Member postings for Doubletop

On the subject of gas. In NZ the only thing readily available is LPG which is a propane/butane mix. The trouble with this is the propane burns off first leaving the butane so the calorific value drops dramatically when the bottle gets about 1/3 full. If you get the bottle refilled at a petrol station they just top it up so now youv'e got less propane. And so that goes on until you either burn off all the butane by some other means than running your loco. Fortunately our local BOC purge the bottles before a refill and a fill of a 3kg bottle is about $12 or 6 quid so you are only chucking away about a pound or two each time.

 

I did ask BOC about pure propane but when they started talking about couriering the empty bottle up to their lab in Auckland it got obvious than it would be more than 6 quid a fill.

 

Pete

I would suggest that it doesn't burn that much hotter than coal, it is more consistent over a larger area rather than hot spots that I'd guess coal is prone to. You have way more control and can shut down immediately which you cant to with coal.

 

I've secured my ceramic with Permatex hi temp RTV (for car gaskets) and its holding up well. It does not burn as a fiercely as the gas torch you'd use to make the boiler.

 

Take a look at the link I've posted for pics of the stainless 'arch'. Arch what the guys call it but its probably only remotely similar to the real thing.

An example of what I've called 'jet' type burners

 

 

Pete

Posted by Dave Bond on 19/07/2011 15:52:15:

 

I run my Rob Roy (3/.5") on propane using a ceramic burner based on a commercial version that I believe came from Bruce Engineering. One of our club members runs his Manor (5") on gas . And a guy in Belgium I've been communicating with has converted an OSLiveSteam Rocket (5") to gas. If you trawl through the American sites you'll find a lot of them running 7.5" locos on gas. These are a mix of ceramic and jet type burners. The only change to the boiler is a stainless 'arch' which restricts the direct draw down the flues and stops the flame being drawn off the burner. Check out link here.

 

 

Pete

Have I missed something here? Isn't this just the same viewer with the additional feature of downloading as a pdf?

 

In the past it was possible (if you were lucky) to print all the pages, that feature disappeared and only the ability to print single pages retained. Now some issues have an extra option to open the .pdf. If I'm not mistaken, in the past weeks, even that appeared briefly then dissappeared to re-appear .

 

Or have I missed something?

 

Pete

 

 

Stew

 

It looks very nice, and even better now its finished. Well done.

 

Pete

Phil

 

Thanks for the detailed reply. I don't have a copy of the Northumbrian articles to hand at the moment to check the original boiler against the recently published version. However, I believe they may be different. Tony Weir stated early in the series that he had made significant changes to the design, one being to lower the boiler as LBSC's version was too high. The tube layout you quote is certainly different. Tony's version, 10 x 3/8" 20swg tubes in three rows 7/16" between rows and 1/2" spacing in each row (off the top of my head as I drilled the tube plate today.)

 

I have worked out the length of the firebox plates to be 3.3125" allowing clearance for the blower, the thickness of the wrapper and a reasonable allowance between the top of the tubes and the plate flange. Hopefully that is 'right'

 

It has occurred to me, since posting the question and re-reading Martin Evans "model loco boilers" book that the firebox could extend below the foundation ring. Most of Martins designs did it that way and the dimensions you have provided for the LBSC version does the same. However, it could foul something in the frames, or not allow the grate/ashpan to fit. I have made mine a little longer as it can always be removed later without affecting the integrity of the boiler.

 

as an aside, on the subject of stuff under the firebox, how does that lubricator linkage work, surely it gets in the way? I'll save that for later though.

 

Thanks again

 

Pete

I've just checked and 2.625 is certainly the dimension to the center line but I can't determine what height the firebox should be above the center line. It can't be 9/16" as it would then be in the way of the blower tube. Which means Johns suggestion of 3.5" would be incorrect

 

Drawings 71 (p 497) and 79 (p498) in part 11 of the series are certainly deficient in a number of places

 

Pete

 

Posted by John Willman on 06/06/2010 21:33:29:

Edited By John Willman on 06/06/2010 21:46:06

I've just found this. Can somebody please confirm John is correct and these plates should be 3.5" and not 2.625"

 

Pete

Clive

 

I have tried exactly what you have described , even to the tube dimensions being the same, and had the same results. As Richard suggests its a secondary air problem and not easy to resolve. I came to the conclusion that poker burners are only any good in any open environment say for a hedgehog or basic water tube boiler.

 

See link below

 

http://www.homemodelenginemachinist.com/index.php?topic=9111.0

 

I think I then moved on to a blow torch type burner pointing down the 19mm tube and the poker became a nice ornament.

