LBSC's Doris versus the Code

[runner42]

Thanks Julian and Ed for the assistance. However I shall not be acting on the recommendations just yet, there has to be a halt to progress since tomorrow we will be flying to Sydney to start a cruise from Sydney to Fiji on Wednesday, the reason is to celebrate our 50th wedding anniversary. It is better that I don't hurry the soldering of the wrapper to the tubes/tube plate assembly and if problems occur at this juncture I shall be distracted on the holiday thinking about it. The tubes and flues after the pickle cannot be photographed because SWMBO has already packed the cameras. This afternoon I got to scrub up and get the smell of copper from my hands. My wife has a very good sense of smell, which gets me into strife sometimes, I thought that as one gets older the senses gets duller, at least it's so from my perspective.

Brian

[Kevin]

Congratulations on your 50th and enjoy your holiday

[Shawki Shlemon]

Congratulation Brian , enjoy your holiday , it is a long time 50 years , ours was last 15 October , that is why I know that . LOL

[ejparrott]

I think you can justifiably say that's more important than the boiler!

[steam4ian]

Congratulations to you both, a well deserved cruise.

Ian

[runner42]

We had a great time cruising the South Pacific, cruise holidays was something that didn't inspire us but we had such glowing reports from friends that we gave it a try. Let me say that it was the best holiday that we have experienced. The ship's staff couldn't do enough for us, the food was excellent the only danger was over-eating. We were amazed how much some passengers managed to stuff away at breakfast lunch and dinner and other times in between. But I would recommend it to everybody, young or old, fit or wheel chair bound. It's the perfect holiday for many.

Having downloaded the many photographs I have now freed up the camera to take the photos of the firebox tube plate/tubes and flues after silver soldering and cleaning.

Tomorrow I shall tackle the dreaded silver soldering of the firebox tube plate/tubes and flues to the firebox wrapper. I shall give it a whole free day to attempt it as today is Gym day.

Brian

PS In the first photograph you can see that the Australian Standard to which the tubes were manufactured stamped on one of the tubes, that should give the boiler inspector a warm feeling that I have sourced the tubes from a bona fide source.  

[runner42]

Although this thread is to delineate the differences between LBSC's boiler design and the AMBSC Code Part 1 and not a work in progress, having indicated in the build order thread of the mishap I had during the silver soldering of the firebox tube plate to the wrapper I thought it appropriate to provide the results of my rework.

What I have realised in silver soldering that the silver solder will flash where the flux has flowed. The difficulty is having enough flux on the joint but not too much that it runs due to gravity and the silver solder follows it. Hence the somewhat messy appearance. However, the boiler inspector is not going to fail the boiler due to the cosmetic appearance.

Brian

[Jim]

Looking good Brian and as you say it's not about appearances but ensuring you have sound joints.

Jim

[jma1009]

hi brian,
that looks very good indeed!
the more you do the easier it becomes and also slightly less nerve-wracking!
do please continue with showing progress on here.
cheers,
julian

[runner42]

Thanks Jim and Julian. The next issue is however a change to be made where LBSC's design deviates from the code. In the diagram you see that LBSC fixed the regulator to the boiler using a strap screwed directly into the boiler, which is a no no. I changed the design by screwing the regulator to the top flange. This required two pieces of brass to be silver soldered to the bottom of the top flange to form fixing points for the regulator. The photos show this.

This modification has caused other problems that I am not sure how to resolve. Stand by

Brian 

PS I have fixed the two brass pieces to the top flange with 10 BA screws so they don't fall off when silver soldering the top flange to the barrel.

[Shawki Shlemon]

I understand that the brass pieces are not part of the boiler but why did you select brass and not bronze or even a piece of copper ?

[runner42]

Hi Shawki,

well the regulator is completely brass construction (as prescribed by LBSC) except for the screwed connection at the output of the regulator, the fixings are brass so this is a bit more of the same. I hope your comment is directed towards strength of the fixings or similar and not associated with that de-zincification issue. I intuitively thought that brass would take a thread better than copper and bronze is difficult (impossible?) to obtain in shapes other than round. I confirm that the flange is made out of gunmetal.

Brian

[runner42]

The code requires that the water gauge bottom visible end shall be above the crown of the inner firebox wrapper by not less than 10% of the distance from the crown to the outer wrapper. In addition the gauge glass shall be long as possible. This requirement is easily met if the distance from the firebox wrapper and outer wrapper is great, however Doris' is 1 9/16" at the front end the highest point and only 1 3/8" at the backhead. This is causing me some angst I have used a water gauge for a trial assembly trying to satisfy both criteria. It fails the first requirement to achieve this would make the gauge glass very small and quite useless as a water gauge.

The first photograph shows the trial assembly of the water gauge showing the length of gauge glass the second shows the ruler set against the top of the firebox wrapper and indicates that the gauge glass is below the firebox wrapper.

I need some innovative thinking by others to if not solve this issue but to improve the situation.

Brian

PS The water gauge shown is a commercial item more suited to a 5" gauge locomotive than a 3 1/2" gauge. I shall be producing a smaller version, however the points that bear upon meeting these criteria can only marginally improved.

PPS Being such a small space between the firebox wrapper and the outer wrapper and the need to keep enough water above the firebox wrapper for safety reasons it appears to me to be a difficult boiler to keep running, always looking at the water gauge and having little time to respond.

