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01-18-2007, 02:09 PM

Michael Press wrote:
> In article
> <1169138022.062154.121440@q2g2000cwa.googlegroups. com>,
> frkrygow@gmail.com wrote:
>
> > Wayne Pein wrote:
> > >
> > > But how about this concept:
> > > http://www.starrotor.com/Engine.htm
> >
> > After gazing at hundreds of "miracle engine" articles over the years,
> > I've decided to ignore any reports that don't include tests of working
> > models. The only one of those hundreds of designs that gained any
> > traction was the Wankel, and it didn't set the world on fire.
> >
> > That page is way too full of phrases like "...is projected to have...",
> > "...should be...," "...is expected to be..."
>
> Can you can tell me why gas turbine engines are not
> practical? They have run well in races.

Well, let's see... just guessing, since I'm not an expert:

The main thing is probably just the expense of producing them and using
them in cars. Gas turbines need very sophisticated materials for
things like the turbine blades, which operate continuously at very high
temperatures and very high rpm.

Regarding the expense of using them, they are far from being a "drop
in" replacement for a piston engine, since their transmissions would
need much, much more gear reduction. (I don't know about their torque
curves offhand, but some adaptation may be necessary there, too.)
Their exhaust is, I think, much hotter, too.

The high temperatures and extreme rotation speeds might cause problems
in crashes, too, when hot shrapnel might be expected.

All these things mean designers are not working with familiar
territory. They'd be doing their best to anticipate problems, but they
might easily miss something that caused big problems later.

It's interesting to note that, even if you had something that was (say)
20% "better" than a standard piston engine and no more complex, it
would still be a hard sell if it were too "different." Car companies
the world over have billions invested in machine tools and production
lines to produce today's engines. They probably won't like to gamble
on replacing all that.

To tie this into bikes: One of America's technical experts on bikes is
Professor David Gordon Wilson of MIT. He's the lead author of the book
_Bicycling Science_ and former editor of the monthly technical journal
Human Power. And, in his professional life, he researches and teaches
courses in gas turbine design. (Or did - I guess he's retired now.)

See http://www.me.mit.edu/people/personal/dgwilson.htm

- Frank Krygowski

01-18-2007, 02:09 PM	#21 (permalink)
frkrygow@gmail.com Guest Posts: n/a	Re: OT Interesting video Michael Press wrote: > In article > <1169138022.062154.121440@q2g2000cwa.googlegroups. com>, > frkrygow@gmail.com wrote: > > > Wayne Pein wrote: > > > > > > But how about this concept: > > > http://www.starrotor.com/Engine.htm > > > > After gazing at hundreds of "miracle engine" articles over the years, > > I've decided to ignore any reports that don't include tests of working > > models. The only one of those hundreds of designs that gained any > > traction was the Wankel, and it didn't set the world on fire. > > > > That page is way too full of phrases like "...is projected to have...", > > "...should be...," "...is expected to be..." > > Can you can tell me why gas turbine engines are not > practical? They have run well in races. Well, let's see... just guessing, since I'm not an expert: The main thing is probably just the expense of producing them and using them in cars. Gas turbines need very sophisticated materials for things like the turbine blades, which operate continuously at very high temperatures and very high rpm. Regarding the expense of using them, they are far from being a "drop in" replacement for a piston engine, since their transmissions would need much, much more gear reduction. (I don't know about their torque curves offhand, but some adaptation may be necessary there, too.) Their exhaust is, I think, much hotter, too. The high temperatures and extreme rotation speeds might cause problems in crashes, too, when hot shrapnel might be expected. All these things mean designers are not working with familiar territory. They'd be doing their best to anticipate problems, but they might easily miss something that caused big problems later. It's interesting to note that, even if you had something that was (say) 20% "better" than a standard piston engine and no more complex, it would still be a hard sell if it were too "different." Car companies the world over have billions invested in machine tools and production lines to produce today's engines. They probably won't like to gamble on replacing all that. To tie this into bikes: One of America's technical experts on bikes is Professor David Gordon Wilson of MIT. He's the lead author of the book _Bicycling Science_ and former editor of the monthly technical journal Human Power. And, in his professional life, he researches and teaches courses in gas turbine design. (Or did - I guess he's retired now.) See http://www.me.mit.edu/people/personal/dgwilson.htm - Frank Krygowski