37 replies to this topic

[MatsNorway]

http://www.caranddri...ll-time-feature

Its a bit dodgy journalism but its a interesting view anyway.

[Magoo]

Nice little story... for a beginner. He needs to hang out here for a while and learn some stuff.

[Kelpiecross]

Nice little story... for a beginner. He needs to hang out here for a while and learn some stuff.

This bloke (and his site) makes everybody look like beginners.

http://www.douglas-s...nusualICeng.htm

[Tony Matthews]

http://www.douglas-s...nusualICeng.htm

Blimey! That's going to take some time...

[MatsNorway]

I really liked the double crank version. Less vibrations right?

Would such a design be able to go more rpms?

[MatsNorway]

I really liked the double crank version. Less vibrations right?

Would such a design be able to go more rpms?

I did not notice the archive. I have been looking through it and the core essence is that every single one is more complex than a two stroke or even a four stroke.

Find me a design that is simpler and worked and ill be surpriced.

Edited by MatsNorway, 16 December 2012 - 19:29.

[MatsNorway]

This one was quite cool.
http://www.pivotalen....html#animation
http://www.douglas-s.../miscIC.htm#bre go to middle.

Not sure but one benefit is that you can have a narrow "piston" and hence reduce the travel time to and from the ports. If we ignore reliability and efficiency it could make some good power for its cubic size.

Edited by MatsNorway, 16 December 2012 - 19:53.

[Wolf]

I'd thought Honda's oval pistons would rank quite high- on manufacturing and machining side of things, anyway... No Napier Deltic (three opposed piston two strokes in triangular arrangement)? And I remember seeing a section view of some old (bus?) engine, might've been English, in '42 Automobiltechniches Handbuch and thinking 'how on earth does that thing work?!?'

I'd have included Hercules engine- only because it looked so splendid in cutaway (with front like a clockwork)...

[bigleagueslider]

I really liked the double crank version. Less vibrations right?......Would such a design be able to go more rpms?

Less vibrations? More RPMs? Why do you think so? An I6, V8 or V12 can have excellent balance. As for RPMs, there is no real difference in the crank mechanism's kinematics, so why would it be able to turn higher RPMs?

On the other hand, the dual crank OP engine would be much more costly to manufacture, and would likely have greater friction losses.

Sure, the weird engines shown are interesting. But being different does not mean they are better. The engineers that design automotive engines are not stupid. There's a very good reason all auto engines look the way that they do.

slider

[Greg Locock]

The Lanchester boxer twin crank is slightly nicer than a regular boxer balance wise, but is paying an enormous price for a fairly small advantage, as the usual boxer arrangement's residual balance issue is not around the torque axis hence easy to isolate.

Mr Self's really big collection of odd engines is missing three that are still being developed- the Bourke engine, the terminally uninteresting and overhyped Scuderi Engine (fair enough) and the strange yet apparently functional Revetec.

Edited by Greg Locock, 17 December 2012 - 05:29.

[MatsNorway]

Less vibrations? More RPMs? Why do you think so?

The rods mass gets "counted out" when its going left right. Dual rods puts less strains on the piston side to side. meaning you can get the piston lighter. having the double rods makes less friction against the sidewalls too.

I quite like the pivotal engine.

Edited by MatsNorway, 17 December 2012 - 18:42.

[PJGD]

The Lanchester double-crank flat twin was the right solution for the time. Engine swept volume was 1,730 cc, and in the light and flimsy chassis of the time ~1896, good balance was key to keeping the car in one piece. A conventional flat twin results in cylinders that are off-set from each other resulting in a rocking couple around a vertical axis, but this 3-rod linkage permits the cylinders to lie on the same axis with no off-set. As Mats says, it obviates piston side thrust too. Further, the counter rotating flywheels cancel out the firing impulse kick within the engine structure so again this disturbance is not transmitted to the chassis. In an era when engine mounting technology was in its infancy, having a well balanced motor must have been a real treat for the early motorist.

Dr. Paul later used the twin counter-rotating crank architecture at both ends of his ultra high pressure opposed piston diesel engine about 15 years ago.

PJGD

[Canuck]

The engineers that design automotive engines are not stupid.
slider

Oh you're just trying to score some points with Greg.

[Greg Locock]

Rarely stupid, occasionally mad. I'd say that on balance engine labs are a more entertaining place to work, simply because blowing things up is more satisfying than bending Armco.

[Magoo]

Lanchester is a very interesting fellow. Developed a number of original ideas, not only in the automotive realm but in aeronautics as well.