 

 

Pete

David

 

I had assumed at least one had been built and was probably running as it featured in the series. Tony mentioned that two others were being built by his colleagues, what I was seeking was an independent opinion. Maybe something you could consider as a topic for ME, a follow up on series such as this, particularly from the originator but also from some of those that have given it a go.

 

Jason, John, Martin.

 

There a whole minefield out there on plans distribution, I had a moment with MHS over the plans for the Rob Roy lubricator. They wanted GBP5 for one A4 page and GBP6 to send it to NZ when it could have been emailed over to me in NZ as a .pdf in 30 secs. In the end the thumbnail on the website provided the information I required. A lost sale for them. However, I can see once they start sending plans as .pdf they have the possibility of them being illegally distributed, completely out of control. As .dxf files the problem would be worse as even more of the IP would be lost.

 

On the quality issue I can sympathise with David and the problems with ensuring plans for articles are correct. No doubt they arrive in various forms and states and somebody has to transcribe them into the magazine format. I can't see him mandating "plans will be submitted as .dxf files" would work as not everybody would have that capability. No doubt this problem has existed for editors since issue 1 of ME. That said the editor is responsible for the quality of the magazine, not the author of the article.

 

Back to the Northumbrian; for now I'm doing this on the cheap based on the articles in ME for me it doesn't warrant GBP40 for the plans, I'll take the risk.

 

Pete

John

 

It would be nice but I don't think they'd do that as those files contain the real intellectual property. If the .dxf's were available there would be hybrids of all sorts popping up as new work.

 

Where dimensions can't be worked out I've taken to redrawing in visio to find the dimension. Of course if you have better cad packages that helps.

 

Pete

The lack of response from successful builders is bit of a worry, even Tony Weale admitted he hadn’t had it going in part 14 of the series. I have had one PM informing me of one running on air and another aborted project. But nobody has informed me of a successful steaming. There is nothing as far as I can see on other forums.

I've made a start on this, basically because I wanted to give the boiler a go, being my first 'real' boiler and I just happen to have enough of the right sized stock to do it. Then I thought that if I do the boiler first and then want to finish the loco the chance is it won't fit. So I did the frames last week and this weekend have the boiler parts ready to go and in the pickle. If that all goes well I may purchase the castings and finish it. Otherwise the boiler can become a stationary plant for one of my beam engines.

As was identified in the series (and there are other instances) dimensioning seems to be an issue, but not a showstopper. Corrections have been posted for the major ones but there are missing dimensions some of which have to be guessed as they can’t be interpreted. As an example; on the corrected frames drawing (part 3) take a set of dividers and select any one of the ¼” dimensions, then step around the others, some aren’t ¼” as drawn, so what should they be? I’ve taken the view that the specified dimension is correct, even if the result isn’t the same as drawn. There are also missing dimensions on the boiler that require interpretation. Be aware of the cut in the boiler tube “Note: that the saw cuts do not extend as high as the centerline but finish approximately 5/8” below it.” If you do this you may end up with the cut being a little too deep and a spoiled barrel. It has caused me grief, but hopefully I’ve fixed it with a modified throat plate. Time will tell.

This isn’t meant to be a put down of Tony’s work I think the series is a pretty good job, but you need to be aware that all is not as it may seem and check everything before applying tools to metal. (no doubt that advice should go for anything you do)

Pete

 

 

I suppose there is one other question. Has anybody made one that is running yet? I searched YouTube but couldn't find any.

 

Thanks everybody.

 

The thread Jason pointed us to identifies that bush E is not dimensioned in part 11 issue 4376. I think the reason for this is sort of covered in part 15 issue 4385 page 266. Tony suggests using commercial components for the blower valve so your bush is dependent upon what you plan to use. Similarly there are no drawings for the water gauge, bypass valve, lubricator and understandably the pressure gauge.

 

I may be new to this game but I learned early on to source the commercial components before you start and then make your parts to suit. Tapping a bush for 5/16 x 40 to find the part you are using can only be obtained in 5/16 x 32 is a bit of a pain when the bush is already in your boiler.

 

regards and thanks again for your input.

 

Pete

Sorry about opening up an old topic but there is a link to all the 15 parts of this series on the Extras page .I am interested in doing this loco but there is an old thread that concerns me regarding drawing errors. I can see the frames were re-issued in part 3 but is there anything else potential builders should be aware of?

 

Can somebody please confirm that all corrections were posted in the 15 issues that made up the series (4355,57,59,62,64,66,68,70,72,74,76,78,80,83 and 4385) and not in any other issue, either the gaps or later issues?

 

If further information is available could the webmaster just add a note to the item on the Extras page so we can all be informed and seek out the corrections

 

Thanks in advance

 

Pete