Hit and miss STEAM ENGINE????

[Brian Rupnow]

Okay, I know---seems like an oxymoron. I have been thinking the last few days of steam engines. I have built 4 steam engines (running them on air) and they all ran well. They also will drain an air tank in fairly short order, because of the high consumption of air. Now---a hit and miss i.c. engine runs on a type of inertial governor, that only lets the engine fire when the RPM's drop below a certain speed. Once it fires, the exhaust valve is held off its tappet untill RPMs fall off again. My idea would never work as a practical engine, but why couldn't one build a steam (air) engine with a pair of large flywheels, and the same type of inertial governor.--The engine would function in normal mode from zero speed and accelerate untill a desired speed was reached. At this speed, the inertial governor would shut off the steam/(air) and the large flywheels would give up their stored energy and keep the engine running untill the engine slowed beyond a critical RPM. When this critical low RPM range was reached, the inertial governor would open the steam/(air) valve again.--Like I said, not a practical engine, but an engine that would run a very long time on a given amount of compressed air.---Has anyone ever done this?

 

[GailInNM]

See what happens when you go away for a few weeks Brian.
Is this sort of what you mean?

http://www.homemodelenginemachinist.com/index.php?topic=3732.0

Gail in NM,USA

 

[Brian Rupnow]

Son of a Gun!!! Thats a beauty. I guess I didn't have an original idea after all.---Brian

 

[tel]

I sort of, almost, did that a few years back Brian - well, it didn't stop the steam, just 'notch up' the cutoff til it was working with minimum steam admission. Worked rather well, if I do say so

 

[tel]

A couple of shots of the engine in question

The valve gear at speed

 

[rickharris]

Hit and Miss on steam.---Has anyone ever done this?

John Toms site has plans for a compressed air hit and miss under IC engines http://www.john-tom.com/html/ICEngines.html

 

[Brian Rupnow]

Time on my hands and a curious mind are an evil combination----

View attachment FULL ASSY HIT AND MISS ENGINE.PDF

 

[Brian Rupnow]

Well, enough of this foolishness for a Saturday morning!! Not to disparage anyone elses drawings/plans, but there seems to be a lot of either missing dimensions or else downright wrong dimensions on the information I have dug up on this project. Of course, that could just be me. ;D ;D This is a fascinating little engine.--Brian

 

[10K Pete]

OK, I gotta ask this question:

Doesn't the flyball governor on a steam engine 'sense' speed, like the governor on a hit and miss, and adjust the amount of steam going into the engine? I seems to me like the regular flyball governor does the same thing.

What am I missing here??

Thanks,
Pete

 

[tel]

Doesn't the flyball governor on a steam engine 'sense' speed, like the governor on a hit and miss, and adjust the amount of steam going into the engine? I seems to me like the regular flyball governor does the same thing.

Well, yes it does, but it doesn't shut the steam off completely, which is what I think Brian is trying to achieve here. Mind you, the Ames type - shown in my pics - could be slightly modified to achieve the same end.

 

[10K Pete]

Ahhhhh, I see. Thanks Tel, ya turned the light on for me! And I think I see where a modification could maybe do the shutoff trick.....maybe. The 'vision' is still fuzzy.

Thanks,
Pete

 

[Brian Rupnow]

10K Pete---To help understand the difference in the two systems---Yes, the flyball type governor does run off engine speed, and it does supply more steam or less steam, depending on the load on the engine and the RPM of the crankshaft. However, the valving on a conventional steam engine is ran independently of the governor, from a mechanical "cam" (eccentric). The valve which lets steam enter or exit the cylinder is going to operate the same regardless of how much or how little steam is entering the cylinder. Because of this, the engine will not "coast" very well.--For example, if the inlet valve was shut off completely, then the piston would have to"pull a vacuum " to go down on the power stroke , which makes for poor coasting. (Kinda like a Jake brake in reverse)
On the hit and miss type of engine, the governor is also speed sensitive, but when hi speed and centrifugal force cause the weights to fly out, the steam inlet valve is rendered inoperative (it stays closed) and the exhaust valve remains open all the time, so that the engine can coast (freewheel) without pulling a vacuum.

 

[Brian Rupnow]

With all due respect to Chuck Fellows, who I believe is the originator of this unique valving system, there seem to be a lack of complete details on the valves inner workings. I have used the drawings posted in the download section, plus a bit of imagination, and the fact that the smallest taps and dies I care to work with are #5-40 to create 3D models of this valving system.--I am not finished yet, but have made a good start. (I have not shown the spring, clip, and washer that are on the bottom of the valve yet.) When I get this sorted out to my satisfaction, I will post complete details (my interpretation), but as I say, any credit for the original idea goes to Chuck Fellows. EDIT--EDIT--EDIT--In case you didn't notice, I had the port in the side of the valve facing the wrong direction. I have edited the .jpg and the .pdf files so that the port in the side of the valve faces in towards the cylinder and I put a #10-24 set screw thru the side of the cylinder head to keep the valve in place.

View attachment INLET VALVE CLOSED EXHAUST PORT OPEN.PDF

View attachment INLET VALVE OPEN--EXHAUST CLOSED.PDF

 

[cfellows]

Nice drawings, Brian. Wish I had your experience and ability with CAD!

This design is one of my earlier versions. Since then I've simplified the design to use a single hole from the head into the cylinder, instead of two, and to simply use a ball bearing for the slave valve instead of a cylindrical piston.

I only note this, because it's somewhat easier to build.

Chuck

 

[Brian Rupnow]

Chuck--are there any plans of this "later version" you speak of?-Where can I see more information about it? I am glad you have chimed in here, I always feel a bit cheesy about posting my interprestation of someone elses design.--Does the later version give the same performance and distinctive "popping" sound?

 

[tel]

this one?

 

[Brian Rupnow]

Yes, Tel---I guess that must be it, although Chuck metions a ball rather than a cylindrical slug as shown. --Do you have the link to whatever thread you got those pic's from please.---Brian

 

[tel]

Regretfully no mate, I just saved the images into my M.E. folder. Also these.

 

[10K Pete]

Well I'll be dipped. Any of those are about the slickest valve setup.......

Sure are some clever folks around here! I'm like a fly on the wall just soakin' it up.

Thanks!
Pete

 

[Brian Rupnow]

Well, this is what it ends up looking like. I used 3 1/2" diameter flywheels to give as much inertial coasting as I could get, The bore is 3/4" and the stroke is 1.236 (Chuck will know why). I used a 1/4" diameter crankshaft with brass one peice bearing blocks. I kept everything as simple as I could, with a one peice crankcase hogged out of aluminum. I'm still not totally clear on the connection between the valve stem and the push rod which activates it, but that will come.

View attachment FULL ASSY HIT AND MISS ENGINE-DRAWING.PDF