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Solenoid Actuated Poppet Valves

Discussion in 'Electronic Basics' started by BretCahill, Aug 22, 2004.

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  1. BretCahill

    BretCahill Guest

    Could a solenoid be constructed to mimic
    the proper valve position vs time curve of a
    engine cam shaft? Maybe a circuit and/or
    several coils in each solenoid?

    It may be tricky or impossible to build such
    a solenoid that works well over all rpms, but
    if it could be built, it could be mass
    produced very cheaply, maybe cheaper than
    a cam system.

    The other concerns such as force necessary to
    accelerate valves (are solenoids orders of
    magnitude more inefficient than cams?) and
    mangled valves from electronic failure (like other
    fail safe systems set the default of every valve
    in a safe position) shouldn't be problems.

    Bret Cahill
  2. Rich Grise

    Rich Grise Guest

    I brought this up some time ago in some mechanical group,
    and they seemed to indicate that it's been tried a long
    long time ago, and abandoned because it's noisy or
    something. Actually, I still think it's a pretty cool
    idea, when you consider how many HP a camshaft/rocker/
    pushrod/lifter arrangement must consume.

    And 100-amp semiconductors are common these days.

    Anybody want to start hacking their cylinder head? ;-)

  3. John Larkin

    John Larkin Guest

    I'd guess that the forces involved are awfully high for solenoids.
    Cooling would be a nasty problem, too. If this worked, the boys in
    Detroit or wherever would have done it by now.

    Interesting: a cam (especially a roller cam) will return some of the
    valve-spring energy to the camshaft when the valve closes, but a
    solenoid won't.

  4. BretCahill

    BretCahill Guest

    John Larkin
    .. . .
    I wouldn't be so sure.

    A solenoid might be or has been built that
    could recapture about as much wasted energy
    as that by a cam. As the valve slowed it would
    recharge the battery or power the next
    cylinder's solenoid.

    In any event your concern is valuable, even if
    wrong. I didn't think about it and I run energy
    balances on everything.

    Bret Cahill

    "The errors of great men are more fruitful than
    the truths of little men."

    -- Nietzsche
  5. John Larkin

    John Larkin Guest

    Ooh, snotty!

    Fast, powerful solenoids have a lot of copper loss, hence the cooling
    problem. Not a lot of energy would be recovered.

    I'd think that a roller cam could recover at least 60% of the energy
    dumped into the valve spring. The exhaust valve does some real work
    against pressure, but that's a different issue.

    But it's not worth arguing about, or analyzing, because it doesn't
    I think about everything. That's more fun.

  6. Bob Masta

    Bob Masta Guest

    I seem to recall reading in mags like EE Times about work
    on "electronic valve timing" or words to that effect.
    I had the impression that they were using solenoids,
    and had similar concerns to yours.

    The "all-electronic car" idea seems to be gaining momentum,
    but it gives me the creeps, especially when they get to
    electronic steering. Seems like they are just trying to make
    everything electronic "because they can".

    However, many years ago I worked for General Motors
    Cadillac Division when electronic fuel injection was just
    coming on board. For a while I was one of team that went
    around the plant rescuing EFI cars that had died. At the
    time it was a really fragile system. There were something like
    32 wires to the EFI control box (which was mostly analog!), and
    almost any of those could disrupt operation if it came out of
    it's little connector. (We carried a supply of paper clips to poke
    them back into their shells.) Worse yet, the early EFI system put
    a massive amount of fuel into the chambers if you pumped the
    pedal when cold-starting, as the drivers were used to doing on
    carbureted cars. This would foul the plugs so badly that they
    had to be replaced in order to start the car. (Simple manual
    cleaning of plugs didn't help.)

    I recall thinking that this was a terrible step backward for
    overall reliability. There were tons of things that could
    completely disable an EFI car, whereas almost nothing
    bothered a carburetor short of somebody dismantling it an
    throwing in a handful of dirt.

