Yeah, .... well, come to think of it - it could've been orange and blue with sort of hardish /soft cover..... I think, but I remember distinctly, I think mine was from the sixties (or was it seventies?) - anyway, I know I did see it, but i'm really no further forward!..... I can safely say that I do know that!
Strokers Galore!
YES! - that is it! (2nd one).
"I remember distinctly"!
That drawing set me off looking for new ways to make a two stroke work well (still haven't got it sorted after more than 50 years) - as soon as i kick the bucket I'll find a way no doubt and hopefully be reincarnated as a successor to Walter Kaaden but this time not to fill the earth with two strokes unless they pass the emission free test - otherwise fulfilling the prophesy, what was it? - "the sun shall cease it's shining and the earth will be turned to shit) - or something like that? - as happened to East Germany after they introduced the MZ engined "Trabant" - let's hope that there is an upsurge in new pollution free two strokes sometime soon !
Ken, Looks like we've read all those books from way back - they were great thing to have around that time, now maybe we can look forward to some new ones (online fine) on two strokes, if all the latest proposals are going to go ahead in that area!
Anyway, that picture with the valve in the middle of the piston crown has stuck with me for somewhere approaching 60 years!
Strokers Galore!
A "poppet" valve, in the piston crown, of Carbon Carbon Composite with large(ish) diameter and modest lift might allow 'acceptable' RPM to be achieved.
That's just with displacement and exhaust effects. If it was mechanically lifted with (say) a link from the crank, higher speeds might be possible.
CCC Density is 1.6 -2 g/cm3, (Al is 2.7 & Ti = 4.5)
Strength up to 700Mpa
Dimensionally stable to 2000C. Higher with a coating (Al melts at 660C. Ti 1670C.)
Transfer direction control by porting the valve throat below the seat.
Hang in there Will, still interesting things happening.
Cheers, Daryl.
TZ250 B model I guess. Very pretty.
Don't you look at my accountant.
He's the only one I've got.
I have most of them as well, and like you say, they were great to have back then. But you needed to keep an open mind; not everything they taught was correct. Or to put it bluntly, not even half of it was correct, so believing everything you read could easily block your mind.
Oh well, maybe it's still the same today .
You are wrong - it's worse! - it's all fantasy now! - at least it was only 50% fantasy then, so we had a 50% chance of learning something and building on it, now it's "act like you play your fantasy games and when it goes wrong, buy something else. or press the reset button and all will be restored"!
The guys here and in ESE etc who are thinking up schemes may not always be correct, but they are at least giving themselves something to feel proud about, ( ie turning an utter piece of crap into a functional thing of beauty) - or even if they don't achieve, then they feel good about trying! - instead of pressing a button and have everything appearing by magic!
I see the same with 3D printers - ie "I want one of those", they're cool and they're cheap ..... then - the same old whinge ...... why does my printer do this? or why doesn't my printer do that? - I'm about to toss mine out of the window - they're crap! - should i bolt on a $100 upgrade on my $250 printer before I actually start using it? .....
i've more or less lost touch with the bike riding scene now, but I'm sure I would find the same thing there!
Give me a break!! ............... maybe I'm wrong and just becoming a grumpy old bastard? ..... but at least I can say - I tried! - but do wish I had started on the foundry stuff much earlier!
Strokers Galore!
Dunno how the picture of that ''youthful rider" got into a post associated with me! - that is pure fantasy! - better get rid of that Darryl!!
Regarding "That valve" ..... I distinctly Remember, ... that, way way back (when I was about that "youthful rider's" age), I had a fantasy attack and devised a "foolproof" method of controlling the outer part of the piston using two (guided) rods with followers attached to the piston skirt, engaging with cams on the flywheels to gently stop it a little before bottom dead centre, hold it there, then re-seat it gently with the other half (attached to the conrod) as it came up again from BDC - I think I finally ended up with a trapped cam to prevent it carrying on at TDC in the event of a misfire! ..... just remembered, i actually ended up with a horizontal pin parallel with the gudgeon at the top of the rod which engaged with a slot (on the outer part) at TDC, this was to be the alternative! ......... but eventually, everything seemed to disappear into the vague mists of time!! - (doesn't mean I was intoxicated or even on the green stuff!) but I mean that i grew up and forgot about it all!
Beat that for April 1st material Frits!!
Strokers Galore!
Yes Rob,
That picture is stuck forever in my mind (just like the Ariel Arrow!) and now i see it has got into your system as well! - but remember, when I conceived that notion, i was about 17 (like the 'youthful rider' in the photo!) - and remember - it hadn't been long since I had found out that Santa Claus and the Tooth Fairy didn't actually exist!
But...... I have still been trying to figure out just how it could be done - ever since it turned up again a couple of days ago!
Strokers Galore!
The atmospheric valve does work ...but not if you want revs and power, as HD concluded nearly 110 years ago.
Diameter is one factor. The force available to open it = the valve area X the differential pressure (atmos to inside cyl)
Counteracting that force is the mass of the valve X the acceleration required to open it in the time available + any spring, if fitted.
In my calculations for the Supercharged (reverse) uni flow in Oddball I was looking at basic 28mm Titanium 4 stroke valves.
Force available with 0.5 atmos Boost (and 0 abs. in cylinder) was around 9.25kg
At 2500 rpm you have 0.006 sec to full open the valve from say 90 atdc to bdc.
For 7mm valve lift, the acceleration required is 388 m/s2.
Maximum permissible weight of a valve at 2500 rpm was around 24g, which is almost realistic.
Unfortunately, the acceleration increases by the inverse of the available time squared.
At 5000 rpm valve mass must be 6g. At 10,000 rpm = 1.5g.
Sufficient lift to achieve a decent Intake/scavenge STA plus the rpm limits are a problem.
Hence Frit's suggestion to make a Christmas wish for Fireproof, pressure-proof, detonation-proof reeds that open at the slightest pressure differential, and with so little mass that they'll allow any rpm...
The other problem I have with a piston crown valve is that we still have a 'petroil' bottom end and are not eliminating a significant source of HC emissions.
On the other end...a super/turbocharged reverse uni-flow with a single, do-nut shaped CCC valve in the head
Real foundry stuff is also coming...
Cheers anyway! Daryl.
The Gnome rotary engine used a piston valve. Of course in a four stroke it had twice the time to function.
Lohring Miller
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