Here are the mistakes: Working alone, with limited skill, intelligence, strength and free hours in the day. Isolation from healthy critiscism. Negative cashflow until the very end, with work paid for out of disposable income. It takes a long time to find out if the idea was right or wrong - possibly decades. Lack of business experience, i.e., ignorance letting the inventor pursue the unsellable or something too difficult to make at a profit. This story, in one way or another, has happened to nearly all of the inventions and ideas represented on these pages.  Aspin started his own company and worked on his engine, off and on, for nearly forty years.  It did everything it promised to, but no company in the world today makes this rotary valve cylinder head. Cross also started his own company.  Again, his engine was a technical success, but no such engines are available for sale today.  Both of these could be exploited tomorrow, since the patent rights are long since expired.  Incidentally, Cross was involved with the development of the linerless aluminium cylinder - now a commercial success, but simply a further development of the poppet valve piston engine. Nicola Tesla's turbine / pump machine was developed and tested in conditions of secrecy and patented.  Despite the high efficiencies he claimed, it was not built commercially (probably due to the long assembly time required for the impellor and the device's tendency to clog).  He spent years perfecting it, but it is now almost forgotten. Miller's idea is the exception, since it is now in the pre-sale stages.  Mazda are making engines using the cycle that Miller invented.  However, since it is nearly sixty years since the cycle was patented, it is unlikely that any money is going to the inventor (if he is still alive) or his heirs. The automotive gas turbine, despite being explored seriously by a number of manufacturers, has also been a failure.  Primary reasons are the engine's high fuel consumption, long throttle lag and high capital cost, although the difficulty of training mechanics must be considered. Ralph Sarich's orbital engine has not been commercially built, due to the complexity and expense of the sealing grid required.  However, he has managed to become one of the richest men in Australia by starting his own company and licensing patent agreements to an innovative fuel injection system and other inventions.  His story is very much the exception to the rule, but he has had to take enormous risks, work extremely hard - and become a very good salesman - to get to where he is now. Other inventors have had disastrous histories.  The man who invented and patented the Singer sewing machine had to fight Singer in the courts for decades before he saw any of the royalty rights he was entitled to.  Charles Goodyear's patents were pirated from him and he died prematurely aged, with only the money from his autobiography.  The inventor of the television saw his patents superceded by Marconi's parallel technology and spent the rest of his life in poverty.  The NSU company was ruined by its decision to produce the Wankel rotary engine, which wore out quickly, had to be replaced (several times) under the 10-year warranty needed for car sales, and bankrupted the company. The NSU disaster, in particular, is the major reason for the conservatism now entrenched in the automotive industry.  All the major manufacturers were caught by this problem, some more heavily than others.  The technical problems of the Wankel have now been solved, but the type's reputation has never recovered. Which brings me to the inclusion of my own ideas on this site.  Having had one commercial failure of my own already (not related to engines), I can appreciate how difficult it can be to get something set up in the commercial world, even when customers have said that they want it. If my ideas are not valuable, then I'd prefer to not waste twenty years of my life working alone and chasing a dream that will fail.  If these ideas are valuable, then other people will also see the merit in them and take over the work of making them a reality. Hamish Edgar January, 2002