A small steam engine

[Maryak]

Rich,

Magnificent :bow:

Almost seems a shame to run it with such a brilliant bling job.

Best Regards
Bob

 

[firebird]

Hi

Very nearly, but not quite. ;D ;D ;D ;D



I hope to have another go tomorrow.

Cheers

Rich

 

[NickG]

What happened Rich? Did you not get enough pressure? Can't remeber whether you did or not but it might help running the steam pipe through the firebox to sort of superheat the steam. Just a thought.

Nick

 

[firebird]

Hi

Very very very nearly ;D ;D ;D........................ but not quite



Nick, I was getting 20psi easy when I tested it but the burner doesn't seem to be working well enough in the enclosed space of the fire box, hence the modification of drilling some air vents around the back to help (hopefully) the rearmost wick to burn. John Bogstandard has also suggested lagging the main steam pipes to help prevent the steam from condensing. The oil/water separator seems to be working but has a lot of water in it for such a short run which would also suggest that water and not steam is getting through to the engine.



Oh well, back to the drawing board, unfortunately not today though.

Cheers

Rich

 

[firebird]

Hi

I haven't had any time in the workshop this week but I hope to get some at the weekend. As mentioned before I intend to drill some holes around the back of the firebox to give more air to the rearmost wick. Should I drill the holes low down or higher up, say in line with the wicks??????

Cheers

Rich

 

[Kermit]

Air flow should be as parallel with the flame as possible. Coming from directly below the flame would be the ideal to shoot for.

Keep it low and deflect below horizontal maybe?..use some kind of vanes inside the opening pointed downward...

being an enclosed area,pointing the incoming air at the floor might get the currents to collide in the center and go upward toward the flame...

 

[firebird]

Hi Kermit

That sounds good, I'll drill drill them just below wick height.

Cheers

Rich

 

[NickG]

Or would keeping the holes high draw the flame up for the oxygen? How does the water separator work?

 

[Krown Kustoms]

I would have never thought a water seperator, that is a great idea. It also looks good.
-B-

 

[firebird]

Hi

Thanks -B-

Nick, the steam/oil mixture enters the separator through the smaller pipe. This pipe is angled slightly downwards and towards the wall where the steam condenses and the oil separates out. The exhaust steam then passes out through the larger pipe and up to the funnel.

cheers

Rich

 

[SandyC]

;D ;D ;D

Hi Rich,

That is coming along very nicely... congratulations... very nicely done.

As far as the air holes are concerned I would suggest that you put at least 3, possibly 4, equi spaced holes of at least 1/2" dia around the rear part of the firebox with their height centred approx level with the top of the burner main tank body.
Spirit burners need a lot of air.

I have a few other suggestions to make, however,I don't have time to write them all tonight (other half wants to go to bed ( can't have any fun these days...LOL)).

I will post again in the morning at some point.

Keep happy.

Best Regards.

Sandy. ;D ;D

 

[SandyC]

;D ;D

Hi Guy's,

This has turned out to be a bit longer than expected so I will post it in 2 separate posts.

PART 1.


OK Rich, as promised here are my observations/suggestions for your small steam plant.

First let me say that you have made a most excellent job of designing and building this model and I am sure it has given you a lot to think about during it’s construction.
From an eye-pleasing viewpoint there is very little to consider as BEING IN NEED OF IMMPROVEMENT and for that you are to be commended.

However, and yes there is always a however, what is pleasing to the eye does not necessarily equate to also being operationally effective/correct/pleasing and when your design/layout is considered from this view-point there are some improvement to be had.
They may not look as good/neat but operationally they will be much better… such is the way of such things… it is rare to get it both ways in this life.

Some of what follows can be reasonably easily achieved with some small alterations, whilst others are inherent in the design and cannot be easily rectified on this unit, however, they can, and should, be considered for your next build.

Do not feel under any obligation to make any of the following changes Rich, they are only meant as recommendations…. In fact, one or two of them you have already made reference to.

I will list the recommended changes/improvements first and the reasons for suggesting them and then go on to suggest possible ways of achieving at least some of them.

Most of the improvements are associated with the pipe work and it’s layout.

In general, all steam and exhaust pipe work should be as short and direct as possible, with as few bends as possible, and should be of a suitable bore size for the pressure and velocities involved.

1/ Your steam feed pipe from the boiler could be made a little shorter overall by eliminating the large loop bends; it should also be lagged (including the short section between the lubricator and the engine inlet valve).

2/ Ideally the exhaust port/and pipe exiting the engine should be at least one pipe size larger in dia. than that used for the steam inlet pipe.
This is because exhaust steam is at a lower pressure and temperature and will have a lower velocity through a given pipe dia. than the higher temperature/ higher-pressure inlet steam.

