bar in the four-jaw chuck. I t is removed and heated to abright red, and the small end is twisted90 deg. This can be done with a heavywrench while the work is held in the vise.Then the piece is rechucked, its taperedsection turned to shape and polished bright,and the work cut off. Drill, saw, and file theforked end to shape, and drill for the con-necting-rod pin. Turn the pin to a force fitin the fork or thread it for a retaining nut.

Make up the connecting-rod brasses fromflat bar bronze stock and the connecting-rod keeper from steel. Cut to length anddrill for the screws that hold them to theconnecting rod. Drill and tap the end ofthe rod and with two 4 48 steel screws as-semble brasses and keeper on the rod. Thecrankpin hole is then drilled and reamedthrough the bearing brasses, and the endassembly is filed accurately to size.Centerdrill a 2% length of drill rod forthe piston rod, thread both ends, and screwit into a hole drilled and tapped in a roughpiston blank made from a ?6 steel disk.Mount the work between centers and faceboth sides of the piston so it will run deadtrue. Then turn it to a nice sliding fit inthe cylinder bore and cut the groove towidth and depth for the piston ring. Thisring, being a standard size, can be pur-chased, though one can be made up in thelathe from a short bar of cast iron if the

Steel bar stock i s rough-turned to shape for theconnecting rod, removed from the lathe, heated abright red, and the small end twisted 90 deg.

This i s the connecting-rod assembly. The brassesare drilled and reamed while screwed together togive a nice running f i t on the % crankpin.92 POPUL R SCIENCE

Back in the four-iaw chuck, the connecting rod isturned for the taper, which i s polished bright,and the piece i s then cut off to length.

The piston i s turned from - a blank that has beendril led, tap ped , and screwed to he piston rod.I t i s faced true, turned to size, and grooved.


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modelmaker is experienced in ring turning.Enough of the parts will now have beencompleted so that you can make a trialassembly and test the piston travel. Assem-ble the base, the column or stancl:~rcl, thebottom cylinder cover, the cylinder itself,the piston ancl piston rod, and the connect-ing rod. Leave off the top cylinder coverso the movement of the piston can bechecked. Likewise it will be unnecessary toput in the glands for the test.If the machining has been accuratelydone, the assembled engine should workfreely when the crankshatt is turned. Notecarefully the travel of the piston, whichshould be the same distance from the topand bottom of the cylinder, clearing at bothpoints by 1/32 . If it should hit at the bot-tom, the piston rod can be turned n littlefurther out of the crossheacl. Place the topcover on the cylinder nncl again move thepiston through its travel. Any bincling at

the top will indicate that the piston is strik-ing there, and a shor tening of the piston rodwill be necessary.

The reverse-lever ring is a section of acircle turned from a square piece of ?6 steelpli~te. It is first chucked in the four-jawchuck, where the center is bored to size.Rechuckecl in the three-jaw with the es-pancling jaws gripping inside the hole, itis brought to proper outside diameter.section o f the ring is nest cut out, and theholes are drilled for mounting the part onthe engine l~nse.

After so much work on bar stock, machin-ing the flywheel will be a pleasant relief.This is made from fine gray-iron casting.I t is rough-turned to size in the three-jawchuck, and the shaft hole is then tlrilledand reamed. The work is next mounted on:1 mandrel held between centers, and thehu b, edges, and inside of the rim are facedto run dead true. TO BE C ~ N T I N U E D

Shaping of the forked end i s begun with a drilled H e r e the conne cting rod is shown with its keeperhole and rough sawing and the fork s brought to brasses pin an d screws tog eth er with the cross-final dimensions by hand filing or milling. head which was described in Part I

It will hardly pa y to make your own piston ring Rough-turned to size from o casting drille d andwhich i s standard size readily available. It i s reamed the flywheel i s next mounted on a mandrelshown here with the comple ted piston and rod. an d its rim and hub ar e fac ed to run de ad true.

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Here s the finished i obas she ll look when youmakethe parts describedin this last installment

The slide valve i s located on the valve rod b y apair of locking nuts that provide travel adiust-ment. The nuts must be a tigh t fit on the thread.

Steam chest and valve assembly. The valve i s notclamped .snugly but floats between the nuts so th atsteam pressure can hold it against the p rt face.174 POPUL R SCIENCEI

uilding theT ONCE the most fascinating and themost difficult part of this engine tobuild, the reverse gear is derived from Ste-phenson's famous link motion. The valverod, which moves the slide valve over theports, is not connected directly to an eccen-tric at all, but to a small block that slidesin a slotted quadrant or link. Two eccen-trics, oppositely offset to give the correctadvance for both forward and reverse run-ning, are connected to the two ends of thislink. control lever connected through adrag link can shift the slotted quadrant andits connecting eccentric rods one way or theother, bringing the link block and conse-

quently the valve into line with either theforward or the backward eccentric, and sodetermining which way the engine will run.When the link block is midway in theslot, no motion is imparted to the valveeven if the crankshaft is turning, and theengine will soon stop. Either side of thisposition, though, the valve will operate withreduced travel. Steam will be cut off duringa greater part of the stroke, saving on fuel,a condition analogous to high gear in anautomobile transmission and precisely thatwhich obtains in a steam locomotive run-ning at high speed with a moderate load.Th e slide valve consists of two pieces ofbronze, the face a piece of % plate in whicha rectangle is cut by drilling and filing toform the steam cavity or recess. To this issilver-soldered a bronze block. The hole forthe valve rod is filed slightly oval with aneedle file so that the valve has some slightplay against the port face and may be heldon it firmly by steam pressure.Turn the valve rod from 5/16 squaresteel rod, shouldering the end to a sliding fitin the guide atop the steam chest and thread-ing the stem with some fine thread such as8-36 or 6-40. Drill the square end for the3/32 pin that will connect it to the linkblock, cut the slot, and file to shape.Eccentrics can be turned from short endsof stock. Chuck a piece 3/32 off center,turn the hub, and drill and ream the 9 shafthole. Then chuck the piece truly in thethree jaw to turn the 1 outside diameterand the 76 groove, and cut off. Make a sec-ond eccentric with no hub. [ u ~he page ]


