1937 65 HP Cooper-Bessemer Type GSD

By Staff
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Dean Unruh's 1937 Cooper-Bessemer Type GSD got a warm reception at the 2004 Oklahoma Steam & Gas Engine Show.
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The flywheel after removal and sandblasting.
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The 'merry-go-round' oiler that originally oiled both cylinders.
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The restoration almost complete. At this point the pony motor had been installed, but the air compressor and air tank had yet to be mounted.
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Right: A younger-looking Dean Unruh and neighbor Stan Melrose lowering the cylinder onto the engine block in 1989. The guys still had a long way to go, but it was coming together one piece at a time. Notice the custom trailer with its cross-mounted suppor
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The oak brake shoe
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The air holding tank
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The engine's placard
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The screen cooler.
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The engine block
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Company: Cooper-Bessemer; manufactured in Mt. Vernon, Ohio, and Grove City, Pa.
HP: 65 at 600 RPM
Serial number: 39852
Bore: 7-1/2-inch
Stroke: 9-inch
Additional info: Originally pumped a 6,100-foot-deep oil well in Coal County, east Oklahoma; Two-cycle engine, 5.3-to-1 compression ratio; decommissioned in 1975; 4,500 pounds total, 910-pound flywheel; burns propane or natural gas

The green beast quietly lays in wait. Quickly, Dean Unruh jumps on the 18-foot trailer. He positions himself near the 4,500-pound 1937 65 HP Cooper-Bessemer’s broad base and reaches toward the apex of the engine to open an air valve to the cylinder head. With a glance at a check valve and a notice of a petcock, everything looks ready to go as he gives a nod to his buddy below.

Perry Hildebrandt turns a valve extending from an air tank to introduce 160 psi of air into the engine’s cylinder head, while Dean nimbly jumps down to the ground to roll the engine’s big 910-pound flywheel over Top Dead Center. A cam off the crankshaft in time with the pistons introduces the pressurized air needed to start the lumbering two-cycle engine. Throngs of people have gathered to witness the rare upright 65 HP oil field engine run at the 2004 Oklahoma Steam & Gas Engine Show in Pawnee.

‘The engine will easily flood if you don’t watch what you’re doing,’ Dean says over the din coming from the Cooper-Bessemer. ‘The carburetor just can’t adjust.’ The crowd looks on in amusement, cluelessly taking the difficult start-up for granted. Dean walks around the engine, inspecting all things large and small on the engine and trailer for problems. It takes an eagle eye, and it’s a duty that only comes with years of experience starting the engine.

Dean knows the subtle intricacies on his Cooper-Bessemer Type GSD, serial no. 39852, because he’s been exhibiting it at Pawnee and other nearby shows for almost 15 years. It’s his largest and favorite engine in his collection, but sadly the Cooper-Bessemer holds deep sentimental ties since his brother Marlin, who helped him restore and show the engine, passed away three years ago.

‘That was our favorite engine … we had so many memories and hours on that engine,’ the Enid, Okla., native affectionately recalls about his time spent with Marlin restoring the engine. ‘We were partners on this stuff – when I see that engine, I see Marlin. It was our favorite because it’s come such a long way. We thought it was hopeless.’

It’s a family affair
The Cooper-Bessemer’s restoration was the culmination of Dean and Marlin’s shared love of old iron, both having caught antique engine fever from their father, Harold. As two of four boys growing up in the Unruh family, both Marlin and Dean accompanied their father to old engine shows, most notably the Waukomis, Okla., show that later moved to Pawnee. Harold didn’t own a lot of engines, but these early memories left an indelible stamp on the young and impressionable brothers. ‘Our dad started taking us to Waukomis and other shows about 30 years ago,’ Dean recalls. ‘He displayed a 1-1/2 HP John Deere and Maytag. We learned the ways of fixing up and restoring this stuff by working on Dad’s. After he died, we started on our own engines … then tractors. One thing led to another because this is a lot of fun and a challenge.’

The hobby just kept snowballing for the two brothers, and bigger and better challenges presented themselves. They finished tractors and smaller engines, but then they got the big call. An old friend in the Oklahoma oil business, Olis Anderson, called to report he had found something that might interest Dean and Marlin: An old 1937 Cooper-Bessemer Type GSD rusting away in an Ardmore, Okla., bone yard.

The 65 HP Cooper-Bessemer once pumped oil from a 6,100-foot-deep well in Coal County, eastern Oklahoma. The propane-burning, two-cycle engine, which works at 600 rpm and has a 5.3-to-1 compression ratio, reliably served in the remote Oklahoma oil country until it was retired in 1975.

The owner didn’t want a dime for it, so Olis took it home with him to Garber, Okla., and wasted no time calling Dean and Marlin. There was just one problem: The brothers had no way to move such a beast home – they had never handled an engine that big. They spent the better part of that winter scratching their heads, wondering how to haul it home. Finally, they decided to customize a trailer to serve both as the Cooper-Bessemer’s trailer and new home.

