rotate your rings? - PeachParts Mercedes-Benz Forum

rickg · #1 05-11-2004, 05:50 PM

Question found on metal working newsgroup:

"Do rings rotate in 4 stroke engines? If they're not pinned in place as in 2 stroke engines, seems to me that they would occasionally line up, allowing blow by . Or is the ocassional loss of compression not enough to be noticed while in operation... Just thinking on a early monday morn... Pat

Answer as given:
This was a question that must have caused Algernon Fortescue-Penberthy many a sleepless night before for he came up with the solution he fitted to his swansong:
The Fortescue-Penberthy 12-85 MKII. A motorcycle for discerning
gentleman of the 1930s..
His solution was to machine teeth in the inner diameter of
the piston ring, and with spur gears, driven via a ratchet activated
by the oscillation of the connecting rod to the piston, providing
the means of rotating the rings. The use of composite rings of the
Hempworth-Owens type, overcame the expansion and ring gap problems, a conventional ring would have posed. Use of long addendum teeth was used to overcome radial expansion. That the Fortescue-Penberthy family
had long been the British importers of Philip-Batek watches as well utilised by Algernon as he made good use of the parts bins in the store.
The final variant that successfully went into production, had gearing that resulted in ring rotation of 1.2 rpm + or - 2.27 seconds per week, at a given engine speed of 3,500 rpm. The Greenwich Observatory certifying the accuracy.
The motorcycle was ultimately withdrawn from the market, due to
watchmakers picketing local Fortescue-Penbethy dealers, disputing the agents rights to service the engines. The owner's manual called for a clean and adjust monthly."

Rube Goldberg would have been proud

Kuan · #2 05-12-2004, 08:59 AM

I've always wanted to see a movie of the the workings of an internal combustion engine from the inside. You know, the way the fireball propogates and such. It would do a lot to dispel mythes about cylinder head "theory." Someone should find a way to place a camera in there. Do the rings really rotate? I mean, after they're seated, aren't there tiny grooves which sorta hold it in place?

rickg · #3 05-12-2004, 10:38 AM

Yeah, they're supposed to stay put. This guy just came up with a creative, sarcastic answer to what he thought was a dumb question

rickg · #4 05-12-2004, 11:41 AM

Be sure and use high speed film and set your F-stop to about 3.5. Should come out good that way.