BRITISH ANZANI INFLUENCED THESE RACE ENGINES BEING BUILT

[se7en]

The loop scavenge engines big advantage is down to its transfer ports,numbering anything from 2 to 5 the crescent 500 cs had 3,and my Yamato has 3, the postion of them is the trick , they are set up so as to make the incoming charge fill the bore and force the burnt charge out, but not to loose to much of the fresh charge down the open exhaust port, also they generally have flat top or shallow dome top pistons, these alone will help the engine rev as they are much much lighter than deflecter type pistons,deflecter type/cross flow engines will give more torque at low to medium revs, but at high revs, about 6000, the weight of the piston will start to put a lot of strain on the reciprecating mass, and the deflecter shape becomes inefficient, most of the high performance 2 strokes of the last 40 or so years have all been loop scavenge, in motor cycles, karts, and hi performance outboards, even the saab cars of the late 1950s and earley 60s that used to do well in rallying were loopers, there are all sorts of induction systems some have disc valves, some have schnell porting, some have reed valves, but the secret is in the positioning of the transfer ports, to maximise the fresh charge, fill the combustion chamber and burn as much of the charge as possible,and get the exhaust out quickley, this puts the BMEP up, so that in turn put the BHP up, there is of course a little more to it than that , but thats the basic difference.

Clive

[Rapier]

Clive, the loopers that I hear most about are the OMCs of the mid 70's, particularly the Stingers, but was the 55 Evinrude Triumph the first successful commercial one, or were there others?

[se7en]

Yes , in the OMC range the Evinrude 55 triumph/Johnson 55 sea horse where there first loopers, however, in europe some of the outboard manufacturers had been building loop scavenge motors for some time, not only there race models but there "fishing" motors, in Sweden, the Electrolux Penta,later to become a much improved Crescent ( later to be badged ,Monark, Archimedes-Penta, Volvo-penta,etc,)had been building loopers since the late 1940s, the most well known and sort after model being the Crescent 500 cs hydroplane motor built in small batches between 1964-1971 I started working for Crescent towards the tail end of that motors life, it really is a cracking motor, we have put that power head in racing motor cycles !!
Other manufactures that built motors using loop scavenge include Carnetti and Selva in italy and Tomos in Yugoslavia, loop scavenge was very popular in europe with foward thinking designers for many years, but no body made much of a fuss about it untill OMC started to use it in 1969, then , most of the boating public thought they had invented something new !!

Clive

[SpiritOfSelkirk]

Well, now I have finally read the European perspective of loop scavenging that most don't like the idea of being uttered in North America. For them even having Anzanis lead the way here in outboard racing by the later 1950s was something hard to swallow south of the border for quite a few but cetainly not Bill Tenney! Between Tenney and Harrison (HRP) with the class A and B Anzani loop engines they terrorized anything in their class and right to the 6 cylinder 1,000cc deflector-crossflow engines. It was out of mind that one Anzani 322cc class B was running 88 miles per hour in 1958 with a whole host of other engines doing middle 80 mile per hour ranges right behind it. Where I am from here in Canada NOA Alky races would see dozens of Anzanis in class A and B requiring elimination heats of 12 raceboats to qualify for a 12 boat 2 heat final on the Sunday. Not until the Quincy Flatheads coming out in the middle 1960s was any serious challenge mounted to Anzani where Quincy more inherited with Anzani going out of production than having beat them out and then Konig changing to loop engines almost the same time too as Quincy that superceded Quincy Flathead loop engines. Crescent engines as Alkys or Gassers here were always few but those that worked with them successfuly in class Super C gas or class C - 500 Alky really made a show of an engine that made little noise but could sure go.

I am looking for some suitable graffix to illustrate loop versus deflector-crossflow technologies suitable for posting here shortly but the does not stop from anyone having something illustrative from sure entering that here. Please do.

