Simplex Boiler

[ozzie46]

I have been able to scrounge up some 4" ID copper pipe for the Simplex boiler but the plans call for 4 1/2 " ID.

Will a 4" ID boiler produce the needed power for the cyl? The cyls are 1 1/2" dia bore by 2 1/8" stroke.

Will I need A smaller bore and are there any other things I need to be aware of?


Ron

 

[GWRdriver]

Ron,
I have one such boiler experience, reducing a 4-5/8" barrel diameter to 4-1/8" diameter in a 1" scale Atlantic. It was reported to me that the boiler steamed like a demon and there was no apparent adverse effect from reducing the barrel diameter. However, I don't recall what the cylinder diameter was and it seems to me 1.5" diameter cylinders are going to want all they can get out of a 4" boiler, especially if worked hard. But based on the one experience I had, if you maintain roughly the same amount of flue heating surface, under normal operating conditions the reduced volume wouldn't be missed.

The impact of such a change will be in three areas. The first will be externally which can be handled with built-up insulation. The second will be that the internal volume of the boiler, the water and steam storage space, will be proportionately reduced. Thirdly, it's possible that the number and/or of flues might be reduced thus reducing the heating surface which will alter the steaming capability of the boiler. Whether the impact is great enough to require a design change in some other area, I don't know, although both conditions can be overcome by an increased firing rate.

PS - Hopefully your scrounged piece of copper is new material. A little oxide on an old piece of unused pipe is OK, but salvaged scrap is not a good thing to use in a boiler.

 

[ozzie46]

Thanks for your input Harry. The inside of the tube doesn't have any scale or anything like that on it. It a has a lot of dust though. It just looks like dull copper. The thickness is 1/8th in.

As I know virtually nothing about boilers I'll need all the help I can get. :big: :big: :big: :big:

Ron

 

[GWRdriver]

Ron,
I'm looking at the Simplex boiler drawings (ME, #3342, Apr 1968) and see a couple of problems. The original barrel is shown 4-3/4"OD and I'm afraid going from that to 4-1/8" is more diameter loss than I think you should consider. Not necessarily because of a loss of steam/water capacity, although there will be that, but because of the ripple effect on the other parts of the boiler.

The barrel and firebox outer wrapper are designed to be of the same tube and IMHO for the sake of steaming capacity you can't afford to make the firebox or water legs smaller or narrower. IF you were to use the 4-1/8" a solution to the diameter mis-match problem would be to make the firebox separate from the barrel and take up the difference at the throat plate which would need to become a full head, that is, one that surrounds the barrel tube.

Another consideration will be the location of the throttle bushing which is pushed up against the top flange of the back head and in that position the throttle assembly would foul a smaller barrel OD. Without looking at other drawings I see no reason why the throttle centerline couldn't be fudged downward a bit but this would be fudging a lot and everything on its axis would need to follow the fudging. The other issue is the flues and at the moment the flue nest is arranged so as to fit neatly into the firebox tube plate but leave reasonable room inside the barrel and in the front flue sheet. Reducing the barrel OD to 4-1/8" would probably eliminate the bottom row of flues and then I think at that point you will begin to adversely affect the steaming capacity of the boiler. One thing does bother me a bit which is that in the transverse firebox section Dear Martin shows the bottom row of flues lying outside the barrel ID! (Oops!)

If I was in your position I would do this . . . I would plan on either buying the correct size barrel tube from a UK supplier, or roll the tube from plate stock. I would split, anneal, and flatten the old tube and use that as far as it would go to make the heads. I think this would be the best use of what you have and make for the least trouble fabricating the boiler.

 

[ozzie46]

Thats the kind of info I was looking for Harry. Thanks.

I guess I'll try to find some 5" tube then as it seems a whole redesign would be in order for the 4 1/8" tube and I don't have that kind of knowledge. Maybe I can use it for a traction engine or a 3 1/2 guage loco.

Ron

 

[GWRdriver]

5" tube

Ron,
I'm sorry to seem to be the harbinger of nothing but negative news (well, some negative news) but I'm trying to save you some trouble and give you a few heads-ups on what to expect. You may be able to find a piece of orphaned 5" tube . . . but it's going to take some luck; 5" tube as a stock size in both copper and steel has been discontinued in the US. It's still a standard size, meaning the mills will still run it by order (1000's of l/f), but pipe distributors and warehouses no longer stock it. The same is true of 3.5" copper. The reason is that years ago mechanical engineers shifted to designing large plumbing installations with either 3", 4" or 6" pipe and let the other two sizes go.

