Oddball engines and prototypes

[ceci]

3 cylinder turbo charged Suzuki Swift (and it was swift it accelerated like you wouldn't believe!)

That is what makes me regret now that I know those engines.
If manufacturers were interested, they will look for where to find the solution to the 2S problem

[lohring]

When internal combustion engines were still at the forefront of mobile power plants, turbo and super charged two strokes were seriously considered. See the Rolls Royce Crecy and Napier Nomad. Since then two strokes still dominate large two stroke diesels and small, low cost power plants. The small IC power plant market is slowly being replaced by electric motors as batteries get smaller and lower cost. Two stroke simplicity and durability is what stands out in both these categories.

Lohring Miller

[WilDun]

When internal combustion engines were still at the forefront of mobile power plants, turbo and super charged two strokes were seriously considered. See the Rolls Royce Crecy and Napier Nomad. Since then two strokes still dominate large two stroke diesels and small, low cost power plants. The small IC power plant market is slowly being replaced by electric motors as batteries get smaller and lower cost. Two stroke simplicity and durability is what stands out in both these categories.

Lohring Miller

Good points Lohring! ..... and as you seem to be suggesting it could be used in the hybrid scene - probably as a constant speed generator engine. However, I don't think the piston ported two stroke supports long piston/cylinder life (but it sure worked well in the racing scene!).
All throughout the "high performance two stroke" era, piston ports were the norm with only the large diesel two strokes having poppet valves (the odd one having sleeve valves as in the RR Crecy) - the poppet valve has been maligned all through its very long existence, yet it has survived -

However, the racing scene did not represent the whole world's needs and the whole world's opinion is really what matters! - the two stroke's reputation has been tarnished through not focusing on exhaust emissions/perceived emissions and also by focusing on racing and forgetting the millions of commuter and tourist bikes and riders.

As a consequence of the (real and perceived) two stroke pollution in this area, the racing scene and increasingly the commuter scene is now dominated by four strokes and the racing machinery looks like the everyday motorcycle - this fits in well with the riders of commuter motorcycles - good for sales!

Before someone comes up with with the remark that the poppet valve is not good in the emission department either - yes that is also true but what a compromise it has been! - and after all, it only produces unseen pollution!

BTW Daryl,
I still have to look at your post thoroughly - and I need to add that I'm no expert (it just looks like I think I am!!) but at least I'm very interested - even if engineering maths (except the simple high school and workshop stuff) escapes me!

[Pursang]

OK, technically it's called a 'reverse' uni flow.

(Although it doesn't reverse and it still flows in one direction!)

Clever Idea, that has been formally tested years ago by Fuji Heavy Industries and Chiba University.

For those that don't know, Fuji is Subaru, which is 16% owned by Toyota, who has a 5% stake in Yamaha.



So Will, your theory is proven! Here are a some of the most profitable motor companies in the world,
with proof of the superiority of this engine and they are sitting on their thumbs...


No cheers for this one, Daryl.

[WilDun]

EFI will probably take me far too long to conquer, maybe i would just use LPG, triggered at exhaust closing position.

Cheers, Daryl.

Daryl,
You don't need to conquer EFI for two strokes, it has already been conquered right here, by Neil - the average guy didn't really pay much attention, but big companies did - and when they take an interest, then it must be ok!

So Will, your theory is proven! Here are a some of the most profitable motor companies in the world,
with proof of the superiority of this engine and they are sitting on their thumbs...
Daryl.

As I have said many times, everything is governed by fashion, not engineering excellence! - but I'm sure they are thinking "lets just sit on it and then be the first to react when fashion changes"!

[Muciek]

Rotary slide Jawa enduro .

[WilDun]

Rotary slide Jawa enduro .

Rotary slide Jawa enduro .

Very interesting - brilliant in fact!
It looks like it may have been around in the seventies, ie in the days when I was young - I can't understand how I could have missed it (but I obviously did!).
That layout does make it a very tidy arrangement -I wonder why it wasn't successful -

Probably better than a reed valve, but possibly not better than a rotary valve, ie from the point of view of it being more difficult to change the symmetry of the timing. There is some asymmetry there (judging by the relationship of the rod to the path of the sliding plate), but I feel that it would have been much more difficult to change the timing than with a rotary valve.

I dunno about the cost of manufacture either.

[WilDun]

Happy Christmas and New Year to all you guys - hope to be hearing from you in 2020.

[Pursang]

.
Seasons Greetings to you Will, and to Everybody else!



Without attempting to change the world, or make any money or find a race class that it could compete in,
I think I will build one of these for a Honda XR Vinduro bike, (I have a rolling chassis in need of a motor).

Still working through the options on this one, but it seems to be a worthwhile exercise.

Advantages:

Over 'normal' 2 Stroke
Extended working stroke before EPO, (All blowdown, no transfer).
Crankcase lubrication separated from combustion. (including valve stems)
Full Scavenging Flush: No charge dilution. Clean, even, low speed running
Additional boost easily available. (plus Turbo-charging for high speed work)
Broad operating power band: (Exhaust tuning for gas extraction only)
Stratified combustion for light load efficiency, (late injection).
Uniform charge for high power, (early injection).
Combinations of charge & combustion processes also available.

