LBSC's Doris versus the Code

[runner42]

Thanks to all for your valued comments, there is enough information there to make an informed decision on how to proceed. I don't have to make the decision yet as there are more pressing issues.

Before silver soldering the backhead I got to convince myself that backhead fittings are going to be ergonomically positioned. Since the code required bushes for all fittings and not as LBSC specified of screwing in straight to the boiler, the consequence of that is that the backhead is a lot busier than had bushes not been required. Also the BI required 8 screws instead of 4 in the regulator bush. Some modifications are required namely the blast valve (?) has to be moved to the manifold position because of the water gauge would interfere with its specified position and a copper pipe connecting to the old position.

Brian

[runner42]

That solution is a no goer, because the height above the boiler to the cab roof is very small so there is insufficient room. I'll try placing the valve on the LHS instead of the RHS, so the LHS longitudinal stay will be the copper connecting pipe from the backhead to smokebox instead.

Brian

[jma1009]

hi brian,
just a few observations!
the whistle valve ought really to be as per Princess Marina (which i have some experience of) on the standard LBSC manifold/turret.
the top of the water gauge fitting doesnt look big enough for the glass to go through it. this might require some further thought.
i can think of a few ideas re boiler fitting arrangements but perhaps best to pm me.
hope you got the last pm ok?
the gaps around the backhead where the firehole fits are going to be problematiic and will require copper inserts fitted.
i can think of a few ways to get round the blower valve problem.
cheers,
julian

[Jim]

I hope you don't mind but just to add to Julian's valuable comments on your back head fittings and the need for copper inserts round the firehole I've attached a photo of how I tackled a similar problem at the corners of the foundation ring on my boiler. Those little bits of copper trimmed from the plates while making them are ideal for this task.

Jim

[runner42]

Thanks Julian and Jim.

Yes the firehole cutout in the backhead was produced before I realised that the code didn't allow square corners so when I made the firehole ring there was that difference in the radius in the ring and square corners of the cutout. But I compensated for this by making the ledge between the two big enough to allow little triangular pieces of copper to rest on the ledge and not fall through when silver soldering. I have the four small pieces of copper already for the gap filling.

The top of the water gauge is big enough to allow the glass to go through.

The fittings are a first try and some I am not happy with but using them to just see how I am going to configure the backhead fittings.

Jim it looks like I shall also have to have some additional copper bits in the foundation ring as I have some gaps in the same place as your picture.

Brian. 

[steam4ian]

Brian

Considering our earlier comments about water level and your not having much freeboard I would suggest you run pipes between the dome and the various bushes to draw steam from the highest part of the boiler. If you don't your blower will draw water and be very hard to control and you will have a wet whistle. could have the injector stop too early also but make sure you have a big enough steam pipe.

Ian

[runner42]

Hi Ian,

yes I will do that. In fact LBSC actually prescribed that. I don't know how I could take the collection point to the dome since the regulator is in the way but I shall take advice on how I could engineer a space like a manifold behind and attached to the backhead that is isolated from the changing water level and with an input from a high point in the Belpaire part of the boiler. Another thing to sort out before I silver solder the backhead.

Brian

[steam4ian]

Brian

Front of the fire box will do.

Ian

[runner42]

Just in case you thought I had gone walkabout and left Doris' boiler to the Maggies, wondering when that backhead would be silver soldered in, well a lot was depending on getting the backhead fittings at their optimum positions. A part of the task was to select a firebox door because the screwed fixings has to be using blind threaded bushes and these need to be silver soldered to the backhead before silver soldering the backhead in position.

I decided to use a two sliding door type, which turned out to be a bit of a challenge, especially coming from a point of ignorance and just having a few photographs available. I didn't realise that to get both doors opening to the same amount takes some careful positioning of the pivot points and length of the levers are crucial.

Now if I had a 3D CAD program this would have been an ideal candidate to see how varying the previously stated criteria would affect the operation. But no, I am without such software and the ability to use it. In pre 3D CAD days the likes of LBSC would have made a cardboard pinned model as he suggested for valve operation, but again that's not me, I didn't even sketch it I went ahead just cutting and filing and modifying it as I went along. This was a frustrating process I almost gave up and did the simple hinged door model as LBSC specified but my square firehole needed the two door sliding model.

Well I have arrived at a solution that provides door opening to within a 1/16" of each other. As you see the levers have been constantly modified but work as required so I have the criteria to remake the levers to nearer correct measurement, but more importantly I have established positional data for the blind fixing bushes and installed these to the backhead. So the backhead can now be installed tomorrow.

