Said I would never do it.

[Rocket Man]

What the H is going on??? I check email it sends me here. I barely have time to read, Reptiles are taking control of our government, the page goes to a different location. Now I am here? I don't care. I don't do politics. I hardly ever turn my TV on nothing there but politics and evil.

 

[Zeb]

Come to thinkpf of it, I think my headset full of cameras is getting bricked January 1st unless I get a facetube account. I might end up getting one for it, but I can see why it's a personal choice. They really want to know how messy my office is.

Now for real politics....

I have books and texts by:
K.N. Harris, Alec Weiss, Kozo Hiraoka, Martin Evans, Tubal Cain, Prof. Andrew Jamieson (who quotes work & formula derived by Sir William Fairburn); John Goodman, et al.

Ooh nice. I'm collecting books on the subject. Hiraoka inspired me to learn draughting the old fashioned way. His stuff is top teer.
Thanks for the advice. I think I read from you sometime back about calculations and am still pretty cautious.
One of my favorite safety warning resources are those empirical failure tests on a PDF floating around the net.
And yes, fatigue cycles are noisy to calculate and the build quality has an effect, which is why I'm slurping up all the knowledge I can. I'm not planning on building anything not already over-enginear'd. The PM boiler is about as overbuilt as it can get with all those rivets. My only deviation might be two stages of flux and squeezing the rivets (no hammering, pulling on solder joints, or fatigue hardening).

 

[Mousetrap]

This is the only chat site I use... Not having spotted any weirdos, maybe I am the weirdo?
K2

You are not wrong.

 

[terryd]

Just be careful -- the reptars and the greys are fighting for control of all governments on erf.

As the Reptars were T Rex' they already had their day. They are still having their day on Antichthon but we'll never know for real.

 

[ninefinger]

Keep calm Richard,
Einstein explained relativity.... "If you are on the same hill-top at the same time moving at the same speed you all look the same". It is only when you are on the subway platform and everyone is moving fast past you in the opposite direction you realise you are "relatively" the odd one. Maybe they are all the wierdos? - And we are the ones who are "sane" (which is a relative term based on abstract ideas anyway!).

Zeb: re: your new book. Does it explain calculations for determining wall thicknesses of flue tubes, or other tubes with the copper "in compression"? - I think this is probably a "bible" for making boilers (Coppersmithing), but it may omit that particular part of boiler design (as do most books) concerning the design of "tubes in compression", particularly if copper.
I have books and texts by:
K.N. Harris, Alec Weiss, Kozo Hiraoka, Martin Evans, Tubal Cain, Prof. Andrew Jamieson (who quotes work & formula derived by Sir William Fairburn); John Goodman, et al.
Yet I have never seen anyone consider that Copper tubes in compression suffer from the compressive strength being as low as 45MPa but only consideration of the Ultimate Tensile Strength, as 210 MPa. (30500 psi.). I.E. the tubes in Compression, if designed using hoop stress calculations using the Tensile strength of annealed copper, will be incorrect for the required safety factors for the boiler. I am still seeking a text that even discusses the matter. I can only assume that "in service" flue tubes etc. at "~20% of their "correct" design strength" are adequate for the 1.5 x NWP Hydraulic test. And copper boilers quickly become "stronger" than their annealed state when heated and stressed, then cooled, repeatedly.
Enjoy your boilermaking - and use a "proven and certified" design, and known (certified?) standard of materials.
K2

Reread your Martin Evans "Model Locomotive and Marine Boilers", chapter 2, with specific reference to page 29 where he discusses flues and firetubes.
Also, if your interested in model boiler design rules then the Australian Association of Live Steamers publishes their code book - for copper boilers its AMBSC Code Part 1 - currently at issue 8 (but others prefer the earlier issue 6 - issue 8 has removed all discussion of girder stays for firebox crowns).
It also list the minimum thickness of fire tubes and flues by diameter, and they are roughly comparable to the values Martin Evans lists. In both cases the relative thickness of the tube to its diameter is greater than that for the outer shell.