I accept that the pipe/port size is not so easily changed on your set-up Rich since this would also mean changing the exhaust connection on the engine and also the inlet side of the OIL TRAP/SEPARATOR so probably best left as is. This is one of the things to remember for the next one.

I would though recommend that you lag the short pipe between the engine and the OIL TRAP/SEPARATOR inlet.

I will come back to the OIL TRAP/SEPARATOR a little further down.

3/ The pipe leading away from the OIL TRAP/SEPARATOR to the side of the funnel should take a continuous RISING path and should be at least ONE pipe size larger than the inlet side, for the same reasons given in (2) above.
I know you have already done this RICH, however, in the light of (2) above it should be one more size larger still.
Also, in this particular case, it would pay you to LAG it.

You most certainly need to eliminate the long horizontal loop section, since this will allow any condensate to accumulate in the horizontal section, which would partially, or totally, block the pipe.

Ok then Rich, the above are the main areas for the most easily achievable improvement, There are other, but they are a little more obscure and I will attempt to describe some of them later.

So how can these more obvious/easier ones be best achieved?


By far the most difficult one is Number 3 above, since the funnel inlet is on the wrong side relative to the outlet from the OIL TRAP/SEPARATOR.

SOLUTION…. Undo the 2 screws holding the main boiler to the burner housing and rotate the boiler 180 deg. And re-affix with the 2 screws. This will place the funnel inlet on the same side as the outlet from the OIL TRAP/SEPARATOR…. (In the words of the Meerkat… SIMPLE)

Take the outlet pipe from the OIL TRAP/SEPARATOR diagonally upwards to the side of the boiler barrel, straight up the side of the barrel and across to the funnel inlet at an upwards angle.

This satisfies both the KEEP IT SHORT and CONTINUOUSLY RISING requirements and eliminates the long horizontal bend.

As already stated above… I recommend that you also lag this pipe on this layout.

The connections for the steam feed pipe and siphon tube for the pressure gauge will need to swap bushes, but otherwise will follow much the same routes as at present.
The only change here would be the length of the steam pipe (get rid of the long sweeping loop bend) and the lagging of the steam pipe.

That should take care of (1) and (3) of the above as far as can be done without more severe changes being made to the main components.
Number 2 we have already dealt with.

 

[SandyC]

And here is PART 2... some of the more obscure things...

OIL TRAP/ SEPARATOR

This component is responsible for more confusion than almost any other as far as model steam engines are concerned.

Amongst model steam enthusiasts it is, more often than not, referred to as a CONDENSER and most people would know exactly what this component was. However, in the true sense, a condenser is the last thing it should be called, since condensing is not its function.

The purpose for its inclusion in our model steam plant is to help extract the waste STEAM OIL from the EXHAUST steam, whilst at the same time NOT CONDENSING the steam itself.

The STEAM OIL is not, as sometime suggested, in a true vapour form but takes the form of small globules of HOT and very FLUID steam oil suspended in, and carried within, the high velocity steam entering the engine.
Some of this suspended oil will impact upon the surfaces of the cylinder walls, piston and other engine components where it forms a fairly even layer of oil, thus lubricating the engine.

Some of this suspended oil will pass straight through the engine and leave through the exhaust port having done no work at all.
Some of the oil that did get onto the cylinder walls and piston surfaces will also leave via the exhaust ports, but some will always remain within the engine. This forms a protective layer when the engine cools after use and helps prevent any corrosion.

So, it is the temperature of the steam that reduces the VISCOSITY of the STEAM OIL such that it is very, very fluid but it is the VELOCITY of the steam flow that carries it in the form of small globules.
The oil is not a true vapour, since that would require very much higher temperatures to achieve.

HOW then do you remove the oil?

Simple answer is… slow down the steam flow velocity and the oil will fall out of suspension.

This is exactly what the OIL TRAP/SEPARATOR is designed to do.

Exhaust steam (carrying some waste oil) will enter the OIL TRAP/SEPARATOR at a velocity governed by the exhaust pressure and the bore of the connecting pipe work.

On entering the main chamber of the OIL TRAP/SEPARATOR, via a smallish bore entry pipe, the exhaust steam is faced with a relatively HUGE space, having a much larger cross section than the entry pipe, GREAT says the steam, I can expand, and I doing so its velocity will fall, as will it’s temperature and pressure.

If the entry steam is also directed towards the sides of the expansion chamber the oil, contained in the expanding steam, will have a large surface on which to collect, so aiding the separation.

The expanding steam, now free of oil, will exit the expansion chamber through the larger bore outlet pipe and can be directed to atmosphere via any chosen route.

