supercharged V12 2 stroke

Hi Dean, Hope you are feeling more comfortable now.

John

Thanks guys, yes i am feeling much perkier now. Sometimes life throws you a bit of a curve ball, good thing i have an excellent catcher looking after me.

dean

Glad you're ok Dean

Coming in late, have to say that I am staggered by the quantity and quality , not to mention rapidity, of the work!

Firstly, a distinction has to be drawn between two stroke engines which are Loop Scavenged, Opposed Piston, or Uniflow. All use different methods of controlling Induction and Exhaust events.

Having spent a lifetime in diesel engine production and development, I disagree with those who say that a two stroke cannot be pressure charged. And there are numerous practical examples to back that view.

General Motors Electro Motive Division have made MANY turbocharged two stroke engines to power locomotives. The EMD engines were, and are, Uniflow engines, with Inlet ports low down in the cylinder, and Exhaust valves located in the cylinder head.

The diesel engine is an ideal candidate for pressure scavenging, in that, unlike a carburetted petrol engine, no fuel is introduced, and therefore lost, during the scavenging part of the cycle.

As already mentioned, currently, the largest and most powerful two stroke diesel engines are the those made for the "Emma Maersk" and her sister container ship. These enormous engines are turbocharged and charge cooled and deliver 108,000 h.p. at about 102 rpm.

The GM V71 and V92 engines were blower scavenged, uniflow, naturally aspirated engines.

Each cylinder had an injection pump and injector, operated by a third rocker lever, between those operating the valves. Fuel delivery was by a control rod acting on each element, connected to the adjacent cylinder by a connecting linkage, which, in turn was connected to the governor.

If air is forced into the Induction side of any engine, after the exhaust ports are closed, even in a loop scavenged engine, cylinder pressure must rise above atmospheric.

Many two strokes were blower scavenged. The Commer TS3 was one. It was an opposed piston engine using one crankshaft located beneath the cylinders, and operating both pistons in each cylinder by means of large rocker levers. The Roots blower was purely for scavenging.

In this context, it is coincidental that Commer were part of the Rootes Group. The Roots type supercharger was invented long before that amalgamation took place. The "TS" indicates that the engines were made in the Tilling Stevens (again, part of the Rootes group organisation), factory in Maidenhead. If the exhaust ports became obstructed by carbon, the boost pressure gauge reading would increase.

The Foden 4 and 6 cylinder engines were Roots blower scavenged In Line engines, used in vehicle, industrial and marine applications. As an experimental unit, Fodens added an exhaust driven turbocharger, and obtained 200 hp from a 4 cylinder, 4 Litre diesel engine, at about 2500 rpm.

For its day, 50 bhp/Litre was quite impressive. Iin contrast, the contemporary Rolls Royce C Range 4 stroke, (2 Litres/cylinder) in Turbocharged and Charge Cooled form were delivering 25 bhp/Litre at 2100 rpm.

The two stroke has an advantage in that every cylinder has a power stroke every revolution, whereas a four stroke has one on alternate revolutions.

Despite this, the pressure charged two stroke is poor on torque back up, and tends to be better suited to more or less constant speed applications, such as marine or locomotive, rather than vehicle.

The Fairbanks Morse, Napier Deltic, Rolls Royce K Range, and Leyland L10 engines were all opposed piston two stroke diesels. The Deltic had three banks of six cylinders, operating three crankshafts, which were interconnected by a geartrain at the front of each bank.

Opposed piston engines use a difference in piston phasing to control port openings for induction and exhaust.

An early opposed piston two stroke petrol engine was the Trojan. Post WW2, Sachs made opposed piston two stroke engines for motorcycles. The engines were made compact by "folding" the cylinder, so that the Inlet port controlling piston ran in a bore which was nearly parallel to that of the Exhaust port controlling piston. The combustion space was at the intersection of the two bores.

The Rolls Royce K Range and Leyland L10 , as primarily military engines, were intended to run on whatever fuels were immediately available, by changing compression ratio and port timings. To do this, the phasing of the upper and lower crankshafts was altered by changing the relationship of the gears in the train connecting the two crankshafts.

So, armed with the confidence of your superb work so far, carry on, and be assured that you CAN pressure charge your engine! For aircraft use it will be great,since the torque requirement will decrease very rapidly as the speed falls. (German aircraft used supercharged two stroke diesel engines during WW2)

Howard

Thanks for the info and encouragement, must confess the latest health drama has taken a bit more of a toll on me than I cared to admit. I find it difficult to keep moving, just not so much energy back yet. Will be a little bit before anything happens again I think but hopefully not to long before progress is restored to the shed and consequently the v12 build. Till then I'm resting up.

cheers

Dean

Wishing you the speediest possible recovery, Dean.

Best Wishes

MichaelG.

Well back again everyone, well rested but still in recovery mode. have the shed cleaned up a bit and am now setting up to machine the supercharger rotor vanes and slots. will update photos when done.

Dean

Well it's been awhile i know but I been kinda busy, but i finally found a roundtooit for this V12 project. Been working on the supercharger recently and have just finished machining the rotor vane slots into the rotor, took a bit of fiddling around to setup but got there in the end. All that's left to do now is polish the vane slots to allow a slippery slippery fit of the phenolic vanes.

here's some update photo's

Hope to have it all done in the next few days or so...............................................hopefully lol

Dean

Hi Howard

The crank case is shared by all the cylinders in this design, so there is no possibility of using crankcase scavenging to charge the cylinder, as is common in small (<1 litre) 2-stroke engines. And there is little chance of accommodating 12 tuned exhaust systems to achieve the exhaust scavenging that is seen on a normal bike engine for instance. Without assistance, it's not going to be possible to get mixture into the cylinders.