 

[Steamchick]

Thankyou Ninefinger:
You have a better memory than I, as I last read this book a few years ago.
I have seen many tables of this nature:
Tubal Cain (Model Engineer's handbook Pages 10.4 ~ 10.5) discusses this also.
As an example:
* Martin Evans quotes a flue tube of 1 1/8"OD x 18SWG (0.048") as suitable for up to 120psi. ("OK" in the UK, but ASME restricts Model Copper boilers to 100psi., and has banned riveting).
* Tubal Cain repeats this information, but states the NWP should be limited to 100psi (7Bar). (His approximation of the conversion).
* I have compared Tubal Cain's table with my calculations of the hoop stress limits for copper tubes in compression based on 45MPa stress limit - further reduced for the temperature degradation as per ASME considerations. I find by "my calculations" that a 1 1/8" flue tube with 14SWG wall should be good for a NWP of 80psi. Obviously this is considerably thicker than Martin Evans et al, and uses a considerably reduced limiting stress (Based on ASME). (And my calculations and "conditions" may be wrong?).
Therefore my conclusion is that the "old" tables for flue tubes do not equate to "modern" calculations for safe limits for design of copper boilers, as indicated by ASME.
Zeb is in Camelot, and I suspect they have a more "old fashioned" perspective of safety there, in order to maintain the freedom to have Dragons, love affairs between the Knights and Queen, etc.. (We no longer have real dragons in England).
I may be "sticking my neck out here", and someone will no doubt try and "chop it off", but simply, I can only publicly state what I believe from my Engineering calculations to be a safe situation for the design of model copper boilers to suit ASME, as many contributors and readers are from the USA...
Incidentally, I am sorry if I have drifted into Engineering away from the political discussions of information exchange on the WWW.
K2

 

[Richard Hed]

Come to thinkpf of it, I think my headset full of cameras is getting bricked January 1st unless I get a facetube account. I might end up getting one for it, but I can see why it's a personal choice. They really want to know how messy my office is.

Now for real politics....

Ooh nice. I'm collecting books on the subject. Hiraoka inspired me to learn draughting the old fashioned way. His stuff is top teer.
Thanks for the advice. I think I read from you sometime back about calculations and am still pretty cautious.
One of my favorite safety warning resources are those empirical failure tests on a PDF floating around the net.
And yes, fatigue cycles are noisy to calculate and the build quality has an effect, which is why I'm slurping up all the knowledge I can. I'm not planning on building anything not already over-enginear'd. The PM boiler is about as overbuilt as it can get with all those rivets. My only deviation might be two stages of flux and squeezing the rivets (no hammering, pulling on solder joints, or fatigue hardening).

"Facetube". I have to say, that made me laugh. Will try to remember that one.

 

[Zeb]

Zeb is in Camelot, and I suspect they have a more "old fashioned" perspective of safety there, in order to maintain the freedom to have Dragons, love affairs between the Knights and Queen, etc.. (We no longer have real dragons in England).

K2

bu...but..there's not a more political discussion than boilers! The camelot I live in....is only a model. It is a silly place.

The risks of boiler operation are slightly less a concern for me than the chemicals involved in making the boiler. I've already saturated my body with some nasty stuff from 20 years restoring antique flying things.

 

[Richard Hed]

bu...but..there's not a more political discussion than boilers! The camelot I live in....is only a model. It is a silly place.

The risks of boiler operation are slightly less a concern for me than the chemicals involved in making the boiler. I've already saturated my body with some nasty stuff from 20 years restoring antique flying things.

When I was a kid (last week), it was common practice for chrome platers to get right into the tub of chemicals or immerse their hands to the elbow in the chems. can you imagine? (what I mean here is, Can you imagine me ever being a kid?) No one in their right mind would do that today. Long gloves of all kinds are now available and othr techniques to put large pieces into a tank. I'm curious, like radioactive materials, what did the chomium salts do to those practitioners in the long run? I couldn't imagine that they would get out scott free of some kind of liver/kidney/cancer disease.

