# Bob's No. 1



## BobWarfield (Jun 29, 2008)

I was taking another gander at the magnificent photos on John Bentley's (The Engine Man) site when I decided to have a go at modeling a similar steam engine. Bentley's engine is loosely based on Stuart Turner's No. 1, so I thought i"d call this design exercise "Bob's No. 1" as well. It's amazing how much time you can spend on one of these and how neat they turn out. I got this far after about 2 hours:







Here are some more views:






As you can see, I've got an interference problem with the con rod at present. I'll have to redesign the standard to clear it. Good thing I could see that in the CAD model, LOL!

This much took me about 2 hours. I'm not sure when I'll finish it. I was feeling kind of inspired and it had been a while since I fired up Rhino3D. I've got a lot else to deal with at the moment, but it was a fun couple of hours. I reckon I'm probably a good 12-16 hours of work from really finishing.

If I do get the drawings finished, they'll make a nice CNC project for me.

Hope you enjoyed!

Cheers,

BW


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## BobWarfield (Jul 14, 2008)

Spent a few more hours on this steam engine this evening and got quite a bit further:











It's been quite a good learning experience for me to sharpen my skills on the CAD program and learn a bit more about what makes one of these slide valve engines tick.

Next I have to finish off the steam chest with its eccentric linkage. I may have to research a reversing gear for it as well.

Cheers,

BW


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## Florian (Jul 14, 2008)

Hi Bob

Why do you plan the piston in that shape? ???
This causes higher wear to the piston because its contact surface with the cylinder is smaller and in the end you will have to replace the piston earlier.

Florian


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## Alphawolf45 (Jul 14, 2008)

Thats exremely good looking drawing, lots better than I can do..Indeed eventually I hope to be able to quick make drawings of some of my ideas and therewith work through some of the variations on the theme.....If a man had the skills , how long would it take to make one of them drawings?..


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## cfellows (Jul 14, 2008)

Bob, tell me again what software you are using here?

Chuck


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## Dick L. (Jul 14, 2008)

Chuck , Bob is using Rhino 3D.


        Dick


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## Bernd (Jul 14, 2008)

That'll be one neat looking engine there Bob. About how tall will it be?

And, Ya, what Florin said. Why the odd looking piston? ???

Bernd


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## Metal Mickey (Jul 14, 2008)

Lovely work, is it a commercial and costly program?


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## BobWarfield (Jul 14, 2008)

Thank you for your kind attention.

Some answers:

- Why is the piston shaped so funny? There is a functional purpose to it. If you look closely you'll spot it. It isn't the only way to solve the problem, but it was an acceptible way to me and easier than the other ways I thought of. I may yet change it, but wanted to get on with drawing the rest of the engine. Besides, a thin piston then becomes an additional safety valve on the boiler.  ;D As for wear, I doubt it'll see enough miles for that to be an issue.

- Time with skills? Unknown, as I don't really claim to have skills. This drawing took me about 6-7 hours. I had to redo several portions 2 or 3 times for it all to work out mechanically. For example, I repositioned the moving assembly to check clearances at top dead center, bottom dead center, and the "resting" positing nearest the standard that it's in. Several problems were discovered and design changes were instituted. I'm sure there will be even more of that with the steam chest and eccentric.

- As was mentioned, the program is indeed Rhino 3D. $788 from novedge.com. Be sure to shop, different outfits discount it differently. I think I got mine for $695. Whether that is a lot or a little depends on your perspective. All these CAD programs are kind of a bear to get any good at, so I wanted one I could live with for a long time. I also bought Alibre and used it for 3 months, but just didn't like it as well. Others strongly prefer it. I'd try several and see what fits, but just remember it'll take you 3-4 drawings to feel at all comfortable enough to make a judgement on which is best.

- Bernd, on size, this one is currently 4" x 2" x 8" tall or so. But the size is kind of immaterial, it's more about proportion. If I like the proportions, I can scale it very quickly in the CAD program to about any size I like. Keep in mind that can change the running characteristics, especially for touchy things like an LTD Stirling. Should be fine for a pretty wide range for this sort of engine though.

