the clean two-stroke thread

[breezy]

maybe kens reed head could be configured to be used as exhaust port . like the opposed piston set up, keeping the exhaust phase away from the fresh charge.

[WilDun]

Yes, saying the transfer slug pushes the exhaust out was 'Pushing it'. Displacing residual combustion products might be a more accurate term.

Cheers,Daryl

Ok, let's just call it "chasing" !

[husaberg]

Yes, saying the transfer slug pushes the exhaust out was 'Pushing it'. Displacing residual combustion products might be a more accurate term.

Cheers,Daryl

Are you suggesting there is REPLACEMENT FOR DISPLACEMENT?

[Pursang]

Ok, let's just call it "chasing" !

'Chasing' sounds a little undignified and uncontrolled.

How about Herding...or Scavenging.


Cheers, Daryl.

[Pursang]

Are yo suggesting there is REPLACEMENT FOR DISPLACEMENT?

Mass Transfer by Volumetric Displacement is the Solution! (for those who don't believe that there is enough crankcase pressure to achieve transfer)


For those addicted to Displacement... there is always one of these----> 3 X 490!



Cheers, Daryl

[Flettner]

A step closer to realising the 175cc single cylinder OP uniflow, in real hardwear.
Even if they do 'make a lot of noise', allegedly.
Notice the injector lugs on the cold end transfers, TPI.

[Pursang]

[WilDun]

Mass Transfer by Volumetric Displacement is the Solution! (for those who don't believe that there is enough crankcase pressure to achieve transfer)


For those addicted to Displacement... there is always one of these----> 3 X 490!



Cheers, Daryl

Yep,
I see things starting to come together and work in harmony here - ie ideas, but also exhausts and transfers working in harmony ..........a few key pieces have now been placed in the jigsaw puzzle to make the big picture of the future two stroke a bit clearer! - hope that there's no lost pieces!

As for that monster engine in the picture - if you want to be a showman, just do it in a car!- things can be hidden under the bonnet! - great dirt track car! - would blow them all away, but check the gearbox often!

Neil - that is sure looking good, but I'll reserve judgment till (as I said above) the picture becomes clearer and there is some understanding of what to judge! ........... and there's Ken's project too - all looking good!

BUT ........... where is Haufen? - we haven't heard from him since he started the thread !!..... is he ok?

[ken seeber]

That’s Dazzling Dazza

I do like the basics of you proposal and I think we’re all talking the same language here:

Getting the fresh charge into the combustion chamber, but, in whatever way we want to describe it, get a descending slug of the remaining mixture, to pass down the cylinder, displacing exhaust gas and also not getting lost out the exh port. Or at least, if it does pass out, then it is returned (by wave action).

Neil’s OP has a fundamental advantage in that he has effectively a cylinder which is twice as long as the UHV. Giving him a greater possibility of maintaining the magical slug. Another advantage is that the porting is asymmetric, lots of radial transfers and, also the 3 exh ports, whereas I am currently dealing with just one exhaust port.
Fundamentally, I think a more undersquare layout with symmetrical exhausts could only be beneficial.

Certainly wish Fletto the best with his OP, he has put a shitload of hard work & passion into it.

For me on the case with the next version of UHV. In this case, I am trying to create a flow towards the comb chamber, but also across and downwards, essentially in the opposite direction of the usual Schnurle flow direction. Also hopefully with the two outer tangential flows colliding and cancelling out some downwards velocity.



For all these UHV valves to date, I am using a 0.2 thick material over a Ø5 hole with a 2 wide perimeter, so therefore each blade cannot be less that 9. As I cast up a few blank heads, I intend to try a squishless version, ie a single flat & circular combustion chamber of bore diameter.

But back to Dazza’s concept. I actually love it and did consider some form of individual petals, radially disposed, but only on a flat head face. One issue being achieving enough lift without overstraining the flexure part of the petal attachment.

.

But angling the petal sealing surface, say at a conventional squish angle, directing the charge to the bowl is really nice. How this is done is the issue. Spherically shaped petals or a series of angled flats. And then tolerancing the petals to seal. Lots of clever guys out there.

[Pursang]

Thanks for the kind words Ken, really I'm just looking over you shoulder.

