Another whats new is really old engine design

[dicer]

I'm surprised there are no threads on the site about this engine.

http://pinnacle-engines.com/

Nothing came up on a search. So how come we haven't heard much about this?

 

[GregLocock]

Great to see a double knocker engine doing the rounds again. And yay, sleeve valves. That'll be one step forward, and one enormous stride backwards. Lovely stuff.

Cheers

Greg Locock


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[crerus75]

Google "Cleeves cycle" and a few hits will pop up, including a picture of their prototype. The company has been featured in Popular Mechanics, and one article says they're developing the engine for an undisclosed Asian scooter manufacturer.

We haven't heard much about this because the world is awash with "revolutionary new engine technology" and there's only so much that the popular media can do to drum up enthusiasm and to differentiate between valid concepts and investor-money vaporware. The same things are promised as have been for every other variation of internal combustion engine-- more power, lower emissions, greater economy, etc. I wish them the best of luck, but we'll see if this ever becomes a production reality.

 

[Tmoose]

Hi Greg,

Which feature is the step forward?

regards,

Dan T

 

[GregLocock]

I like the idea of double knocker architecture in some applications, although I must admit small scooters doesn't immediately spring to mind as an obvious application. If you need an under floor engine that is refined eg in a people carrier then they make an interesting fewer cylinder alternative to a boxer 6, for example. Basically you trade off the balancer shafts of a 2 or 4 cylinder against having two cranks. But yes, it is not an architecture that has set the world on fire, and I've never worked on one.

Cheers

Greg Locock


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[MikeHalloran]

I haven't seen or heard one in IRL, but I'm fascinated by the Napier Deltic, which has three cranks, 18 cylinders, and 36 pistons in a very compact package, and actually ran and produced a lot of power, given military level maintenance.

Start at ptfnasty.com if you are curious.


Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

/Pairs/ of Deltics were used in British Rail Class 55 locos in the UK. That's a lot of piston rings!

Cheers

Greg Locock


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[dicer]

The fun part is of course tying the 2 crankshafts together, sleeve valves and lubrication don't always go together either. And always the talk of this and that. Is there any dyno data yet???? I'd like to see some numbers.

 

[Lou Scannon]

...And yay, sleeve valves. That'll be one step forward, and one enormous stride backwards. Lovely stuff.

I'm by no means a proponent of sleeve valve engines, Greg, but I think it's fair to say that they had a good innings in the very competitive field of reciprocating aero engines in the 40s and 50s. In terms of (take-off) power density per frontal area or mass, they were not uncompetitive with comparable poppet valve engines. BSFC is more difficult to pin down due to the multitude of confounding variables, but I believe they had a slight edge overall, in that regard, insofar as it is possible to make apples-to-apples comparisons. This is attributed to the higher mechanical compression ratios enjoyed by sleeve valve engines, which has in turn been attributed to either the absence of a hot exhaust valve as an uncontrolled source of ignition, or the superior swirl conditions in a sleeve valve chamber promoting faster combustion; either of which permit a higher knock-limited compression ratio, other things being equal.

And for the record, I see no chance of a revival of sleeve valves (in commercially viable reciprocating engines) anytime in the foreseeable future. Poppet valves and their supporting systems have received a prodigious amount of development since the demise of reciprocating (and hence sleeve-valve) engines in the first echelon of aviation power units, and the ground that would need to be made up by sleeve valves, to make good over 50 years of dormancy should be give serious pause, to anyone considering a sleeve valve development project, for commercial application.

For those interested, there is well written historical comparison of sleeve and poppet valve engines here.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[GregLocock]

What a fantastic website, thanks for that.

Cheers

Greg Locock


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[MikeHalloran]

Well, there's another six hours I won't get back.

Thanks, Hemi.


Mike Halloran
Pembroke Pines, FL, USA

 

[Lou Scannon]

What a fantastic website, thanks for that.

Well, there's another six hours I won't get back.

Always glad to help [waste your time]

For those into aero engines or aviation in general, Flight Magazine has posted a scanned archive of all their issues from 1909-1995. It is date range searchable on alpha numeric strings, so I have found many interesting articles by searching, for instance, on "Merlin" or "Griffin". I haven't had much success with multiple terms - I seem to get all the results for each term taken individually, instead of a narrowing of results. Have fun!

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[SomptingGuy]

Top floor of the Science Museum in London. Just next door to my college and over the road from my hall. Free to students of their neighbour. I could spend all day poring over the aircraft engines.

- Steve