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Chapter 6

MAKING THE FIRST

INTERMEDIATE MODEL

The original plan for the Rice Husk Energy

Project workshop was to have a modest range

of tools and equipment for itting and assembly

and to rely on the main Kumudini Welfare Trust

workshop to carry out most of the machining

operations. We reasoned that this work would be

done in the periods that the main workshop was not

preoccupied repairing a broken-down jute press or

overhauling a tugboat. Not long after the project

started we could see that this arrangement would

not be practical and decided to fully equip the

RHEP workshop. A large Indian lathe and later

a medium-sized Chinese all-geared lathe were

procured. Kumudini shifted a large radial-arm drill

from their dock and a universal milling machine

from the central workshop to our project. Both of

these British-made machine tools turned out to be

invaluable for our work, and it was very convenient

to have them close at hand.

In re-designing the engine we capitalized on the

availability of skilled patternmakers (Fig. 6.1) and

several different foundries. Most of the iron casting

was done in a small foundry, (Fig. 6.2) where melts

Figure 6.1

Pattern makers working on the pattern for the unsuccessful irst design for the engine body

Figure 6.2

In a small foundry, molten cast iron is poured into a series of moulds.

The crucible has been heated in a small gas-ired furnace.

5-HP sTIRlINg ENgINE

Figure 6.3

Figure 6.4

The cast iron crankcase for

our irst intermediate model

Fly-cutting the face of the far

side of the crankcase with the boring

head mounted on a long arbor

Figure 6.6

The project review team in May

1983: from left to right, Mary Fontaine

(TAF), Craig Kinzelman (Sunpower),

Bob Barnes (USAID), Eldon Beagle

(TAF), Bruce Chagnot (Sunpower),

Mrs. Joya Pati (KWT), Mr. Callahan

(USAID), Sherry Plunkett (USAID).

Figure 6.5

After turning its lange on a lathe, the

crankcase was mounted on the milling

machine, where it remained unmoved for

most of the remaining machining operations.

Here the near side is being faced.

were done in a crucible heated by natural gas with

an electric blower supplying the combustion air.

several melts were done each day, so if a pattern

was given in the morning we could usually pick up

the casting in the afternoon. sometimes the casting

was not long out of the mould when we picked it

up, and was still too hot to handle. The problem

was easily solved with a loop of heavy twine that

formed a carrying handle. The charge for iron

castings was about one dollar a kilogram. large iron

castings like the crankcase and body were done in a

large foundry with a cupola furnace that was ired

once every week or two. Non-ferrous castings were

done in another small foundry that specialized in

aluminum and gun metal (bronze) casting.

From Phase 2 onwards there were half-yearly

reviews held in Bangladesh, usually in May and

November. In Fig. 6.3 the May 1983 review team

was meeting in Mrs. Pati’s ofice at Kumudini

Welfare Trust with representatives from the Asia

Foundation, sunpower, and UsAID.

Crankcase

The design of the crankcase incorporated two

large symmetrical side ports that accommodated the

bearing case on one side and an inspection port on

the opposite side (Fig. 6.4). Machining the lange

that bolted to the body proved to be a problem

as there was no easy way to hold the casting in a

lathe. This was solved by casting and machining two

angle plates that enabled us to mount the crankcase

on the faceplate of the large lathe. The remaining

operations were carried out on the milling machine,

which was still in the KWT workshop at this point.

Figure 6.5 shows the near side of the casting being ly

cut. Using a long arbor, the far side of the crankcase

MAKINg THE FIRsT INTERMEDIATE MoDEl

was similarly faced and then bored to size (Fig. 6.6).

Without moving the casting, the holes for the swing

link and bell crank pivots were drilled, reamed, and

then faced with a ly cutter (Fig. 6.7). By completing

this machining sequence in one setting on the

milling machine we could be sure that the pivots

and crankshaft would be accurately aligned and

perpendicular to the axis of the cylinder.

groove ball-bearing races. The pressure seal was a

custom-made leather cup seal packed with grease.

Body

In some of my early designs for castings I made

the mistake of trying to integrate several features

in one casting. This was easy to do on the drawing

board, problematic for the patternmaker, dificult

to cast, and sometimes impossible to machine. so

it was with my irst body design that I happily

incorporated cast feet. This involved complicated

pattern-making and resulted in a huge casting.