I find this program has been extremely useful in machine work for me. While CAD is indispensible for CNC, it's also darned handy for manual machining work. For example, when I was making up the Team Build I immediately redrew the parts with decimal dimensions instead of fractions and stuck the prints up in the shop with magnets. Perhaps more interesting is the ability to "calculate by drawing." For example, to figure the mechanical clearances on the steam engine above just by moving the parts as they would in the working prototype and taking dimensions you can "measure" what's happening without resorting to trigonometry. Or, when I was fitting my collet chuck to a backplate, I knew I had an error, but wanted to figure out exactly how to compensate for it. I describe how I used the CAD program to do that here:

http://www.cnccookbook.com/CCColletChuck2.htm

All in all, not sure I could be very productive without my CAD program. For those that are curious, a bunch more of my drawings are up on my web site here:

http://www.cnccookbook.com/MTCNCRhinoPen.htm

They give a little idea of what you can do with Rhino3D even if you're not all that skilled like me!

Cheers,

BW


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## CallMeAL (Jul 14, 2008)

Nice drawings!! :bow:

I am not trying to hijack your thread, but the questions about CAD and drawing programs lead me to ask if anyone uses Google's drawing program SketchUP?

I have used it to lay out some of my model stuff and it is quite amazing for the price: Free! ;D It is fun and relatively easy to use especially if you've not used a 3D drawing program. Try the download here:

http://sketchup.google.com/

An example:


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## Bernd (Jul 15, 2008)

BobWarfield  said:
			
		

> Thank you for your kind attention.
> 
> Some answers:
> 
> - Why is the piston shaped so funny? There is a functional purpose to it. If you look closely you'll spot it. It isn't the only way to solve the problem, but it was an acceptible way to me and easier than the other ways I thought of. I may yet change it, but wanted to get on with drawing the rest of the engine. Besides, a thin piston then becomes an additional safety valve on the boiler. ;D As for wear, I doubt it'll see enough miles for that to be an issue.



Looks like you won't have to cut an opening in the top and bottom heads for the steam to enter the cylinder? 

As far as an additional saftey valve for the boiler I won't think so, but I could (and usally am) wrong. 



> - Bernd, on size, this one is currently 4" x 2" x 8" tall or so. But the size is kind of immaterial, it's more about proportion. If I like the proportions, I can scale it very quickly in the CAD program to about any size I like. Keep in mind that can change the running characteristics, especially for touchy things like an LTD Stirling. Should be fine for a pretty wide range for this sort of engine though.



That's a pretty good size. I like the idea of being able to scale it once complete. 

Bernd


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## Brass_Machine (Jul 15, 2008)

Nice engine so far Bob! I really like the design.

*highjack

Bob is being modest about Rhino3D. I tried to use it and just couldn't wrap my head around it. However, I started using Alibre and that works very well for me. Maybe we should start a different thread about 3D cad software instead of highjacking Bob's thread about his engine.

*/highjack  ;D

Eric


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## Brass_Machine (Jul 15, 2008)

Duh! forget to ask Bob the question I wanted to in my previous post... 

Bob, are you going to CNC the base or cast it?

Eric


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## Florian (Jul 15, 2008)

Hi 

I have seen the purpose of this strange looking piston. 

But i think there is a much better way of doing it: 

Take a 4mm endmill and cut a groove to the end of the cylinder (The endmill parallel to the piston), then your Pison just needs two very small chamfers.
Like that: 






(hope you can recognize what i mean) 

otherwise.. just tell me and i will make a sketch.

By the way, to reduce the weight of the moved parts, you can make a circular U-groove on both sides of your piston (just like the real ones)

Cheers
Florian


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## BobWarfield (Jul 15, 2008)

Florian, you did see the purpose of the piston bevel, and I do like your idea better! I will amend the drawings...

Brass, I would like to do both. CNC and cast. CNC is a wonderful way to produce the casting molds and casting is tremendously more economical on expensive brass than turning great big blocks into chips. What remains to be seen is whether I'll have time to build a foundry furnace and learn to cast. Just so darned many things to learn, do, and build in this silly hobby. I do think CNC and casting are great bedfellows though. 

You also illustrate my point when I tell everyone that which CAD program I like is not important: you need to go try several and see which one YOU like. They're all different, all idiosyncratic, and they all have their pros and cons. Most of all, they all take a lot of learning. I can't imagine being proficient in more than one. You'll be making a fair time investment, so you want to make sure you like it well and won't have to switch later.