The following is a picture of a Quincy Flathead 60 cubic inch (1,000cc) Loop engine crafted by USA builder Dick Olthoff who changed its manufacture from aluminum castings to machined from billet aluminum blocks and crankcases. Horsepower is about 200+HP at 9,000rpm. More still for the 66 and 99 cubic inch versions there were few of. This is the kind of engine that has never seen a full throttle all out straightaway runs in kilo trials to see just how fast it could actually go in speed flatout and held. Speculation is somewhere about 155mph. On closed courses the engine would twist and at times break raceboats framing etc. they were run on just from their sheer power and torque. This engine fires 12 with exhaust ports opening every revolution (60 degrees of firing) giving the motor world records for sound production nothing has challenged since. The crankshaft and rods as with all Quincy Flatheads are Mercury Mark75 or Mark78 for the 6 cylinder Flatheads and on down still Mercury cranks and other components down to 4 and then 2 cylinder Flathead engines. Early on Quincy loop technologies had no effect on Mercury even though well known to Merc, Quincy did use Mercury internals and some external peripheral components as well, who stayed with deflector technology longer than OMC did making some real lemons in the process that did not do the Mercury name any good where OMC went loop and went ahead years earlier than Merc did.

Enjoy the picture.

[SpiritOfSelkirk]

For the next post of a different engine with something familiar is the Parker Loop engine by Bud Parker who also made aftermarket parts like exhausts systems for other engines like the earlier Mercury padded block by Quincy Alky Deflector-Crossflow engines (from the mid 1950s onward) as well as their Modified gasser versions highly regarded in Modified classes still today.

The Parker Looper though looking like a Quincy Flathead and using innards of Mercury like them too was a departure from you would expect though the engines look so similar. The Parker had different porting systems and the head used belled combustion chambers instead of a Quincy Flathead with offset combustion chambers similar to Anzani. As an Alky the Parker Loopers were much fewer and less successful than their Quincy counterparts. Both Quincy and Parker used split window dual exhaust ports per cylinder which kept them on open megaphone pipe systems where engines that had a single or split window single exhaust ports per cylinder to one pipe adopted expansion chamber exhausts systems and their supercharger like characteristics like Konig, Yamato and others that soon eclipsed Quincy and went on to set records themselves as the 1970s, 80s on onward progressed.

Enjoy your view of the Parker Looper.

[SpiritOfSelkirk]

This engine is interesting as it is the techologies Konig changed from. This was the typical Konig Deflector-Crossflow technologies had to leave behind for Loop technologies and then adding evolving Expansion Chamber exhaust technologies to become the success engine of the 1970s and later effectively challenging Quincy Flatheads with their open pipes for Alky classes supremecy in North American racing.

In this case these early Konigs used a variety of tried exhausts some weird, wonderful and evolutionary. Featured on this class A (15 cubic inch or 250cc) engine it is sporting Quincy Welding exhausts typically used on 2, 4 and 6 cylinder Mercs where 2 elbos are coupled to one giving about a 15% rise in horsepower over the factory block figure. Other exhausts seen on these early Konigs were single megaphone pipes 1 per cylinder as well as pipes as long as the type you would see as airhorns on highway heavy hauling tractors (trucks). Needless to say Konig soon found that Deflector technologies were a evolutionary dead end for them they had to leave or would fail in surviving the outboard racing game.

Enjoy the picture.

[SpiritOfSelkirk]

The TWO STROKE internal combustion engine differs from the more common four-stroke engine by completing the same (thermodynamic) cycle in only two strokes of the piston, rather than four. This is accomplished by using the beginning of the compression stroke and the end of the combustion stroke to simultaneously perform the intake and exhaust functions, which is called scavenging. This allows a power stroke for every revolution of the crank, instead of every second revolution as in a four-stroke engine. For this reason, two-stroke engines provide high specific power, so they are valued for use in portable, lightweight applications such as chainsaws as well as large-scale industrial applications like locomotives.

