Front End situation

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Front End situation

Post by DaveLathrop57 on Sun May 12, 2013 1:28 pm

There's nothing left in the smokebox apart from the old exhaust stand. So, we can work within the parameters of it and the stack to design a new efficient exhaust system.

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Re: Front End situation

Post by Overmod on Sat May 18, 2013 8:12 pm

Can you provide details from the existing drawings as attachments or files for comparison and a design start point?

Is it 'permissible' to use a fatter or non-circular stack on this locomotive?

Is the boiler equipped with blocking plates as in the Master Mechanic front end, and if so how many pieces survive? Again, current pictures would be good.

I for one would like a full four-pipe/Kordina setup for exhaust. Size that for effective back-pressure reduction, etc. We can then tinker with the Kordina length, skirt and height parameters, entraining, screens, etc. at leisure.

The alternative would be to work up some form of Giesl with distinct ports to the cylinders -- I can't help but think of the principle of the 4-stack VO in this context! What you would get is a kind of rolling entrainment from one end to the other, in the direction drawing the combustion gas (front to rear if plates and screens fitted) rather than the typical Kordina round-robin pattern...

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Re: Front End situation

Post by DaveLathrop57 on Sun May 19, 2013 10:40 am

In this instance the stack is a very visible part of the historic appearance, and will stay what it is (apart from repairing the hole in it). We're also pretty much staying with the exhaust stand base as it is cast into the saddle. what we can create is everything in between. This still allows us a lot of latitude in terms of improvement on the original design since there are NO bits of it left, and they'd probably be rusted to uselessness if there were.

I'd also mention that 17 hasn't been a great drafter either. We'll get into that a bit and see how we can make it better. The nozzle has been bored oversize at some point in the past, and the petticoat pipe is as designed on the drawing otherwise. The 17 drawings have been posted on the NorserNet archive for years now, please feel free to view them as you see fit.

Dave

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Re: Front End situation

Post by Overmod on Sun May 19, 2013 12:46 pm

Dave, give us a precise URL to where 17's drawings are.located.

Would also help to have dimensions of the stack, and a couple of views of the existing as-cast base, including if possible views of the part of the passages visible from the top. Can you borrow a borescope for some more detail?

Nigel seems to have been reasonably successful in mating cast ports to a proper four-way "stand" over which the kordina would go. Lost-foam techniques will simplify making this.

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Re: Front End situation

Post by DaveLathrop57 on Sun May 19, 2013 1:00 pm


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Re: Front End situation

Post by Low_Water_Odom on Sun May 19, 2013 5:32 pm

Since the drawings haven't yet been uploaded to the hosting site, I'm doing a temporary workaround by uploading JPEG versions of the drawings to my Photobucket site. Here are the drawings for the smokebox arrangement (as delivered, not indicative of what's there now), the stack, and the exhaust nozzle:






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Re: Front End situation

Post by DaveLathrop57 on Sun May 19, 2013 5:42 pm

Thank you Hugh. As mentioned, the stack and the base the exhuaust stand bolts on to remain - everything else in between is no more. That's our opportunity........

Dave

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Re: Front End situation

Post by Low_Water_Odom on Sun May 19, 2013 6:33 pm

Meanwhile, I've found some free file hosting services. These have significant limitations (you can only download one file at a time), but it's one way of hosting and sharing the files. Here's the PDF scan for the exhaust nozzle:

PDF scan of boiler drawing

I'm not sure this is worth the trouble, but we'll try it for a while.

Hugh

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Re: Front End situation

Post by Overmod on Sun May 19, 2013 9:43 pm

Free hosting service is essentially worthless to me -- it downloads to Firefox in some format that Mac OS X cannot recognize as .pdf, and no matter what I try, Adobe Reader reports the file as 'damaged' when I go to open the download.

I get more mileage out of the .jpg versions, and of course it's a massive waste to provide scanned images as .pdf documents instead of ... well, images.

Here's the front-end situation as I see it: The entire geometry is going to be driven by the stack dimensions and taper, and this means that the draft arrangements will be scaled small but efficient, rather than 'super-efficient Lemprex' or whatever. I do think that since the blast stand is gone, there is no point in re-creating a tapered single nozzle; I'd go to the four ducts and Kordina, as indicated, and think about changing the shape of the petticoat to a 'diffuser' curve (spin it or hammer on an English wheel to shape, perhaps).

