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Oil Field Masterpiece – Part II

Author Photo
By Staff

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Craig Prucha's 25 HP Swan out in the sun at the Coolspring Power Museum where it's on long-term display.
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The Swan is really coming together by June 1999.
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A justifiably proud Craig Prucha runs the Swan during the Coolspring Power Museum's fall show in October 2000.
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Fitting the new head in February 1999. Note the fixing bolts, two of six 38-inch-long tie rods that bolt the cylinder assembly together and to the bedplate.
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Machining the cylinder-locating plate.
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Machining the shoulder on the new piston-connecting rod.
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Trial fitting cylinder sleeve (with piston).
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Mixer and governor before disassembly.
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The restored mixer and governor highlight the work that went into this engine's restoration. Note the new governor gears.
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Editor’s note: This article is the second
installment of a two-part series chronicling Craig Prucha’s
restoration of a 25 HP 1901 Swan oil field engine. Part I appeared
in the March 2004 issue of GEM.

With the engine bed and cylinder prepped, I turned my attention
to the sideshaft assembly. The sideshaft was pretty well rotted
away, so I made a new one from stainless steel and bought a new set
of gears for driving the governor. The new gears are nice, and they
came with a small hole bored in the center so I could machine the
gear’s bore for my particular application. I was very fortunate
to find gears that exactly matched the center distance of the
sideshaft and the governor shaft. There are, however, some
differences between the original gear set and the new gear set. For
one, the number of teeth per gear is different (although the ratio
is the same), and the tooth profile of the new gear set is
different.

The governor assembly was the next part of the restoration to
tackle. The governor shaft was rusted solid in the governor
housing, and the governor housing had a crack in it from rust and
moisture swelling and expanding. The governor parts are pretty
fragile, so to make sure nothing broke during disassembly I drilled
out all the pins holding the governor balls. I cut off both ends of
the center shaft and heated up the housing with a torch. I did this
repeatedly – followed by a good soaking in kerosene – but I still
couldn’t get the parts to free up. Finally, I put the governor
housing in a press, and the shaft started to move. The shaft
finally came out, and I repaired the cast iron governor housing by
welding the crack with Ni-rod and grinding it flush.

Heads Up

With a materials list in hand, I made another trip over to my
friend Dave Johnson’s shop and got the necessary stock to
fabricate a new head and cylinder sleeve mounting plate. The engine
was also missing the brass bearing halves for the connecting rod
big end and the strap that holds the big end and bearings together
on the crankshaft. Using a bearing half of similar size from
another engine, I fabricated a pattern for two bronze castings, one
for each bearing. I fabricated the strap for the connecting rod,
and after getting the bearings back from the foundry, I machined
them up.

I first squared up the bearing halves on a shaper and clamped
them in a four-jaw chuck on my lathe. I put a piece of 0.060-inch
nylon shim stock between the two bearing halves and machined the
bore to size. I faced each side of the bearing assembly, and
machined a chamfer into the inside diameter of the face to make
clearance for the radius of the crankshaft. Finally, I drilled an
oil hole and cut oil grooves in the bearing surface. I assembled
the bearing halves together with the strap and the connecting
rod.

Next, I turned to pouring the crosshead babbitt. Before I could
pour the babbitt, however, I had to finish the  cylinder
sleeve mounting plate and mount the cylinder sleeve. And that meant
I had to finished fabricating the new piston connecting rod – all
or which play a critical role in aligning the crosshead.

The cylinder sleeve and piston came back from the shop, and the
connecting rod turned out nice and fit the piston well. I
temporarily rigged the sleeve to the bedplate, installed the piston
and piston connecting rod in the sleeve, connected the rod to the
crosshead and spent a lot of time lining everything up to make sure
the crosshead ran true with the piston. Once this was done, it was
time to pour the babbitt. The pour went great, and I poured extra
babbitt on the top side of the crosshead so I could machine the
final height of the crosshead bearing surface. This also insured
that the top of the crosshead would be parallel with the bottom: A
final inspection showed the crosshead was properly located. The
Swan was starting to look like an engine again.

Cylinder Mounting

1 fabricated six new 38-inch-long, 1-1/4-inch-thick tie rods
(the rods that bolt the head and cylinder assemblies together and
also to the bedplate). I also had to finish turning the outside
diameter of the new head and drill the six mounting holes for the
tie rods. This wasn’t without its challenges, as I discovered
the six holes for mounting the head were not evenly spaced. I wound
up having to transfer the position of the holes from the existing
head and labeling the new head’s orientation. Also, the
original head had a boss or protrusion that went 3-1/2 inches into
the combustion chamber. That’s an awful lot of material to
machine, so as an experiment I made the new head flat. I did this
to increase the combustion chamber size, which also lowered the
compression.

Now it was time to start assembling the cylinder. I had already
bolted the sleeve on with some temporary ‘T’ bolts. The
water jacket and the combustion chamber each have two cast ears to
bolt them together and hold them in position while assembling the
six tie rods. The head and cover plate were the last two pieces
that had to go together, and I cut gaskets for every interface.
With everything lined up – checked and double-checked – I started
tightening up the tie rods. Before I put the final torque on the
tie rods, I loosened the bolts holding the water jacket and
combustion chamber together so they would not fight against the tie
rods.