Over 'normal' 4 Stroke
Power stroke per revolution, (twice the torque).
Cooler intake via head: less heat soak from ex valve & port.
No poppet valves in exhaust path.
Piston exposure to 'hot' gas reduced, (No exhaust stroke).
No cam drive & valve spring losses, (Pressure differential intake valves).

Disadvantages:
Supercharger required, Turbocharger optional, ( A Marketing +ve !)
Intake air warmed by blower.
Finding 'economical' (DIY) options for Direct FI.
Possible exhaust restriction around cam drive side of cylinder,
(Uneven heat load, particularly for air cooled engines).

Cheers, Daryl.

[ken seeber]

Dazza,
You've got me half interested for different reasons.
Are you going to run a double lobe cam or run it at crank speed?
Obviously you'll need to have a full skirted piston adjacent to the exhaust port(s)
Enjoy the rain..

[Pursang]

Dazza,
You've got me half interested for different reasons.
Are you going to run a double lobe cam or run it at crank speed?
Obviously you'll need to have a full skirted piston adjacent to the exhaust port(s)
Enjoy the rain..

Hi Ken,
Hopefully the rain put some fires out on the way through!

I first considered crank speed, then welding up some double lobes.
At this point, I am now planning to use un-cammed, differential pressure intake valves.
Like old school, atmospheric intakes, (or combustion resistant reeds).

Reasoning is this: I want the intakes to open as soon as the blow-down has reduced cylinder pressure to below blower boost pressure.
I want the intakes to close after the exhaust has closed and the cylinder is at full boost pressure.
No need for a camshaft to control this. The valve position will be managed by the pressure balance, not heavy springs.

Thanks for the tip re: the piston. Something to consider.
Short circuiting shouldn't cause a major problem with a reversion free exhaust (turbo could help this)
Might be important that the bottom of the skirt maintains a 'seal' to keep the crankcase separated from the exhaust??
Then again, this might provide PCV!
If necessary, could be a good opportunity to use a Flettner, bolt-in gudgeon, full circle, piston.

I am planning to use the redundant cam chain to drive the blower. (Aisin AMR300 looks to be the most affordable option)
At 300cc per rev, it's a little bit big for a 100/125 but I can drive with the cam sprocket at 2:1 and have plenty of scavenge volume or plenty of boost (or both).

Cheers, Daryl.

[Frits Overmars]

... combustion resistant reeds...

Fireproof, pressureproof, detonationproof reeds that open at the slightest pressure differential, and with so little mass that they'll allow any rpm...
Did you try talking to Santa about it?

[lohring]

I just had a "discussion" about intake reeds on another forum. The highest duty reed intake valve I know about is in the combustion chamber of model pulse jet engines. I suspect that the pressures and temperatures in piston engines are considerably higher. The most serious limitation of poppet valves will be rpm. A sleeve valve should be able to run faster, but the flow pattern may not be ideal. Flettner on this forum has built a lot of different two strokes including uniflow designs. I'm not sure where he is on his sleeve valve engine.

Lohring Miller

[ceci]

Fireproof, pressureproof, detonationproof reeds that open at the slightest pressure differential, and with so little mass that they'll allow any rpm...
Did you try talking to Santa about it?

Those are the reasons why I switch to a metal spring hinge mechanism, it is more complicated in all aspects, but with more operational guarantees

[WilDun]

I just had a "discussion" about intake reeds on another forum. .............................The most serious limitation of poppet valves will be rpm. ........................
Lohring Miller

In the mid sixties there was a guy in England who converted a Triumph twin to a similar (poppet valve) system. - It did work of course, but he mustn't have taken it too seriously cos it seems to have disappeared from the scene!

Also in the sixties, there was a serious attempt by an Italian company (IMI Milan - from memory) who made one with a 4 valve head (poppet valve) for karts, but that also was in the sixties and couldn't compete with the rising performance of the 'conventional' two strokes.
The camshaft ran at half speed with 2 valves opening simultaneously - I think that they were probably the exhaust valves though and the crankcase was still used in the normal manner for the fresh charge - the half speed camshaft idea was no doubt to keep the poppet valves running at at sensible speed!

However, we are probably not thinking only competition engines here - it's really only everyday use of the two stroke that will guarantee its existence - competition engines possibly being derived from them of course, but perhaps its use in a generator role is most likely - as (I think) you believe as well Lohring?

These are all just my opinions and of course I could be wrong, but as I see it, it's the only way out for the two stroke at the moment ie using something like Daryl's arrangement.
As a good affordable lightweight powerplant the two stroke is an excellent choice, so long as we don't clutter it with "extras" but we do have to take the slightest hint of pollution seriously (ie as it is seen by the general public and dumb politicians ).