1944 Kahlenberg B-5

The name Kahlenberg may inspire only quizzical looks from a modern diesel pickup enthusiast. If you operated boats on the Great Lakes from about 1900 into the 1980s, you knew them as engines sometimes compared to Swiss watches that every fisherman and tug operator could afford to run.

The Coolspring Power Museum’s Kahlenberg B-5 is a five-cylinder inline with a 10 x 10.5-inch bore and stroke, displacing 4,123 cubic inches and making 150 hp at 340 rpm. Calculated torque at peak power would be 2317 lbs-ft. The engine starts with air and is a directly reversible engine. The engine weighs approximately 8-tons. Included with the engine were two identical bronze water pumps (no longer installed), one used as a bilge pump and the other as a cooling water circulating pump. Should one fail, they could be switched. An air compressor was also built onto the engine and an air tank was supplied for starting air…. and to operate your Kahlenberg air horns!

Early Days

Brothers William and Otto Kahlenberg opened a machine shop in Two Rivers, Wisconsin, on Lake Michigan just north of Manitowoc. Seeing a future need going largely unfulfilled, Kahlenberg Brothers Company soon turned to building two-stroke gasoline engines for small boats on the lakes. Their first went into a fishing boat in 1897 and that set a course for the business. They were a pioneer company in offering affordable small to medium-sized marine engines for boats on the Great Lakes and soon gained a high reputation. One of their notable engine features was direct reversing with no muss or fuss and it played well with the fisherman on the lakes, as well as yachtsmen and commercial boat operators of all types.

Originally, Kahlenbergs did not have reversing gears. Instead, to reverse, the engine was stopped and restarted in the opposite direction. This was very common with large marine two-stroke diesels, and is seen even into to modern times. When changing from ahead to astern, the engine was declutched from the propeller and a band brake was applied to the flywheel (inside the housing at the rear) to stop the engine. Air is applied to turn the engine ahead or astern, fuel is delivered and the engine runs in the opposite direction. Kahlenbergs were noted for making this process particularly easy and it could even be done with a remote control in the wheelhouse. A Kahlenberg may or may not have reversing gears. They first offered this option in the 2-cylinder models in the 1930s but gradually expanded it into most of the offered engines, though all the engines were still capable of being reversed. Typically, the gearbox did not have reduction gears. With engine that turned in the range of 275-400 rpm and swung large propellers, they weren’t needed.
From here we can see the engine governor, just above the front flywheel. You can see the red air line going into part of it. If there was a “secret sauce” to the Kalenbergs, it was the governor and related controls. They were much simplified and more user friendly than most in the era. Plus, they allowed remote controls, so the engine could be controlled from the bridge. In the era, that was a big deal. While this B-5 has a reversing gear, the engine can be reversed`

By the turn of the century, Kahlenberg began expanding their engine line to include larger powerplants and servicing markets beyond the Great Lakes. In 1914, William began the development of a two-stroke oil engine. Their first production models were available in 1916, a 50-55 horsepower two-cylinder and a 75-85 horsepower three cylinder, each sharing a 9 x 10 inch bore and stroke and a modular design. These were dual-fuel engines that started on gasoline, with one small carb per cylinder and an ignition system. When warmed up, they were switched over to a fuel injection system using a heavier, less volatile fuel oil, often only a few steps above crude oil. Like the earlier gas engines, they were direct reversing.

The New Kahlenberg

By 1922, the dual-fuel engine had been refined into what was termed “The New Kahlenberg Oil Engine,” redesigned as a hot-bulb engine without the gas start. The line quickly expanded to include engines from 20 to 200 horsepower, two to four cylinders, and with a couple of combinations of bore and stroke. A great deal of refinement went into the reciprocating components and it was said the Kahlenberg oil engines had one of the most robust and easily serviced lower ends in the industry. The crankshaft main bearings were external and could be replaced without tearing much of the engine down.

Alternately called hot bulb, oil vaporizing engines and later semi-diesels (not a technically accurate term) they didn’t use heat of compression alone to achieve ignition. The combustion chamber had a hot spot onto which the fuel oil was sprayed. If that surface was sufficiently hot, the heavy oil was vaporized, heated and very close to ignition, if not right at ignition temperature. The heat of compression, even with a relatively low ratio (5 or 6:1) was just enough to set it off if everything worked right. The optimal ignition timing was highly variable according to the fuel used (some vaporized more quickly than others) and Kahlenberg included the means to easily adjust injection timing and air volume according to speed, load and what fuel was being used at the moment. With a light, easily vaporized fuel, timing would be retarded. For a heavy fuel that was slower to vaporize, injection timing needed to advance to give it a little more time. Air volume was adjusted with an air damper to achieve the clearest exhaust at any given speed but mostly it was all the way open except for idle or low speed operation.

None of the oil engines were very efficient compared to a true diesel but they had a place in the market due to the very inconsistent quality of fuel oil back in the day. Diesels were very particular about fuel and the required fuel was not easily available everywhere and more expensive than ordinary fuel oil. Even when better fuel became readily available, soon becoming known as “diesel fuel,” the oil engine was still popular because it could be run on lower grade, cheaper fuel. The lower grades of fuel tended to have lots of “stuff” in it, like asphalt, so it left deposits, but oil engines were designed for relatively easy combustion chamber cleaning. Oil engines were most efficient with a slightly heavier oil than the diesel fuel we know today but they did/do fine on #2 diesel. Kahlenberg was at the top of the class as oil engines went and were among the more efficient on the market.

