3 1/2" Jubilee 264T regulator advice

[Greg]

Hi,

I'm designing the boiler for my Martin Evans 3 1/2" Jubilee and need a bit of advice to sort it. I was looking for some suggestions on the arrangement for the regulator.

I live in Australia and so have to redesign it to suit the Australian code. I think I've got it all sorted except for the regulator and the stays below it. The regulator tube was 3/4" and I have already reduced it to 5/8".

They way it is with my revised design it won't be possible to get the regulator in the boiler because of the dog leg in it and the firebox stays. The original design had girder stays but the Australian code doesn't allow girder stays between the top of the fire box and the outer wrapper.

Does anyone have a suggestion on how I could do it? The steam intake for the regulator is in the section of the tube above the firebox. It does not have a dome.

Thanks for your thoughts, Greg

Original design 

[GWR 101]

Hi Greg, can't help with the boiler design as I have not got that far with my Jubilee and you obviously have different boiler code requirements than the UK. However looking at the drawings and in particular sheet LO23/5A which is the "improved" boiler design including the Nicholson Syphon there appears to be more cross stays than the original design, yet no mention of a revised regulator.

I did notice that the original regulator design has a sloping front section of 1/2" dia. and not a dogleg. I see that you have reduced this to 3/8" OD I assume to obtain easier access, I just wondered if a sloping front tube of your new size may help.? Apologies if you have already considered this. Regards Paul.

ps. In a previous thread the benefits of fitting a syphon were discussed and the consensus was that at our scale the effect would be minimal.

[Greg]

Hi,
I also have the 5a design. I was originally going to do it with the siphon then decided it was probably more hassle than it was worth. Both the 5 and 5a boilers appear to have one row of cross stays above the firebox and a girder down each side of the regulator, so the same in that regard.

On the original design  couldn't see how the angled regulator pipe would work at the front because the bush gets screwed on and surely it needed to be square for that to work. No idea how it's meant to work on the 5a version either. My dog leg was just my way of showing it square on the smoke box end so the blue bush could screw on. It could obviously be a different shape but would need to be in line at the smoke box end and so the offset from the back head would be the same.

Here's the revised 5a version.

[GWR 101]

Hi Greg, yes I see your point about the problem at the smoke box end I assume that a very small length of the tube would be parallel to the bush. Anyway that does not solve your problem and although I know of a fellow club member who has a Jubilee he is in the UK so it is built to the original design.

So sorry but I have not been of much help, I will PM you if that's ok with some additional thoughts. Regards Paul.

[runner42]

Hi Greg,

your dog legged output tube is predicated on the need to have a bush on the smokebox tubeplate as required by the code and the presence of this bush requires that the output tube is at right angles to the smokebox tubeplate. However the dog leg is impractical because of the need to have in line regulator and in line output tube that can be screwed in during assembly. The only recommendation I have that you have another piece of say brass that is squared sectioned with two opposite threaded holes that take on one side the output of the regulator and on the other the input to the regulator output tube. The steam pathway is connected by internal drilling of the additional brass section. The difficulty is how is this additional brass section installed in the boiler, one option is that it is installed through the bush shown on the barrel or that it is part of the boiler's construction.

Brian

[peteh]

Brian,
Wouldn't the block need to be bronze to stop dezincification(sp)?

[Greg]

Thanks Brian for the suggestion. I had a look but because it's a tapered boiler I don't think I could make it work as the bushing is too low. I could reduce the pipe down further from 3/8" but the 1/2" hole may be a bit tight too. It was a good idea.

Yes Pete the block would need to be bronze.

[runner42]

Greg, my second recommendation was to make it part of the boiler construction. I have already modified your drawing to accommodate a copper section that sits between the firebox crown and the outer wrapper very near to the barrel and forms an additional stay. The construction could be round so that fixing to between the firebox crown and outer wrapper is a matter of drilling holes of the right size and position. This additional stay would be closed at the firebox end and open at the outer wrapper end. This open end would facilitate assembly of the regulator and output tube and then plugged after assembly. This method would require a possible modification to the regulator by shortening its length, but something that could be overcome.

Brian

[runner42]

Oct 26, 2016 6:17:29 GMT peteh said:

Brian,
Wouldn't the block need to be bronze to stop dezincification(sp)?

Pete,

I agree that dezincification of brass exposed to steam is a real issue. However, many of my colleagues used brass extensively in the manufacture of backhead fittings and parts of the regulator. Martin Evans actually specifies brass tube for a screw type regulator and LBSC recommends the use of brass bar for the manufacture of the regulator for Doris where no casting is used. Dezincification will take place but the rate on a relatively large piece of metal will be small and these components will not result in a catastrophic failure if dezincification results in failure. The only areas where brass should not be used is say for example in fasteners for items attached to the boiler. You will note that I have recommended the use of copper in the above because it is acting as a stay.

