84 replies to this topic

[Magoo]

If you admire craftsmanship and ingenuity---and we know we do---you will get a kick out of this 7-cylinder radial engine built up from air-cooled VW parts. Check out the lathe and mill work. 

 

 

 

 

Video: Amazing 7-cylinder radial engine built from VW parts -- see it run! | Mac's Motor City Garage.com 

 

 

 

 

[gruntguru]

Amazing. I wouldn't be running it too fast or long before organising some lube to the valve gear! Actually I didn't see any lube system detail?

[Kelpiecross]

Very nice.

Here is another unusual (and much fiercer-sounding) radial.

[Magoo]

Amazing. I wouldn't be running it too fast or long before organising some lube to the valve gear! Actually I didn't see any lube system detail?

 

From the exhaust smoke it appears to be premix. Castrol, one hopes. 

[Wuzak]

Very nice.

Here is another unusual (and much fiercer-sounding) radial.

 

http://www.desertair...0cc-radial.html

Edited by Wuzak, 05 October 2014 - 00:17.

[gruntguru]

From the exhaust smoke it appears to be premix. Castrol, one hopes. 

No doubt the valve gear is "pre-squirt".

[manolis]

Hello.

Quote from http://www.pattakon....ttakonPatAT.htm


In comparison to the convetional Radial engine:



(master rod / articulated slave rods, click http://www.pattakon....atAT/Radial.exe to download
the controllable windows exe program / animation)

the Cross-Radial with the four cylinders and with the forked connecting rods is a true "vibration free" engine (better balanced than the "master-slave-rods" Radial regardless of the number of cylinders of the later), it is also a true "symmetrical" engine: all the four cylinders run under the same conditions: same piston stroke, same piston motion profile, same connecting rod leaning (thrust loads), etc.
As the Radial.exe at http://www.pattakon....atAT/Radial.exe demonstrates, a typical Radial (master rod / slave rods) cannot help running with substantially different piston strokes in different cylinders.


Did you ever think of such asymmetry?

When you run the abovementioned “windows-exe” visual-basic program spot on the significant difference among the master cylinder piston stroke and the piston strokes of the “side” cylinders; if you press the c key on the keyboard, the program shows the direction and strength of the inertia force resulting from the motion of the center of gravity of the set of all pistons: there is a noticeable (and variable) phase difference between the direction of the overall inertia force and the center of the crankpin as well as a variable amplitude of this inertia force, i.e. a radial - no matter how many cylinders it comprises - cannot be fully balanced without using additional “external” balancing shafts.

With the slide-bars at left –top you can chose the number of cylinders (from 1 to 35), the “con-rod to stroke ratio” (master-rod) and the eccentricity of the crank-side-pins of the slave rods.

Despite their asymmetry (think of trying to optimize an engine wherein some cylinders run at more than 5% longer piston stroke that others, and wherein different pistons follow substantially different motion profiles), the Radial engines dominated in the aviation because of their lightweightness and “packaging”.

By the way, take a look at the matter added recently to the Portable Flyer at http://www.pattakon....pattakonFly.htm

Thanks
Manolis Pattakos

Edited by manolis, 06 October 2014 - 04:10.

[gruntguru]

Very nice.

Here is another unusual (and much fiercer-sounding) radial.

 

Fabulous sound.

[Magoo]

Very nice.

Here is another unusual (and much fiercer-sounding) radial.

 

 

$5000 for a model airplane engine. I'm sure it's worth every penny, but $5000 for a model airplane engine. 

[Magoo]

No doubt the valve gear is "pre-squirt".

 

 

The story goes that someone asked W.O. Bentley how his rotary aero engine was lubricated. He looked at the man with a puzzled expression and said, "Try and stop it." 

[Lee Nicolle]

$5000 for a model airplane engine. I'm sure it's worth every penny, but $5000 for a model airplane engine. 

It is a BIG model aeroplane. So I guess big bucks for the components.

As for the VW7, VW used from memory the pushrods to feed oil to the top which then hopefully gets back down the pushrod tubes. So one would have thought that would work here too. There has to be a pressurised oil system somewhere to lube the crank and ancillaries.

