# Chucks Single--Conventional Valving



## Brian Rupnow (Aug 19, 2009)

Just to prove that I'm going completely gaga with LOWS (Lack of work syndrome) I decided to see what was involved in a redesign of the Chucks Horizontal engine that I built, to put conventional valving in it. This managed to burn up most of yesterday, and did give me insight into valve timing and design that I didn't have before.


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## Brian Rupnow (Aug 19, 2009)

And to see it in an exploded view---


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## Brian Rupnow (Aug 19, 2009)

I'm not actually sure that I will do this. I like my engine just as it is, with the current valving on it and the hit and miss governors. This was more of an intellectual exercise to better aquaint myself with the design of small steam engine valving, and to see what would actually be required to make this change. If anybody out there in steam engine land wants to make this change I will post detail drawings of the parts so you can machine them.---Brian


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## bearcar1 (Aug 19, 2009)

Nicely done Brian. :bow: Wish I could produce CAD drawings such as those but do not have the software or the training to do so. It would make life so much easier to do things that way, I think. Now, for your next assignment, redesign the head utilizing poppet valves. ;D ;D

Regards

BC1
Jim


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## black85vette (Aug 19, 2009)

Thm: Nice, straight forward, and simple to build.  I think just from a fabrication stand point, since I only have a milling attachment for the lathe, I would break the head / valve assembly into 3 parts. Valve front and back and head. I think it would cut down on some milling. I have always liked that type of valve for its simplicity.

I am looking at several plans for this type of engine for my next project. I have not decided to stay with a set of plans or incorporate parts of each that I like. I usually vary from the plans anyway to make use of materials I already have on hand. By far this is the simplest way to go for the valve.

Go ahead and post the drawings and I will have a go at incorporating it into my project.


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## Brian Rupnow (Aug 19, 2009)

Okay---You asked for it. Now I want somebody to build it and let me know how it worked.





View attachment NEW CYL HEAD.PDF


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## Brian Rupnow (Aug 19, 2009)

And the valve body---





View attachment VALVE BODY.PDF


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## Brian Rupnow (Aug 19, 2009)

the valve---





View attachment VALVE FOR NEW HIT-MISS.PDF


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## Brian Rupnow (Aug 19, 2009)

The eccentric rod assembly





View attachment ASSY OF ECCENTRIC ROD.PDF


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## Brian Rupnow (Aug 19, 2009)

The eccentric---





View attachment NEW ECCENTRIC.PDF


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## Brian Rupnow (Aug 19, 2009)

And the new flywheel for one side only---





View attachment FLYWHEEL FOR ECCENTRIC SIDE.PDF


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## ozzie46 (Aug 19, 2009)

Brian, Thanks for posting them.

  Any particular reason the eccentric strap and flywheel are in .jpg format instead of .pdf like the rest of the files? Just wondering. scratch.gif scratch.gif scratch.gif


 Ron


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## Brian Rupnow (Aug 19, 2009)

ozzie46  said:
			
		

> Brian, Thanks for posting them.
> 
> Any particular reason the eccentric strap and flywheel are in .jpg format instead of .pdf like the rest of the files? Just wondering. scratch.gif scratch.gif scratch.gif
> 
> ...



Ozzie--I hadn't noticed that. I fixed it.---Brian


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## Cliff (Aug 19, 2009)

Brian,  I just wanted to tell you how much I enjoy your post's I have read most all of them and really enjoy how you design and build your engines if I might make a suggestion why don't you design and build a multi cylinder engine one that really makes you use your brain Cliff.


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## Brian Rupnow (Aug 19, 2009)

Cliff  said:
			
		

> Brian, I just wanted to tell you how much I enjoy your post's I have read most all of them and really enjoy how you design and build your engines if I might make a suggestion why don't you design and build a multi cylinder engine one that really makes you use your brain Cliff.



Cliff---I'll take that as a kind of left handed compliment. My poor old brain is stretched right to the limit messing about with these one and two cylinder engines. You have to remember, that up untill 2 years ago, I really had no experience running a lathe or a mill. Truly, I get as big a thrill out of a simple single cylinder engine as I would out of a multi cylinder monster.---Brian


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## Brian Rupnow (Aug 20, 2009)

This morning I changed the plain eccentric strap to an adjustable length assembly and changed the eccentric detail a bit as well.