While we're on the subject, look carefully at the file format support your preferred program offers. Will you be able to exchange files with others in the common formats? Autocad, IGES, and several others (can't remember right now) are real important. If you will ever care about CNC you want to make sure you can share files with the CAM software out there to generate your g-codes. 

Honestly, the CAD/CAM/CNC world is too hard right now. Too much too learn. Manual machining is a lot to learn for starters, and then to have all this computer stuff on top of it is hard.  Then you have to throw all the electrical/electronics/motion control on top of that. I do computers for a living, so I actually like the silly buggers and tolerate it. Go figure.

Cheers,

BW


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## BobWarfield (Jul 16, 2008)

Here is a slight refinement on Florian's suggestion:






Since it'll be CNC, it's just as easy to cut a pocket with the 1/8" end mill as do a straight plunge groove. Hence I did a "Hot Rod Porting Job" on the cylinder.

For those curious about Rhino3D, I captured what it took for me to do this little redesign on a page:

http://www.cnccookbook.com/CCBobsNo1SteamPort.htm

It's almost all pictures showing the step-by-step. It gives a good flavor for what it's like to use Rhino, at least for my limited skill level. The whole thing took me about an hour including making the web pages and tweaking the screen shots. Figure twenty minutes or so if I was just using Rhino and not documenting anything.

Lots of advantages to this new design. I need to redo the piston and "mill" the passages from the steam chest, but you can see what the new idea looks like. It actually simplifies the manufacture of the cylinder and I would think improves performance.

Thanks Florian!

Cheers,

BW


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## Florian (Jul 16, 2008)

Hey Bob

If you do it exactly that way, it won't work. The grooves are to long (in the cylinder). 

What i mean is something like that:






Florian


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## BobWarfield (Jul 16, 2008)

Florian, the size of piston and the stroke are such that both steam passages are never uncovered at the same time at either end of the stroke. The piston always covers one port or the other, or in the exact middle of the stroke it leaves them open and balanced (hence it won't self start if left in exactly that position).

Remember, that's why the piston started out looking funny in the first place. The original steam port arrangement was almost exactly what you've shown except that the holes were made closer to the cylinder centerline to clear the flanges.

Spent about 2 hours after I posted working on the eccentric. I did some research on that because I am trying to decide whether to provide a Stevenson linkage and wanted to see some examples. I found several articles that may be of interest. First, the "Steam Happens" page lists lots of steam launch pictures all together for easy reference:

http://earlmorse.org/steamboatingpages/steamhappens2/steamhappens2.htm

Many have the linkage and all are very similar to this engine with some minor variations.

More interesting was a page from the "Encylopedia Titanica" that gives enormous detail about the steam propulsion of the ill-fated Titanic. I really enjoyed this page and got sidetracked for quite a while reading it:

http://www.encyclopedia-titanica.org/titanic_prime_mover.html

These ships were amazing feats of engineering in their day, and a suprising number of photos survive. 

I'm still debating whether to provide a linkage, but I will likely finish the design without ala John Bentley's and then do a linkage design as well. The parts are "modular" with CAD so I can easily produce a second with the linkage. Also, assemblies like the cylinder and steam chest can be interchanged onto new designs very easily. Horizontal mill engine anyone? Scale the cylinders to produce a triple expansion?

Cheers,

BW


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## Florian (Jul 16, 2008)

Hi Bob

I have something for you: 

http://www.tcsn.net/charlied/
These are computer based simulations of all the different valve gears. I think this will help you. 


I still don't see why you want to make your steam ports like your model shows it... :-\

I think, what i have shown you is quite easy to realize. Just need a 4endmill (center-cutting), then clamp the cylinder at a ceratin angle to get the right direction for the steam ports. Then you use the endmill to bore the ports. 

Florian


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## SandyC (Jul 16, 2008)

Hi Bob,

You stated: - 





> the size of piston and the stroke are such that both steam passages are never uncovered at the same time at either end of the stroke.&#160; The piston always covers one port or the other, or in the exact middle of the stroke it leaves them open and balanced (hence it won't self start if left in exactly that position).



On the contrary.... this is the one place the engine would be most likely to self start.

On a single cylinder engine, the no start positions are at TOP and BOTTOM dead centres... or very close to them depending upon valve lap/lead etc.

It is not the piston position that determines this... it is the valve gear and on a single cylinder engine with the piston at 1/2 stroke then the valve would be positioned such that both the INLET and EXHAUST ports were open.

