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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
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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.
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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
50
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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
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The pattern (right), core box (top), and casting (left) for the bearing case
51
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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
Ü
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
52
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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
Ü
The cast iron cylinder with milled ports
Ü
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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