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## SandyC (Aug 20, 2009)

;D

Hi Guy's,

Brian: - Interesting modification you have made which goes a long way to displaying the different valve operating linkages that can be used on this type of engine.

One question I have though...... why have you chosen the eccentric throw to be 0.308" when the valve only needs to travel 0.25" between full steam/air and full exhaust?

I accept that this may make setup a little less exacting, however, this just seems a large amount of lost/wasted travel and also makes the eccentric and eccentric strap larger than necessary.

Did you have a specific reason?....... Not picking holes, I'm just curious. 

Next version should be DOUBLE ACTING with SLIDE VALVE or PISTON VALVE.   ;D ;D

Best regards.

SandyC


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## Brian Rupnow (Aug 20, 2009)

SandyC  said:
			
		

> ;D
> 
> Hi Guy's,
> 
> ...



Sandy--I'm still figuring this valve business out. It seems that for every possible configuration of valving, it changes. In this case, the throw on the crank is 0.62". That should mean that the throw on the eccentric is exactly half that, or 0.31. However--and this is the part that was driving me crazy--on this particular configuration it seems to be half the crank throw, minus the port diameter in the valve (which is 0.125") minus 0.031" to give a grand total of 0.154" eccentric offset.  I didn't come by that calculation out of thin air. I went so far as to model an engine by Rudy Kahoupt, just to see how he handled it. After setting it up that way and doing the animations, it seems to work correctly. Its not just a matter of how far the valve has to travel to cover and uncover the ports---There is also a big consideration given to "DWELL"---How long the valve stays in a particular location. I am currently machining the peices I designed to see if what I calculated actually works.---Brian


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## Cliff (Aug 20, 2009)

Brian Rupnow  said:
			
		

> Cliff---I'll take that as a kind of left handed compliment. My poor old brain is stretched right to the limit messing about with these one and two cylinder engines. You have to remember, that up untill 2 years ago, I really had no experience running a lathe or a mill. Truly, I get as big a thrill out of a simple single cylinder engine as I would out of a multi cylinder monster.---Brian


Brian I understand but I still enjoy your post's especially when you are making a engine. Cliff.


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## SandyC (Aug 20, 2009)

;D ;D

Hi Brian,

Yes I agree valves and valve timing etc can be somewhat confusing at times.

Ok that explains your reasoning and on the face of it has resulted in at least a workable solution, however, I am not quite sure where you latched on to the idea that the eccentric throw had any direct, or indirect, relationship to the crank throw. Perhaps this came from Rudys&#8217; writings but I am not aware of all his work.
One thing is for sure though, that idea is simply not true.

The crank throw only dictates the stroke length of the cylinder and the only possible bearing this would have on the valve gear would be in defining the correct cross sectional area required for the steam/exhaust ports for a given maximum speed of rotation. In this case the stroke length would dictate the maximum velocity of the piston. I.E. a long stroke engine rotating at the same RPM as a short stroke engine would have a much higher piston velocity and this in turn would effect the size of the required steam ports.

The actual formula for port cross sectional area is: -

    a = Av/V

Where A = the area of the piston in sq ins.; 
	 v = piston speed, in feet per minute;
	 V = velocity of flow of steam, in feet per minute.
       a = port cross sectional area, in sq. ins.

The values of V commonly used for the steam velocity are 4000 for the EXHAUST and 6000 for the INLET, however, in the case of a slide valve or piston valve, where the same port is used for both Inlet and Exhaust the lower figure of 4000 should be used.
This will determine the required (minimum) cross sectional area for the ports.

Having calculated the required cross sectional area then the actual shape/dimensions of the ports can be determined&#8230;. In your case this is a 1/8&#8221; dia hole&#8230;.. in most slide valve engines it would be a more rectangular shape and generally would have a length of between 0.6 and 0.8 x the bore of the cylinder and having a width large enough to achieve the cross sectional are required.

Once this width is determined then the required valve travel can be defined and it is THIS that dictates the THROW required from the eccentric.

