fuelessspaceengine

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systemthe sun.Power is ample to drive a midget water

pump or spin a display turntable. For in-door exhibits, such as in Science Fairs, aheat lamp can replace the sun. As a mantel-piece model, the engine can be operated onpaper matches, alcohol, or fuel tablets.

If you have no lathe, you can buy allparts machined in a kit. With a smalllathe, you can make the engine of commonmaterials: electrical conduit, brass tubing, ametal cigar tube, 1/2" dural plate. A kit ofmaterials is also available.

Mount stock for the engine frame inthe lathe and bore the cylinder recessesas shown in the step-by-step drawing. Re-cesses and cylinders may be threaded, butit's easier to make them push fits and cement

the cylinders in.Boring the displacer recess breaks through

the port to the power cylinder. Don't for-get to drill and tap the hole for the glandbefore removing the piece. Bore the bearing

C O N T I N U E D

A PS reader showed us how

to harness the sun

First published in PS in 1961 foralcohol firing, this model Stirlingengine has been built by manyreaders. One of them, Mr. ValmerNixon of Ottawa, Canada, a techni-cal officer of the National ResearchCouncil, added such refinementsas a sliding block for the crankpinto turn in, and an outboard dis-placer-rod bearing.

Intrigued by the idea of operat-ing the engine on solar energy, he

did so with both an 8" auto-head-light reflector and a spun-alumi-num reflector (photos at right).

Setup is reversed for an 8" auto-headlight re-flector, which operates engin e at mode rate speedwith kerosene used as a lubricant. A tilt basefacilitates aiming reflector at heat source.

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Mounted inside an 18" reflector so that sunlightis focused on the end of the displacer cylinder,the engine runs at full tilt. Wear dark glasses toprotect your eyes from the hot spot.

By Harry Walton

OCUS sunlight on this model engine,and it runs at full speed, fueled bythe biggest nuclear reactor in the solarF


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plate as shown. After boring the housing,press it squarely into the plate.

Drill tapping-size holes through the cyl-inder standard into the plate for two 3/16"bolts. Ream out the holes in the standardto clearance size; tap the others.

To align the crank disk, shaft, and crank-pin, follow the sequence shown. After cut-ting off the disk, chuck it by the shaftand face the outside. Support it on the

Use a center findera rod with a ball drivenon near one endto locate centers for boringcylinder recesses. By filing off bottom cornersof the workpiece and using a raising blockunder the headstock, it becomes possible todo the machining job on this small lathe.


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ends of the chuck jaws to press the crank-pin in with the tailstock feed.

The displacer cylinder is made of thin-wall steel conduit. Twist a 3/2" piece ontoa tight-fitting arbor center-drilled for tail-stock support. Turn down all but 5/6" ofits length to leave a wall less than 1/64"

thick. Leave the 5/16" unturned portion atone end the original diameter.

To close the thinwall end of the cylin-der, first solder a bit of sheet copper toa scrap of tubing you can chuck. Turn thecopper to a close fit in the cylinder. Meltthe disk free and silver-solder or braze

C O N T I N U E D

Where to order engine kits

Machined engine parts and an 18"reflector with engine mount can beordered (by number) from Techni-Kits,Dept. S, 350 Broadway, NYC 10013.705 Machined engine kit $19.95706 Reflector and mount 7.95

707 Machined engine kit,reflector, and mount 24.95708 All materials for machining

engine, ball bearings, fly-wheel casting, glass foam .... 9.95

For postage and handling, add to theabove prices 50 cents east of the Mis-sissippi, $1 west of the Mississippi.

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it into the cylinder. Soft solder won't do.Check for air leaks by blowing into the

open end with the joint under water.Cut fins out with a circle cutter. Chuck

them and bore to a slip-on fit on the dis-placer cylinder. Cement them in place.

The displacer must be loose in the cyl-

1 1 0 P O P U L A R S C I E N C E J U L Y 1 9 6 5

inder to let air pass it, but not so smallthat it leaves much air undisplaced. Coat

the turned head and the inside of the cigartube with cement before joining them. Putcement on the threads of the rod beforescrewing it in. Hold the finished displacer

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Amazing "Space" Engine You Can Build[C o n t i n u e d f r o m p a g e 1 1 0 ]

under hot water. Bubbles will rise fromany leaks, which must be closed.

Cellular glass foam, sold in the form ofabrasive blocks, makes a displacer that can-not leak. File teeth on a piece of cylinderstock, drill a foam block3/32",and feed iton a rod against the rotating cutter.

To assemble the crankshaft, first drivea ball bearing up against the disk (use apiece of tubing to press against the innerrace only). Insert the shaft in the hous-ing, set the crank disk on a solid support,

and press the second bearing into place,pushing against both races.

Make the power cylinder from seamlessbrass tubing or a 5/8" bushing. Polish the borewith abrasive cloth on a dowel. Bore the

piston; then, on an arbor, turn it to a tightfit in the cylinder. Finally, hone it with afine stone to a free but reasonably airtightfit. With one end of the cylinder held shut,the piston should resist entering, air behind

it acting as a spring. Mount the rocker on its pivot pin with

the crankpin in its slot. Turn a nut onto thecrankpin, screw on the crank web, and lockit concentric with the crank disk by jam-

ming the nut against it.Cement the power cylinder in with auto-body solder or a good metal-to-metal ce-ment. Look through the port to see if thepiston comes almost to the bottom of the re-cess. If not, add a washer behind the wrist-pin fork. If it hits, file a bit off the end ofthe fork. Put cement on the fork screwbefore tightening it.

Adjust the displacer rod in the rockerhead so that the displacer moves full stroke

without hitting the recess or the end of thecylinder. Check this while holding the cyl-inder in place. The displacer stroke can bevaried by raising or lowering the rocker pinin its slot. Cement the cylinder in only

when you're certain that the displacer actionis correct. Take care not to clog the portwith cement.

You should now feel compression as youturn the shaft and push the piston in. If you

don't, check cylinder joints, gland, and pis-ton head for leakage.

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