DEFLECTOR OR Crossflow-scavenged (MERCURY OUTBOARDS SINCE CIRCA 1950 ONWARD WENT LOOP IN THE 1980s, OMC went loop earlier than Merc)
In a crossflow engine the transfer ports and exhaust ports are on opposite sides of the cylinder and a deflector on the top of the piston directs the fresh intake charge into the upper part of the cylinder pushing the residual exhaust gas down the other side of the deflector and out of the exhaust port. The deflector increases piston's weight and its exposed surface area, and also makes it difficult to achieve an efficient combustion chamber shape. This design has been largely superseded by loop scavenging method (below), although for smaller or slower engines the crossflow-scavenged design can be an acceptable approach.

LOOP-scavenged - Schneurle porting (ANZANI, CRESCENT, QUINCY FLATHEAD (later) KONIG, HARRISON, (later) OMC, YAMATO, PARKER, ROSSI, KONNY etc.)
This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel air mixture strikes the cylinder head then follows the curvature of the combustion chamber then is deflected downward. This not only prevents the fuel/air mixture travelling directly out the exhaust port but creates a swirling turbulence which improves combustion efficiency, power and economy. Usually a piston deflector is not required, so this approach has a distinct advantage over the cross flow scheme (above). Often referred to as "Schnuerle" (or "Schnürl") loop scavenging after the German inventor of an early form in the mid 1920s, it became widely adopted in that country during the 1930s and spread further afield after World War II. Loop scavenging is the most common type of fuel/air mixture transfer used on modern two stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop scavenged two stroke engines. This operational feature was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ and Walter Kaaden. Loop scavenging, disc valves and expansion chambers worked in a highly coordinated way that saw a significant increase in the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha and Kawasaki. Suzuki and Yamaha enjoyed success in grand Prix motorcycle racing in the 1960's due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was that the piston could be made nearly flat or slightly dome shaped. This enabled the piston to be appreciably lighter and stronger and consequently tolerated higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes and compression losses.

[SpiritOfSelkirk]

FOLLOW THIS LINK TO AN ANIMATION OF A LOOP CHARGED 2 STROKE ENGINE ON YOUR INTERNET BROWSER.

http://www.vf750fd.com/blurbs/stroke.html

FOLLOW THIS LINK TO A STATIONARY COMPARISSON BETWEEN CROSSFLOW AND LOOP CHARGE TECHNOLOGIES.

http://www.maxrules.com/fixtheory2.html

FOLLOW THIS LINK TO WIKIPEDIA INTERNET ENCYLOPEDIA FOR ALL THE DIFFERENT VERSIONS AND COMBINATIONS OF TWO STROKE COMBINATIONS.

http://en.wikipedia.org/wiki/Two-stroke_engine

THE FOLLOWING IS A GOOGLE DATABASE OF GRAFFICAL VARIATIONS OF 2 STROKE ENGINES.

http://images.google.ca/images?hl=en&q= ... 4&ct=title

Enjoy all the animations and still graffix.

[twister]

In my dim & distant past I used to race karts, which in my class used (maybe still do for all I know) the old Villiers 9E motorbike engine. That was designed in something like 1948, and was loop scavenged ('loop charged' in the US). As a complete aside, my one and only claim to fame was that in 1973 I raced against a Mr Nigel Mansell in the British Championship at Cadwell Park... So it's not a new technology.

The important thing to remember is that, in a 2-stroke engine, fresh gas is incoming at the same time that exhaust gas is outgoing, while the piston is around BDC. This has to be managed somehow.

A deflector engine has just one transfer port, directly opposite the exhaust port. To stop the incoming gas going straight down the exhaust, the piston has a deflector (ie shaped) top, which directs the incoming gas upwards towards the combustion chamber while the exhaust gas flows down & out through the exhaust port.

The problem with a deflector on the piston is that you can't then optimise the shape of the combustion chamber in the head, and also compression ratio is limited. The combustion chamber ideally needs to be a sort of hemispherical bowl with a flattened bit (known as the 'squish band') around the periphery, kind of a flying saucer shape.

