|
Post by Deleted on Dec 22, 2013 12:46:04 GMT
Hello all------IAN, could you just "Expand" on that statement a bit please---ie}-- copper tubes rolled into copper firebox tubeplates for over a century and a half ??( Sorry about that awful pun !!), where would that have been then ??------ Agreed re}-- no longitudinal stress at the tube holes, but I'm looking at the top, left general area and thinking that could do with a few stays maybe ??.....DIANNE, just remind us what the designed Working Pressure is please.... we may be going a bit overboard with our comments ??
|
|
|
Post by Deleted on Dec 22, 2013 12:49:21 GMT
Personally I couldn't see why Silver Solder in the normal manner can't be used here.....I notice that no one responded to my question re}---visually checking their internal joints ??---- Blimey JULIAN, looks like we're agreeing on something here ??....Pop the Champagne corks !! LoL ...
|
|
uuu
Elder Statesman
your message here...
Posts: 2,838
|
Post by uuu on Dec 22, 2013 13:27:19 GMT
Try this:
Tubes. The tubes are put in from the smokebox end, the holes in the front tubeplate being, for this purpose, made slightly larger than the outside diameter of the body of the tubes. The tubes themselves are enlarged at the smokebox end, and swaged down to a slightly smaller diameter at the other end where they pass into the firebox tubeplate. At the latter end the tubes project into the firebox for about f in. to allow for 66 beading over " the ends up against the copper tubeplate. They are tightened in the holes by means of a tube expander, a special tool provided with a number of rollers. This is placed inside the tubes, the metal of which is rolled outwards until they are a tight fit in the holes. In the
3 (5350A )
24 STEAM LOCOMOTIVE CONSTRUCTION
case of steel tubes a ridge or beading is also rolled on the tube on the boiler side of the firebox tubeplate. Brass or copper tubes are expanded and secured by driving short pieces of steel tube (called ferrules) tightly into the ends which pass through the tubeplate. At the smokebox end the tubes are merely expanded, neither beading nor ferrules being used.
From Steam Locomotive Construction and Maintenance 1921 by Ahrons
|
|
|
Post by Deleted on Dec 22, 2013 13:53:14 GMT
Hi UUU, thanks for that useful input.......... Yes, that's how you roll and expand tubes allright...have done so on quite a few occasions down the years....Have not encountered either Brass or Copper tubes though..I'm not saying they don't exist, just not come across them..that's all.. Maybe private contractors and small shunting locos had them but I imagine the expense might be an of-putting factor ??.. Food for another thread,eh ??
|
|
|
Post by RGR 60130 on Dec 22, 2013 14:48:13 GMT
I have seen many instances of non-ferrous tubes rolled into non-ferrous tube plates on ships though they are usually of the brass/ bronze variety rather than copper. These instances include smaller sizes of tube plates down to 4" / 100mm diameter. Alan, you must have come across these in your Navy days even if you didn't realise it.
A rolled tube will have a slight staying effect because the tube will thin down where it passes through the tube plate and spread a bit either side. A final wack in the end of the tube with a taper drift after rolling helps this effect a little bit as well as giving a nice lead in for a tube brush.
Co-incidentally I've noticed a lot of emphasis placed on longitudinal staying which while obviously very important isn't the be all and end all of boiler design. Taking the scenario to the extreme i.e. without any longitudinal staying at all, the ends will become hemispherical and the boiler will fail by splitting along it's length. This is subject to the joints not failing and the material thickness being the same for the ends and barrel. The reason behind this is because the forces that are trying to split the barrel are twice those that are trying to blow the end off. This is why all barrel openings for fittings or manway doors are reinforced by the use of bushings or doublers. (sorry if this is off topic a little bit but I'd imagine some will not be aware of that and may find it of use or interesting).
For your boiler Dianne, I think you've taken a sound approach and I'm enjoying the thread which I hope you'll find time to continue.
Reg
|
|
|
Post by Deleted on Dec 22, 2013 15:15:06 GMT
Hello Matey !! ( For the land-lubbers that's a jovial, fellow mariner's greeting..but NOT including a tot !!)----------------- REG, most of my Boilers were either Admiralty or Babcock 3-Drum types and to the best of memory they were steel tubes.( Forever checking for scabbing and pitting so must have been steel)...The thought occurred that maybe the condenser pack under the main turbines could have copper tubing ??...As you say, I might not have been aware at that time, as my capacity was more in operational mode than actual overhaul.........The "Hands-on" experience came via the Heritage Railway scene( SVR ) where the bulk of locos are so-called "Modern" eg}-- dating from the late 20's to late 30's and steel tubing was then the order of the day....I suspect that for a flexing, twisting environment of railway operation coupled with that "Heat Cycling" mentioned earlier then the non-ferrous option would have been dropped by then ??............................... Blimey !!.. it's been a while now since I've had to do the theoretical on boiler shell failure but what you say there seems to ring a bell....Looking at a typical locomotive - type Belpaire Boiler there are overlapping,riveted, LONGITUDINAL joints which should be below the water line I think ??.....this being the first failure point...The least number of openings in the shell the better hence the steam "Fountain" or manifold in the cab to supply a multitude of other uses............That experimental LNER W2 4-8-4 with a marine boiler didn't fair too well either I think ??------------------- YES !! Keep on going, DIANNE............ EDIT----Have been getting the mono-brayn-cell fired up !! We also had small, oil-fired boilers on board for "Domestic" duties (Dhobying, hot-water showers etc) and again these may well have contained non-ferrous tubing ??
