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Thread: The Bucket Foundry

  1. #4426
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    10th February 2005 - 20:25
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    Quote Originally Posted by lohring View Post
    The Gnome rotary engine used a piston valve. Of course in a four stroke it had twice the time to function.

    Lohring Miller
    The Gnome rotary was a totally different scenario, - the pistons did not reciprocate, it could be called a pure rotary. - If you study carefully the path of the piston either in a drawing (but better in an animation) it can be seen that the pistons move in a circular motion and the only reversals come in the oscillating conrods (and poppet valves).
    So really the only "reciprocation" which takes place is "relative reciprocation" obtained by the crankshaft axis being offset from the axis of the path of the cylinders/pistons (does that make sense? - hard for someone like me to explain so check an animation). - anyway check at 1:40 in the animation below and it will be clear!

    I guess that i'm trying to say is, that in the case of the radial rotary engines, a valve in the piston crown would not be subjected to the reversals it would be faced with in a normal engine layout - but it would be subjected to centrifugal forces!

    Some (a lot of) guys have done animations claiming they are gnome rotaries when in fact, what they are showing are normal radial engines (with reciprocating pistons) rather than rotary radial engines - they don't seem to understand the different concept!! - the crankshaft should be standing still and the cylinders rotating - could they even be considered 'rotary piston' engines? - or does rotary piston only refer to the piston/cylinder relationship?

    This is a good animation though - I don't understand the language (probably German?) - very good. :-

    https://www.youtube.com/watch?v=zX6ZlYYIsNU
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  2. #4427
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    20th January 2010 - 14:41
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    Quote Originally Posted by Pursang View Post
    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 limitations of valves to follow cams let alone atmospheric conditions is why F1 uses pneumatics rather than mathmatics
    the hardley engine was a joke on the Valve technology
    Ages ago i posted the ""KOENIGSEGG freevalve



    I would open the valve direct from underneath with a variable length solenoid
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  3. #4428
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    28th August 2015 - 00:01
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    I understand that the Gnome was a completely different case. It's the only example of a widely used piston valve I could think of. It was still an era when engine design hadn't consolidated around a few concepts. Some really inventive things were tried.

    Lohring Miller

  4. #4429
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    Quote Originally Posted by lohring View Post
    I understand that the Gnome was a completely different case. .......... Some really inventive things were tried.

    Lohring Miller
    Yes, sorry Lohring, - didn't mean to give the impression that I thought you were wrong!, I do realize that I tend to get carried away sometimes, but then, that's me!
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  5. #4430
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    28th August 2015 - 00:01
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    No worries. We old people tend to get crotchety as my great grandmother would say.

    Lohring Miller

  6. #4431
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    Quote Originally Posted by lohring View Post
    No worries. We old people tend to get crotchety as my great grandmother would say.

    Lohring Miller
    Yes, and (certainly in my case) we tend to say the the things we think, when earlier on we knew better or were afraid to say!
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

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