I bet thye mixtures are all over the place too, a common plenum fed at all angles. Though equal lengths at least.

Edited by Lee Nicolle, 05 October 2014 - 22:31.

[Wuzak]

That was the original purpose of the centrifugal compressor in aero engines - to try to get even mixture distribution.

 

Looks like that engine would be similar to early radial engines if the oil supply to the valve gear is as you suggest Lee. That is, a total loss oil system.

[Lee Nicolle]

That was the original purpose of the centrifugal compressor in aero engines - to try to get even mixture distribution.

 

Looks like that engine would be similar to early radial engines if the oil supply to the valve gear is as you suggest Lee. That is, a total loss oil system.

VWs are fairly basic,,, but do have oil to the valve train and valve covers.

While an interesting concept it should be practical. With some work  I guess it could be. The very major work done to make a crankshaft and I guess control blades etc yet alone the making a 7cyl camshaft and distributor is over shadowed by the lack of valve covers and top end oiling

[NeilR]

yep, I saw the VW radial a while back. Impressive.

[Fat Boy]

Interesting enough, but they did kinda take the easy way out with poppet valves and all......I mean, make it a double row with sleeve valves a'la Bristol and *maybe* we can talk....

 

 

 

 

 

Just kidding. This thing is awesome. I wasn't suprised a bit to see that it came out of Holland. Those crazy Dutch are always tilting at windmills (pun fully intended).

[Wuzak]

VWs are fairly basic,,, but do have oil to the valve train and valve covers.

While an interesting concept it should be practical. With some work  I guess it could be. The very major work done to make a crankshaft and I guess control blades etc yet alone the making a 7cyl camshaft and distributor is over shadowed by the lack of valve covers and top end oiling

 

Here is the "camshaft" for the R-2800.

 

 

 

One track is for the exhausts and one for the inlets.

 

There is one cam ring for the front row and one for the back row. They had 4 lobes, and operated at an 8:1 reduction. 

 

Since he is using a one piece master rod, he must be using a two piece crank. I wonder how he has joined the two together.

Edited by Wuzak, 07 October 2014 - 08:06.

[Kelpiecross]

Very interesting stuff. My initial reaction was to wonder how 9 cylinders shared 4 lobes at 1/8 crank speed. In a radial the number of lobes is independent of the number of cylinders - one lobe at 1/2 crank speed is all that is needed for a 1, 3, 5, 7, or 9 cylinder radial. As for the 4 lobes - this must be an attempt to keep the surface speed of the cam and roller followers down to a acceptable figure.
You could actually build a conventional inline engine with a 2 lobe-1/4 speed cam (there has been a few of these)or like the radial a 4 lobe-1/8 speed cam.

Edited by Kelpiecross, 07 October 2014 - 11:24.

[Wuzak]

If you had one lobe that would mean it would activate the valves of every cylinder in sequence.

 

The firing order of a 9 cylinder radial being 1-3-5-7-9-2-4-6-8.

 

I am thinking that multiple lobes would help prevent the valves opening every revolution.

[Allan Lupton]

If you had one lobe that would mean it would activate the valves of every cylinder in sequence.

 

The firing order of a 9 cylinder radial being 1-3-5-7-9-2-4-6-8.

 

I am thinking that multiple lobes would help prevent the valves opening every revolution.

Quite right.

You need a number of lobes and a reduction ratio such that the next lobe opens the valve of the next cylinder but one in never-ending sequence.

[Magoo]

Yes, as Manolis et. al. have pointed out, radials have a number of interesting characteristics. The more you look, the more interesting they get. 

[Magoo]

Hello.

Quote from http://www.pattakon....ttakonPatAT.htm


In comparison to the convetional Radial engine:



(master rod / articulated slave rods, click http://www.pattakon....atAT/Radial.exe to download
the controllable windows exe program / animation)

the Cross-Radial with the four cylinders and with the forked connecting rods is a true "vibration free" engine (better balanced than the "master-slave-rods" Radial regardless of the number of cylinders of the later), it is also a true "symmetrical" engine: all the four cylinders run under the same conditions: same piston stroke, same piston motion profile, same connecting rod leaning (thrust loads), etc.
As the Radial.exe at http://www.pattakon....atAT/Radial.exe demonstrates, a typical Radial (master rod / slave rods) cannot help running with substantially different piston strokes in different cylinders.


