Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Wednesday, August 17, 2011

Tales of Coffman: In Praise of Engine Starters

Difficulty with starting our lawnmower recently reminded me of the under-appreciated class of devices called engine starters. We take them for granted, never offering a word of praise over the years; then at the first sign of trouble we consign them to the nether regions. As consumers most of us have experience with only two kinds. One is the recoil starter for small engines, in which a pull on a cord provides inertia to the engine crankshaft and direct current to the spark plug. The other is the ubiquitous electric starter on our cars, in which a battery-powered motor turns the engine over.

But there's lots more variety, then and now. Early carmakers experimented with compressed-air starters and ones drawing acetylene gas from the supply for the headlights. 

RC aircraft enthusiasts sometimes use a cordless drill to start tiny gasoline engines. When I worked in construction with my brothers, we drove a variety of stick-shift gasoline-fueled trucks and appreciated the option that a standard transmission gave us to roll-start the trucks on a hill.

Starting a diesel engine needs extra power since the fuel must be compressed more than with a gasoline engine. On some old Caterpillar dozers, the operator used a recoil starter to get a small gasoline engine going, and then used that power to crank the diesel engine. Also handy: a can of starting ether, aimed at the air intake.

A common method for firing up large gasoline and diesel engines of yesteryear was the Coffman starter. Inserted into a sturdy breech, a blank shotgun cartridge sent a blast of pressurized gas down a steel tube. In some versions the hot gas spun a turbine that transferred its inertia to the engine for starting.

A powder start is smoky and loud, as in this video showing its use with a jet engine. Here's a rather lengthy but interesting video of how to start a "Field Marshal" diesel tractor with a Coffman starter. The breech is at the front of the tractor, rather than at the driver's seat. The process includes the use of what looks like a cigarette as a glow plug. (Glow plugs are particularly important when starting diesels at low temperatures, because the frigid engine block steals heat from the compressed vapor).

Pros: the Coffman starter was lighter and smaller than crank-driven inertial devices or the battery-and-electric-starter combination. It was well suited for starting big-engine aircraft and tanks in remote areas. 

Con: run out of powder cartridges, and you're out of luck.  

The Flight of the Phoenix (1965, remade in 2004) raised the profile of Coffman starters, because the characters' triumphal return to civilization can't start until the radial engine does. In the movie, a group of airmen and oilfield hands undertake to salvage something flyable from a wrecked twin-engine C-82A Packet in the Sahara Desert. 
After the improvised monoplane is hammered together Capt. Frank Towns (played by Jimmy Stewart) undertakes to crank over the gang's improvised single-engine monoplane with a Coffman starter, but has only seven cartridges to do so. The radial engine is so big there's no other way they'd be able to start it up. Defying the plane's designer, an irritating German, Towns uses one cartridge to clean out the cylinders, firing it with the magneto off. The engine eventually catches, of course, so our heroes can complete their self-rescue by flying to an oasis. 

I think the triumphal scene as the engine catches and warms up is a bit long, but when it comes to guy-movie moments, it hits the mark.

2 comments:

  1. Charles F. Kettering with Henry Leland invented the first practical electric starter for automobiles:

    http://en.wikipedia.org/wiki/Charles_F._Kettering

    http://en.wikipedia.org/wiki/Starter_motor

    That itself save a lot of grief. Even in the best weather & engine conditions, crank starting was difficult & hazardous.

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