Re: Valve ports, engine rpm & their effective limits?
Posted by:
Carl Helsing (IP Logged)
Date: June 08, 2006 04:35AM
<HTML>I have had a few ideas and also experienced strange coincidences.Back in the 1970's I worked mounting tires at a Firestone store.An old fellow,probably in his 70's happened to walk in and I heard him mention that he had a Wiily's Knight with the sleeve valve engine.Those disappeared probably by the early 1930's.Someone who knew I did small engine repairs(lawn and garden size)had left a technical manual by a guy named Smolen,showing the complete workings of the sleeve valve system.If you're not familiar with it,the valves were simply two sleeves around the piston,attached to, their own cranks,and sliding up and down just as the piston does,opening and closing ports at the head area.The manual had a late1920's date.Anyway,I told the old fellow he could have the manual,since it was of no use to me,and he had the actual automobile.I think he gave me 5 dollars for it.I have a model steam oscillating engine from Germany,given as a gift by my brother.I played with it for a couple weeks,and the piston seized in the cylinder.They had used a short little slug of metal as the piston.There was no crosshead or guide of any type at the piston end.Instead of mounting a guide bearing,which I could have done,I instead used a brass sleeve,internal precision fit,and a longer cylinder of the same brass.The brass is model material of close increments,one tube sliding within the other,maybe a thousandth tolerance.The engine is still running after ten years of fiddling.Valve and piston ideas-(some for toys)The main thing I wanted to tell you,since yoy have some ideas,is of a concept I have had of having a "hybrid" of an internal combustion engine with a steam auxilliary utilizing all the water the internal combustion engine can boil to steam,right down to ends of the exhaust manifolds.A thermal efficiency concept.Could have been some of that type somewhere,tho they would likely be isolated so-called specialty items in possibly small industrial use,time period,20'-30's-Just ideas and stories-enjoy-(also-valve idea for all the air that can be packed into a cylinder)
<a href="mailto:ghunsaker@mexicomo.net?subject=Valve ports, engine rpm & their effective limits?">Garry Hunsaker</a> wrote:
>
>
> I am wondering if there is anything remotely like a rule of
> thumb as to how short a stroke, and therefore a limit to how
> short a duration a steam engine’s ports can remain open and
> still properly ‘charge’ the cylinder. The steam engine has
> enough problems with out adding windage restrictions. (Or is
> this what engineers refer to as ‘shock’?) What has brought me
> to this question is looking at the three cylinder engine in
> my old Subaru Justy. It’s 3.27” stroke is almost liveable.
> (To be honest, I think I need to check out the crankshaft on
> the Chevy Geo. There are a heck of a lot more of them around
> to choose from)
>
> The only thing in the way of data I have had in the past to
> work with was J. N. Walton’s book on Doble. I have been
> hunting around today for the numbers I ran several years ago,
> that Doble outlined for his triple expansion engine, but I
> still haven’t come up with the place I put them to make sure
> I didn’t lose them... (So what else is new.)
>
> Shooting from memory, I believe I was aiming at 50 to 60 hp.
> Any way, the one thing I do remember is measuring my old 1970
> VW van. The best I remember I came to the conclusion that by
> running the engine at roughly twice the speed of the
> differential gear I would have the effective torque of the
> standard VW van about half way between first and second
> gear. (The acceleration should be interesting to say the
> least)
>
> For those that might be curious, I had intended to lay the
> resulting engine on its side on the left side of engine
> compartment. By adding a splined stub shaft to the end of
> the crank, and running that into a gear box, I would have to
> create using the side plates, bearings, and third member from
> the VW, I thought I could make this work.
>
> I was still scratching my head on how, or if I needed to, set
> the gear box up for backlash adjustment on the deferential
> gears I would have to come up with. The thought did occur to
> me to create new side plates so the outer bolt circle, and
> its corresponding surface would be slightly eccentric in
> relation to the third member support bearings. I figured
> throwing the axles a few thousandths out of their original
> position wouldn’t bother those CV joints too much. Though
> making exactly matching eccentric side plates in relation to
> a set of perfectly divided and aligned bolt circles still had
> me wondering on the how the heck am I going to do that???
>
> The advantage of placing the engine to one side was it would
> leave better than three quarters of the engine compartment
> open for a steam generator. Using the info I was beginning
> to pick up from the SACA back then, I figured by using
> extended surface tubing in the pre-boil sections of a
> monotube boiler, I could keep the size down to where the
> whole package could be hung on a square tube frame and
> attached to beefed up versions of the original engine and
> transmission mounts. There should even be room for a water
> tank forward of the differential, and enough room to place
> most of the auxiliaries above the engine and out of the road
> grit and grime. The exception being the water pumps, I hoped
> to get those below the level of the bottom of the water tank.
> The only thing I didn’t envision attaching to this package
> was the condenser. That I planned placing on the left side
> of the body with lovers cut in the body to shove the heat out
> with an electric fan-s.
>
> I was still finding myself with too many questions. A few of
> which I have had answered thanks to this form and the SACA
> discussion list. Before I started hacking out metal, melting
> down old Cummins diesel pistons, making patterns, and all the
> other fun stuff that goes with experimental prototypes built
> on no budget, I thought I had better have a bit more
> understanding of what is going on, and if such a short stroke
> engine could ‘breath’ properly under steam at the RPM I
> envisioned. I believe that may have been around 800 foot per
> minute piston speed at 70 mph and 2100 rpm, which is
> considerably faster than I care to drive one of those old
> vans. Though mainly, I didn’t want to end up spending a few
> years creating such a monstrosity and discover later it would
> have a top speed of twenty two miles and hour.
>
> I have several other questions, but they can wait till
> later. And don’t get too freaked on my original tipple
> expansion thoughts. As far as piston engines go, I am now
> convinced the uniflow is the only way to go. And the use of a
> constant volume steam exaust motor to drive the water pumps
> and cylinder oil injection in relationship to engine load
> seems wise.., and will probably lead me to even more questions.
>
> So if you are still reading this...
> You must be as addicted to steam as I am..
> Garry
> PS: I envisioned this menagerie at around 800 psi and 800F of
> steam, though at the moment, I don't remember the lbs per
> hour I came up with. It does seem like I was going to end up
> with about half the surface area in tubing of the engine
> Doble had outlined in Walton's book. (This was before I had
> heard of extended surface tubing, and about that time the
> universe put my life on hold)</HTML>