|
|
jma1009
Elder Statesman
Posts: 5,913
|
Post by jma1009 on Dec 22, 2013 21:36:22 GMT
hi alan,
yes i think we both agree, though am surprised at the lack of critical comment on dianne's boiler design which i cant see meeting UK approval. perhaps im just a bit too outspoken and forthright with my opinions in these matters and not bothered who i upset or offend! dont forget one end plate takes all the stress and force from the cylinder fitted inside.
i agree entirely with Reg apart from his last sentence ("sound approach") which seems to me to contradict everything he said in his previous paragraph. Reg, do you agree with a butt joint for a dome? and effectively butt joints for the end plates?
cheers, julian
|
|
|
Post by wdiannes on Dec 22, 2013 22:47:28 GMT
DIANNE, just remind us what the designed Working Pressure is please.... we may be going a bit overboard with our comments ?? Jeez, I am away for a day and this thread goes wild! The manufacturer of the 4" pipe rate it at a working pressure of 140 PSIG at 350F and I have been using 150 PSIG as my design pressure. Operating pressure will probably be 50 to 75 PSI, depending how much tractive effort I can get with the finished locomotive - no point running above the pressure required to slip the wheels. But for all the design calculations 150 PSI is being used to calculate the safety factors. Julian, the dome is not a "butt fit". The dome passes through the shell, is flared on the inside, and silver soldered to the shell (all the way through) with "Safety-Silv 45", a Harris product with a tensile strength greater than that of copper (which means the copper will tear before the silver soldered joint pulls apart - same goes for the end joints). As for " dont forget one end plate takes all the stress and force from the cylinder fitted inside" that constitutes a whopping 7 pounds!
perhaps im just a bit too outspoken and forthright with my opinions in these matters and not bothered who i upset or offend! No, you just don't understand the basics of mechanical engineering which is why you can't comprehend the degree of safety in this design and keep posting critical comments because it isn't done the way somebody wrote it up in a book. If we only did what has been done in the past, we would still be riding in horse-drawn carriages. Engineering is what allows us to progress and not be bound by 'tradition' and the way things used to be done. You know, quite frankly, what is written in some 'model boiler code' (no matter who's) doesn't impress me in the least if it isn't backed up by the mathematics to PROVE it is safe and I don't care how long it has been done that way or how many have been built. If it doesn't have the numbers behind it, it isn't worth the paper it is written on. If I could ban you from this thread, I would in an instant. You just create post after post of criticism without the science, mathematics, or engineering to back it up!
|
|
|
Post by marshall5 on Dec 22, 2013 23:54:55 GMT
Sorry Dianne but I think you are over-reacting by suggesting that another Forum member be banned for expressing his opinion, we all have different ways of doing things and sometimes we just have to agree to differ. In the UK we are tied to a set of boiler regs and whether you,I or anyone else agrees with the calcs behind them or not we just have to live with them - or not run our engines. FWIW I think you are making a big mistake not silver soldering your tubes at this stage - if you steam the loco and later find they are leaking it's going to be near impossible to get the joints clean enough. I don't see any advantage in not soldering them, different if it was a steel boiler. Just my 2 cents worth. Ray.
|
|
|
Post by wdiannes on Dec 23, 2013 0:12:56 GMT
I understand your limitations where you have a specific code you must abide by and that code does not set out the requirements for alternatives. Fortunately in 'the colonies' we are not so tightly hemmed in and have the opportunity to use mechanical engineering to prove or disprove any particular design.
What I find extremely frustrating is that the same criticism comes back again and again and although I address the points, either what I say is not understood or is ignored because it just keeps coming back unchanged like a religious dogma.
I considered silver soldering the tubes but the support offered by the tubes is not required to provide strength - the Safety Factor is already in excess of 40 without the tubes. If they are silver soldered it would be an incredibly difficult task to change a tube if that was ever required in the future (not that I expect to live that long LOL!). At least with soft solder tubes could be changed without reheating the boiler and the silver soldered joint coming apart.
|
|
|
Post by Ruston92 on Dec 23, 2013 0:19:07 GMT
I think it is unfair to say that someone doesn't understand the basics of mechanical engineering. From all I've seen of Julian on this forum he is a very wise engineer and is only trying to offer some advise. Well done for going off your own back and designing this very unique locomotive, which I will love to see when it is finished, but part of engineering is taking advise off your peers.