Are we enlarging the size of the steam pipes going to the cylinders? I'd think about providing additional chest volume just above the valves, which would prevent wiredrawing during the fast period of admission (a la Chapelon) but allow the average steam demand to be supplied through smaller diameter pipe.

I would keep the blocking sheets and doors more or less as drawn. although again I'd like to experiment a bit to see if convergent-divergent flow smoothing through the 'throat' where the cylinder saddle and the two steampipes converge will give better flow. It should be possible to induce some 'cyclonic' flow with vanes attached to the substantial area of netting at the front ... and that lip and its dimensions are a kludge, but we'll make that geometry variable (with a few 'brass nuts') so we can do effective fine tuning and flow observation on it.

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Re: Front End situation

Post by DaveLathrop57 on Sun May 19, 2013 11:09 pm

Interesting ideas.....few oil burners use any blocking hardware. I'm hoping Michael Guy and Dr Koopmans will chime in here soon.

Dave

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Re: Front End situation

Post by Nigel Day on Wed May 22, 2013 3:47 am

So if you have your limitations of the exhaust pipes and the old chimney at very best all you can fit is a compromised Lempor. At very least for oil firing and heavy or waste oil you will need a good Lempor or better. What's wrong with a new visible chimney if its done to the same style as the old?

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Re: Front End situation

Post by JJG Koopmans on Wed May 22, 2013 6:15 am

Mmm! Looks like a Master Mechanics front-end. Can't really read the numbers. Chimney base width 16 in and top 18,5? Length B, which one? Orifice size less than 5.25, meaning that chimney throat is oversized. Nothing on orifice throat distance. Agree with Nigel about compromised Lempor. However my suggestion is to play with modifications to the front-end and gather measured information. That would be a better contribution to the community that just posing the final solution
Regards
Jos

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Re: Front End situation

Post by Low_Water_Odom on Wed May 22, 2013 11:06 am

Hi guys- I'm away from home this week and have limited time to post. Glad to see the discussion is starting to roll along.

I just saw that the drawings (PDF scans of the original Vulcan construction drawings) have been uploaded to the internet here:

http://www.engine17.org/nhvx110/

Hopefully you'll be able to download any you're interested in.

Hugh

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Re: Front End situation

Post by DaveLathrop57 on Wed May 22, 2013 11:51 am

Jos and Nigel.....how lucky can we get in terms of expertise in this subject? Thank you both for joining in.

Nigel, I don't see any problem making a new chimney that duplicates the outer appearance of the old one if it will make for a much better front end - or, we could line it with a fabricated steel funnel in the required shape. The old one needs repair anyhow, so easy to include other internal alterations.

Let's check out the newly posted drawings and see if the numbers can't be read when downloaded and enlarged.

Dave

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Re: Front End situation

Post by Overmod on Fri May 24, 2013 7:28 am

JJG Koopmans wrote:Orifice size less than 5.25, meaning that chimney throat is oversized. Nothing on orifice throat distance.

If 'improving' this within the Master Mechanics setup (hypothetically retaining that general setup for the moment), what should be done to take advantage of the 'oversize' at the throat, with the assumption that the existing stack height and taper is retained? If we go to four-nozzle and kordina with noncircular duct profile, what is the optimal shape and dimensions at the upper end for best theoretical action at the throat, and what does that imply for back-pressure reduction and exhaust flow?

... my suggestion is to play with modifications to the front-end and gather measured information. That would be a better contribution to the community that just posing the final solution.

I believe this is one of the more significant reasons for the experiment with 110, and that appropriate access porting, easily-changed-out components, and some variable geometry be incorporated to facilitate it.

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Re: Front End situation

Post by DaveLathrop57 on Fri May 24, 2013 10:45 am

I'd remind evereybody that there's NOTHING in the damn smokebox right now between the top of the saddle and the bottom of the stack, which sits on the smokebox without coming inside. Something needs to be made.

Two of the 3 international opinion leaders in front end design have started to express some ideas here - Michael Guy is not heard from yet. Perhaps he has some idea about what the initial build might be based on his procedure?

Yes, once we get her up and running we can experiment and tinker, especially if we can build a partnership with the university engineering schools in terms of technical testing technology. We don't have any concrte proposal to apporach them with yet.

I'm going to start another part of this forum dedicated to 17. We know she's not a great steamer, and we have more opportunity to get some actual hands-on going there while we think about 110. Maybe that will help alleaviate some of the frustration.