The B-5 is a two-stroke, crankcase-scavenged oil engine. It has no valves and breathes in and out via ports in the cylinder liner, which the piston covers or uncovers during it’s stroke. The crankcase of each cylinder is separate and sealed. On the upstroke of the piston, once the inlet port is covered by the piston, the interior volume of the crankcase increases and a partial vacuum is created. Spring loaded inlet valves (red arrow in image) on both sides of the crankcase then open and the crankcase fills with air. When the piston starts down after the firing event, releasing the spent fuel via the exhaust port, crankcase volume is reduced, the crankcase inlet valves close and positive pressure is created. When the piston drops below the inlet port, air is pushed into the cylinder starting the process again.

The oil engine required a heat source applied to the combustion chamber for starting… typically a kerosene torch. The torch heated up the bulb on the outside of the chamber and that heat transferred into the dome inside the combustion chamber, providing enough heat to vaporize the fuel when the injector sprayed it there. Kahlenberg built kerosene torches onto each cylinder of the engine but from the mid-1930s, Kahlenberg engines also included an electric glow plug system which Kahlenberg claimed heated the chamber enough to start the engine… even into very cold conditions. That’s been reported as not quite true and like many electrical devices of that era, the systems tend to fail more often than owners preferred. As a result, the torches remained in use and were preferred by many of the Great Lakes fishing boat operators right to the end. In later years, when diesel fuel was common, the torches were plumbed to use the same fuel as the engine.

We don’t have a clear picture of when all the different Kahlenberg engine models were introduced after the initial 1922 updates, but we can see in the oil engine line, there were four series engines, A thru D, denoted by their bore and stroke. With the exception of the D-Series (7 x 7.5-inch bore and stroke), which came only as a 20-24 horsepower two-cylinder, each series were available in two, three and four-cylinder configurations, with the B (10 x 10.5 bore and stroke) and C-Series (12.5 x 14-inch bore and stroke) also available with five and six cylinders. The highest-power Kahlenberg oil engine was the C-6, displacing 10,308 cubic inches and making 300 horsepower at 327 rpm. That’s 4,448 lbs-ft at that speed and more at lower rpm. The C-Series debuted in the mid-1930s and used a significantly different combustion chamber design. We have not found specs, but suspect it also had a higher compression ratio to reflect the general improvements in fuel quality.

Into Diesels

Kahlenberg retained their hot bulb engines almost to the last of their engine manufacturing era. They weren’t completely replaced by two-stroke diesels until the early 1950s and they continued to rebuild and resell their older engines into the 1970s. As hot bulb engines go, they were very refined and had a great reputation on the lakes. Kahlenberg did developed a line of true diesels and introduced them in 1954. The Model E were two-stroke turbocharged engines offered in four, five, six, seven and eight-cylinder configurations making up to 750 horsepower. It was a good powerplant but, unfortunately, a bit late to keep Kahlenberg competitive in the marine and stationary diesel markets. They had largely ceased manufacturing them by 1960, though they continued making parts and rebuilding them for at least a decade after.

Another bit of secret sauce was the engine bed. The crankcase sections were bolted to it. Note that the main bearings are between the crankcases and accessible without tearing much of the engine down. The mains on most Kahlenberg engines were also water cooled.

The Story Isn’t Over

Kahlenberg had diversified their manufacturing lines almost from the beginning by manufacturing propellers. This was one secret to their success with marine engines because they supplied a matching prop with every engine. In 1930, they also moved into signaling devices and became a world presence in air horns. Starting in the early 1960s, Kahlenberg began moving their primary business away from engines, where they no longer had a large market share, and more into the air horns where they were renowned. Today, Kahlenberg Industries is still family-owned and a major presence in signaling devices. Many U.S. Navy aircraft carriers use Kahlenberg horns and their line goes down into recreational boating. They still also make propellers and do a lot of custom manufacturing, including for the Defense Department.

Long Service

This B-5 engine is on display at the Coolspring Power Museum in Eastern Pennsylvania. It was built in 1943 and reportedly installed into a vessel named Shiloh that was built in a Michigan shipyard about that time. It’s said that vessel was a “motor tender” and used at some point by the Corps of Engineers on the Great Lakes but we have not been able to confirm it. The vessel was sold in the early 1980s to a company in South America but on the way out of the area, it cracked a cylinder liner. The new owners repowered the vessel with a more modern engine and donated the Kahlenberg to Coolspring.

Here is a new B-5 from a catalog from the same era when the Coolspring engine was built.

While nearly 40 years in service seems like a big deal, there were still quite a number of Kahlenbergs in service, on the lakes, and elsewhere, in the 1980s. That number has dwindled to just a handful today. Commercially we could find only one, a BT 75-90 three-cylinder in the 48 foot fish tug, Elsie J. She’s still owned by the same family that had her built in 1945, and fished her until 1976, when commercial fishing was made difficult by legislation and regulation. The family maintained her all these years, at first hoping for changes in the restriction that would allow her to still be a viable commercial boat. Along the way, she was restored and converted into a charter boat, still running the original Kahlenberg oil engine.


Coolspring Power Museum

Jensen Charters- The Elsie J.

Kahlenberg Industries

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