Did you ever think of such asymmetry?

When you run the abovementioned “windows-exe” visual-basic program spot on the significant difference among the master cylinder piston stroke and the piston strokes of the “side” cylinders; if you press the c key on the keyboard, the program shows the direction and strength of the inertia force resulting from the motion of the center of gravity of the set of all pistons: there is a noticeable (and variable) phase difference between the direction of the overall inertia force and the center of the crankpin as well as a variable amplitude of this inertia force, i.e. a radial - no matter how many cylinders it comprises - cannot be fully balanced without using additional “external” balancing shafts.

With the slide-bars at left –top you can chose the number of cylinders (from 1 to 35), the “con-rod to stroke ratio” (master-rod) and the eccentricity of the crank-side-pins of the slave rods.

Despite their asymmetry (think of trying to optimize an engine wherein some cylinders run at more than 5% longer piston stroke that others, and wherein different pistons follow substantially different motion profiles), the Radial engines dominated in the aviation because of their lightweightness and “packaging”.

By the way, take a look at the matter added recently to the Portable Flyer at http://www.pattakon....pattakonFly.htm

Thanks
Manolis Pattakos

 

 

Thanks! A person could spend some hours fooling around with this. 

[Allan Lupton]

Yes, as Manolis et. al. have pointed out, radials have a number of interesting characteristics. The more you look, the more interesting they get. 

Yes, but he picked on the different strokes that result from the master/slave con-rod system. If that really bothers you, try the Systeme Canton-Unné as used in the Salmson radials!

 

Edited by Allan Lupton, 07 October 2014 - 16:47.

[gruntguru]

If you had one lobe that would mean it would activate the valves of every cylinder in sequence.

The firing order of a 9 cylinder radial being 1-3-5-7-9-2-4-6-8.

I am thinking that multiple lobes would help prevent the valves opening every revolution.

 

 

Quite right.

You need a number of lobes and a reduction ratio such that the next lobe opens the valve of the next cylinder but one in never-ending sequence.

The last piece of the puzzle is - the cam rotates in the opposite direction to the crank. We need Manolis to provide an animation!

[Wuzak]

The last piece of the puzzle is - the cam rotates in the opposite direction to the crank.

 

Thanks. I was trying to work out how the cam would work with lobes 90° and cylinders 40° apart, meaning that the next cylinder to activate is 80° away.

[Kelpiecross]

The last piece of the puzzle is - the cam rotates in the opposite direction to the crank. We need Manolis to provide an animation!

I certainly need a Manny animation - I still can't picture just how it works.

[Wuzak]

A 9 cylinder radial based on Honda XR600 cylinder barrels and heads, with overhead cams.

 

http://thekneeslider...-radial-engine/

 

http://thekneeslider...running-strong/

 

 

[manolis]

Hello.


Quote from the Internet:



the camshaft-disk rotates at 1/8 of the crankshaft speed, at opposite direction.


And here is a GIF animation from wikipedia:



the camshaft-disk rotates at 1/4 of the crankshaft speed at opposite direction.


A way to avoid the mind-boggling valve-train is to eliminate it:



The above animation shows a two-stroke cam-less even-firing Cross-Radial engine; it is as vibration free as the best V8, it has firing intervals equal to those of a V8 four-stroke, it has four-stroke-like lubrication (plain bearings, forced / splashed lubrication in the crankcase, oil scraper rings), it can utilize a central scavenging pump (a turbocharger, for instance), etc.



The above animation shows the moving parts of a Cross-Radial PatAT from various viewpoints. The connecting rods and the pistons are properly machined to provide wide bearing surface wherein the heavy loads are taken, keeping at the same time the piston bore low and the crankpin short. A single plane bearing (the yellow part around the crankpin) serves all the connecting rods "unconventionally" (it rotates inside their big ends, being secured to the crankpin).