[bigleagueslider]

..........Dr. Paul later used the twin counter-rotating crank architecture at both ends of his ultra high pressure opposed piston diesel engine about 15 years ago...........

PJGD-

Marius Paul's TRC OP recip engine used 4 cranks per cylinder (2 cranks & conrods per piston). While the TRC prototype engine had excellent thermal efficiency, it was due to the extremely high cycle pressures and temperatures and not the cranking mechanism. The friction losses in the dual crank/conrod TRC reciprocator were probably a bit higher than a conventional single crank/conrod arrangement. The TRC engine configuration simply shifts the friction losses that normally occur at the piston skirt to the piston's opposing crankpins, and these forces acting on the crankpins are eventually reconciled at the dual crank phasing gear's mesh point. So in reality, there is no free lunch here.

Having said that, there was actually a very good reason for using the dual conrod/crank configuration on the TRC. The TRC OP engine was designed to operate at peak combustion pressures of 275 bar. It is unlikely that a conventional single conrod/crank mechanism design would have been capable of handling those combustion pressure forces.

Lastly, the dual conrod/crank configuration did have one serious limitation. The wide swing produced by the dual conrods & crank throws limited the practical stroke length, since it created significant interference with the lower end of the cylinder bore.

slider

Edited by bigleagueslider, 19 December 2012 - 01:16.

[PJGD]

Lastly, the dual conrod/crank configuration did have one serious limitation. The wide swing produced by the dual conrods & crank throws limited the practical stroke length, since it created significant interference with the lower end of the cylinder bore.

slider

Lanchester's flat twin SI engine was mildly under square [Ø5.0" bore x 5.375" stroke]; the UK RAC Horsepower tax which forced highly under square engines came in somewhat later. Dr. Marius Paul's TRC engine, being an OP would have been highly under square too [bore & stroke not immediately to hand]. My guess is that the issue that you have raised was not a big issue for Lanchester, but I can quite see that it would be for the TRC OPE.

PJGD

[bigleagueslider]

...... Dr. Marius Paul's TRC engine, being an OP would have been highly under square too [bore & stroke not immediately to hand]. My guess is that the issue that you have raised was not a big issue for Lanchester, but I can quite see that it would be for the TRC OPE......

PJGD- The TRC OP engine had the same bore and total stroke as a Detroit Diesel series 92 engine. These dimensions were chosen so that the DDC series 92 could serve as a baseline to judge performance.

[MatsNorway]

The TRC engine configuration simply shifts the friction losses that normally occur at the piston skirt to the piston's opposing crankpins,

But crankpins got smooth finish, clearance and a oil film covering them. while the piston is scraping the walls clean with its seals..

So i doubt the no reduction in friction on the piston vs crankpin part.

But did you say that the increased angle on the rods was reducing efficiency? ok.

What about the pivot engine????????

Edited by MatsNorway, 19 December 2012 - 18:23.

[Lee Nicolle]

This bloke (and his site) makes everybody look like beginners.

http://www.douglas-s...nusualICeng.htm

There is a few that he missed too. The rotary valve section missed the rotary valve head that was fitted to early Holden blocks in the early 60s.. Manufactured here in Adelaide it was never super succesfull but was used in some road cars as well as a few racecars. There is some pics on the Early Holden Racing thread.

[onelung]

Dodson Valveless 2 stroke, ~3.0 litres. The "no trouble" car (so they claimed...). From around 1908-1912 or so.

[Greg Locock]

Very similar to the Twingle which 'powered' thousands of mopeds in Europe throught the Sixties.

http://puch250.wordp...twingle-engine/

Some hapless dude reinvented it recently and SouthWest Research are enhancing their income testing and developing it further.

http://www.scuderigr...t-cycle-design/

Basically if you call them piston charged 2 strokes then you can include the fabulous Bourke Engine

http://bourke-engine...eneral_info.htm

...and of course any crankcase compression 2 stroke.

[Grumbles]

Basically if you call them piston charged 2 strokes then you can include the fabulous Bourke Engine

I really enjoyed this story about some old men and their Bourke engine, very entertaining but I have no idea whether it is true or not. And apologies if I've already posted it - I've got a feeling I'm turning into one of those codgers that tell the same story over and over...

[desmo]

I really enjoyed this story about some old men and their Bourke engine, very entertaining but I have no idea whether it is true or not. And apologies if I've already posted it - I've got a feeling I'm turning into one of those codgers that tell the same story over and over...

Great stuff!

[Magoo]

I really enjoyed this story about some old men and their Bourke engine, very entertaining but I have no idea whether it is true or not. And apologies if I've already posted it - I've got a feeling I'm turning into one of those codgers that tell the same story over and over...