To construct the custom trailer, they shortened a 40-foot, three-axle flatbed trailer to 18 feet, stripped it down, balanced it and ‘beefed’ it up with I-beams running perpendicular across the trailer. The brothers still had more work to finish on the trailer, including some custom add-ons, but it was now stable enough to hold the heavy engine for its trip to Enid.

Once safely in Enid, the Cooper-Bessemer’s restoration entailed the usual work – but the going was tough. ‘It was rough,’ Dean remembers. ‘The cylinder was completely frozen because it had sat in the bone yard for so long. The head had filled with water and removing the piston was a huge pain. We used hydraulic pressure combined with about every kind of solution for removing a stuck piston … Coca-Cola, WD-40, penetrating oil – everything. Then, one day it just popped out.’

Everything was disassembled. The crankshaft was removed from the block, the pulley and clutch were taken apart, cleaned of dust and grime, and pipes and fuel lines replaced. The rings had to be replaced, as did the Timken bearings on the flywheel, the head gasket and crossarm seals inside. The brothers also honed both cylinders, and gave the whole engine a good sandblasting.

The Cooper-Bessemer uses three oilers for lubrication. There’s an oil injector on the cylinder, an oil dipper on the crankshaft and an oil pump on the governor. The original ‘merry-go-round’ oiler on the engine is quite unique, Dean says, because its rotating eccentric pushes four piston plungers that in turn push oil to the two cylinders, on both sides of the block. Something told Dean and Marlin, however, that the old rotating oiler shouldn’t be trusted since supplying the cylinders with lubrication is exceptionally important.

‘I didn’t use this oiler system because there was no indication the oiler was putting oil up to the cylinders,’ he says. ‘I replaced it with a drip-type oiler that I could see being pumped through window indicators, and I can adjust the amount I want to pump. This system made me feel better, knowing I’m getting oil to the cylinders.’

Dean’s concern for giving the cylinders enough oil is understandable, but he’s also concerned with over oiling them. The oil that drips over the cylinders eventually collects in four pockets leading to valves located at the bottom of the block. These pockets need to be occasionally drained or the engine will suck up and burn the excess oil, which can lead to a runaway engine. ‘Even if the fuel line is shut off, the engine will continue to run out of control until it’s suffocated,’ Dean warns.

Purists might notice the Cooper-Bessemer’s original fan-cooled radiator is conspicuously missing. Dean says he’s had conversations with a fellow in Winoka, Okla., who says he used to run the engine and had seen the radiator on it years ago, but where it is now is anyone’s guess. A Cushman-style screen cooler was improvised and works just as well.

‘People like the screen cooler at shows because they can see the water cascading down into the hopper,’ he says about displaying the finished restoration. ‘I’m still looking for an original, though, and if I ever find one I’ll use it.’

Putting it together
To put it back together, Dean and Marlin enlisted neighbor Stan Melrose to help with the hoisting and placement of the unusually tall, upright oil field engine. First, the block was stationed on the trailer, the crankshaft and pulley put into position and the cylinder head lowered by crane onto the block. Piece by piece, the engine’s various components were added to the trailer, including the screen cooler, pony motor and propane gas tank. Buttressed supports along the four corners of the trailer were added to stabilize the engine upon start-up.

‘There’re ‘criticals’ when you start this thing,’ Dean says about the shaking engine upon start-up. ‘The engine will shake for a minute at a low rpm until it gets up to speed. Once it gets past that critical speed, it balances out real good.’

Also added to the trailer is a unique, adjustable resistance plate that puts pressure on the flywheel to create simulated work. ‘It’s a smooth-running engine, but the two-cycle wants to pull something or it runs uneven.’ The resistance plate consists of nothing more than an oak brake plate and two water spigots to reduce the temperature and friction. Once adjusted, the resistance is set just right, and the engine seems to settle down as if it were a workhorse comfortably harnessed to a plow.

Tribute to Marlin
This Cooper-Bessemer is now a complete, self-contained unit that travels exceptionally well behind Dean’s 1/2-ton pickup. Over the years, he’s added an original Cooper-Bessemer logo, a wooden placard with restoration pictures, an air horn just for giggles and a few sundry personalized add-ons like a mono-grammed plate and faux moonshine bottle below the water tank. It’s obvious that Dean has fun with the setup wherever he goes.

The Cooper-Bessemer Type GSD is Dean’s crowning achievement, but it’s also a tribute. A plaque for Marlin, centrally positioned in his honor, reads, ‘In Memory of Marlin Unruh – The Cooper-Bessemer was his pride and joy.’ It’s a fitting tribute for Marlin wherever the engine travels. It’s probably safe to say Marlin wouldn’t have it any other way.

Dean Unruh is looking for other collectors who have information about Cooper-Bessemer Type GSD engines. Contact him at: Route 3, Box 429, Enid, OK 73703; (580) 234-0151.


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