Thanks
Manolis Pattakos

Edited by manolis, 08 October 2014 - 05:55.

[gruntguru]

The last piece of the puzzle is - the cam rotates in the opposite direction to the crank. We need Manolis to provide an animation!

Perhaps not the last piece.

 

The number of inlet (or exhaust) cam lobes must be equal to (number of cylinders - 1) / 2 so 4 for a 9 cylinder, 3 for a seven cylinder, 2 for a 5 cylinder and 1 for a 3 cylinder.

Camshaft speed of course needs to be engine speed / (2 x number of lobes).

[Allan Lupton]

Perhaps not the last piece.

 

The number of inlet (or exhaust) cam lobes must be equal to (number of cylinders - 1) / 2 so 4 for a 9 cylinder, 3 for a seven cylinder, 2 for a 5 cylinder and 1 for a 3 cylinder.

Camshaft speed of course needs to be engine speed / (2 x number of lobes).

Yes that's right - I thought that was a bit too technical for this threadn so did not detail it.

Also too technical are the reasons why, splendidly colourful as the animation is, one row of the four-cylinder two-stroke is not as balanced as is claimed and wouldn't work with just a turbo-supercharger. Mind you as there is no induction system shown . . .

[mariner]

Great thread, big piston radials are fascinating things.

 

My favourite radials are those WW! ones where the crank is fixed to the firewall and the whole cylinder assembly rotates i.e a rotary in those days. It helped cooling but made fuel distribution tricky. So the power control was largely by the ignition. As they fly a huge wasp type noise climbing, then as they dive total silence as the pilot cuts the mags. At the bottom of the dive he flicks the mag. switches on and HOPEFULLY the prop rotation fires it up.

 

You watch the demo. flight heart in mouth as the plane rushes towards the ground noiselessly praying it restarts.

[Lee Nicolle]

A 9 cylinder radial based on Honda XR600 cylinder barrels and heads, with overhead cams.

 

http://thekneeslider...-radial-engine/

 

http://thekneeslider...running-strong/

 

 

This one I like. It seems far more practical and complete.

Though I dont know as I would like to fly in a plane powered by it! Swamp boat maybe

LPG is different.

I think his brake cooling is a little much,, a decent washer pump misting water through the brake vanes should be enough.

And run under the Hills Hoist.

[Magoo]

If you keep your eyes open at garage sales, swap meets, Fleabay, and so on, you can find these old operator manuals on radial engines (and all kinds of combat equipment). Evidently, they printed plenty for the war effort.

 

These manuals are really quite excellent -- extremely straightforward and to the point, since they were meant to educate people with limited knowledge in a very short time. No frosting on it. Terse, in a word. Lots of illustrations and data charts and other info for rapid reference. 

 

 

 

 

[Allan Lupton]

How different, how very different, from the Bristol sleeve valve drive gear:

 

[Wuzak]

The Armstrong Siddeley Deerhound was a 3 row air-cooled radial. It had a differnt valve system - overhead cam..

 

 

[manolis]

Hello Allan Loupton.
You write:
“Also too technical are the reasons why, splendidly colourful as the animation is, one row of the four-cylinder two-stroke is not as balanced as is claimed and wouldn't work with just a turbo-supercharger. Mind you as there is no induction system shown . . .”

You can use the pattakon balance program at
http://www.pattakon....duc/balance.exe
to check and compare the vibration-free quality (or balancing) of the PatAT 2-stroke 4-cylinder single-row Cross-Radial with that of the best V-8 4-stroke.

But this Cross-Radial arrangement is so simple that you don’t need to run a program to compute the unbalanced inertia forces, torques and moments.

In the following I give a brief explanation:

Suppose the Cross-Radial is arranged like a cross.
Take the pair of the upper and lower pistons (1st pair), take also the pair of the two side pistons.
The center of gravity of the 1st pair is at the projection of the crankpin center on the perpendicular axis (if it helps: the two connecting rods form an isosceles triangle). The center of gravity of the 2nd pair is at the projection of the crankpin center onto the horizontal axis. The center of gravity of the two pairs is at the middle of the line interval from the crankshaft center to the crankpin center. By a pair of balance webs secured to the crankshaft (as in the animation), the total unbalanced inertia force is zero. The total unbalanced inertia moment is also zero (because everything is moving onto the same plane: the plane defined by the cylinder axes). As for the unbalanced inertia torque, the four pistons are disposed at 90 degrees from each other, just like the four pairs of pistons in the even firing V-8 4-stroke.
Do I miss something?


