Steam Power Systems Bus

There were three California Clean bus projects that became operable in 1972: SPS, Brobeck, and Lear.  The three developers were given about two years to design, build, test, and put into regular bus operation, a steam powered bus.  The purpose was to produce clean air and they each made a bus that ran in regular service, at least for a test period.  There is a publication labeled “California Steam Bus Project, Final Report of the Project Manager” put out by Scientific Analysis Corporation, with Kerry Napuk being project manager, and it is not dated.  One of the most intelligent quotes I have seen in years is in this report.

Here is the quote: “Finally, any comparison of three steam buses built in two years at a total cost of $8 million to production diesels developed and produced over forty years at perhaps a total cost of $10 billion raises certain questions.”  The problem found with these three buses was fuel economy.  The specifications for the project were to not take up any passenger space and to use an existing bus chassis and to get everything done in a short time.  Everything had to be crammed into a small space.  Because the bus thing was funded by the California legislature it was dependant on the whims of the political winds.  There was no assurance that anything would be funded or purchased after these test models, and nothing more was done, making it difficult for the three companies to recruit and keep good staff.  Much was learned and nothing was retained from the experience.

Here are some photos of the SPS, later to be called Dutcher Industries, a company founded and funded by Cornelius Dutcher, whose main fame was having been a Harvard classmate of Kennedy and whose secondary fame having to do with inherited money from the family who made it building the Panama Canal, steam bus.  Dutcher attempted to use his money do make a difference and to do some good.

He got snookered by Ken Wallis right after Bill Lear parted ways with Wallis, and, in fact, most of the Lear steam engineering staff went to work for Dutcher.  Wallis did not last long at Dutcher either and he went on to making  jet airplane silencers, if the memory is correct.

The photos tell the story of what was made, how it fit, and the amount of engineering development that took place,  but there is an interesting story coming from the people who worked on the bus and it had to do with acceleration tests.  The lesson is one with many parts.  Those of us who are experienced steam people know two important things; buses do a lot of stopping and starting, and, steam engines are natural hybrids in that they are very good at stored power.  To modify that last point, a steam power plant is very good at stored power if it is designed for that.  Instead, the SPS people designed their bus steam power plant for conventional steady state high efficiency operation.  They made a monotube boiler, although the photos show some mulit-path something going on.

The people working on the project told me that when it came time to wind the boiler coils they started with a piece of pipe 500 feet long.  They had to drill a hole in the wall of the shop and put traffic cones out in the parking lot and have half the crew standing out there to keep trucks and whatnot from running over the pipe.  A boiler, or more precisely, a steam generator, needs two main things: it needs a burner putting out the btu’s required and then it needs sufficient square footage of surface area to get the heat transferred to the water.  The SPS people got this all figured out right and it worked and then the government told them that they had to pass an acceleration test.

So they found an abandoned air force runway two miles long and did a standing start flat out acceleration and what happened is what an experienced steam person would have been able to tell them if he had been plied with enough beers.  As soon as the accelerator was stepped on, the steam throttle opened wide open and the pressure in the boiler dropped a few hundred psi and all of the hot water in the 500 plus feet of tubing produced a bunch of steam bubbles all along its length, as anyone studying Keenan and Keyes steam tables would have been able to predict.  These bubbles pushed a whole lot of hot water through the tube into the superheater part, flooding it, and then either cool steam or hot water went into the engine.  Cool steam and hot water do not have much energy in them and thus the steam engine was only able to produce a small fraction of its design horsepower.  The bus rolled along for a mile before the steam generator emptied itself of enough water so the burner would have a long enough superheater  to look at so it could produce good quality steam.  Then the bus took off at full design power just about when the brakes needed to be applied to prevent running off the end of the runway.

There are any number of good easy and practical solutions to getting a steam bus to accelerate rapidly and then to build up stored energy while waiting at the stop light to make another acceleration run for half a block.  It is much easier to do this with a steam engine than it is to accelerate a diesel engine/automatic transmission combination, in fact.  The steam bus would have many advantages over the diesel both in acceleration and in quietness while idling while loading and unloading passengers.  It is interesting that no one told the clean air bus people that they were expected to do an acceleration run, so they could design for it.  It is even more interesting that the people working on the bus never figured out what a bus did, or what a steam power plant did well.  I attribute this failing to them all being very good engineers.  What is needed on any new steam development project is a good designer.  Only after there is a good design does one want to turn an engineer loose on the project.

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