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Precise w ork i n l a y i n g out m a c h i n i n g a n d h a n d f i f t in g wi l l be r e w r d i n g w i t these parts.J U L Y 947 75


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Face both smooth, slip them on a short pieceof %/ rod, and rivet together at exactly theangle shown in the drawings.

1 To make the eccentric straps, cut twopieces 1% long from 3/16 by Y cold-rolledsteel for each strap. Lay out, drill, and tapthe bolt holes for fastening the two halvestogether. Those in the lower half are drilledout to clear the 7/64 bolts. With the halvesbolted together, each blank is chucked andbored to a running fit on its eccentric. Theoutside is then roughly sawed and broughtto final shape by hand filing.Eccentric rods are turned from Ti squaresteel. They should be cut slightly long toallow for shortening in the bend. Lay outthe hole in the fork end after bending,measuring from the shoulder at the threadedend. Drill, slot, and file the fork to shape.With dividers, carefully lay out the reverselink on % steel plate. To make the slot,drill a series of undersized .holes, drill be-tween to overlap them, and finally file to theradiuses. Drill for the eccentric-rod pins andfinish ihe outside by filipg to shape. Notethat the link block has sides of the samecurvature as the link slot, in which it shouldbe a perfect sliding fit, without play.The reverse lever and its quadrant, draglink, and clamping nut offer no special diffi-culties. With the various short pins and thevalve-rod nuts, you are ready to assemblethe valve gear. One of the photos shows itin a trial assembly, less the reverse lever.Assemble the steam chest, valve, valverod and adjusting nuts, and gland as in thephoto on page 174. Be sure the valve ridesfreely on the rod so that its face may belifted a trifle above the bolting surface ofthe chest in the position shown-enough toallow for more than the thickness of a gasketbetween chest and port face. To allow fullcontact with the port face, the adjustmentnuts should be drawn up only to positionthe valve, not to clamp it. Either tap thenuts somewhat less than full thread depthfor a tight fit on the rod, or make two thinnuts out 6f each one to provide locking.With the cylinder and running gear as-sembled, mount the steam chest temporarilywithout the cover and connect the eccentricro s to the link. Set the two eccentrics onthe shaft so that the crankpin throw bisectsthe angle between the eccentrics. You canthen observe the valve travel by turningthe crankshaft.Steam ports should just begin to open asthe piston reaches top or bottom dead cen-

ter. The valve should uncover both ports toan equal degree, and at no point expose theexhaust port. These conditions will best beobserved at full forward and full reverse set-ting, with the link block at the two ends ofthe slot. At intermediate positions valvetravel will be shortened, and cutoff-theclosing of the port last admitting steam-willoccur earlier in the stroke. If setting thevalve nuts does not correct valve 'travel, it

Each eccentr ic is turned separate ly . Round stocks chucked 3/32 off. cente r and the shaft hole isdr i l led. I t is then center ed and the outside turned.

The eccentr ics, one without hub, ar e then r ivetedor p inned toge ther . A f te r each pa i r o f s trap ha lvess bo l ted toge ther , the ins ide d iameters a re bored .

One or both eccentr ic rods are of fset s l ight ly soas to br ing the center l ines of their forks direct -ly over the center l ine of the assembled eccentr ic .


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may be necessary to reset the eccentrics, oreven shorten or lengthen their rods.Assemble the engine, using oil freely on

all moving parts, with gaskets and graphitedgland packing. Run it in at low speed onsteam or air, or by outside power, until theparts have worn to a good fit nncl lost any,initial tightness. The steam line shoulcl havea lubricator to oil the cylinder.Beware the temptation to throw over the

reverse lever at high speed. While the en-gine should stop at mid-clu:~drnnt setting,you ll want a throttle valve for fuller control.It s well to add asbestos lagging and asheet-metal jacket to the cylincler to mini-mize condensation, and to start up slowlyuntil the cylinder is hot and any condensatehas escaped via the exhaust. Being ofcast iron, the engine will safely stand pres-sures up to 100 lb. EN

short piv ot stud connects the dr ag link to th e Chucked in the four-iaw a piece of '/4 square steelreverse link. Also above is the link block shaped i s turned down t o form the handle of th e reverseto ma tch th e slot which fits the valve-rod fork. lever. Holes must be loc ated as in the drawing.

Ho w the reverse gear will be assembled on the en- At i ts lower end the lever pivots on a stud tha tgine. The qua dr ant on the steam chest receives the screws in to the rin g which wil l it self be bolt edclamp screw that locks the reverse-lever setting. t o the bare. The clam p nut is f it t ed wi th a handle.

R V RSL V R

Sfee/DRILL 3 3yy

motor a vapor (vapeur - vertical steam engine)

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