ON the steam side of the piston...&#160; as the piston approaches say 70% - 80% stroke the valve gear (slide valve) would first close the inlet port (known as CUT-OFF) and the piston would then be pushed further along it's stroke by steam expansion.... at a point somewhat closer to the cylinder end the slide valve would open the EXHAUST port for that side /end of the cylinder.(known as RELEASE)

On the EXHAUST side of the piston.... from slightly before the beginning of the stroke the SLIDE VALVE would be in the EXHAUST open position and as the piston moves towards the exhaust end it pushes the spent steam out of the cylinder....... it remains in this state until almost at the end of the stroke...say 85% - 90% or so (depends upon exact valve timing etc..... at which point the slide valve CLOSES the port (known as COMPRESSION) and any remaining steam is then compressed by the advancing piston into the top/bottom of the cylinder..... the idea is to get the pressure up to almost the same as the incoming steam at the commencement of the next stroke.

The COMPRESSION is governed by the point of valve closure and the clearance volume of the cylinder at the exact DEAD CENTRE (either top or bottom).... to this end there is always a clearance space between the piston and the cylinder end cover (on a 2" dia cylinder this could be as much as 1/16" or more).
The clearance space also includes the volume of the steam transfer passages, which you have just made ENORMOUSE by your modification.... this will actually make the efficiency of the engine LESS rather than MORE..... remember steam engines do not operate in the same way as an internal combustion engine and huge transfer ports are just not needed.... indeed, they can be detrimental.

The other down side to your LONG WIDE ports is that you increase the likelyhood of piston blow by (I.E the steam can more easily blow past the side of the piston closest to the large port area, unless you make the piston much longer than normal.

I am impressed with your basic design, however I think you would be well advised to reconsider using such large cylinder port openings.

Take a good look at some of the valve gear on the links FLORIAN has provided I think you will see more clearly how the valve gear actually works...... it will also show the valve timing as % of stroke.

Have fun.

Best regards.

Sandy&#160; ;D ;D


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## BobWarfield (Jul 17, 2008)

Sandy, you raise some interesting points. I see now that my drawing has the timing 90 degrees out of phase with the max speed timing. My version would run very slowly. Max performance would inject max steam with the piston at top.

The point you make about the efficiency of large versus small steam ports is an interesting one too. You're looking to maximize the expansion ratio available for efficiency's sake. This is another neat thing you can do with the CAD program: you give it a shape, it tells you the volume. So I took a look at the volume of the steam ports--my design is 2.4 times the volume of the other. But what impact does this have? It changes the volume at top of stroke by only about 5%. Methinks that can't have a big effect on performance. With CNC, it would be so easy to simply make up both steam port variations that I am inclined to do so and observe under actual test conditions which one appears to work better. If I don't like the large additional port area, it's trivial to just cut an arc of lesser extent with the endmill right back to plunging the cutter with no arc. The point was really to save the angled set up and provide clearance around the piston.

After a little search, I found there is more at work here than has been discussed. Clearly there is some size port that is simply too small to flow enough steam relative to the timing of the engine to be efficient. The question is what that size may be? There may be a size that is too large as well because of the deleterious compression effect you mention. I did find a fascinating a fascinating discussion of this here:

http://www.trainweb.org/tusp/philosophy.html

The Wardale entry does suggest maximizing the flow characteristics of the steam input in a way that will increase their volume it seems. These suggestions are pretty similar to internal combustion hot rodding in many ways. The emphasis in any case is on maximizing the pressure differential between intake and exhaust.

Lastly, this valve timing thing is troubling. Not so much from the standpoint of the eccentric gear. If nothing else, a Stevenson linkage lets me vary that timing continuously after the fact so I can find the sweet spot empirically if nothing else! Rather, I'm troubled in considering the effect on timing that the relative dimensions of the slide valve, the stroke of the slide valve, and the steam ports will have on the engine's effective timing. The example I used was Bentley's, and it's pretty straightforward. From the photos, he's got three passages identical to mine and a slide valve cavity that just covers 2 adjacent passages. There is not a lot of "dead" area on the valve in his design to block off all the passages without exhausting in order to let steam expansion do it's work. The literature certainly talks about injecting high pressure steam and then letting it expand. It appears to me that most of the model slide valves I've seen don't do this very effectively. Instead, steam seems to be feed pretty continuously through the power stroke and then we abruptly switch to exhausting. 