Dave

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Re: Front End situation

Post by Overmod on Fri May 24, 2013 3:32 pm

I think my posts are disappearing again. Opinions (mone only, alternative thoughts welcome):

1) We want as long a convergent/divergent passage forward of the front tubeplate as we can manage, so re-creation of the general Master Mechanic plate arrangement makes sense even with oil firing.

2) I am treating stack size as a hard constraint, partly for 'political' reasons and partly to keep project money on the other sorts of improvement. Jos has already mentioned that the throat size is too large, not too small, and given the size of the firebox and the anticipated lower draft requirements with better thermo elsewhere, I think Nigel's four-streamlined-nozzle-into-a-Kordina arrangement ought to work perfectly well, and be pretty easy to fabricate. I believe that the flow separation in a Kordina should allow each of the four passages to be somewhat larger than a multiple nozzle would allow, so that might be a further way to reduce back pressure and/or improve smoothness of drafting (important for oil firing)...

3) I repeat that a good variable 'blower' system, that keeps draft normalized and smooths the speed at which firing changes downward with throttle or VG changes, is going to be a valuable thing for waste-oil firing.

I'll get rid of this if it turns out to be a duplicate post. Apologies in advance if it is...

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Re: Front End situation

Post by Nigel Day on Fri May 24, 2013 4:51 pm

Why a MM front end? No ashes to deal with? Just adds gas flow resistance. The only reason to have any plating in an oil burner is to even the gas flow across the tube plate and that can be done by other means.

The cost of the chimney flue is very small compered to other costs. Every thing else is fabricated to avoid expensive castings. Four way Kordina? All the exhaust pipes are there I assume, so work from above them. So where is a new Kordina needed? The stand and blast pie and flue are all simply bolt in parts, so if alternatives are wanted its an easy fix. Some of the logic of choke and nozzle sizing talked of here makes no sense to how I understand things relating it to the whole? So where do you get the fundamental size of the choke or blast pipe before you can work the rest out?

The best front end I have so far done for oil is the one on Abt 3 it's a cross between a lempor and a Lemprex plus other refinements. It makes Lempors old technology. Some of it is still under development and little can be said at the moment of the absolute detail due to intellectual property and the rights of my employer. I now consider Lempors old technology. I don't understand why you want to make such a complex issue of the front end? a good lempor will do everything you need to ask of it for oil firing on this loco. It true that there are now alternatives to design the next generation of front ends but that's way out side what's being debated here and will become reality before this loco is usable so I don't understand why there is an immediate desire to sort out this in the early days of this project.

Complex blower connected systems are un nessicary if you put a pressure gauge on the blower line.


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Re: Front End situation

Post by Overmod on Fri May 24, 2013 7:17 pm

Good to see you on here!

Nigel Day wrote:Why a MM front end? No ashes to deal with? Just adds gas flow resistance. The only reason to have any plating in an oil burner is to even the gas flow across the tube plate and that can be done by other means.

I'm all for it if it can be done without the longer passage. I consider the plating in this style of front end to accomplish more than just reversal for cinder extraction.

I would also say, a bit defensively, that if conversion to solid firing is kept as an option, you'd want to keep at least the ability to put sensible screening in the smokebox. That might be difficult without recourse to plates.

The cost of the chimney flue is very small compared to other costs.

Yes, but still significant. Also historical, and reading between the lines, political.

I should go on record here: I would turn you loose on this without a qualm, aside from this one concern. But if it remains a concern the whole front end design would have to be made to accord with that one piece.

Every thing else is fabricated to avoid expensive castings. Four way Kordina? All the exhaust pipes are there I assume, so work from above them. So where is a new Kordina needed?

I had thought the Kordina acted as a shaping vane for the flow coming out of the nozzles, to do a little velocity-pressure conversion (a bit like the first stage of a Kylchap diffuser). But now with the added benefit of extending up from short individual nozzles close to the cylinder block, and performing some shaping of the jet contour as you get up to where the entrainment zone starts.

No, I'm not irrevocably wedded to the idea and yes, I'll defer to people who have Done This All Before.

The stand and blast pie and flue are all simply bolt in parts, so if alternatives are wanted its an easy fix

No argument whatsoever -- in fact, the point I wanted to make in that regard is that everything be specifically designed so it will come in and out in a 'modular' fashion, and replacement parts made up with known dimensioning and tolerances to fit without tinkering. (You may remember me commenting about 'brass nuts' -- the idea is to keep hardware from seizing or eroding even after substantial time in service. Call it a DFM concern...