In Rich’s case it is passed up through the inside of the funnel to aid the burner drafting of the boiler.

NOW for the tricky bit… Whilst the steam is expanding and slowing down in the expansion chamber it gives up some of it’s LATENT heat to the walls of the chamber… if this heat exchange is too high then the steam WILL CONDENSE back in to water.

The trick is to have a large enough chamber; with a large enough surface area to slow down the steam and collect the oil that drops from suspension, but without making the chamber so large that it can take too much heat from the steam.
To this end the cooling MASS of the OIL TRAP/SEPARATOR, and any heat absorbing surfaces it is in direct contact with, must be given close attention.

The best balance is to arrange for the temperature of the chamber walls to be just a shade lower than that of the steam, which will also aid the oil separation by way of increasing its viscosity a little, but still remain above the condensation temperature of water steam.
By allowing the outside walls of the chamber to be in contact with the surrounding atmosphere then this will conduct some heat away from the chamber walls…but this should not be too excessive or the steam will condense on contact.

SORRY RICH, but on this one you have got it a TAD WRONG… you have bolted yours down to a very large heat sink.

I would suggest that you introduce an insulation layer between the OIL TRAP/SEPARATOR and the BASE PLATE.

The steam leaving the OILTRAP/SEPARATOR should, in an ideal world, take the shortest possible route to atmosphere.
In practical terms, as in your case Rich, a certain length of pipe work is necessary.
Now, the exhaust steam is at very low pressure and also is very close to condensing temperature so the need to maintain this temperature until it reaches the atmosphere is paramount, otherwise it will condense in the pipe and create un- wanted issues… hence the suggestion to LAG it… furthermore, if the pipe is mounted in a continually rising format, then any condensate that does form, especially whilst the set up is warming up, then it will pass back into the expansion chamber under gravity.

Finally Rich, you expressed some concern over the amount of condensate collected in the OIL TRAP/SEPARATOR even though you only made a short run… Well, think about the MASS of the engine, it’s standard and the base on which it is mounted, compared to the relatively small amount of HEAT available in the small amount of steam contained in the cylinder. When your engine is cold (first starting) most of this HEAT will be extracted by conduction into the MASS of the engine (resulting in condensate inside the cylinder) and will continue to do so until the engine MASS reaches steam temperature… this could take some time… especially if you also consider the HEAT loss away from the engine MASS through its large surface area being in contact with the surrounding air.

Ok Rich, and Guy’s, that will do for now… Rich has come a very long way in such a short time and has learnt a great deal on his journey… there are a good few lessons to be learnt from this latest endeavour and I am sure he will make the most of his experiences with it.

Best regards to all.

And remember, no one knows all the answers, some of us may have more experience in certain areas but never the less can still learn new things, and there is always something to learn from everything we do.

SandyC. ;D ;D ;D

 

[firebird]

Hi Sandy

Thank you very much for taking the time, and interest, in my little engine. Your input is very much appreciated. :bow: :bow: :bow:.

As you have mentioned I have learned a lot over the past couple of years but there's still a lot more to learn, don't go away ;D ;D ;D I will certainly bare in mind all you say for the next project.

I have always favoured making up my own designs rather than following a set of instructions so work on the basis of lets have a go and learn as I go along.

I will follow your suggestions starting with getting the burner right and then tweak each piece till the engine runs ok then leave it at that as I am keen to pursue other projects, time permitting.

Once again many thanks for your invaluable help, keep it coming.

Cheers

Rich

 

[firebird]

Hi

I did the mod to the firebox as a start today. After I had stripped it out it fell off the base. It seems super glue isn't good enough for this job so I ally welded it,just around the back where it wont be seen too much.

Here it is clamped together and in the brazing hearth after being welded.



Here it is set up in the mill having 7 3/8 dia holes drilled.







I'll run a new boiler test in a while.

Cheers

Rich

 

[firebird]

Hi

YEEEEEEEEEEEEEEEEEEEEESSSSSSSSSSSSSSSSSSSSSSSSSSSSS

;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

*beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer*



Cheers

Rich

 

[PhillyVa]

Hi Rich,

Sweet and I would ;D too.

Philly

 

[vlmarshall]

Hi

YEEEEEEEEEEEEEEEEEEEEESSSSSSSSSSSSSSSSSSSSSSSSSSSSS

;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D

*beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer* *beer*
Cheers
Rich

Hahahahahaha, congrats! The great big smile was a nice touch. :bow: :bow: :bow: ;D

 

[zeeprogrammer]

That was great! Congratulations. Great smile too.
I do like that hand wheel. Awesome stuff.

 

[arnoldb]

Great job Rich! :bow:
And that smile looked just like this: ;D

Well Done!