Brian

[mutley]

HI Greg, may i suggest sealing the regulator tube with an O ring at the front tube plate rather than a screw thread?

Andy

[Greg]

Hi Brian, sorry overlooked the second suggestion. It is an interesting idea I will have a bit more of a think about that one.

Hi Andy, I thought the front of the regulator tube would need to be threaded to pull it into position. I'm assuming with an o ring the regulator would just be pushed into position from the firebox end. Is that what you were thinking?

Greg

[mutley]

Hi Greg, Yes pretty much. The flange on the backhead keeps it in place and an O ring on the front tube plate seals it at the front. It's what I've done on a 7.25" gauge boiler.

[flyingfox]

Hi Greg, hope you will be as satisfied with your Jubliee, as I was with mine.

How about making the regulator body as you suggest, 5/8 dia, then silver soldering the exit pipe into it, with its kink, arranged so that it fits directly into the bush, lining up square to the bush, which could be screwed on, but I know the O ring seal is easier, and i would recommended this method. If the pipe were soffened, then it could be slightly bent to get the correct alignment

Also, I would suggest that the single superheater flue, used with a radiant stainless steel superheater is the way to go.

regards
Brian Baker

[Greg]

Hi Brian,

I hope it's worth the effort and is a good steamer. The problem I'm having is with the firebox stays being so tight on the underside and sides.  I think unless the regulator is perfectly straight it won't feed in. So I can't see the front part feeding in. If I could have used the girder stays there would have been more room and I'm sure it would have worked ok.

I was originally going to go with the one superheater tube, but went I decided against the siphon design I went back to three superheaters as per the original. One superheater certainly would make the smokebox a lot simpler. With the larger superheater the overall number of tubes are less because the rest of the tubes don't fit in that well. This was the best I could do.

I have a few questions about your Jubilee. Is it a good steamer? What thickness wrapper did you use? I have been designing mine with 2mm wrappers to keep the firebox as wide as possible, but this has reduced the stay pitch which has made it harder to design. If I went with 2.5mm copper wrapper it would be easier, but I would lose 2mm of width in the fire.

Greg

[flyingfox]

Hi Greg, good to hear from you.
I think that if the curves in the wet header feed pipe were a gentle radius you would be able to wriggle them in.
I went for the single superheater flue to make it simpler in the smokebox, there is not much room inside it, even with a split smokebox.
The loco was built starting in Aug 1980, and finished in 53 weeks, including the boiler, wish I could build them that quick now.
It steams well, and ran faultlessly, until the second IMLEC I entered in when a superheater blew. It has run many miles in various countries, and i found that its 77lb weight manageable, as well as giving a good ride.
I am just starting a doubled up version for 71/4 gauge.
used 3/32 for the inner firebox wrapper, but made the stay pitch as shown.

regards
Brian B

[Greg]

Hi Brian,

53 weeks is a very quick time to have built your loco.Your feedback on the 3/32" wrapper an it being a good steamer is very helpful. I was concerned about it not being a good steamer and so I was really tying to keep the firebox as wide as possible, hence me trying to get a 2mm wrapper to work.If your loco works well with the thicker wrappers then there's obviously no need to use a thinner wrapper. If I go with a thicker wrapper I think I can make it all work. The thicker wrapper means less stay too, which obviously make sit easier. I'll also go with the single superheater tube.

Here's my revised design

I may be able to go with the disc regulator, but if needed I could go with a shorter tube as suggested by Brian(runner42) and possibly go with a screw regulator. This might make it possible to go even smaller with the pipe if needed.



Thanks everyone for their thoughts and advice.

[flyingfox]

Hi Greg, screwdown regulator every time.

regards
Brian B

[firebox]

Hi Guys, just signed up for this forum! My name is Nigel Woolley from up in the Hunter Valley NSW. Greg, the Princess Marina has similar problems, as do any of these tapered barrel boilers. I fixed a Jubilee boiler for a club memeber from SLSLS West Ryde which was an import from the UK with the chassis. It was not up to code, but we made it so. It had a cranked main steam pipe and screw down regulator, with a double threaded bush at the front, and a flange at the backhead. The girders were useless as they weren't joined to the firebox plates sufficiently, so I installed some rod crown stays on a rectangular pattern which were splayed away from the regulator to give some more room. The spacings were calculated as per code using the stay pitch circle in the advanced design guidelines. The outer wrapper was 3/32" and inner 1/16" which allowed us to get a further spacing on the outer firebox, giving more room for the regulator again. If you really get stuck with the transverse stays in the way you can up the thickness of the outer wrapper to 3mm. Hope that helps.