You may get lucky and find a piece of 5" tube - I got lucky a couple of years ago and found an orphaned length of 3.5". But I stopped looking for 5" years ago and for all I know now someone who has everything (like a McMaster-Carr) may have brought it back. It's worth a look, but you are most likely to find it languishing in the scrap rack at a larger mechanical/plumbing contractor's. As an aside, someone recently listed a full 20ft length of 8" Type L copper on eBay! 8" diameter!! That stuff can't be had anywhere any more so never say never. (Of course the 8" wasn't cheap but that beside the point.)

If you do find some 5" one option to think about is splitting that tube and rolling it down to 4-3/4" and use a strap joint along the bottom, then nothing has to be redesigned which I would think you'd rather not do. You could go one step up to 6", which is available in cut lengths, and do the same thing.

 

[ozzie46]

Thanks again Harry.
Don't worry about the bad news bit. This is stuff I need to know.

Maybe I'll just start looking for flat sheet and roll my own. Of course that means building a roller but making tools is just as good as making engines. :big: :big: Or split this pipe and add a 1" strip and make it 5".

Ron

 

[SBWHART]

Hi Ron

Harry is spot on with his advice, Simplex is a very popular engine over her in the UK there are a couple that run at our club when I was looking into building the boiler for my loco I talked to the chaps about how they built their boilers and its seems a lot go for the flat plate and tube rolling method with a lap joint down the join.

I take it you have some ware to run your loco it may be worth asking around the track, loco builders are a helpfull bunch.

Good luck

Stew

 

[Dan Rowe]

Ron,
You might give Mueller Industries a shot. The website states a price per foot for 5" copper for types K, L and M. Make sure you are sitting down.

http://www.muellerindustries.com/
Click on products then copper tube.

Dan

 

[GWRdriver]

Don't worry about the bad news bit. This is stuff I need to know. . . . . Or split this pipe and add a 1" strip and make it 5".

That's an intersting thought. According to my calcs the gap would actually be around 2" which would call for say a 3-1/2" wide strip (to provide two laps) or two butt joints with a say 1.25" to 1.5" wide strap across each one. But I've done an awful lot of reading (going back ages) and I don't recall seeing a double joint used in a model boiler. That's not saying that someone hasn't done it, or that it wouldn't be safe (which after all is our principle concern) but when nothing appears in print over that long a time there is a message in there for me somewhere which is that such a joint is to be avoided.

 

[ozzie46]

Harry, how about copper rivets in the laps at the joints along with the silver solder?
My local small hardware store stocks flat head 1/8 rivets. Two rows of rivets at each joint.


Ron

 

[GWRdriver]

Ron,
Riveting a lap or butt-strap joint is SOP and here's the way I do those, and I have done firebox stays in almost exactly the same manner. I use regular round head copper rivets ("snap" head in the UK) with the head placed on the inside. On the outside surface, where the rivet shank comes through, I countersink the holes to an OD of maybe twice the diameter of the rivet. The purpose of this it give the silver solder a place to "puddle" around the rivet and in essence make a "head" on that side of the seam which when filed off near flush won't be weakened. There should be a little meniscus of solder climb up the rivet shank, but very little. I don't pound any of this up tight. I relieve and coutersink or deburr the holes so to give the solder plenty of opportuntiy to make its way into every void. Ensuring that solder penetrates completely acros a strap joint is obviously important but it's not nearly as much of a piece of cake as you might think. I not only chamfer the edges and rough up the mating surfaces with a rasp (to provide solder channels) but under certain conditions I also drill a few small "supply" holes near the butt (but not over it) so that I can feed solder directly into the center of the strap. Naturally the supply holes and any feed channels must be left filled with solder.

If you wanted to use the local hdwr shop rivets that should be OK, just make sure they are solid copper, and you can still put the flat-heads on the inside, the solder will make a nice collar around them. See, something positive for a change.

 

[ozzie46]

Thanks again Harry. I've got a lot to think about before I make up my mind as to which way to proceed. Meanwhile I've got a lot af stuff to build on it yet so it will be a while before I get the boiler.

If you think of any thing else I may need to know just let me know.

Ron