Mixer

With this done, I cut gaskets and put the valve chests on. Next
up was the mixer, which needed a little work before I could bolt it
up. I re-cut the seat for the gas valve (it holds the gas back
until it sees a vacuum from the engine) and made a new shaft for
the butterfly valve. I reamed out the shaft holes in the mixer
housing and installed new bronze bushings. With that work done the
mixer was like new.

With the mixer installed, 1 could install the governor assembly
and line things up to pour the babbitt for the governor and the
sideshaft. This required a lot of measuring, as the governor,
sideshaft and crankshaft have to line up and have the correct
relationship with each other so nothing binds up. After checking
the setup a couple times, I poured the sideshaft bearings.

The next step was attaching the connecting rod to the
crankshaft, and with those parts assembled it really started
looking like an engine again. For the first time since I’d
bought the Swan, the piston and crosshead moved together when the
flywheels were rotated. What a great feeling! I noticed in setting
up the engine that it got tougher to set the bearings as I
progressed – it’s tough to feel the drag on things like the
crankshaft and crosshead when the mass of parts starts coming
together. Yet, everything seemed to be working well as the
flywheels rotated: The governor balls actually went around – what a
site!

I still had to fabricate the exhaust cam lobe, which was missing
from the engine. I made the lobe of the exhaust cam quite wide to
make sure I had enough material to achieve the right duration on
the exhaust valve. I used the existing intake cam lobe as a
reference, since they are effectively similar aside from the
exhaust cam lobe profile being different than the intake cam
lobe.

This led me to the rocker arms, which needed some attention. I
had to make a new rocker arm pivot shaft and had to bore the pivot
holes in the rocker arms and press in new bushings. Both rocker
arms also needed new rollers and shoulder screws, which I made. I
also fabricated new valve adjusters.

Fresh Air and First Fire

Suddenly, it was time to pull the Swan out of the shop and put
the final touches on it. The flywheels still had to be painted, a
chore my two sons Joseph and Christopher took care of once the
engine was outside. I installed the gas line and gas valve, and
also fabricated and mounted an air intake pipe and choke plate. I
fabricated a hot tube chimney and plumbed up its gas line. I
finished rebuilding the governor linkages and welded up the pivot
holes, re-drilled them, reamed them to size and made new pivot
pins. All this work made for a nice, responsive governor.

The day finally arrived to start the Swan. I hooked up propane
tanks and an accumulator, lit the hot tube and oiled up the engine.
I rotated the flywheels to make sure everything was working
properly and stopped the engine on its power stroke for priming.
Not sure exactly where to set the gas and air, I made an educated
guess. Was the hot tube the right length? How much fuel would it
need? How much air? I’m sure many of you have been in this
situation.

When I felt things were ready, I primed the engine with gasoline
and back-kicked it. I did this quite a few times, but I didn’t
even get a pop out of it. Looking around my shop, I saw my Ferguson
TO30 tractor. I backed the tractor up to the engine and put a belt
over the flywheel. I don’t really like starting an engine this
way, so I spent a lot of time making sure everything was lined up
right. With the compression release open and the tractor pulling,
the Swan’s flywheels started to rotate. After making sure the
belt was tracking okay on the flywheel and everything on the engine
was working properly (sideshaft, rocker arms, valves, etc.), I
closed the compression release, opened the gas valve, and the Swan
fired in a few short seconds. It was firing erratically and running
lean so I gave it a little more gas – but it was running. Quickly,
I went over to the tractor and put the PTO in neutral. With a small
pipe, I slid the belt off of the flywheel. Wow! I wondered how long
it had been since the Swan had last run under its own power.

It wasn’t knocking or making any load-related noises, so I
started adjusting the gas and air mixture (it’s a
throttle-governed engine). After a few minutes of adjusting, the
Swan started slowing down and hit every time – it sounded nice.
After about 20 minutes of running – and my heart going a mile a
minute – the engine made a loud bang, but kept running. Listening,
I could hear a hissing sound every time the piston came up on
compression. I discovered that a cover gasket on the exhaust valve
chest had blown, so I shut the engine down. Also, I didn’t have
any water in the engine, and it was starting to get a little
warm.

After removing the cover and gasket from the exhaust valve
chest, I decided to machine the cover mounting surface and true it
up. I cut a new gasket and reassembled the cover.

I plumbed cooling water to the Swan, then checked and readjusted
anything that needed attention. My good friend Stiles Bradley
stopped by to lend a hand, and I lit the hot tube and oiled the
engine again. We primed it and back-kicked it, and with the two of
us working together the engine fired. 1 had left the gas and air
settings where they were from the last running, and the Swan took
off right where it left off. What a day! We watched the Swan run
and fiddled with adjustments here and there, but boy, it was
running nice. When the engine fires I can hardly hear a bang.
It’s more like a whisper. I have the entire restoration on a
four-hour video, and I love watching it and reliving the
experience. It’s a great-running engine, and it’s currently
on display at the Coolspring Power Museum in Coolspring, Pa.

I would like to give special thanks to Stiles Bradley and
everyone else who helped me with the Swan’s restoration. I
couldn’t have done it without them. Thanks.

Contact engine enthusiast Craig Prucha at: 6810 Ellicott St.
Road, Pavilion, NY 14525; cprucha@antique-engine.com

Published on Apr 1, 2004

Gas Engine Magazine

Preserving the History of Internal Combustion Engines