BTW, luv yer jokes, keep them up.

 

[ninefinger]

this boiler discussion really belongs elsewhere but I can't help myself. The nerd in me is being drawn out - or its my OCD. Maybe if we chat over on a facebook group the governments of our various jurisdictions will step in and set us straight?

Martin Evans does not call out 18 S.W.G. for copper - he lists that for stainless steel. For the 1-1/8" tube he lists 16 S.W.G. (0.064") in copper as suitable for 80-120 psi or 33% thicker than you stated. I'm not terribly worried that my boiler I'm building is going to come apart by collapsing the tubes under normal operation. That is what the safety factor in the calcs is for, and the fact that thousands of boilers have been made to these "standards" without issue is testament to the safety factor being sufficient.

Also, there is the complication that while the pressure does try to collapse the tube radially, there is almost certainly an axial tension on the tubes that may or may not paly a role in preventing collapse. (or make it worse?) any volunteers to model it up in CAD and perform FEA on it?

 

[Steamchick]

The longitudinal stress adds to the failure mode, as far as I understand from the calculations that "technical papers" on the subject of stress indicate. But it is complicated because the tensile stress is combined with a perpendicular compressive stress (as the sum of squares so they become additive) but the stress limit varies depending on the stress of each vector. So to judge them independently is really the only way I know how, unless a mathematician can teach me otherwise.
I agree that safety factors exist. What I am saying suggests some old designs achieve safety factors of as low as 2 or 3 ish instead of 8, when compared to modern stress limits? Probably why "old" designs have not failed, but "not adequate" for modern thinking for insurance, certification, public exposure, personal safety, etc? (IMHO). It does not change the real "safety" of a boiler, as the metal does not change, but it changes the "risk" of failure (and litigation) when a boiler is de-rated to have a higher safety factor.
ASME seems very specific as to the limited tensile stress on pressurised copper boiler components, but I have not yet seen how it manages compressive stresses.
Hadrian's wall, the Colluseum in Rome and other buildings were not made to modern regs, but have lasted thousands of years. (Except for people robbing stones!).
I am just advising caution, and doing full calculations for any NEW designs, to the regulations appropriate to where you live/insure your stuff. On new designs, the calculations shall be checked by an appropriate expert as part of the initial certification (in UK practice). Designs that have previously been certified and proven are accepted on the basis of precedent. But I suggest you should be sure you are using good quality materials to suit those designs.
A bit like aircraft, this may suggest you could copy the design of De Havilland Comet window in a copy of that design, but the history records this design has been rejected following failures. So check that you copy a GOOD design with GOOD history, and without later changes being incorporated.
My Simplex boiler (after repair) will need re-certifying when I have made repairs (if the repairs are good!) But I shall de-rate it to 80psi NWP instead of the 100 psi on the drawing, as some flue tubes are "inadequate" for 100 psi compared to my interpretation of ASME Engineering ideology. Just because this may become a working boiler in a public area, covered by the Club's insurance, and it seems sensible to be as safe as "Modern thinking" requires for new stuff. Who am I to ignore stress limits or whatever determined by the experts in ASME? They have knowledge, expertise and history that didn't exist when Martin Evans and others designed their boilers.
So you do what you think is right and I shall do what I think is right, especially when advising people on a public site like this one. And surely as "Model Engineers" we should responsibly use the "best" within our knowledge, skills and expertise?
And I have not yet mentioned de-rating to account for distortion factors, stress concentraton factors etc..
There are plenty of worms in this can!
In my professional employ I had to consider far more than just the simple Hoop stress on tubes.
Please forgive my ramblings on this subject. Tell me to "Shut up!" If apropriate. No offence will be taken.
Cheers!
K2

 

[SirJohn]

I have an old 1960s mini bike that I road when I was in grade school & high school. My sons road it too. Now its for sale.

Is your mini bike still for sale? can you post a photo? I have a brother that collects motor cycles and bikes who may be interested.
John