The PatAT Cross-Radial is not using the crankcase as the scavenging pump (see at http://www.pattakon....ttakonPatAT.htm the respective single cylinder animation). A single turbocharger for all the four cylinders is adequate (just like in the giant marine low-speed two stroke engines: a single turbocharger can feed all cylinders).

Please explain where you see the problem.

Thanks
Manolis Pattakos

[Magoo]

Great thread, big piston radials are fascinating things.

 

My favourite radials are those WW! ones where the crank is fixed to the firewall and the whole cylinder assembly rotates i.e a rotary in those days. It helped cooling but made fuel distribution tricky. So the power control was largely by the ignition. As they fly a huge wasp type noise climbing, then as they dive total silence as the pilot cuts the mags. At the bottom of the dive he flicks the mag. switches on and HOPEFULLY the prop rotation fires it up.

 

You watch the demo. flight heart in mouth as the plane rushes towards the ground noiselessly praying it restarts.

 

 

I love the radial rotaries as well. They are about the most enchanting piston engines ever devised. 

 

And while this might be a little hard to wrap one's brain around, the rotary was successful because it answered or avoided many of the issues that plagued IC piston engines of the era. It worked as well or better than anything else going at the time, which is worth a moment of contemplation. 

[gruntguru]

The PatAT Cross-Radial is not using the crankcase as the scavenging pump (see at http://www.pattakon....ttakonPatAT.htm the respective single cylinder animation). A single turbocharger for all the four cylinders is adequate (just like in the giant marine low-speed two stroke engines: a single turbocharger can feed all cylinders).

Please explain where you see the problem.

Thanks
Manolis Pattakos

Scavenging requires a positive pressure differential (inlet pressure > exhaust pressure) which will not exist under starting, transient and certain other conditions. One solution would be a motor/generator unit which would have the additional benefit of allowing efficiency gains via compounding. (Thought I should bring this thread back towards F1 )

[manolis]

Hello Gruntguru.

You write:
“Scavenging requires a positive pressure differential (inlet pressure > exhaust pressure) which will not exist under starting, transient and certain other conditions. One solution would be a motor/generator unit which would have the additional benefit of allowing efficiency gains via compounding. (Thought I should bring this thread back towards F1.”


Quote from http://www.pattakon....takonPatPOC.htm :

The lubrication, the scavenging (electrically controlled turbocharger), the injection, the combustion chamber etc of the OPOC engine fit to the PatPOC engine, as well.

End of Quote


Bill Gates with a couple of dozens of million of US dollars is among the famous investors of EcoMotors; their OPOC engine is based on such a turbo-compound system (an electric motor / generator coupled with the turbocharger).

This (turbocharger coupled with electric motor) is vital for variable revs / variable load applications (like automobiles, motorcycles, trucks etc).
But for aviation applications (wherein most of the time the engine runs at constant revs and constant load) a conventional turbocharger could be adequate.

Take the case wherein the Cross-Radial 4-cylinder PatAT is a direct injection Diesel engine.
Reasonably it starts and keeps idling even with a simple / conventional turbocharger.
The Diesel engine at idling runs on very lean mixture.



Even with tapped exhaust the engine can turn several (say 10?) times before the oxygen in the cylinders is completely “consumed”.
But the exhaust is not tapped.
And because the exhaust port opens first, the inevitable over-pressure into the cylinder (due to the combustion of the small quantity of injected fuel) pushes the air to the exhaust giving direction to the air motion.
During the “overlap” of the exhaust and transfer ports this motion continuous (there is no throttle valve in a Diesel).
After the BDC, when all ports are closed and the compression begins, a small part (say 20%) of the gas compressed during the last compression has been substituted by fresh air (it is like operating the engine at “heavy” internal exhaust recirculation). This way the engine keeps running.
Increasing progressively the revs, the turbocharger gets gradually into play providing the required pressure for the scavenging.

