BEWARE

John will you get some "cop-on" Im taking the sensorsed.!!!! mind you I surprised you havent mentions flywheels on this one you have on every other!!!

regds Derek

Ah Derek! how really luvverly of you -- an invitation to start on "Flywheels 2"...

"Flywheels 1" was never finished because Peter Tibbitts & Slick have not responded to the 25 page treatise I gave tham both. Lot of mistakes, of course, because I lacked information and the old grey cells have shrivelled up and gone Matt Black with trying to work in Jewels and Newtons etc ... etc... And they probably could not understand the Old Hat lingo anyway...!

PLUS ... and this IS important -- the bloke who raised the subject of flywheels refuses to read more than two lines of any posting. Squeezing a 25 page treatise into 2 lines requires more than a magician!!

We all know why a flywheel is required -- don´t we!

At 500rpm or at 12,000 rpm the crankshaft in its 360degrees of one rotation speeds up and slows down according to its `turning- moment´ -- or power-stroke -- and its resistance to motion.

i.e. The turning-moment is when the piston is travelling down from TDC and is when the crankshaft speed is at its maximum (in one rev, that is...) say for about 90°. The crank is at its slowest speed when the piston is compressing the incoming charge on its was towards TDC. Thus during the 360 degrees of one rotation (whether at 500 or 12,000 rpm) there are speed fluctuations of the crankshaft that the inertia of the rotating parts has to overcome or the engine slows or stops altogether. .

Plus, of course, there is the resistance to rotation of the mechanical friction within the system and the fact that the piston comes to a dead stop at TDC and BDC. This mechanical friction is increased by these acceleration/decelerations and by the compression pressure which, of course, is a function of the compression ratio -- plus the many other factors involved with the piston and con-rod ... etc ... etc...

I´ll not go further than that, into that -- although I ought to...

... A single cylinder 125 without any more than a 2kg crank assembly that can rev to 12,000 rpm (200revs per second!) -- win races, with reliabilty -- suggests that the 125 does not need anything much in the way of flywheel energy to overcome its speed fluctuations, anyway -- its attached rotating masses are obviously enough ...

Uh oh! Door bell!

Have to stop -- our waterboard people are checking on our white light radiator heating -- catch up later.

Cheers!

I´m back! We have two water meters that don´t record any flow -- could become awkward sometime in the future?!

So why does the 175 need largish flywheels when the 125 can do without?

The stored energy of a flywheel increases exponentially with engine speed (more than squared...) and curves I have produced show³ this conclusively. i.e. That is, a small, light 125 flywheel stores 4 more times as much energy at 10,000rpm than it does at 5,000rpm BUT a large, heavy 175 flywheel stores 3 to 4 times as much at both those speeds. So a 175 with big/heavy flywheel -- at 10,000 -- has 12 to 14 times more stored energy in its flywheel than does a 125 with a small flywheel. Thus it can be seen -- from facts we actually know -- is that although the 125 does not appear to need a flywheel and the 175 does -- the additional flywheel energy seems to be assisting in the overcoming of whatever difficulty it is that exists in the 175 ....

The distinguishing difference of the 175 from the 125 is the bore size incurring larger resistance to motion during compression and combustion -- especially if the piston-ring(s) are similar to the Dykes ring in using compression and combustion pressure to put more radial pressure onto the cylinder walls. The point I made about the stored energy in the flywheel being used to complement the engine output power during clutch-slip with high engine revs (acting as torque-converter) has been doubted by a good engine tuner -- so I humbly offer it up to you, the reader, to find fault with that conclusion.

³ ... I showed these curves, of energy storage against engine speed, in different flywheel sizes at the Cadwell last meeting and was told by the recipient they were NOT UNDERSTANDABLE so I am really at a loss what to do to explain this any further --

-- best left alone, NOW -- I suppose!

... But "Flywheels 2" does not seem to want to go away.

I welcome more opinions on this subject.

Cheers!