    Nowadays, though, EFI is the norm and they certainly seem
    to have gotten their act straight. Overall, seems far more
    reliable than carburetors. So, maybe someday we'll feel that
    way about electronic valve trains and steering. OK, so maybe
    a few catastrophic failures in the learning curve to stimulate
    new ideas.... <g>

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
  7. BretCahill

    BretCahill Guest

    John Larkin in
    I never actually said you were wrong, just that
    even if you were wrong, the issue was valuable.
    It's interesting electric motors can be 95%
    efficient but something linear is only 0.1%
    Sounds reasonable.
    There are some web sites with solenoid
    engines that supposedly run.
    That's what we want to hear. Just don't delete
    my Nietzsche quote next time.

    Bret Cahill
  8. John Larkin

    John Larkin Guest

    That is interesting. One difference is that motors have magnets (or
    fields) but solenoids generally don't. A linear voice-coil actuator is
    sort of half-and-half, and can be reasonably efficient as a
    mechanical-to-electrical converter. A solenoid only stores energy in
    its inductance (which admittedly decreases in the dropout direction,
    which pumps some energy back into the winding) but a millisecond
    high-power solenoid will have to have very low inductance and run at
    very high peak current, so will be very lossy. A solenoid is just a
    linear variable-reluctance motor!

    Oh, it can be made to work, like variable valve timing and all sorts
    of other tricks. But it sounds outrageous to me to replace a nice
    reliable cam and a belt with two solenoids and a heap of electronics
    per cylinder. I think the 42-volt boys sometimes advocate electrical
    valve actuators (and power steering, and air conditioning.) When it
    becomes commercially successful and commonly done, I will be suitably

    I guess you could do the Cadillac variable-number-of-cylinders trick.
    You'd have to when a solenoid or a driver fails.
    You can't restrict my Freedom of Snip rights.

  9. Eric R Snow

    Eric R Snow Guest

    Greetings Bob,
    I used to shudder at the thought of "drive by wire" systems.
    Mechanical systems just seemed so robust and forgiving when they do
    fail, because often the failure isn't complete, but happens over time.
    But, I had the left front suspension break and fold under a car I was
    driving. In a parking lot going about 10 mph. There was no controlling
    the car. Another time, I heard a squeak coming from the engine
    compartment of an econline van I was driving. I turned on the turn
    signal to change lanes over to the emergency lane. Before I got there
    the shaft going throught the water pump let go and the fan screwed
    itself through the radiator. These were sudden failures with no
    warning ar just a second or two warning. But many electronic systems
    are much less likely to fail. And they really don't wear out. My Dad's
    company makes machines which check the probe cards which check the
    finished wafers before they are sliced up into seperate dies. He's
    been an electronic engineer for about 50 years. When I told him I had
    a chip fail in a 20 year old machine he said that the chip was damaged
    when new. He said it most likely was not damaged by age or run time.
    And that the type of chip it is should function virtually forever. So
    I'm waiting for the all electronic car.
  10. BretCahill

    BretCahill Guest

    A lot of people seem worried about a computer
    glitch causing the valves to get mangled, etc.
    but the drivability of a motor vehicle drops to
    zero anyway without the computer. For the
    past 20 years automotive computer failure
    hasn't been that big problem.

    Besides there are various fail safe protections
    that could be implemented.

    Bret Cahill

    Eric R Snow in
  11. BretCahill

    BretCahill Guest

    (Bob Masta) in
    I hate the way every microwave oven is
    different. Just put a dial on the #@!&%! thing
    and forget being cute with a lot of buttons.
    Good story.
    Maybe someone knew what he was doing.
    In politics we're talking trillions of dollars down
    the drain.

    An unreliable piece of electrical or mechanical
    junk is positively charming in comparison.

    Where do I sign up?
  12. BretCahill

    BretCahill Guest

    John Larkin in
    That's what started it. Instead of one engine,
    I'ld have 2. A low power high efficiency engine
    for 50 mpg and a high power low efficiency
    engine in case you needed to haul something
    or get on the freeway fast.

