Hi,
OK - this may be a bit of a rant but I need to voice my opinion about Mr Green's engine.
I've visited Mr Green's website a number of times, and each time I notice more errors and misleading statements.
I think it is a bad idea to buy these plans (in whatever form they may be) as it seems that the designer has some rather misguided ideas and a poor understanding of both mechanics and basic steam-engine concepts.
This website / engine design has been discussed in another thread in this forum (see under "Novel steam engine transmission to rotary motion idea"). I stated my initial opinions in that other thread.
In the website the designer makes a number of unsubstansiated claims that are worded in a way that seems to be deliberately misleading:
1) He claims that the engine will run on a couple of PSI with low steam consumption ("low volume" to quote the site) but you cannot change the laws of physics or thermodynamics - the available output power at the shaft will be very small and the motor will not be able to do any useful work under these contitions.
2) He talks about "efficiency" without defining how it is measured, and makes illogical statements such as "The output shaft continues rotation while the pistons stand still. The result is that the efficiency is increased dramatically." - I am lost for words......
3) He claims the design "eliminates the crank" yet the animated gif clearly shows that the flex rod connects to an off-set pin (a crank) on the flywheel.
4) He claims the design "eliminates side force" but the cyliders oscillate (and so are subject to side forces) and at the base of each cylinder there is a bearing tube to prevent the side forces twisting the pistons out of alignement within the cylinders (the equivilent of a crosshead in a normal engine).
5) He claims the design is a great step forward because it does away with the lower cylinder glands and seals (in other words it has single acting rather than double acting cylinders) as if this is a new concept.
6) He claims the advantages of low maintenance - but ignores the boiler maintenance required.
7) He lists benefits of:
- Costs little to build,
- Extremely lightweight,
- Very small profile for economy of space.
All of which ignore the requirement for a boiler - note the picture of the engine installed in a boat.
8 ) He states "The flex rod is nearly frictionless as the flexing is like a spring in which the energy required to flex it is returned in equal amounts." but if you look at the operation of the unit, one end of the flex rod is at a fixed point on the frame on the axis of the output shaft and the other on the (non-existant) crank - a fixed radial displacement from the axis of the output shaft. In other words the rod does not oscillate and bend from side to side, but twists maintaining a fixed curve. There is no "spring action" involved at all.
It just goes on and on.
For me, two of the most worrying issues are:
He dismisses problems of steam generation with the statement that "the boiler requirements are minimal". (If he applies the same level of engineering theory to his boiler design and construction as he shows in the rest of his website, I would imagine that most members of this group would take care to stay as far away from any of Mr Green's boilers as possible.)
Second,he claims that:
"The unique feature of the "Flex Rod Transmission" is that it produces an intermittent movement whereby the valve movement is stopped in its open and closed position during the power and exhaust strokes. This gives prolonged, fully opened valve timing."
Most steam engine designs go to great lengths to REDUCE the valve open times (through the use of variable "cut-off") to get maximum energy from the steam expansion - it seems the designer of this device does not understand this rather basic concept.
Given the points above, I suspect that any plans produced by the designer will have many errors and ommisions.
This sort of poor presentation of ideas and design gives engineering a bad name.
Finally, the design has been patented for five years, but Mr Green does not give any instances of satisfied commercial users on his website.......
Ian.