Most of the large diesels mentioned have defined, mechanical exhaust (and inlet) valve arrangements, whether poppet valves (like most marine and rail diesels) or sleeves (opposed piston engines) or ports (for the inlets). However, the volumetric efficiency of a large marine diesel without a blower of some form would be pretty miserable. The thermodynamic efficiency of a diesel engine (and gasoline) is improved by supercharging and unlike a gasoline engine, there is no issue with detonation which limits the compression ratio and ultimately the maximum cylinder size of gasoline engines.

Whether you call it scavenging, charging, supercharging, blowing or whatever, this fine little engine will need some form of positive charging if it is ever to fire up. It's a pragmatic and sensible realisation. Besides, it gives us armchair experts something to pontificate about!

I'm fascinated by Dean's incredible work here. I couldn't achieve anything in the same class as this and I'm marveling at the progress. Keep it up Dean - hope your health doesn't keep you out of the workshop too much! Looking forward to each update and hopefully some engine noises soon.

Merry

An excellent sumary of 2 stroke engines by Howard, as used in industrial, automotive and marine applications.

Just a quick note (as an ex-Leyland test engineer), the Leyland engine was designated L60. It was developed primarily for use in battle tanks. The L10 was a more recent Cummins truck engine of 10 litres, a conventional 4 stroke and nothing to do with Leyland.

Dean, always look forward to seeing the latest update on this amazing build.

Regards, Mick

OK soooo....................... I managed to find a few more roundtoits and have finished fitting the super charger rotor vanes to the rotor. They all have a nice and free sliding fit and good end clearance, made all the gaskets for the two end covers and the manifolds. Below are some photos showing the finished blower assembly fitted to the rest of the engine.

This photo is a view down the carb intake hole and shows the vane in the slot. Once I got the whole assembly together I couldn't resist trying the supercharger out to see how much blow it would give. I hooked up the starter motor to it and there was a very definate blowing of the air coming out through the sump holes in the bottom of the block!!!!!!!!!! Fantastic I would say!!! Quite a loud noise from the blower so I think it might have a very interesting sound when its running.

So the next step in the construction is the finishing of the liners. I have started lapping these using the same technique that Ramon describes in his ETA build thread. I have used this system before when i made the V8 (here's a link to the youtube video of the v8 being hand started for anyone interested. https://www.youtube.com/watch?v=Np7zvGrc3U0 )

The liners are firstly honed and then lapped with 14 micron diamond paste, then cleaned. When they are all at this stage the lap is then cleaned and reloaded with 0.5 micron diamond paste and all the liners are then brought up to a mirror finish before fitting the pistons to each individual liner making up 12 matched piston liner assemblies.

Here's a couple of photos of the start of the lapping process.

Hope this keeps the interest satisfied for a few more days, hopefully i will be able to finish the lapping of all the liners in the next couple of days, untill then.......................................................................

Cheers

dean

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Dean,

I have "quoted" your first two photos of this amazing thread, as a qick reminder of how it started.

Thank You for sharing your journey.

Beyond that: Words fail me.

MichaelG.

Thanks for the kind words, It has been a very long road for me and somewhat longer than i expected but the end is in sight.

cheers

dean

Can't wait to hear this fire into life!

Excellent work, Dean!

Well, hope you guys n gals all had a very merry christmas and sante brought you all the hoped for goodies? Here's wishing you all a very happy new year with plenty of shed time and productivity with all the new toys you got for xmas...................

Cheers

Dean

Hi all, once again sorry for the tragically long time between updates, pressures of life and all that drama, but never mind I have managed to find a small bit of shed time and I have taken a break from the unimaginablely boring task of lapping 12 cylinder liners to save my sanity and have gotten on with the four carbs. I have finished machining the bodies and throttle barrels, fuel jets and fuel delivery rail. Photos below show the progress to date

Well thats all for now, hopefully i'll find a few more roundtuits and get the rest finished soonish LOL

Cheers for now

Dean

Was wondering how you were just the other day Dean. Keep on trucking.

OK So it's kind of a miracle I know but here is the next little bit achieved on the V12 build. I have managed to get the throttle levers built and ready to fit to the throttle barrels, then onto the throttle linkage system. Here are some photos for you.........

Hopefully I'll be able to get a bit more done this weekend

Cheers for now

Dean

Well progress has been somewhat slower than I had hoped and plagued with a few problems, but I guess if it was easy everyone would be doing right? I have managed to get the four carbs finished and the throttle linkage assembled but not without some frustrations photos below show some of them

So those of you with a keen eye will probably notice the overtly shorter fuel jet in the top fuel rail, This was the first rail I made and it had been threaded internally for a threaded needle assembly, This proved to be a mistake as there wasn't enough meat in the wall thickness and the one became two!!!! bugger!!! Hence the second fuel rail redesigned for a needle carrier and not a threaded needle. Oh well live and learn I guess.

This photo shows the new rail and the levers fitted to the barrels before being cleaned up.

This photo shows the replacement fuel rail being test fitted, Who can see a small problem here i wonder?!!!!

So here we have the finished article and although it hopefully looks all good there is a rather annoying large problem I discovered upon trying the throttle travel movement................... as in it doesn't................ move that is........................ BUGGER!!!!!!!!!! I found the reason after looking at the photos. There is a slight difference in the height of the the fuel jet base after being soldered together. This meant that when the nuts were done up and the preload set it pulled the jets out of true inside the barrel, thus causing the barrel to bind in the carb body. I am looking at how to fix this at the moment probably just separate the jets and use silicone fuel tube in between each jet. below is a couple of photos showing idle and wide open throttle postions.

Thats all folks will call again later

cheers

Dean