On the other hand, yes a motor/generator unit can be coupled with the turbocharger (as in the OPOC of EcoMotors).

Thanks
Manolis Pattakos

[Lee Nicolle]

How different, how very different, from the Bristol sleeve valve drive gear:

 

HELP !

[Kelpiecross]

Perhaps not the last piece.
 
The number of inlet (or exhaust) cam lobes must be equal to (number of cylinders - 1) / 2 so 4 for a 9 cylinder, 3 for a seven cylinder, 2 for a 5 cylinder and 1 for a 3 cylinder.
Camshaft speed of course needs to be engine speed / (2 x number of lobes).

This radial engine cam timing business is a bit trickier than I thought.

By working through the numbers given above for various types of radial engine I can see that it certainly does give the right answers - and it also shows why the cam ring must turn in the opposite direction to the crank. However I have to admit that I don't see why it works. It is not hard to see why the engine speed must be divided by the number of lobes times two - but if I wanted to get the desired firing order of moving two cylinders along each time it fires - I don't instantly think "Well, to get that firing order I need to take one away from the number of cylinders, halve that number and that will give me the number of lobes to use". Is there a simple way of looking at this to explain why it works?

Also, the more lobes that are used/the slower the cam speed means that the actual cam "lump" on the ring must be shorter to get the same duration.

[Kelpiecross]

I love the radial rotaries as well. They are about the most enchanting piston engines ever devised. 
 
And while this might be a little hard to wrap one's brain around, the rotary was successful because it answered or avoided many of the issues that plagued IC piston engines of the era. It worked as well or better than anything else going at the time, which is worth a moment of contemplation.

The rotary engine is also interesting in that, despite its resemblance to a radial engine it was a true "rotary" - the pistons described a circle and they didn't accelerate up and down as in a "normal" engine. Apparently the rotaries were notably smoother in their running than a similar-sized radial.

[Allan Lupton]

Thanks, Gruntguru, for explaining the turbocharger problem which I'd have done, had I not been elsewhere.

There is a language problem in the refutation of GG's point as a turbo-supercharger (colloquially turbocharger) is a device that uses a turbine to drive a compressor (and at start-up there is no exhaust for the turbine to extract energy from). What seems to be being described by Manolis is an electrically-driven supercharger, which can of course run before the engine rotates.

 

As for the balance of the four-cylinder unit on its own, I'd say that the normal effects of trying to balance reciprocating mass using rotating mass are not cancelled out, as they are with various conventional configurations of multi-cylinder engine.

[manolis]

Hello Alan Lupton

You write:
“As for the balance of the four-cylinder unit on its own, I'd say that the normal effects of trying to balance reciprocating mass using rotating mass are not cancelled out, as they are with various conventional configurations of multi-cylinder engine.”

Please be more specific.

Can you compare the best V-8 four-stroke you know with the Cross-Radial 4-cylinder PatAT in terms of unbalanced inertia forces, unbalanced inertia torques and unbalanced inertia moments?

Suppose they both have same pistons, same connecting rods, same stroke.

How much bigger, according your calculations, is the unbalanced inertia force of the Cross-Radial as compared to the unbalanced inertia force of the best V-8?
According my simple-minded analysis, the Cross Radial is better, but the V-8 is very good, too.

We can argue forever about how much beautiful (or ugly) the Radial-7 with the VW parts is, about the usefulness of such a project etc, but not for the balancing of an engine.
Because the balancing has to do only with maths and physics.

Do read at http://www.pattakon....attakonEduc.htm and learn to use the balance.exe program. It is a useful tool.


With a single scavenging pump serving all the four cylinders of the PatAT Cross-Radial, with four-stroke-like lubrication, with a vibration-free quality better than the best V-8 and with a top “power to weight” ratio, don’t you think it is a good alternative for small airplanes, paragliders, helicopters etc?

Thanks
Manolis Pattakos

[manolis]

Hello Kelpiecross.

The Radial_Cam.exe program at http://www.pattakon..../Radial_Cam.exe explains your questions about the valve train of the Radials.