To sum this up then, the eccentric throw required for a directly connected valve drive (such as you are using) is dictated solely by the valve travel required to fully open the cylinder port to either STEAM or EXHAUST, which in turn is directly related to the port width in the steam chest.
Sadly this is not the case with the more complex valve gears such as &#8216;Stephensons&#8217; link etc where several other factors such as die slip and other geometric angularity losses would need to be taken into account, however, they are for another time.


The valve you are using is known as a Line on Line valve having neither LAP nor LEAD and in your case it is an INSIDE ADMISSION valve, since the steam/air is fed into the valve centre chamber.

In this type of valve the lands of the valve piston are exactly the same width as the steam ports&#8230;. In your case this is 1/8&#8221;.
With the piston at TDC the valve is positioned such that the land covers the port exactly and from this position it would only need to travel 1/8&#8221; in either direction in order to either fully open the port to steam or to full exhaust, therefore, the total travel required would be 0.25&#8221;&#8230;.. It can of course be made more, however, it serves no real purpose and only results in additional wear on the valve piston and bore.

This 0.25&#8221; is the required total throw from the eccentric, so the offset (eccentric radius), as you know, would be half of this&#8230;. In this case it is 1/8&#8221; or the same as the steam port width.

The eccentric would be positioned such that the CROWN (high point) of the eccentric is at 90 degrees to the crank and trailing (lagging behind) the crank for the given direction of rotation. 

I attach a PDF showing such a piston valve (albeit for a double acting engine) from which you should be able to work out the movement of the valve in relation to the piston/crank angles. Clockwise rotation is shown.

For a single acting engine (as yours) just ignore the right hand cylinder port, the right hand valve land and the inner bore shown on the valve&#8230; these are only required for double acting&#8230;. And the central groove should be a minimum width of 2 x the port width&#8230;. The remainder of the right hand side can be the full solid diameter.

Hope this is of some help, but if not, or you need some further input, then just shout.

Best regards.

SandyC ;D ;D  


View attachment Piston Valve Inside admission with no lap or lead (line on line).pdf


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## Brian Rupnow (Aug 20, 2009)

SandyC--You may very well be right. I simply don't have enough background in steam engines to agree or disagree with what you are saying. I do know that I have built a beam engine, (The one featured in this months "Home Shop Machinist") and a twin cylinder horizontal engine, and they both have the eccentric set up to have exactly half the offset on the eccentric that there is on the crankshaft.---And they both run very well!! When I set out to make this modification to my "Chucks Horizontal" I was uncertain of how to approach it, so I modelled a similar engine with a similar valve arrangement from plans originally done by Rudy Kahoupt. I know that one works well, because a friend of mine built the engine from Rudys plans. My 3D software allows me to assemble the engine, then rotate it slowly and study the valve mechanism at all degrees of rotation on my computer. I know that "It works on the computer" are famous last words, but the proof of the pudding is in the eating, as my mother used to say. I'll have this modification finished next week, and then I'll see if it works. One thing about it---If it doesn't work, I will certainly post that on this thread. I am not afraid to post my failures as well as my successes.---Brian


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## Maryak (Aug 21, 2009)

Brian,

Just to give you a feel for what Sandy is saying.

In a full sized engine with a stroke of around 50" and a boiler pressure of 180psig, the valve travel would be around 7"

A ratio of ~1:7

In some triple expansion engines the valve travel can vary between cylinders eg 48" stroke; HP valve travel 6 1/2," IP 7," and LP 8"

Think about the additional rotating mass balancing problems if the valve travel was half the stroke and the engine at say 150 rpm.

Hope this helps.

Best Regards
Bob


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## SandyC (Aug 21, 2009)

;D ;D

Hi Guys,

Ain't valve gear fun :big: :big: :big: :big: :-\ :-\ ;D ;D ;D

Brian,

Don&#8217;t get me wrong my friend; I am not saying your design will not work.
In fact I expect it to work just fine, just like all your other engines, since the valve over travel is, in this case, not going to present any major issues.

What I was trying to establish was how you came up with the eccentric offset and your explanation provided the answer. No problem on that score and in this particular case it should not give you any issues.

Ok, having established your method, what I am now trying to convey to you (and any others who may be following this thread) is that the required valve travel, and hence the eccentric throw are not directly related to the crank throw but to the required cylinder port width, which in turn is related to piston speed, piston area and steam velocity.

Piston speed is directly related to rpm and the engine stroke, so in this instance crank throw is important&#8230; but not in the way you are relating it.

