That's a 200-lb. load — four 504b. bags — entirely supported on a cushion of air.

OU'RE almost ready to believe inflying carpets when you open thethrottle and see a 200-lb. load float

eerily off the ground. Tip the handlesslightly and you have to brace yourself tokeep this wheel-less Flying Cart from skit-tering down the drive faster than you want

CONTINUED

HOW I BUILT THE

Flying CartBy Hubert Luckett

162 POPULAR SCIENCE JULY I960

Plywood, plastic, and aluminum make the airframe

FINISHED "HULL" showing how fan shroud androunded contours in the plenum chamber areobtained, using sawed-to-shape plywood coveredwith a skin of sheet aluminum and plastic film.

ALUMINUM IS FASTENED to inner curve of strutsby bending a flange over flat against the ply-wood, and securing with stapling gun. Alumi-num is slit every 1-1/2" to make a smooth bend.

to follow. More—you can easily trundle a 100-lb.load across a soft, soggy lawn with this machineand never leave a mark.

The Flying Cart is a true ground-effect machine(GEM). It has no wheels. It glides on a cushionof compressed air supplied by a modified chain-saw engine and a four-bladed wooden prop.

I built the "airframe" of ordinary lumberyardmaterials for $59.75. If you're well supplied withplywood scraps you can cut that figure in half.Engine and props are from an outboard air-driveunit sold by Airboats, Inc. (3323 N. FlorissantAve., St. Louis 7). New, they cost $130.

How it got that way. The cart didn't start outas a search for an improved wheelbarrow—ithappened the other way around. The buildingitch came with the first story I read about airsleds, and intensified with each story thereafter.It was a challenge to build a totally new kind ofvehicle before all the development problems weretrampled to death—and all the unanswered ques-tions were answered—by multimillion-dollar re-search programs.

I doodled the requirements. It would have to be:• Reasonably easy to build with ordinary

home-workshop tools.• Adaptable to continuing changes and experi-

Write for fuller drawingsWant to build the Flying Cart? The drawing

at left shows enough for you to proceed on yourown. For larger scale drawings, send $1 to: FLY-ING CART, Popular Science, 355 Lexington Ave.,New York 17, N. Y.

CROSS-LAPPED STRUTS are clampedbetween main frames, glued andscrewed to the spacer block. Notefloor flange that anchors leg of theplatform covering engine.

PLASTIC FILM is folded double un-der the clamps. Sheet-metal screwshold the two aluminum clampingstrips. Plywood clamp at bottom isheld by wood screws.

CONTINUED

Add the deck, motormount, and prop

DECK IS SEPARATE ASSEMBLYheld by bolts securing the motormount. Side rails are notched toengage upper corners of thestruts and rabbeted to receive1/4"-plywood deck cover. Wire-mesh blade guard is clampedbetween deck and hull.

MOTOR MOUNT is bolted throughthe deck and upper main frame.Hardwood blocks clamping ends ofeach pair of angles add rigidity tothe mounting assembly.

PROPELLER MUST BE BOLTED to thehub after the engine is in place.Vanes were added after the firsttrials to counteract torque effectand improve the air flow.164 POPULAR SCIENCE JULY 1960

mental modifications, yet functional in its mostelementary form.

• Large enough to carry a practical load—nota toy.

• Small enough for one man to handle andnot pose an awkward storage problem.

• Cheap enough for a modest budget.All of these points apparently ruled out a rid-

ing vehicle. So when someone suggested an airbarrow, it seemed like a happy choice.

The one that didn't work. Take one leftoversheet of plywood that happened to be 34" by 48";nail one-by-fours to the edge to form an openbox; cut a hole 24-1/2" in diameter in the centerof the plywood sheet, and you have the body ofmy first "feasibility-study" model. A 1/2-hp. elec-tric motor driving a 24", three-bladed cast-alumi-num exhaust-fan prop supplied the air. I wantedto see if the crudest possible rig would provideany encouragement to go ahead with the project.It almost didn't. When I switched it on, theshop filled with a wild roar and a dense cloudof dust, but there were no signs of levitation.The air stream was hitting the floor and bounc-ing right back through the fan blades.

I extended the sides to 16" to get the fanfarther from the floor. This time it teetered onthe brink of floating. Backwash through the fanwas greatly reduced. I rigged up a crude equal-arm balance and found that the machine required

[Continued on page 226]

Author's sketchbookshows future plans

CONVERSION TO AN ANNULAR JET will beeasy. According to theory, it should ridehigher off the ground. Il l try a flat plywoodbottom first, then tackle the problem of mak-ing a properly shaped core like this.

A LIGHTWEIGHT with keen bal-ance may be able to ride it as is,with the throttle relocated on areversed set of handles—butonly on a smooth surface.

BIG DREAM awaits a cooperativeneighbor. Two carts joined to-gether (with engines turning inopposite directions) offers ex-citing riding possibilities.

-A

INVERTING THE ENGINE would lower center ofgravity and allow use of standard prop with anengine rotating in conventional direction.

AN OVERSIZE SKIRT with a drawstring in thebottom edge may improve stability and perform-ance as an air barrow over rough terrain.

165

226 POPULAR SCIENCE JULY 1960

How I Built the Flying Cart[Continued from page 164]

68 pounds to balance with the motornot running—only four pounds when itwas turned on.

Scarcely a resounding success. But inspite of air leaks, turbulence, fan ineffi-ciency, and high weight-to-power ratio—I was getting 64 pounds of lift. It wasn'thard to think up reasons for going ahead.