So Charles Harrison and others realised that, if you could get the gas flow to work with an almost flat topped piston, the engine could have a more efficient combustion chamber. The solution was to use a pair of transfer ports, one either side of the piston, facing inwards and backwards, away from the exhaust port. The incoming gas then went around the 'back' of the bore, looped round & up, filling the combustion chamber while driving the burnt gas out of the exhaust port - hence 'loop scavenging'.

Many US stock outboard designers hung on to crossflow technology for many years, while most others had moved to loop scavenging.

Later loop designs had 3 transfer ports, one opposite the exhaust, which worked together to achieve the necessary flow, and allowed the combustion chamber bowl to be off-centre, so improving mixing of charge and efficiency.

One of these days I'll have to pull apart and photograph the porting of my 1960s works-built Anzani 250 which holds the current UK record. I forget how many transfer ports there are, probably 5 or 6 - they're all over the place! CMBA members might like to know that a certain Mr John Tassell was involved in building this motor...

Hope this gives some explanation.

[SpiritOfSelkirk]

Twister brought the loop story so much further back it is still hard to comprehend what was spawned in the 1930s that took the 1950s to really have it take off like some racehorse as the Anzanis did in North America in the later 1950s that really shook up racing. Indeed many companies looked to racing grounds to prove durability and reliability to the public for the consumer goods engines that came out with improvement after improvement as part of that tide. For me it was having that front row seat at the races as a young pitman doing bull work in the water launching and retrieving raceboats so many Anzani powered ones, crowds so impressed with Anzanis got to their feet for every race they had to get the good view.

When it came to carburetting, porting intake and exhausts to produce maximum power was taken to extremes with Alky racing in North America. In particular in the hands of Ron Anderson and Jim Hallum both from USA's Region 10. ports for these engines quite conservative for stock racing for gasoline use went BIG! Methanol on the other hand compared to gasoline produced dramatically more power but uses twice the amount of fuel in the air-fuel mix the engines inlets, intake and exhausts ports need to be dramatically larger to transfer the properties of the 140 octane fuel to the volumes required or extreme racing use. It also that needs higher compressions to release methanol's dramatic properties to where compression ratios of Anzanis went to 14 to 1 to handle it all and they did. Inlets and ports twice normal size became quite normal to this racing scene.

Anderson and Hallum too experimented with puff or boost ports added to piston skirts above the main skirt window to give the engine on last shot of intake supercharging before the mixture was fully compressed for firing bringing on the power stroke down. "Finger porting of cylinder wall porting" as Twister described as having happened in UK aparently never happened in North America. Not until makers like OMC and Mercury got into Loop engine powered larger OPC tunnel boat with multi-litre displacement V-6 engines were those ever seen quite later in the game. This rear port opposite the exhaust port produced a vacum cleaning effect that both pushed and dragged the spent air-fuel out of the cylinder making for a better charge increasing power output as a result successfuly improving the engine moreso just as Twister dexcribed.

Twister described an intake transfer in cylinder port appearing opposite the exhaust port in addition to the side transfer ports that originally produced the loop engine. Between the three intake transfer ports they would flood out the spent charge with an improved loop charge from 3 directions towards the exhaust port not seen before that worked. In North America, Bill Tenney saw the need of extra transfer ports too but he did his additions from underneath the exhaust port where he added two more intake transfer ports also produced a 3 way directional flood of air-fuel and even more so pushed the spent exhaust out blowing more air-fuel upward in a loop with the other 4 ports making the Anzani a 6 port tranfer intalke port systen where dyno readings went off the scale. Six port Anzani 322cc engines were producing some 500 horsepower per litre albiet unreliably breaking many parts in the process. Very few of these 6 intake transfer port engines ever hit the race courses before Anzani stopped producing the engine effectively shortening its further accomplishments on midWestern race courses by 1967. Neither Hallum nor Anderson ever went that route and indeed it was only in these recent times they came to know that such Anzanis with these improvements ever existed. Still, it was their Northwestern Region 10 racers and developers who kept on going years later still setting speed records 3 years after Anzani was in steep decline in racing completely in the rest of Canada and the USA but not there in Region 10 where records kept falling until other engines arrived to take over where they the Anzanis left off.