Brian

[Jim]

Good to see you making progress Brian.

Jim

[ejparrott]

Good work Brian. I've got the same exercise to go through with my engine in due course. It's supposed to have a swing type door, and I've designed the boiler to have both sets of bushes, but I much prefer sliding doors so that's what I'm fitting!

[runner42]

Thanks Jim and Ed,

well I managed silver soldering the backhead this morning, just the 4 stays for the backhead to be made and silver soldered in and fixing the 3 longitudinal stays and the blower pipe from backhead to smokebox. For these stays LBSC specified blind nuts screwed into the backhead and smokebox with an internal thread to connect to the thread established on the longitudinal stay, the larger thread is 5/16" x 40 tpi and the smaller 3/16" x 40 tpi, both threads having the same tpi enables the blind nut to be screwed on both threads at the same time. What type of sealing medium is used for the 5/16" thread screwed into the backhead and smokebox, or is silver soldering these in position the better option since they aren't likely to be removed?

Brian    

[uuu]

Solder them. Like the other stays, they're a structural element of the boiler, and never need to come out.

Wilf

[Shawki Shlemon]

Brian , depending on the length of your boiler , according to the code the silver soldered longitudinal stays should not be more than 40 times the diameter of the stays , for example if your stays are 1/4" dia then the maximum length is 10" otherwise they have to be screwed , refer to the boiler code . I wouldn't like to be in your shoes if you silver solder them without the agreement of your boiler inspector .

[uuu]

Just for clarification - I'm suggesting screwed/nutted as designed, and then soldered in place.

Wilf

[runner42]

Mar 8, 2015 9:32:03 GMT Shawki Shlemon said:

Brian , depending on the length of your boiler , according to the code the silver soldered longitudinal stays should not be more than 40 times the diameter of the stays , for example if your stays are 1/4" dia then the maximum length is 10" otherwise they have to be screwed , refer to the boiler code . I wouldn't like to be in your shoes if you silver solder them without the agreement of your boiler inspector .

Thanks Shawki,

that is something I had forgotten. However, does it refer to a straight stay silver soldered directly to the boiler? In my case, as Wilf has indicated I have blind nutted terminations on the stays an outside diameter of 5/16" x 40 tpi threaded to the boiler and an inside thread of 3/16" x 40 tpi threaded to the stay. I was proposing of silver soldering over the nutted terminations as belt and braces  to ensure no leakage at the thread to the boiler?

Brian

[Jim]

As Shawki has said, you should be discussing all this with your boiler inspector as he will be the person who has the responsibility of checking and hopefully passing your boiler.
The boiler inspectors I know are like Shawki, helpful and constructive folk who are keen to see us build safe and AMBSC compliant boilers.

[Shawki Shlemon]

Brian , why do you want to silver solder the screwed ends ? using thread sealant and lock nuts will do the job , if you want to deviate from the code then see your boiler inspector and discuss the matter with him but I advice not to deviate from the code without approval . It is your boiler and your decision .

[runner42]

Shawki, I am not going to silver solder the longitudinal stays.

Referring to the code at para 3.4.3 it says that longitudinal stays secured by threaded fittings shall be hard-drawn (un-annealed) condition, and fitted after all silver brazing operations are completed. Well that says it all, to attempt to silver solder over the screwed fittings is going to affect the un-annealed condition of the stays. The rationale, I assume for having them un-annealed is that no stretching should occur and affect the securing function of stay. Thanks for raising the issue.

Another instance where the code has been well thought out.

Brian

PS I have just changed my avatar to include my face. I was inspired by others who let the forum members see what they look like. I am often interested in where fellow members live and their background and how they came to model engineering and putting a face to the subject, but some have no details attached to their avatar at all. But for those that says no thanks to the face it is only temporary because when the boiler is complete and tested it will replace me between the smokebox and tender.

[beekay50]

Brian,
I hope you will forgive me butting in on your thread but the content is very interesting to me. I am in Dubai and completing a 3 1/2 inch Hielan Lassie to LBSCs design. The part complete package I bought as a starting point included a boiler and drawings. The age is unknown but seems to be mid 50s at a guess. It obviously doesnt have a boiler certificate and I have the intention of finally returning to the UK and would like to steam the train there. I work in the oil industry and will have the boiler hydro tested in our UL listed test facilities prior to steaming here in Dubai, however it seems from your thread that the original LBSC design does not meet current code requirements and whilst it may be perfectly sound and pressure safe it will not comply with the various codes . I appreciate you are in Australia but  would appreciate any guidance on this issue.


Many thanks


Keith