Have I misunderstood these designs or is that in fact what is happening? I suspect I need to go back and look carefully at the impact of those relative dimensions. I suspect small changes might have a big impact.

I recognize that in all likelihood the little models are greatly simplified relative to their prototypes and probably are not anything remotely close to design efficiency. That's fine, I'm not building a moon shot here, I'm just curious. 


Cheers,

BW


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## SandyC (Jul 17, 2008)

Hi Bob,


All good clean fun is it not?

Ok, I think I can see where the confusion lies.

It would appear that you are, to some degree, confusing increased port cross sectional area with the volume of the cut-outs you are making in the cylinder wall.

Taking a look at David Wardale&#146;s design criteria for RED DEVIL you will see that CRITERIA 3 calls for MAXIMISING PORT DIMENSIONS to achieve max flow.

For this read&#133;. SUFFICIENT DIMENSIONS for the volume of steam required.

He also states in CRITERIA 6&#133;.. MINIMISE cylinder CLEARANCE VOLUME.

You are quite correct in your thinking regarding the ports being made too small for the amount of steam; however, there are other things to consider when designing them&#133;. Making them unnecessarily large being one of them.

Ok, so how do we proceed? 

The PORTS we are discussing are those at the steam chest end of the transfer passages&#133;. I.E. the ones that the slide valve directly opens and closes.

The size of these, and the steam transfer passages leading to the cylinder, will be determined by the velocity of the steam and must be sufficiently large that the steam is permitted to follow up the advancing piston without pressure drop, at the highest engine/piston speed.

The minimum dimensions of the required ports can be determined using the following: -

&#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; &#160; a=Av/V

Where a = cross sectional area of the port in sq in.

&#160; &#160; &#160; &#160; &#160; &#160; A = Area of piston in sq in.

&#160; &#160; &#160; &#160; &#160; &#160; v = piston speed in feet per minute.

&#160; &#160; &#160; &#160; &#160; &#160;V = Velocity of steam in feet per minute.

The values of V commonly used are 4,000 for the exhaust and 6,000 for the steam inlet.

These values can be increased to as much as 6,500 and 8,000 respectively where high speed; high-pressure engines are concerned.

For most model purposes the lower, commonly used, figures are generally more than adequate.

Having calculated the minimum required cross sectional area for the ports, it also follows that the cross sectional area of the transfer passages needs to be at least the same&#133;. Making them larger is of no real value and can lead to an unnecessary increase in cylinder clearance volume, which can have other detrimental effects. 

Now then, it is clear from the above that the velocity figures given would result in different cross sectional areas for both steam and exhaust&#133;&#133;. Not a problem if the design calls for separate inlet and exhaust ports, as in say a poppet valve engine or a Corliss rotary valve engine.

In a slide valve engine, or piston valve for that matter, this is clearly not the case; since the same port/transfer passage is used for both inlet and exhaust alternately at each end of the cylinder.

In such a case, the port and transfer passage dimensions should be calculated for the EXHAUST VELOCITY&#133;&#133; I.E. use the 4,000 figure.

As for valve design and valve timing etc, well: -

Bentley&#146;s example is indeed exactly as you have stated, i.e. the steam is admitted for pretty well the whole stroke and then exhausted&#133; thus making no use of EXPANSION.
His valve is what is known as an EDGE-ON-EDGE (or LINE-ON-LINE) valve, having neither lap nor lead and such a valve cannot make use of expansion. 

What is required is a valve with STEAM LAP at the very least&#133;. Other things will determine if lead is necessary as well.

If you e-mail me your own e-mail address (see my profile) I have some articles and diagrams I prepared for another forum explaining how it all works.

They are too big to post directly here but I can e-mail them to you if you would like to have them.

I hope this helps you a bit more.

Best Regards.

Sandy.&#160;   ;D ;D


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## BobWarfield (Jul 17, 2008)

Sandy, you are a wealth of useful information!

I will PM my email forthwith.

Thanks for your help,

BW


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## SandyC (Jul 17, 2008)

;D ;D

No problem Bob, happy to help where possible.

PM with promised info has been sent, hope you find it useful.

Best Regards.

Sandy.