I like your new head, years ago I spent some time investigating improvements to Flathead 4 strokes.
They can be way better than most people expect.

In my proposal, the radial reeds and exhaust ports are an attempt to eliminate or minimise any Schnuerley flows.

For a prototype, build at home, I would be machining flats in the head for each reed to seat on.

Compound curved reeds? spoons? might be a way down the track.
There is also a possibility that actual reeds aren't required.
Flow & pressure differential controlled 'flap valves' might be an option.

Re: bore and stroke ratios, I think there will be a balancing act between these.
A narrow bore reduces your transfer area (A high tapered squish angle gets some back).

I think exhaust duration will be a key factor as the transfer obviously cant begin until sufficient blowdown is achieved.
It will be possible though for it to continue until around EPC.

Cheers, Daryl.

[Frits Overmars]

A narrow bore reduces your transfer area.

You may want to give this a bit more thought Daryl.
If you wish to maintain the original cylinder capacity, halving the bore will require quadrupling the stroke, which will double the transfer area as well as the transfer area per cc.

If you want to maintain the original stroke, halving the bore will mean dividing the cylinder capacity by four, and since the transfer area is proportional to the halved bore, multiplied by the original stroke, this transfer area will only be halved and the transfer area per cc will once again be doubled.

[WilDun]

You may want to give this a bit more thought Daryl.
If you wish to maintain the original cylinder capacity, halving the bore will require quadrupling the stroke, which will double the transfer area as well as the transfer area per cc.

If you want to maintain the original stroke, halving the bore will mean dividing the cylinder capacity by four, and since the transfer area is proportional to the halved bore, multiplied by the original stroke, this transfer area will only be halved and the transfer area per cc will once again be doubled.

Ok, but does the introduction of a supercharger make any difference to this already complicated (to some of us) scenario?

[ceci]

If you want to maintain the original stroke, halving the bore will mean dividing the cylinder capacity by four, and since the transfer area is proportional to the halved bore, multiplied by the original stroke, this transfer area will only be halved and the transfer area per cc will once again be doubled.

This is applicable in the opposite direction.
"Schnuerley". It allowed machines that started in 1945 with a bore of 45.6 mm and a stroke of 60 mm = 98cc, due to the use of a piston with baffle and limitation of the transfer area.
They will increase their capacity at the same time as their performance B 60 mm and S 60 mm = 174.77 cc, increasing up to B 72.5 mm and S 60 mm = 247.69 cc.
It was not only an increase in capacity, but also an increase in the transfer area.

[Pursang]

Hi Frits, thanks for your input in this less Racey section.

You may want to give this a bit more thought Daryl.
If you wish to maintain the original cylinder capacity, halving the bore will require quadrupling the stroke, which will double the transfer area as well as the transfer area per cc.

If you want to maintain the original stroke, halving the bore will mean dividing the cylinder capacity by four, and since the transfer area is proportional to the halved bore, multiplied by the original stroke, this transfer area will only be halved and the transfer area per cc will once again be doubled.

For regular transfer ports, for sure!

But, Under Head or Squish Reed transfers are limited to the Squish area.
Halving the bore reduces the available area by factor of 4
So, 4 times Stroke for same cc = 4 times transfer velocity. Is this a Good or Bad thing? I don't know, testing required.

Cheers, Daryl.

[Pursang]

Ok, but does the introduction of a supercharger make any difference to this already complicated (to some of us) scenario?

Well, Ken has already demonstrated a Reverse Uni-flow 2 Stroke running without an external pump.

So, at this point a supercharger is just additional 'complication'. Boost would raise the HP potential, but also increase the likelihood of fresh charge escaping via the exhaust.

Plenty of development opportunity to create a 'clean' burning, case transfer, RUF engine by optimisation of bore/stroke, transfer port area, reed orientation and flex rate, exhaust configuration & duration, etc, etc. (Plenty of scope for TPI too!)

Of course, not all solutions are Mechanical!
If someone develops a smokeless 2 stroke Oil, that smells like fresh cooked donuts And extracts CO2 from the atmosphere we could all be riding Kwaka H1 Mach L's.

Cheers, Daryl.