Figure 6.9 shows the feet of this casting being

faced on an old but wonderful metal-planing

machine driven through a lat belt from an

overhead line shaft in the Kumudini workshop.

In the end there was no way to mount the casting

Bearing case

Having the bearing case and crankcase

as separate castings simpliied the design and

machining operations. But, as with other castings,

this added to the weight of the engine. Figure

6.8 shows the bearing case casting, core box, and

pattern. The crankshaft of the IM-1 engine was

mounted in the bearing case with standard deep-

Figure 6.7

After the crankcase was bored to size, the seats for the

bell crank and swing link pivots were drilled and reamed.

Here the pivot seats are being faced.

Figure 6.9

Figure 6.8

The abortive irst design for the engine body mounted

on the planning machine to have the feet faced

The pattern (right), core box (top), and casting (left) for the bearing case

5-HP sTIRlINg ENgINE

on our milling machine, and the design was

scrapped. The second version of the body omitted

the feet and could easily be machined. In the irst

intermediate model the body was anchored to the

foundation with the hot end bolted to one end

and the crankcase to the other end (Fig. 6.10).

jacket of the cooler. This greatly reduced the size

of the aluminum cooler casting. After machining

the cooler on a lathe, we took it to an industrial

assistance organization equipped with a large

vertical slotting machine to have the internal slots

cut (Fig. 6.11). The leading edges of the internal

ins were iled to provide streamlining, (Fig. 6.12)

and inally the external grooves for cooling water

were milled (Fig. 6.13).

As an alternative for the aluminum cooler

I designed one that would make use of copper

tubes. The body of this irst model, the copper

tube cooler, was a large iron casting that also

served as the body and the cylinder of the engine.

It was drilled to receive a large number of copper

Finned aluminum cooler

one of the most problematic components

of the engine was its cooler. In the prototype

the aluminum cooler also formed the structural

connection between the hot end and the

crankcase, so the casting was large. In our engines

a cast-iron body physically connected the hot

end and crankcase and also formed the outer

The foundation for the second version of the engine body nearing completion

Filing the leading edges of the internal ins to reduce air low friction. At this

time we didn’t realize that the spots on the casting by Fazul’s knee represented a

porous spot and would pose a serious problem for us.

Figure 6.10

Figure 6.12

Figure 6.11

Figure 6.13

After we machined the aluminum cooler sleeve on one of our lathes, it was taken to

a specialty shop, where the internal ins were cut on a vertical slotting machine.

Radha milling the external cooling-water

grooves on the aluminum cooler

MAKINg THE FIRsT INTERMEDIATE MoDEl

Figure 6.14

Figure 6.15

Drilling holes

for the copper tubes

in the cast iron

cooler body

Fitting the aluminum cooler and cast iron cylinder in the engine body.

The castings for the irst copper tube cooler are in front of the packing crate.

tubes through which air would move from the

hot end to the cold end of the engine. Cooling

water would be conined by a cast-iron jacket. The

castings for the cooler body and the water jacket

can be seen in front of the empty packing crate

in Figure 6.14. In this picture Fazul has itted the

aluminum cooler and cylinder in the body of the

engine. A second crankcase, in front of the work

table, is about to be mounted on a lathe faceplate

with two cast-iron angle plates. In Figure 6.15

Momotaz is drilling holes for the copper tubes

in the cast-iron cooler body. The problem we

ran into was that because of the mass of the

cooler casting, we couldn’t achieve the necessary

temperatures for brazing the copper tubes to the

body, and this design was abandoned.

Cylinder liner

The thin steel cylinder of the prototype had

become oval to the point that there was signiicant

leakage past the piston ring. We made our cylinder

from cast iron as a sliding it in the cooler with a

wall thickness of 5 mm. The Xylan that was never

used as an antifriction coating for the piston and

displacer was put to good use as an anti-corrosive

coating for the outside of the cylinder (Fig. 6.16).

Crankshaft assembly

The crankshaft was built up from a mild

steel shaft with a cast-iron counterweight/

web. In Figure 6.17 a key-way is being milled

for the crankshaft to lywheel key. Figure 6.18

shows two crankshafts with different sizes of

The cast iron cylinder with milled ports

Milling the keyway in the crankshaft for the lywheel

Figure 6.16

Figure 6.17

Figure 6.18

Our irst crankshaft (right)

and a later model with more

counterweight. The crank throw

is about to be itted in the new

crankshaft assembly (left).

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