In 1999 I had the chance to visit the Paterson Museum in Paterson, N.J. It was a dreary, rainy weekday and I was passing through on my way to attend a conference at Stevens Tech in Hoboken. At this time I had been into the engine hobby about seven years.
As I toured the museum, I went to look at the "Fenian Ram," secretary of the Navy John Holland's submarine. The placard said it was powered by a Brayton cycle engine. Now my interest was piqued and I approached the curator, Bruce Balistrieri, and told him about my hobby and my interest in such an unusual engine. He asked me if I would like to climb inside and see it for myself ... I was in there for the better part of an hour.
The Fenian Ram
The Fenian Ram was designed by John Holland and launched in 1881. Upon first seeing his design, Holland proclaimed it as "a fantastic scheme of a civilian landsman." Holland's brother, Michael, had been introduced to the Fenian Movement, who sought Irish independence from British rule and had organized a skirmishing fund. The purpose of the fund was to build a three-man submarine to use against the British Navy. Work on Holland's boat started in May of 1879 at the Delamater Iron Works in Manhattan, N.Y., and was launched into the Hudson River two years later. The Ram's hull was 31 feet long and roughly 6 feet in diameter, with a shallow conning turret on top. Armed with a coaxial pneumatic "dynamite gun" in the bow, the 19-ton boat was intended to support a crew of three: a commander, an engineer and a gunner. The Ram was capable of nine knots, depths of 50 feet and stayed down for as long as an hour during tests, which took up to two years to complete. The Fenians, frustrated with Holland's delays and faced with internal legal squabbles, stole their own boat and hid it in a shed in New Haven, Conn., where it remained for 35 years. Holland had nothing more to do with the Fenians, and the boat was eventually donated to the city of Paterson, where it sits now.
A Unique Brayton
The Brayton cycle engine differs from the familiar Otto cycle in that instead of compressing the air/fuel charge and then igniting it, the Brayton cycle injects a compressed air/fuel charge into a cylinder where it is ignited and continues to be injected and burned for roughly half of the power stroke. After the air/fuel injection ceases, the remaining hot gases in the cylinder are allowed to expand until the bottom of the stroke is reached. Then an exhaust valve opens and the spent mixture is forced out of the cylinder. The Brayton cycle is referred to in engineering lingo as a complete-expansion diesel cycle, or Joule cycle. A modern jet engine is also called a Brayton cycle, but instead of pushing a piston, the compressed fuel/air mixture is burned and allowed to turn a turbine.
The Brayton engine in the Ram is a unique design. It has two tandem cylinders driven from both sides on the outside of a crosshead between them. The crankshaft has two throws in the same position. The front power cylinder operates off of compressed air generated by the rear cylinder, and a receiver stores the excess compressed air. Fuel is metered in the intake ports by small injection pumps. These pumps were crude by today's standards, employing a plunger and slide valve to direct the fuel to the cylinder. The valve mechanism, fuel pump and governor appear to be driven off of a toothed chain. On the top ends of the power cylinder are openings that I believe are for inserting either a preheated platinum sponge or a burning wick. In operation, the igniters are inserted in these ports and the air is turned on. The Brayton literally air started itself.
John Holland was clever in using a Brayton engine in his submarines, as the excess compressed air was probably pumped into large tanks in the front and rear of the submarine for blowing ballast and possibly operating the engine. I do not know whether the sub ran powered while underwater using the stored compressed air. If it did, I am sure it would not have traveled far since the pumping cylinders were capable of pumping the air tanks to 80-100 psi. The trail of bubbles from the sub operating under power would have been a dead giveaway as to its position.
All the literature I've seen on the Brayton has shown the pumping cylinders to be about 50 percent of the power cylinder volume to maintain adequate air volume for running the engine. Lyle Cummins' book, Internal Fire, has an excellent chapter on this unique engine.
Brayton's first engines compressed a mix of gas and air in a receiver where it was then metered into the cylinder. A screen plate between the compressed gas supply and near the intake valve prevented the compressed gas mixture from exploding in the receiver. Still, explosions in the receiver did occur, popping a safety valve much to the discomfort of the operator.
Later Brayton engine designs utilized oil vaporization at the intake valve area by a wick arrangement. As the air rushed by on the admission period, atomized oil was carried through the screen or grating into the cylinder.
The grating in the intake valve area was a key element for keeping the combustion products within the cylinder. The Brayton always operated with less pressure in the power cylinder than the compressed air supply. Additional volume of gases to produce useful work was generated by burning fuel in the cylinder.
Since Then ...
Most of the illustrations in Cummins' book show a sideshaft driving the governor, valves and fuel pumps. Perhaps space constraints in the Fenian Ram necessitated using a chain-like affair to drive them. As you can see in the photos, space was limited inside the Ram. I had to crawl down on top of the large bevel gear that drove the propeller to get inside. No doubt being aboard this submarine while under power would have been a scary experience given the spinning flywheel, gears and reciprocating crosshead flailing away. It makes you wonder what a quick tip or bump could have done to one of the crew members.
I took these pictures in late April of 2005. Since my first experience inside the Ram, the museum staff appears to have cleaned up much of the inside, and the engine appears to be in a very stable state of preservation. While much of the engine appears to be frozen with rust, it could probably be freed up with little effort. Still, the Fenian Ram offers a wonderful opportunity to view one of the truly unique inventions in the history of internal combustion development.
If anyone is interested in this unique type of engine I'd be glad to try to answer any questions you may have. One of my back-burner projects is to convert a 2-cylinder opposed-piston compressor to a Brayton cycle oil engine.
The Paterson Museum is located in the Great Falls Historical District just off of Interstate 80 in Paterson, N.J. They can be contacted at: Thomas Rogers Building, 2 Market St., Paterson, NJ 07501; (973) 321-1260.
Contact engine enthusiast Paul Gray at: 3437 Blue Ball Road, North East, MD 21901; 302-598-5113; firstname.lastname@example.org