Lets take a couple of examples: -

1st lets take an engine with 1&#8221; bore and 1&#8221; stroke rotating at 500 RPM

2nd Lets compare this to an engine of 1&#8221; bore but having a 5&#8221; stroke rotating at 100rpm.

If you use the formulae I gave you in my last post, and using 4000 for the steam velocity, you will see that in both these cases the required port cross section area is identical at 0.01635 sq ins.

edit: in the previous posted formulae I neglected to state that the resulting cross sectional area (a) is in sq.inches. Original post edited to add this fact. end edit.

The piston speed is also the same in both cases (83.333ft/min) but the strokes are not; with the second example being 5 times greater.

In both cases the required port cross section can be obtained by drilling a hole of 3.7mm dia (0.145&#8221, this being the nearest generally available drill size (actually a number 27 drill).

The required piston valve would need to have a land the same as the port width (0.145&#8221 and the total travel required would be twice this value (0.290&#8221 in order to open the port fully to both steam and exhaust.

From this it is clear that the eccentric throw is only required to be the same as the port width at 0.145&#8221;.

Clearly the same valve and eccentric dimensions can be applied to either of the example engines and both would work to the design specifications.


Ok, lets compare this to the values you would get using your method for these 2 examples: -

In example 1 the stroke is 1&#8221; so the crank throw is 0.5&#8221;.

If you now deduct half of this we arrive at 0.25&#8221;.

If we also deduct the port width (0.145&#8221 we arrive at 0.105&#8221;; which is smaller than the port width.

You then go on to further deduct &#189; the port width (0.0725&#8221; which results in 0.0325&#8221; for the eccentric offset.

The result would be an eccentric having a total throw of only 0.065&#8221;.

Clearly this is not correct since it results in an eccentric with far to small a throw.



In the second example we have a stroke of 5&#8221; so the crank throw is 2.5&#8221;

Deducting &#189; of this we arrive at 1.25&#8221;.

If we now deduct the same 1&#189; x port width from this (0.145" x 1.5 = 0.2175&#8221 we arrive at an eccentric offset of 1.0325&#8221;, which will result in a total throw of 2.065&#8221;

Again this is clearly not correct since we now have an eccentric with an extremely large throw.

Ok Brian, please do not think for one minute that I am picking holes in your design&#8230; nothing could be further from the truth.
What I am trying to do is help you to understand the theory a little better, I hope it will be seen as such.
This whole issue becomes far more important when you come to designing double acting engines where the valve travel must be constrained to quite tight tolerances&#8230;or very strange things, or even damage, can occur.

To this end, I trust the above will go some way to your understanding and help you to design your engines more easily.

Best possible regards.

Sandy. ;D ;D


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## Brian Rupnow (Aug 21, 2009)

whoops!!! Somehow I missed posting this one.





View attachment INFEED PIPE.PDF


View attachment INFEED PIPE.PDF


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## Brian Rupnow (Aug 21, 2009)

Today I made the intake pipe and soldered it to the valve body. I also completed the eccentric cam and slid it onto the crankshaft. (By the way, that cranshaft isn't as badly chewed up as the picture makes it look.) Hopefully I will get the eccentric strap made up this weekend so I can try this engine out.--It wil do quite nicely with one flywheel on the far side from the cam for try-out.


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## Brian Rupnow (Aug 22, 2009)

Well---This is it!!! Perhaps my valving design is a bit "wonky" according to sandyC, but ya can't argue with success. (Sandy--I will try and incorporate your design into my next modification.)


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## vlmarshall (Aug 22, 2009)

Sandy, thank you for that excellent information. I've saved it as a text file for future use. ;D


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## Brian Rupnow (Sep 3, 2009)

Of the 5 steam engines I have built, this design is probably one of the simplest and best runners of the lot.--Especially when made with this relatively simple valve set-up and cylinder head instead of the "hit and miss" version. If anyone admires these engines and is looking for a "first engine" to build, I highly recomend downloading my plans from the download section of the forum and using this cylinder head/valve arrangement to get their feet wet. If you want to try building the governor and the "Chuck Fellows patented Pop Pop cylinder head/valve arrangement", it can always be added at a later date. This is a great little engine, in either guise.---Brian


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