[Shawki Shlemon]

This is a common problem on a lot small boilers particularly of old design . the best way to solve it in my opinion as mentioned above fit a bush on top and use that for top feed for water gauge , I have done that more than once , its quite easy and functional .As for my previous remark , I personally don't fit anything inside the boiler made of brass even if the plans say so . your boiler , your decision . I respect your decision .

[steam4ian]

Brain.

I concur with both Shawki's and Paul's comments. I don't know what LBSC was smoking when he designed Doris's boiler. Compare the freeboard over the crown sheet on Doris with that of Juliet. IMHO the crown sheet should never be higher than 5/8th of the boiler diameter.

Consider this experience. You leave the station on the level with 1/2 a glass. Descending out of the station falling grade the water drops to the bottom nut and continues at this point on the long down grade, the water just appearing and you hope the pump is keeping up. You add a bit more water to the boiler just to be sure because as you brake to enter the tunnel the water moves forward in the boiler and disappears. You hope it will reappear when you start climbing. If all is well you come out of the tunnel with water showing in the glass as you start the climb; open the regulator more and the water rises above the top nut. If all is not well you either prime in or coming out of the tunnel or you find you have very low water. You are now faced with a long climb and having to run the injector against falling boiler pressure. All this on a loco on which the change in grade is sufficient to change the3 glass from top to bottom nut AND on which opening the regulator will raise the water from bottom to top nut, worse closing the regulator can make the water disappear altogether. I haven't added the effect the safeties opening has on the water level.


One thing in your favour is the Belpaire outline which means the water surface does not reduce so much with level. On round top boilers this effect can be a real pain and yet I have never seen it written about.

As for the gauge you can put a bush in the top of the outer wrapper to feed the top of the water gauge. Alternately there is a neat little fitting soldered to the outer wrapper threaded for your water gauge and providing a passage to the steam space. See the Juliet boiler design as typical.

It is permitted to sleeve the gauge glass so the water is not visible below the 10% point, alternately a longer bottom nut can be fitted.

BTW I spent a happy afternoon driving a friend's loco at the club only using the injector, no axle or steam pumps. I must admit to preferring just using the injector/s as you have more control over boiler pressure, a necessary option as we get familiar with the new coal (rocket fuel) and tend to over fire.

Regards
Ian

[runner42]

Thanks Ian, Paul and Shawki for your input. It is sobering information, however I am buoyed by the fact that many Doris' have been built and seemingly operated OK. I shall keep the water gauge positions as is and to satisfy the code requirements add a sliding sleeve over the glass of a length equal to the bottom visible position and the 10% above the wrapper mark.

Brian 

[steam4ian]

Brian.

I would strongly recommend taking the top of the gauge glass off a bush in the outer wrapper of the firebox. This way you have a useful length of glass. I have looked at the Doris boiler plans and a transition from climbing to descending 1:50 will move the water about 3/8" in the glass. Due to where your steam off take is for the regulator you should be able to have water up to the about the top bushing if climbing with the regulator open. With what you propose you will not be able to see this water level. If you don't know where the water is under these conditions you will not know where it will finish up if you are on a down grade.

By way of info, a certain highly prized loco at the club was built with the gauge bushings too low, the glass was sleeved to solve the firebox crown problem but the resulting glass proved too short to read and the inevitable happened.

Regards
Ian

[ejparrott]

If you're making your own fittings, I'd suggest making the bottom fitting taller so that a sleeve is not required but the 10% level is naturally dictated by the bottom nut. You don't want a sleeve falling off, or being forgotten about when replacing a glass.

[Deleted]

(1) Real engines always had gauge glass protectors . Various designs but for present purposes a protector consisting of a square thin metal tube with a slot window would serve . A bit more prototypical and the slot window can be right dimensions to cover problems at lower end of glass . Also consider fitting a diagonal stripe back screen .

(2) There are alternative water gauge designs which may give you more scope for adaptation . One to look at would be the end sealed type as again used on many full size engines . Neville Evans described several for his engine designs and these worked extremely well .

(3) Before I forget - congratulations on making a Doris boiler that actually fits the engine ! No joke - its too high up even as designed and many running Doris models have the boiler higher up still to get it in .

(4) I see that you have no allowance for lagging . May I suggest that you consider at least fitting thin metal cover sheeting so as to give better appearance , something clean to paint and something to attach handrails to .

(5) Anecdote : I think that three of the very few model boiler explosions ever reported were all of Doris design because idiot LBSC advocated using Sifbronzed butt jointed main barrel seams .

(6) I'm a real world engineer and as far as I'm concerned design codes are things to be treated with the greatest suspicion . Always best to design from fundamentals and then see if there is any compatability with design code . I have more than once sucessfully challenged twaddle published in design codes and had the codes ammended .

michael w

[jma1009]

hi brian,

there is no need in any miniature loco for the gauge glass to show anymore than required in the boiler. i think you can improve on your top fitting of the water gauge but this wont affect my previous comment. all you have to do is be canny with the water level when running - this can take a bit of practice and experience but isnt difficult. the optimum readings on a 3.5"g loco are by definition within very small margins.

i dont agree with michaelw re sifbronzed joints.

unless your backhead bushes have been done with say high melting point stuff such as silverflo 24 i would have grave doubts about them when silver soldering the backhead to the outer wrapper. in particular the firehole ring to backhead requires a huge amount of heat which will melt anything in the vicinity done with ordinary easyflo or silverflo 55.

cheers,
julian