Talk:Free-piston engine

Untitled
My understanding is that the concept did not work. No one has ever gotten one to run and a two cycle stroke requires the slowing of the piston by the crank shaft for exhaust evacuation so it could never work? No one could have commercialized this ever? DARPA has declared it not practical and the research concluded as a failure. I have not been able to confirm either way but a wiki article filled with wishful thinking and not one reference should be deleted until someone knows. 69.39.49.27 (talk) 08:05, 25 August 2009 (UTC)

The concept works and FPEs were in commercial use around 1940-1960. Look at some of the references and you will find more info. The problem today is to control the engine sufficiently accurately to meet today's requirements, but there is a lot of work going on in this area. Do you have a reference for the DARPA evaluation? 84.144.65.56 (talk) 12:36, 25 August 2009 (UTC)

For reference; there was a British registered ship (M.V. Morar - 9000 tons DWT.) which sailed with a free piston engine for a few years - during the 1960's. The concept did work, but only in a very limited sense. To achieve operational reliability comparable with a conventional motor ship, it was necessary to have a much larger staff of marine engineers permanently aboard the Morar. This proved to be uneconomical and the ship was eventually re-engined. —Preceding unsigned comment added by 78.105.232.146 (talk) 12:26, 29 September 2009 (UTC)

The loudmouth engine and others
July 1957 Science Digest and September 1950 Popular Mechanics. http://www.jgokey.com/jetenginesrockets.htm There's also much information on various pulsejet and other odd engines. —Preceding unsigned comment added by Bizzybody (talk • contribs) 06:18, 15 December 2009 (UTC)

Concept works
Should add info on Linear Combustion Engine alternators. The concept works, and would be used in nearby future for UAVs and surface military robots (TALON, etc), many portable applications.

Some links:

A Swiss homepage in German and English language with detailed information: http://www.freikolben.ch — Preceding unsigned comment added by 92.104.231.122 (talk) 18:47, 24 March 2012 (UTC)

AeroDyne corp MICE ultra-portable generator http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA504220

Czech technical university http://www.lceproject.org/en/

Hope China would start producing cheap devices in nearby future :) — Preceding unsigned comment added by 95.25.227.82 (talk) 15:42, 9 August 2011 (UTC)

Gas turbines
Could someone please verify and clarify this? Gas turbines would appear to be pistonless engines and these turbines seem to conflict with the descriptions given in the first two paragraphs of this article. Are gas turbines "free piston" engines, or "piston free"? 173.68.56.71 (talk) 21 October 2011


 * Piston free. The point of a free piston engine and its similarity is that it's like the core of a gas turbine (compressor, combustor and the turbine that drives the compressor), but without the power turbine. Its difference is that it uses a reciprocating piston for compression, rather than a rotating turbine. The cycle is similar, but it's spread over time rather than through the length of a gas turbine engine. The technology is simpler to build a free piston than a turbine, which is why they appeared early on (1930s), although once manufacturing of turbines became more established, we've seen little of them since. Andy Dingley (talk) 20:38, 21 October 2011 (UTC)

DIAGRAMS ARE NEEDED, in order to illustrate geometry and how it works. Never did the old saying that "a single picture tells more than a thousand words" was so true like in this article. Amclaussen. — Preceding unsigned comment added by 192.100.180.20 (talk) 23:12, 23 December 2011 (UTC)

You can find a lot of information on the homepage http://www.freikolben.ch, there is also a movie that explains the Free Piston Gas Turbine. Please feel free to ask for more information about this unique technology.--FreePiston (talk) 13:09, 1 April 2012 (UTC)

turbines
I agree that there should be a picture of a free piston turbine but much more recent than the "Popular Science" version.

One main advantages of an FP turbine was that the working temperatures were lower than the pure gas turbine so less exotic and expensive alloys were required. One account mentioned that simpler grades of stainless steel could be used for turbines. The gas turbine "creep" factor caused by high temperatures and which requires regular engine changes was almost eliminated.

The FP military air compressor, that I saw, was almost uncanny with a complete lack of vibration at all speeds. It was as powerful as a much larger standard piston air compressor. Only one of the military present had any idea as to how it actually started and worked though.

Free piston turbines were fitted to several mine sweepers and seemed reasonably successful. The mentioned extra personnel required was more likely to be a requirement for engineers familiar with FP engines than the usual crew. Few today could even mention FP engines let alone describe the working principles. AT Kunene (talk) 08:28, 7 November 2012 (UTC)

Robert Huber
I'd like to include something about Robert Huber (1901-1995) who was introduced to Raúl Pateras Pescara by Aurel Stodola and worked for Pescara from 1924-1962. Huber was apparently known as "Mr Free Piston". Biscuittin (talk) 01:45, 27 March 2015 (UTC)
 * I have created Robert Huber (engineer). Please expand it if you can. Biscuittin (talk) 22:08, 27 March 2015 (UTC)

Timeline
It seems that free piston engines are older than is generally thought. Brown-Boveri patented one in 1913 (see Linear compressor) long before Pescara's patent of 1927. It seems that, from about 1940, gas turbines fed by free piston engines were quite widely used for marine and stationary applications but faded away in the 1960s following the retirement of Pescara's chief engineer, Robert Huber. Biscuittin (talk) 01:44, 27 March 2015 (UTC)
 * The article needs to distinguish between free-piston engines doing work (compressors and linear alternators) and free-piston engines as gas generators (driving turbines). There are major differences between them both in technology and in age. Andy Dingley (talk) 11:50, 27 March 2015 (UTC)
 * Agreed. Are you proposing a separate article for Free-piston gas generator, which is currently a redirect? Biscuittin (talk) 14:21, 27 March 2015 (UTC)
 * I think they can probably be covered as sections in one article. Andy Dingley (talk) 14:43, 27 March 2015 (UTC)
 * OK. Biscuittin (talk) 22:06, 27 March 2015 (UTC)

Question
One thing puzzles me about Free-piston engines. The piston stroke presumably changes according to the load on the engine. When it is idling, I would expect the stroke to be too short for the engine to function. On the outward (firing) stroke the pistons would not move far enough to uncover the inlet and exhaust ports. On the inward (compression) stroke they would not move far enough to achieve the required compression ratio. Comments please. Biscuittin (talk) 14:31, 27 March 2015 (UTC)

Possible mistake in date.
First generation

In 1807, de Rivaz tested an early engine that operated a free piston on a chain. 

I guess correct date 1857. It is all I managed to figure out based on Goole books. Someone who have access to that magazine, please verify. The Holm (talk) 23:44, 11 October 2015 (UTC)
 * No, it's 1807. Same year as he patented it. Some years before he died in 1828.  Why would you begin to question this?
 * Mind you, I don't know why de Rivaz is even mentioned here - he had nothing to do with free piston engines. His engine had mechanical power take off from its piston, via a chain in tension. Andy Dingley (talk) 23:54, 11 October 2015 (UTC)


 * as this discussion now misses context: diff link -- MichaelFrey (talk) 16:52, 18 July 2021 (UTC)

earlier works/patents

 * https://freikolben.ch/motorentypen.shtml
 * https://www.freikolben.ch/kompressoren

-- MichaelFrey (talk) 17:25, 28 July 2021 (UTC)