The rotation of the cam-disk at the opposite to the crankshaft direction is not mandatory.

Depending on the rotation direction of the cam-disk, the number of lobes is different.

For instance, the Radial-11:



needs 6 intake lobes and 6 exhaust lobes in case the cam-disk rotates at the same direction with the crankshaft (the green polygon and circles); the same Radial-11 needs only 5 intake cam lobes and 5 exhaust cam lobes in case the cam disk rotates at the opposite to the crankshaft direction (the purple polygon and circles). The rotation speed of the cam-disk is lower in the first case.
Consider the circles as the points wherein the “intake/exhaust overlap” happens.

If you want to change the rhythm of the animation, click on the window and the move the mouse. To keep the selected rhythm, click once more.

Thanks
Manolis Pattakos

[Allan Lupton]

Sorry Manolis, but the "Pattagon" link gets to a site with no indication of its credentials and all that can be seen is a lot of unhelpful text - I expect it has animated displays if one knows how to trigger them.

I am too old to be impressed by that sort of thing, but also too old to have total recal of all the Theory of Machines lectures I heard in enough detail to reproduce them here.

 

Again we seem to have a language difficulty as I cannot see that a "scavenge pump" is relevant to "all the four cylinders" of your engine - it's the crankcase that has to be scavenged of oil which is part and parcel of the dry sump lubrication system you would have to have.

[gruntguru]

He means an air pump for 2 stroke cylinder scavenging.

[GreenMachine]

How different, how very different, from the Bristol sleeve valve drive gear:
 

I think one of those is out by one tooth ....

[gruntguru]

Well spotted G.M.

[Kelpiecross]

Thank you Manolis - my computer refuses to let me watch the animation.

I see your point about 5 and 6 lobe cams. I can see how the various cam timing schemes can be worked out on paper by empirical (if that is the word) or trial-and-error methods but not by intuition (again - if that is the correct word). Maybe there is no "intuitive" method and the cam timing schemes were originally just trial-and-error on paper.

Edited by Kelpiecross, 10 October 2014 - 04:05.

[manolis]

Hello Allan Lupton

You write:
“Sorry Manolis, but the "Pattagon" link gets to a site with no indication of its credentials and all that can be seen is a lot of unhelpful text - I expect it has animated displays if one knows how to trigger them.”

At the bottom of the Home Page of the pattakon web site at http://www.pattakon.com, the SiteLock company (the global leader in web site security, as they claim) verifies (http://www.pattakon.com/index.html# ) that the pattakon.com web site has been scanned and is malware-free.


You write:
“I am too old to be impressed by that sort of thing, but also too old to have total recal of all the Theory of Machines lectures I heard in enough detail to reproduce them here.”

While I cannot get the reasoning behind rejecting an idea so easily, the above is OK with me.
On the other hand you can consider the possibility a so simple engine (the Cross-Radial 4-cylinder PatAT) to be better balanced and way more “symmetrical internally” than engines like the Bristol Hercules (14 cylinders in two rows) and the Bristol Centaurus (18 cylinders in two rows).

Internal asymmetry?
Suppose you want to use direct injection in these Bristol Radials. The quantity of fuel injected in the master-rod cylinder should be some 5% fewer than the quantity of fuel injected in the “side” cylinders, otherwise other cylinders will run lean and others rich!


You write:
“Again we seem to have a language difficulty as I cannot see that a "scavenge pump" is relevant to "all the four cylinders" of your engine - it's the crankcase that has to be scavenged of oil which is part and parcel of the dry sump lubrication system you would have to have.”

Consider this:



giant marine low-speed two-stroke (as shown at http://www.pattakon....takonPatMar.htm ) which, just like the Cross-Radial 4-cylinder PatAT, uses conventional crankcase lubrication. Several cylinders use the same turbocharger for the scavenging. This is so because the space underneath the piston crown – just like in the case of the PatAT Cross-Radial – is sealed from the crankcase.
So, please forget how the typical two-strokes work (crankcase scavenging) and look again at the PatAT Cross-Radial.

Thanks
Manolis Pattakos