I've always enjoyed that story too. In the broadest sense, it's essentially the story of any number of Revolutionary Engines. O true believer.

[Greg Locock]

I've always enjoyed that story too. In the broadest sense, it's essentially the story of any number of Revolutionary Engines. O true believer.

I contacted the author a few years ago and he says it is based on actual events.

[Magoo]

Here's some of my favorite two-stroke jiggery-pokery.

[onelung]

BTW - how does one spell "weird...?" Anyway...



And not too dissimilar (or wierd) was the Fairchild-Caminez..

[desmo]

Nice. I can't recall seeing a cam engine with axially asymmetric lobes before. We did an oddball engines thread (or probably several) yonks ago, they're archived though I suppose so can't be directly commented on. Let's see.

http://forums.autosp...?showtopic=1782

http://forums.autosp...?showtopic=1793

Alas, almost all the embedded images are loooooong gone

[onelung]

Nice. I can't recall seeing a cam engine with axially asymmetric lobes before. We did an oddball engines thread (or probably several) yonks ago, they're archived though I suppose so can't be directly commented on. Let's see.

http://forums.autosp...?showtopic=1782

http://forums.autosp...?showtopic=1793

Alas, almost all the embedded images are loooooong gone

Yes indeed, the cam-type engines (both of 'em) were in the second of those links.
I rarely delve into the Tech forum, and in any case I suspect that thread post's from before I even started into the Autosport Bulletin Board so not too guilty re the repetition.
Still, an old codger like myself seems to be needing more and more memory jogging, anyway!

[gruntguru]

A nice feature of the aircraft cam engine with 2 lobes is the inbuilt speed reduction - each piston will reciprocate twice while the output shaft rotates only once. Aircraft engines usually need a reduction gearbox to run the prop at an efficient speed.

EDIT. The maths/geometry involved in making those rockers push and pull the pistons - with asymmetric cam lobes!!! Makes my head hurt.

Edited by gruntguru, 01 May 2013 - 23:51.

[Greg Locock]

Here's a modern, efficient, lobe engine.

http://www.revetec.com/

He's trying to get it certified as an aero engine.

[gruntguru]

Very efficient indeed. The big question is where does the efficiency come from? The explanation on the website is mumbo-jumbo:

"The point of maximum mechanical advantage or transfer is around 20-30deg ATDC (when the piston moves approximately 10% of its travel) making the most of the high cylinder pressure. This compares to a conventional engine that reaches maximum mechanical advantage around 60-70deg ATDC. (after the piston has moved through just over 40% of its travel, losing approximately half of the cylinder pressure)."[/font]

OK, so they can produce unconventional piston velocity profiles. This may help with combustion and/or help reduce heat loss to the cylinder but any talk of mechanical advantage is pure uninformed gobbledygook.

[Greg Locock]

He's a rather frustrating bloke to talk to as he believes all sorts of weird stuff, while at the same time being happy to get external testing done.

[gruntguru]

The external testing does wonders for his credibility.

[Bloggsworth]

I seem to recall a two cylinder Trojan engine with a single "V" shaped connecting rod that worked both cylinders at the same time - Mind you, it was in the 50s or 60s that I last saw a drawing of it, so my memory may be faulty.

[Kelpiecross]

A nice feature of the aircraft cam engine with 2 lobes is the inbuilt speed reduction - each piston will reciprocate twice while the output shaft rotates only once. Aircraft engines usually need a reduction gearbox to run the prop at an efficient speed.

EDIT. The maths/geometry involved in making those rockers push and pull the pistons - with asymmetric cam lobes!!! Makes my head hurt.

Even a simple SOHC-with-rockers valve gear layout is very clever - the valve lift diagram is perfectly symmetrical but the cam profile is assymetrical to take into account the varying rocker ratio as the cam lobe moves across the surface of the end of the rocker.

The "Dynacam" engine with cylinders and pistons etc. parallel to the axis of the engine's rotation has a similar "half-speed" effect on the output. The promoters of the engine claim the engine has double the torque of a normal engine - another case where torque/power etc. gets a bit confused.

The Dynacam engine has been promoted at regular intervals from the 1940s up to the present day - there is plenty on the internet about it.

Edited by Kelpiecross, 02 May 2013 - 12:10.

[gruntguru]

Even a simple SOHC-with-rockers valve gear layout is very clever - the valve lift diagram is perfectly symmetrical but the cam profile is assymetrical to take into account the varying rocker ratio as the cam lobe moves across the surface of the end of the rocker.

What makes the aero cam-engine even trickier is its desmodromic - using the same lobe!