The one that worked. Poring over allthe research papers I could find, I cameup with these rough specs:

• Shape—square. For a given area,power, and operating height, the shapewith the shortest perimeter gives themost lift. A square is the closest practicalapproach to the optimum circular shape.

• Size—5' by 5'. The most significantfactor in GEM performance is the"height-diameter" ratio (h/d). Withinlimits you can trade one for the otherand carry the same load. A larger vehiclewould operate higher off the ground, butit becomes clumsy to use and a problemto store.

• Design—plenum chamber. This islike an inverted saucer with the air cush-ion retained inside the bowl. It's the sim-plest of the proven GEM configurations,and gives good hovering efficiency closeto the ground.

• Power—chain-saw engine. The ten-tative design promised to lift about 30 to35 pounds per horsepower, as nearly as Icould estimate. A reasonable payloadwould require five hp. The lightest five hp.I could think of was a chain-saw engine.

• Propeller— ??? This turned out tobe a shopping problem. I was gettingdiscouraged about finding one that wouldfit the shaft, blow the right way for en-gine rotation, and provide optimum loadfor the engine. But a half-dozen problemswere solved at once when the Airboatsunit was suggested to me. It uses a five-hp. Power Products chain-saw enginewith reversed rotation and has a properlymatched prop.

Building the air frame. Problem: Howdo you make a close-fitting duct for thefan and a smoothly contoured bowl forthe plenum chamber with ordinary wood-working tools? Fiber-glass laminate wouldgive the needed shapes, but would becomplex to mold, and also would be tooheavy in the required strength. A skilledtinsmith could do it with sheet alumi-

CONTINUED

How I Built the Flying Cartnum, using aircraft-type construction, butthat was beyond me.

Plywood frames sawed to shape andcovered with a skin of aluminum andplastic were the answer. The final designproved to be easy to build and turnedout surprisingly strong and rigid for itsweight. The completed machine, includ-ing the engine, weighs only 80 pounds.

Building the Flying Cart. First I cutout the two 32" squares of 1/2" plywoodand the eight 3/8" plywood struts. I madea trial assembly of these parts, whichform the backbone of the vehicle, using5" bolts and TeeNuts to clamp it together.All other dimensions were taken directlyfrom this framework. After all the woodframing members of the "hull" were nice-ly fitted, they were taken apart and reas-sembled, with waterproof glue and woodscrews for all joints.

The sheet aluminum was fastened onnext. The inner edge was screwed to the.1/2 "plywood first. The sheet was thenpushed in tight against the inner curve ofthe struts and the bottom edge screwedto the one-by-two bottom frame. The 1/2"overhang at each end of the aluminumsheet was snipped every 1-1/2", the liphammered flat against the strut andstapled with a stapling gun. The fanshroud went on next, with the top andbottom edges fastened in a similar fashion.

Enclosure of the plenum chamber wascompleted by clamping six-mil polyethyl-ene across the corners, using the twol/8"-by-l" aluminum strips and the sawed-to-shape l/4"-plywood bottom piece.

The deck was assembled dry, placed inposition and the notches for the strutsmarked. After the notches were cut, itwas reassembled, with glue and screws.

First tryout. I didn't wait for suchniceties as handles, throttle control, bladeguard, and proper motor support, to seeif it would work. With the major struc-ture finished, I bolted a pair of angles di-rectly to the frame to support the motor.

The engine took hold on the third pullof the starter rope. With a roar from theunmuffled exhaust and a cloud of dustfrom my driveway as it was swept cleanby the air blast, the Flying Cart wasfirst airborne at dusk one Sunday after-noon. It rose about three inches fromthe ground and hovered there. Startledfaces popped up in neighboring windows

228 POPULAR SCIENCE JULY 1960

How I Built the Flying Cartand a horde of small fry materializedfrom nowhere. Cries of "What is it?" weresoon replaced by, "Can I ride?"

I soon paid for my impatience. Themotor support proved to be too limberand vibration broke the straps holdingthe gas tank.

Back in the shop, the motor supportwas stiffened by clamping the ends of theangles tightly between hardwood blocksand adding a second pair perpendicularto the first. Handles and flexible-cablethrottle control came next.

Remembering the demand for rides, Imade a removable platform to cover theengine. Supporting legs went through 1"holes in the deck and top main frame andwere anchored with slip-in floor flangesscrewed to the bottom main frame.

Early trials of the finished vehiclequickly led to the first two modifications.It would carry a load nicely on smoothpavement, but got into trouble on roughground or going over a curb. A flexibleskirt at the bottom caused the rigid partof the craft to ride high enough to clearobstacles. The skirt easily conforms touneven surfaces and retains the air seal.This also eliminated most of the pushingin climbing hills. By holding the machinelevel on a slope, all the air escapes onthe downhill side, thus providing thrustto push the cart uphill.

If you let go of the handles, reactionto the prop torque made the whole cartspin around. Vanes set in the air streamcounteracted this, after a bit of fussingto get the correct pitch. An unexpectedbonus resulted: The vanes seemed tosmooth the air flow in the plenum cham-ber and gave a measurable improvementin lift.

The plastic corners are a considerableaid to the experimenter. With cloth rib-bons stuck to various surfaces inside thechamber, a light shining through onecorner •will let you observe air-flow pat-terns through the other three. Some curi-ous things have shown up. Under certainoperating conditions, part of the air flowseems to want to give a negative lift.It may actually be creating a suctionthat is limiting the operating height ofthe vehicle. Next step: modification ofthe air flow to eliminate this apparentnegative lift. The machine may yet proveto be large enough to ride successfully.

m