Some of the logic of choke and nozzle sizing talked of here makes no sense to how I understand things relating it to the whole? So where do you get the fundamental size of the choke or blast pipe before you can work the rest out?

ONLY because if the size of the throat is fixed, and the taper upward from that point is fixed, you can start with some known values of nozzle characteristics -- at least up at the entrainment zone -- and it is then possible to work backward from there to optimize low backpressure for a given degree of exhaust effectiveness.

That is manifestly NOT how it should be done with a complete clean sheet of paper. Listen to Nigel and Jos, and let them duke it out if that is how the design can be 'sold' to the powers that be...

It's true that there are now alternatives to design the next generation of front ends but that's way out side what's being debated here and will become reality before this loco is usable so I don't understand why there is an immediate desire to sort out this in the early days of this project.

We're just discussing options and possibilities. As you note, the design will start to be pruned back fairly soon, and it'll be a comparatively long time before any actual front-end fabrication for testing -- let alone final 'production pieces' for service -- will need to be done.

Complex blower connected systems are unnecessary if you put a pressure gauge on the blower line.

What I was proposing, though, is considerably different. The idea is NOT to have to watch the gauge; it's to keep draft changes 'seen' by the burner relatively slow and smooth, so that waste-oil firing has as few gotchas as possible. I don't see anything more complex than a couple of draft gauge sensors -- with the equivalent of dashpots to do the smooth transitions. (And you do not care what the nominal pressure on the blower line is, because it's throttled to produce the control draft at the reference point regardless of pressure or steam quality...)

It occurs to me that there is another potential advantage to that kind of system: automatically recovering from 'puffs' and flameouts without particular danger. If the burner flame goes out but a little more stuff is sprayed or dribbled, the draft can be modulated to produce clearing before reignition (either from spark or flameholder) is conducted at the burner.


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Re: Front End situation

Post by DaveLathrop57 on Fri May 24, 2013 8:58 pm

OK, let's assume for the moment we will want to build a Lempor or something close and fit it into the existing smokebox with the original chimney - on the outside, we can change the inside of the chimney any way we want. How would we do it?

Dave


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Re: Front End situation

Post by Overmod on Fri May 24, 2013 9:12 pm

I will be watching the next few posts on this thread with great attention.


Last edited by Overmod on Sat May 25, 2013 6:33 am; edited 1 time in total

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Re: Front End situation

Post by DaveLathrop57 on Fri May 24, 2013 10:29 pm

I wish I could see into the future like that......assume this post isn't included.

I think many of us don't know how to start thinking about designing a Lempor or other improved exhaust for a locomotive that isn't running in which a lot of compromise is necessary. It would be of interest to learn how to think it through. It may not be the most perfect approach, but I think it beats another MM clone.

We've had contact with 3 experienced experts, 2 have actively posted, and all take different approaches. I think there's a lot to learn from comparing approaches and priorities also. This is as much art as science from my pespective right now.

Dave

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Re: Front End situation

Post by Nigel Day on Sat May 25, 2013 10:01 am

So confirm for me three things I can't read for curtain from the drawings. The cylinder diameter, the tube length and smoke box diameter.

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Re: Front End situation

Post by Low_Water_Odom on Sat May 25, 2013 10:19 am

Nigel Day wrote:So confirm for me three things I can't read for curtain from the drawings. The cylinder diameter, the tube length and smoke box diameter.

Cylinder diameter = 16 inches

Tube length = 12 feet (there are 175 x 2 inch diameter flues)

Smoke box inside diameter = 52.25 inches

In case anyone couldn't read the stack drawing:

Stack height = 42 inches

Stack upper outside diameter = 18.5 inches

Stack wall thickness = 7/16 inches

Stack lower outside diameter = 16 inches

Note regarding drawings- Many of these Vulcan prints were "general" drawings used for many different engines. Many of the sheets will have a table at the right with numerous different dimensions in it and corresponding letters; the letters are called out on the drawing. The line containing the appropriate dimensions in the table will be highlighted with an arrow at the left of the table; sometimes this arrow is VERY hard to pick out. The stack and smokebox arrangement drawings are both like this.

Hugh

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Re: Front End situation

Post by Low_Water_Odom on Sat May 25, 2013 10:20 am

Here's a copy of the 110 diagram I drew for future reference:


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Re: Front End situation

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