Please keep posting pictures of your progress.
Cheers,
Pete
|
|
|
Post by wdiannes on Dec 23, 2013 0:26:36 GMT
....but part of engineering is taking advise off your peers. Indeed, but lets talk ENGINEERING and give an engineering counter-point! Show some calculations to back your position rather than just 'quoting code'. If there is a flaw in my design, I would like to know about it, specifically where. Opinions in engineering don't count without the numbers to back them up.
|
|
|
Post by wdiannes on Dec 23, 2013 2:01:20 GMT
All the details are contained in my earlier posts but for those who don't want to bother to sort them out and do the calculations, here is a summary of the design verification:
Barrel O.D. = 4.130", area = 13.396 inches squared Barrel I.D. = 3.834, area = 11.545 inches squared Area of barrel edge = 13.396-11.545 = 1.851 inches squared.
Using the tensile strength of copper @ 23,600 pounds/inch squared (which is lower than the tensile strength of silver solder), the failure stress of the joint will be = 1.851 inches squared x 23,600 = 43683 pounds. (The tensile strength of silver solder is such that deflection of the end plate will cause the copper to bend without the joint 'ripping apart'.)
Using a centre stay of 1/4" dia copper, the tensile strength of the stay is (0.250/2)squared x Pi x 23,600 = 11579 pounds
Strength of circumference joint + stay = 43,683 + 11,579 = 55,262 pounds
At a pressure of 150 PSI, the load on the end plates (ignoring the area reductions for flues and tubes) is 11.545 inches squared x 150 pounds = 1732 pound.
Safety Factor = strength / load = 55,262 / 1732 = 32 (at 150 PSIG)
If the area of the end plates is reduced by the area of tubes and flue, the Safety Factor is even higher.
If I have made an oversight or a miscalculation in my analysis, please point it out. Otherwise I consider the matter of this design CLOSED and will no longer respond to any further debate on this subject!
|
|
|
Post by jordanleeds on Dec 23, 2013 2:19:29 GMT
Cant see why expanding them would be an issue.. it worked for the stephonsons!
|
|
jma1009
Elder Statesman
Posts: 5,913
|
Post by jma1009 on Dec 23, 2013 9:00:24 GMT
hi dianne,
i am pleased that there is now a flange to the dome/barrel joint as this wasnt shown on your original drawing.
thank you Ray and Pete!
cheers, julian
|
|
|
Post by GWR 101 on Dec 23, 2013 18:15:20 GMT
Hi Dianne, think its a great build, I live not far from Ironbridge and think it played a great part in our industrial past so a wonderful choice. I hope you don't mind but have sent you a PM. Regards Paul
|
|
|
Post by wdiannes on Dec 23, 2013 18:45:31 GMT
I didn't have any rubber of suitable characteristics to make an expander so I decided to caulk the tubes with soft solder. While I had the boiler on the hot plate, I decided to touch up one spot on the silver solder that I wasn't happy with so I took the temperature up to soldering temperature. Something very strange was going on! I was getting a large green halo around the hot plate flame and around the oxy-acetylene flame. Something was gassing! It must have been from the 'lead-free solder' or from its flux because I have never seen this before. By the time the silver solder was touched up, I was having trouble breathing and was coughing - I had to get out of the shop into the fresh air! (It is -30C so I didn't have the exhaust fans running.) It has been 2 hours now and I am not coughing any more and I can breathe better but just a warning fro others: if you are using products you aren't familiar with BE CAREFUL!
|
|
|
Post by alanstepney on Dec 23, 2013 21:02:03 GMT
A Morse taper can be used as a drift to expand a tube. Not ideal but better than nothing.
I'm not so sure about the soft solder though. (Perhaps it is a good job that I am not <still> a boiler inspector, and the one examining it.)
|
|
|
Post by wdiannes on Dec 23, 2013 21:39:36 GMT
I don't have anything around the shop with an OD of 1-5/8 - none of my tapered tooling is anywhere near that size - but that's a neat idea for smaller tubes.
The soft solder doesn't have to carry any load - it is purely a seal. With a melting point of 700F it isn't even plastic yet at 350F
Or maybe I am missing your point of concern?
|
|
|
Post by Ruston92 on Dec 23, 2013 23:26:03 GMT
I am in no means a expert boiler maker, but I think the solder you have used will just melt off into a nice puddle on the floor when you steam it.
As for your green halo, if you were using the white powder flux (cant remember its name at hand) that often burns green with a toxic gas given off.
|
|