diy plans - model steam marine engine

7/22/2019 DIY Plans - Model Steam Marine Engine

1/5

Model Marine EngineRequires No Castings

214 P O P U L A R S C I E N C E

EXHAUST PORTS No. 29 DRILL

No. 29DRILL

(STEAMPORT)

CYLINDER BLOCK

No. 31DRILL

CROSSHEAD-GUIDEBRACKET

R E A M

CYLINDER COVERS

TAP6- 32

R

No.29DRILL

(STEAMPORT)

CYLINDER SUPPORT

No.31 DRILL

VENT,No.50 DRILL

VALVE LINERCROSSHEAD

GUIDE

FLYWHEEL

T H R E A D18

5 - 40

THREAD

STEAM INLET.DRILL

REAM

MAIN BEARING

GLAND

5 - 40

THREAD

COLUMN10-32

THREAD

ENGINE ASSEMBLY

10 - 32TAP

4-46TAP

BASE STEAM MANIFOLD(INTAKE)

No.51DRILL


2/5

Building this power plant looks

tricky, but it is justa series

ofsimple operations. Follow

them in photos fromA to Z.

By C. W. Woodson

LTHOUGH the little two-cylinder steamengine above has been simplified for

easy construction, this does not show inperformance or looks. The model has twodouble-acting cylinders with inside-admis-sion piston valves. Boreis 1" andstroke.875".Steam is exhausted through ports drilled in

the cylinder walls, greatly simplifying thevalve gear.Reverse gear has been omitted for sim-

plicity, but the engine can be made to runin either direction by resetting the eccen-trics. Slip-eccentric reversing could beadded easily.

With 75 lb. of steam or air the enginewill kick over at about 1,100 r.p.m., provid-ing ample power for a 48" to 60" model boat.

All parts are machined from scrap-binpieces of brass, bronze, dural and steel.After the final assembly, pour a bit of water-diluted Noxon silver polish into the cylindersand valve liners and rotate the crankshaftby hand to lap the moving parts to a smoothfit. Then wash the polish out, oil all parts,and full steam ahead!

JANUARY 1953 215

Please turn the page for A-to-Z photos.

A

HEX

SCREWS

DRILLWASHER.

5 - 40TAP

CROSSHEADVALVESPINDLE EYE

CRANKSHAFTNo.31 DRILL

(UPPER)

PISTON

TAP 6 - 32

(LOWER)TA P1 8

CYLINDER COVERS6-31

THREAD

TAP5 - 4O

ECCENTRICS

REAM

PISTON ROD

TAP 5 -40

DRILL

V - GROOVES

DRILL

PISTON VALVES CONNECTING ROD

REAM

6-32

TAP


3/5

216 POPULAR SCIENCE

All set up. Prior to installing Crosshead-guide support, Cylinder block is solid chunk

crankshaft, main hearings are shown with columns, is cut of brass or bronze. Lay outalignedbyslippingthemon a from " brass plate. Three centersforcylindersandvalve-straight piece of .312 drill holes are drilled first, using the insert holes and bore out 1"-rod and clamping in position. base as a spacing jig, and then dia. cylinders in lathe. MakeHoles are thru drilled in base layout of shape is made, using final pass with a honed, round-for mounting screws. All hex- holes as reference points. Col- nose boring bit fed slowly forhead screws are turned from umns are " drill rod cut to maximum smoothness. Cylin-.125" steel hexagon rod and length, shouldered for " at der is lapped with Noxon silverthreaded 4-48. Corners of hex bottom, .375" at top and threaded polish after assembly, thenheads are rounded and polished. 10-32 at both ends. washed and oiled.

C r a n k p i n s and crankshaft Web ends are finished and Completed crankshaft is setends are made from .312 drill brought to dimension in the up between centers and testedrod. Turn both ends of the pins lathe. As each web is forced for accurate alignment. Crank-and the inner end of the shaft onto a shaft or crankpin sec- pins are set at 90, giving shaftsections .002" oversize for a tion, it is chucked and turned a smooth-running quality withforce fi t in the .188 reamed to an .687 radius from the four evenly spaced impulsesholes in the webs. As no tru- center of the far hole. It is not to each revolution. This allowsing cut is made on the crank- necessary to pin the force- it to run without a flywheel,pi n surfa ces, the dri ll rod fitted webs to the shaft, but although performance is im-should be held in a collet or driving pins in undersize holes proved if one is used. Chancesindicated true. is extra insurance. of stalling are also lessened.

Here are the 26 steps

in the construction

of the engine.

