Re: Solenoid Actuated Poppet Valves
From: BretCahill (bretcahill_at_aol.com)
Date: 08/24/04
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Date: 24 Aug 2004 04:20:38 GMT
John Larkin jjlarkin@highlandSNIPtechTHISnologyPLEASE.com in
>Message-id: <vk3ki0hucb91bpjmke3nlcp08l423kbka5@4ax.com> writes:
>
>On 23 Aug 2004 13:04:00 GMT, bretcahill@aol.com (BretCahill) wrote:
>
>>John Larkin jjlarkin@highlandSNIPtechTHISnologyPLEASE.com in
>>>Message-id: <jotii0to28debeg7rogmmgo87e9hfcffp7@4ax.com> writes:
>>
>>>On 23 Aug 2004 03:15:07 GMT, bretcahill@aol.com (BretCahill) wrote:
>>
>>>>John Larkin jjlarkin@highlandSNIPtechTHISnologyPLEASE.com
>>>>>Message-id: <f2uhi0pie2pgvadslflcqh85sq87uc48m4@4ax.com> writes:
>>>>
>>>>. . .
>>>>
>>>>>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.
>>
>>>>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.
>>
>>>Ooh, snotty!
>>
>>I never actually said you were wrong, just that
>>even if you were wrong, the issue was valuable.
>>
>>>Fast, powerful solenoids have a lot of copper loss, hence the cooling
>>>problem. Not a lot of energy would be recovered.
>>
>>It's interesting electric motors can be 95%
>>efficient but something linear is only 0.1%
>>efficient.
>>
>
>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!
>
>>>I'd think that a roller cam could recover at least 60% of the energy
>>>dumped into the valve spring.
>>
>>Sounds reasonable.
>>
>>>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
>>>work.
>>
>>There are some web sites with solenoid
>>engines that supposedly run.
>
>
>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
>humbled.
>I guess you could do the Cadillac variable-number-of-cylinders trick.
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
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