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## tel (Jul 18, 2008)

Nice going Bob, but I agree with what others have said here - the admission notches don't need to be anywhere near as deep as you are showing. As a rough guide, think the depth of the spigot on your covers (the bit that goes into the bore) x2


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## BobWarfield (Jul 18, 2008)

Tel, I prefer my approach to the one you've shown. It's just a lot simpler and faster to build than either having to create a setup for the angled hole or in this case soldering tubes to carry steam. As I say, if I do build the engine, it's trivial to try it and see how it works. I have investigated Sandy's area formula and will likely reduce the size of the port somewhat. The cylinder is one of the easiest parts to produce, particularly with the steam port arrangment I've shown. If it doesn't work, I'm not out much.

Cheers,

BW


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## SandyC (Jul 18, 2008)

Hi Bob,

Hope you got the info I sent and that it has helped you a bit with the valve timing questions.

Another thing you might need to consider is how your proposed admission ports will effect the use of piston rings.

If you try and use silicone o-rings then these will be very quickly destroyed by passing over the exposed passage edges... they will&#160; expand into the passage and then get caught up on the sharp bottom edge.... the sharp vertical edges will also try to cut through the ring.

If you use expanding metal rings, (cast iron split rings) then you run the risk of the gap getting into that part of the bore (unless you pin them) and the end/s could spring out a little into the passage, due to not being supported...... again the result would be a mangled ring and probably, in this case, a mangled bore.

I accept that your method may be easier than angle drilling, however, this don't make it mechanically correct.... one possible alternative would be to machine the main cylinder with a larger bore, machine the ports as you have drawn, then press fit a true bore cylinder liner having small admission notches at each end... in line with the main passages.
This would certainly eliminate the piston ring problems, and still allow you to eliminate the angle drilling.

Just something else to consider.

Keep at it.

Tel,  nice radial engine.... is that one of Westbury's?   CYGNET ROYAL perhaps ?

Best regards.

Sandy. ;D ;D


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## BobWarfield (Jul 18, 2008)

No need even for a bore liner. With a thick enough cylinder wall, one could simply drill the vertical passage (analagous to tel's pipes) and then groove the very top of the cylinder. Given that it's CNC, unless you dislike the thicker walls, this is again, just as easy as the approach in the drawing. 

I'm done worrying about the steam ports at the moment for the drawing. As I say, I plan to make ithe first one as drawn. If it works well enough, I'll stop there. 

Right now I am focused on the eccentric.

Cheers,

BW


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## tel (Jul 18, 2008)

SandyC  said:
			
		

> Tel,  nice radial engine.... is that one of Westbury's?   CYGNET ROYAL perhaps ?
> 
> Best regards.
> 
> Sandy. ;D ;D



Well spotted Sandy, it is indeed my fabricated version of the Cygnet Royal


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## tel (Jul 18, 2008)

BobWarfield  said:
			
		

> Tel, I prefer my approach to the one you've shown. It's just a lot simpler and faster to build than either having to create a setup for the angled hole or in this case soldering tubes to carry steam. As I say, if I do build the engine, it's trivial to try it and see how it works. I have investigated Sandy's area formula and will likely reduce the size of the port somewhat. The cylinder is one of the easiest parts to produce, particularly with the steam port arrangment I've shown. If it doesn't work, I'm not out much.
> 
> Cheers,
> 
> BW



Fair enough Bob - nothing wrong with a bit of experimentation either, it's just that I have got very comfortable with drilling those angled steam passages over the years, here's another of my fabricated creations, but it doesn't show anything of the innards.


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## BobWarfield (Jul 18, 2008)

Nice one Tel!

BW


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## steamer (Sep 13, 2008)

Hey Bob,

Here's another method of putting in steam passages that are wide and narrow.





Not exactly a fine representation of a steam cylinder, but "squint" a little if you could.

Mill the passages in the block and then press in a cylinder sleeve.  Mill the top where it meets the head and your as close to as cast as one can be, without all the core drift....

Dave


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## BobWarfield (Sep 13, 2008)

Very nice, Dave!

Best,

BW

PS The drawings are close enough I would be CNC'ing if I had my machines converted. Here's what I've gotten to:











I'll definitely give it a whirl when I get the CNC conversions done.


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## steamer (Sep 14, 2008)

Hi Bob,

Yeah I figured you were ready to cut, I was reading through your thread and saw the discussion about ports....and remembered that little kink.


Dave


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