Base and main bearings. Crankshaft websare cut fromBrass base plate, " thick, is steel bar stock, .188 by .375.cut out for two crankcase wells. Shaft holes are drilled .437Large holes, tapped 10-32, are apart, using jig to assure uni-for supporting columns; small form spacing. After drilling,holes, tapped 4-48, are for the webs are cut off, stackedbearings. Main bearings are in a drill-press vise and reamedtwo pieces of " brass soldered to make absolutely certaintogether for machining, then holes are spaced right. Endsunsoldered to form upper and of webs are machined later inlower sections. the lathe.


4/5

Valve-insert holesare reamed". Intake and exhaust portsare drilled. Valve liners"brass tubingare drilled in onewall. Liners are then turned180 to line up holes withports and locked with set-screws in block end. Steam-inlet holes are drilled throughblock and one wall of liner

from front of block.

Cylinder covers are turnedfrom 1" brass rod. Inside faceof upper and lower covers areturned to a snap fit in cylinderbore, using cylinder as gauge.Then they are cut off, reversedin the chuck and finished.Piston-rod packing-gland holeshould be drilled and tappedin lower cover before cutting

off.

Packing glands (at right inphoto above), are turned from.625 brass rod and threaded tofit lower cylinder cover. Glandis drilled and reamed .156for piston rod and upper endof hole is counterbored forpacking. Four .063 holes inflange are for adjusting pinto tighten flange on graphite

packing.

Valve eccentricsare made intwo parts and joined by a sin-gle setscrew. The body or bear-ing was turned in the three-

jaw chuck; the cover platewith off-center collar, in four-

jaw chuck. The collar is drilledin the lathe, then used as a jigto locate the hole in the body.Straps are thick-wall tubing ofproper inside diameter.

Piston valves, turned frommild steel, should be perfect fitin valve liners. Oil grooves arecut with V-shaped cutter bit.Lower ends are slotted anddrilled for adjusting eyes,which are threaded onto ec-centric rod and held in properadjustment by lock nuts. Rodsare threaded into eccentricstraps.

Cylinder-block supportis cutfrom .188 brass plate. Holesfor supporting columns mustmatch those in base. Supportis chucked in lathe and boredto receive the .375 collars of thelower cylinder covers. Six No.38 holes for the screws thatjoin plate to underside of blockare then drilled according tothe layout.

Connecting rods, developed from lengths of

steel bar stock, are made in successive stages:(O) The steel bar is centered in the four-jawchuck, centerdrilled at the free end, and support-ed by the tailstock center while the middle sec-tion is rough-turned. (P) The big end is thenclamped in a vise, the rod heated almost whitehot and the small end bent at right angles to thebig end. (Q) When cool, it is set up in the latheagain and turned to finished size. (R) The littleend is then cut out and filed to shape and the big

end drilled for the two bearing-cap screws. The

bearing cap is cut off the big end, the meetingsurfaces smoothed, and then joined with the twocap screws.

The crankpin hole is then drilled and reamed.312. (S) The big end is clamped on amandrel and turned to shape, and the littleend is drilled for a .125 rivet that links it to thecrosshead. (T) The finished con rod looks likethis after machining.

Turn the page for the six final steps.


5/5

Crossheads are shaped from " brass and aslipper of .063" brass is soldered on foot. Anyerror in the crosshead-guide support can bemade up by a l t e r i ng thethicknessof the slipper

plate. The heads of two hex-head screws ride inslotted crosshead guide; setscrew and washerhold assembly together.

Trial setup. Smooth action of moving parts ischecked by setting up lower half of engine androtating crankshaft by hand. Crosshead-guidesupport should be placed in proper position on

columns to check crosshead travel in slot. Upperends of guides are later supported by bracket onupper assembly.

Pistonsare turned from brass or dural rod to aneasy fit in the cylinders. Parting tool is used tocut groove for piston ring. Center of piston isdrilled and tapped for 6-32 thread on upper endof piston rod. Piston is then faced, cut off and

reversed in the chuck for facing opposite endand bringing to dimension.

Cast-iron piston rings, of standard 1" size, arepurchased commercially and fitted to pistons.Lower end of piston rod is threaded 6-32 to fit incrosshead. Lock nut is tightened against top sideof piston after upper end of rod is threaded into

center hole to prevent piston from working looseon piston-rod threads.

Upper assembly is tested for smooth action,bracket for upper ends of crosshead guides iscut from brass angle. Setscrews holding washers

to crossheads have shoulders turned to lengththat will bring washers up against slotted guidewithout forcing them tight. Setscrews join cylin-der supporttocylinder.

2 1 8 P O P U L A R S C I E N C E

Petcocks on cylinder covers are dummies butcould be drilled and used as gravity-feed oilcups. A displacement oiler should be fitted for

model-boat use. Caps for valve liners are drilledNo. 50 to vent space above valves; they areturned to a snap fit. Intake manifold is " tubingsoldered into turned fittings. END

diy plans - model steam marine engine

Documents