    Someone mentioned a convertable 4 stroke/
    2stroke engine and either you had to slide the
    cam shaft off the rocker arms or you had to
    operate the valves some other way.

    Bret Cahill
  13. John Larkin

    John Larkin Guest

    Actually, existing engines are awfully good. Their only problem is
    that most of them are designed to accelerate 5000 pounds of ugly steel
    surrounding one 110-pound soccer mom. We don't really need more
    efficient engines as much as we need higher gas prices. No major
    technological breakthroughs are needed to make that happen.

  14. colin

    colin Guest

    i seem to remember hearing long time ago that the amount of instantaneous
    power required for a solenoid to operate normal valves with return springs
    is so large that the resulting inefeciencies leads to a very large power
    consumption making it rather ineficient. maybe with latest magnets or
    posibly even high temperature superconductors it wld be advantagous. maybe a
    stepper motor could be used instead, with a similar arangement used inside
    disc head actuators.

    however there are alternatives, depends what you are trying to acheive,
    variable valve timing has been acehived with hydrolics on lotus and now
    other cars i think, however why restrict yourslef to popet valves, consider
    desmodronic valves wich have no return spring but rely on a 2nd mechanical
    or potentialy electromechanical force to return the valve, and the presure
    inside the cylnder finshes the job.

    alternatvly the cam shaft could simply be driven by a steper motor, or the
    cam shaft cld be driven in the normal way but a mechanism driven by a steper
    motor could alter the angle of the cam shaft relative to the drive drive

    there was talk about an all ceramic engine being 10 years away but i heard
    this wel over 10 years ago i think, i always wondered about the posibility
    of sliding valves, maybe just a rotating disc, posibly ceramic just like in
    some taps, they are very efiecient in the amount of energy required to
    operate them and give good life.

    Colin =^.^=
  15. James Newton

    James Newton Guest

    Anything is possible, but if you just want variable valve timing try

    Convert the lifters to have little thin rollers on the end... sort of
    like tiny inline skate wheels but made from steel and running on a
    bearing. Now the lifter is only useing a narrow section of the
    circumference of the cam lobe.

    Next, make each cam lobe segment very narrow and stack several
    different shaped lobes right next to each other.

    Finally, shift the cam shaft in and out as it turns.

    I personally did a VERY crude version of this years ago on my first
    "hot rod" as a teenager. I wanted to grind the cam shaft as several of
    the other "gang" had done, but I knew my dad would kill me if he ever
    heard the car running rough so I ground HALF of each cam lobe, added a
    crude lever system to shift the cam in and out about 1/4 inch which
    was all the play I could get out of the cam journals. It was enough,
    and I could idle quietly out the drive way, reach under the dash, pull
    the lever and be "one of the cool ones."

    Of course I totalled the car about 6 months later and my Dad did the
    worst possible thing to punish me: He cried. Later though, when he
    noticed the "modification" he helped me start a rebuild on the car.
    Didn't finish it, but I took it as a sign he had been impressed.

    Anyway, I've never seen such a thing since, but I've been out of cars
    for a long time.
  16. BretCahill

    BretCahill Guest

    Someone suggested a 2-stroke/4-stroke
    convertable engine. 4-stroke if gas was
    expensive and four stroke if you needed more

    The sliding cam was the only way other than

    Bret Cahill
  17. Clint Sharp

    Clint Sharp Guest

    Fiat use a scheme like this. Their system uses two meshing cross cut
    gears, one internal and the external one is rotated to push/pull the
    camshaft in and out to a different portion of the profile
  18. BobGardner

    BobGardner Guest

  19. Thats' been done already, they're still ironing out the bugs.... not
    ready for domestic use 'yet'.

    I must say I just 'love' the possibilities this will introduce.
    Imagine an engine that could putt around in city traffic & still go
    like a Ferari on the open road.

    Australia isn't "down under", it's "off to one side"! (home of the Australian Cobra Catamaran)
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