Author Topic: boiler stays  (Read 13427 times)

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 12697
  • Central Massachusetts, USA
Re: boiler stays
« Reply #15 on: October 24, 2016, 04:18:01 PM »
Thanks Jason, and I';m glad you understand my point.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: boiler stays
« Reply #16 on: October 24, 2016, 04:24:26 PM »
DaveCLM is this Julius de Waal's version of the 3.5" horizontal boiler, if so I have the original which tells you how to do the stays.

J

Offline SandCam

  • Full Member
  • ****
  • Posts: 136
  • West Coast of Scotland UK
Re: boiler stays
« Reply #17 on: October 24, 2016, 04:44:58 PM »
As I said earlier if using bushed stays then all the ones I have seen thread the full dia of the stay. The bush is then threaded internally to fit the stay and externally to fit tapped holes in the tubeplate. I suppose you could just solder in te bushes but I would prefer to see then full dia all the way.

I'll scan a picture later of a drawing that shows then done this way.

I have never had a problem silver soldering 660 and it is resistant to dezincification so no problem in a boiler :) though I mostly use it for fabricated cylinders.

J

Jason, understood, but my point is what is drawn on the drawing?, was the drawing signed off for construction?, and does the part conform to the drawing?

I'm being pretty anal about this, because it's a boiler, and I know the laws on that side of the pond are pretty strict.   Now would be a good time for Sandy or a Boiler inspector to inspect the components and make a judgment before it's all silver soldered together.   It's far easier to recover from an error now before that happens.   Now if you're that guy...GREAT!   ....but I am approaching with a great deal of caution.    I have yet to see any stamped drawing that says this is right or wrong.   

Dave

Hi Guys,

Daveclm,

The diameter and strength required for stays is determined by the area supported and the load on that area.

Both Jason and Dave are quite correct to question the type and method being proposed.

The 2 facts we don't know are the working pressure and the surface area in square inches that requires the support, hence, to make a sound judgement both would need to be known.

Solid Drawn PB has a typical tensile strength of 31250psi in the fully annealed state, however for stays a x10 safety factor is applied when calculating stay strength under UK boiler stress regulations. (and pretty much the same worldwide)

From the photo's of the proposed stays it would appear that the 3/16"OD  has been reduced to around 1/8th inch dia and then threaded at ,perhaps, 5BA.
This would reduce the effective cross section of the stay to approx 0.0075 sq in. at the root of the thread giving a breaking stress of just 23.4375lb each.

I.E... (0.0075 x 31250) /10 safety factor = 23.4375lb each.

Whereas the full 3/16" stay directly soldered into the end plates would each have a breaking stress of 86.28125lb... which is approx 3.7 times stronger per stay.

Even threading the outside of such a stay and using a dual threaded bush, as Jason has suggested, would still reduce the strength of the stay to that afforded by the core dia of the chosen thread... the bushes do not change this regardless of how big they are.

So, to recap... Davecls can you supply the following: -

Which boiler design are you following.

The working pressure of the boiler.

The outside diameter of the end plates and the thickness of the material used.

The outside diameter of the centre flu.

The horizontal spacing between the stays and the vertical spacing from the top of the end plate.

I can then get a better indication of the expected loading and take it from there.

Meanwhile... don't solder anything yet.

Best regards.

Sandy. ;D


Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 12697
  • Central Massachusetts, USA
Re: boiler stays
« Reply #18 on: October 24, 2016, 05:31:54 PM »
Thanks Sandy.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline daveclm

  • Full Member
  • ****
  • Posts: 22
Re: boiler stays
« Reply #19 on: October 24, 2016, 06:56:22 PM »
hi sandy
i dont no the name off the boiler, it just says on the drawing horizontal centre flue boiler drawn by af campbell and sandyc argyll scotland.
the boiler tube is 106 copper 1.6mm 16g bought from kennions, dia is 31/2", centre flue is 1 1/2" 106 1.6 16g tube, the end plates are 106 3.2mm 10g i known a bit over board on thickness i allready had it.
the gallow tubes i think thats what they called are 20gauge the stays are 3/16 not 3/8 which i said they where. max wk pressure is 60 psi 4 bar and typical wk pressure 45 psi. the only thing i have changed is the chimmny is on the out side off the boiler. dont know if this makes any difference to the boiler.end plates are just under 86mm tight fit. dont know how tight they shoud be.

thanks dave

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 12697
  • Central Massachusetts, USA
Re: boiler stays
« Reply #20 on: October 24, 2016, 07:10:48 PM »
You're in good hands Dave.....


Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Jasonb

  • Full Member
  • *****
  • Posts: 9466
  • Surrey, UK
Re: boiler stays
« Reply #21 on: October 24, 2016, 07:23:21 PM »
As said you are in good hands, I'll leave it to SandCam to sort you out who is the SandyC on your drawings though they do tell you how to mushroom the ends of the stays.

It may help Sandy to come up with a rescue plan if you could say what size hole you have drille din the end plates for the bush, hopefully they can still be used but I have a feeling the stays won't be able to.

Offline daveclm

  • Full Member
  • ****
  • Posts: 22
Re: boiler stays
« Reply #22 on: October 24, 2016, 07:31:13 PM »
jasonb
the holes are sloppy 3/16, same as the bronze rods.

thanks dave

Offline SandCam

  • Full Member
  • ****
  • Posts: 136
  • West Coast of Scotland UK
Re: boiler stays
« Reply #23 on: October 24, 2016, 11:20:47 PM »
hi sandy
i dont no the name off the boiler, it just says on the drawing horizontal centre flue boiler drawn by af campbell and sandyc argyll scotland.
the boiler tube is 106 copper 1.6mm 16g bought from kennions, dia is 31/2", centre flue is 1 1/2" 106 1.6 16g tube, the end plates are 106 3.2mm 10g i known a bit over board on thickness i allready had it.
the gallow tubes i think thats what they called are 20gauge the stays are 3/16 not 3/8 which i said they where. max wk pressure is 60 psi 4 bar and typical wk pressure 45 psi. the only thing i have changed is the chimmny is on the out side off the boiler. dont know if this makes any difference to the boiler.end plates are just under 86mm tight fit. dont know how tight they shoud be.

thanks dave

Hi Dave,

So...  af campbell and sandyc argyll scotland... couple of real dodgy character those two... I know them really well >:D :censored: :LittleDevil: :ROFL: :lolb:

Your boiler is known as the MEM 3 1/2" diameter Horizontal boiler and it is in fact one of my designs. :naughty: ;D

If you have all 5 sheets of the drawings then you will find the details for making the stays at the bottom left of sheet 2... just be sure to make them at least 1" longer than required so that installing them is less of a struggle... the excess can be cut off after they are soldered in place (stand the boiler on end with the mushroom heads at the top and solder them first, then turn the boiler over and solder the other end).

You will need to use the full 3/16" dia PB for these stays and silver solder them straight into the end plates after forming the mushroom head on one end and without any threading required, so unfortunately the ones you currently have will not suffice since they are nowhere near strong enough.

Each stay is supporting an area of 1.236 sq ins if spaced as per the drawing and is subject to 74.16lbs of load at 60 psi. and at 45psi the load would be 55.62lbs.

Each stay has a breaking strain of 86.28lb so no fear of them breaking even at the higher pressure.

You mentioned you have used 1.5" diameter tube for the centre flue rather than the 1.75" diameter called for and also that it is 10swg.
This is not a real problem other than you will expend a bit more heat from the burner actually heating the water, since this heat will have to pass through the much thicker walls of the flu... and you will have a bit less heated surface area which will effect the boilers steaming rate.
The other issue will be the burner... you will need to reduce the size of this for both the outside tube ring and the actual burner body in order to maintain sufficient clearance around the inner burner tube for the required secondary air flow.
Reducing the size of the burner will, of course, reduce it's heat output capability and you may struggle to keep steam pressure up... especially if you go above 45psi.

Having the funnel on the outside of the end plate should not be a problem... it certainly makes it easier to build.
The tubes inside the flu are simply called cross water tubes... Galloway tubes are a different thing altogether, albeit they perform a similar task.

You say your stay holes are a sloppy 3/16"... How sloppy?... ideally you need them to be only about 0.002" - 0.003"MAX  larger than the bronze stays since silver solder is not good at filling large voids.(Note... this close clearance applies to all silver soldered joints)

If you don't have the whole set of drawings then just PM me your email address and I will send you a complete new set.

Finally, I see you have chosen not to fit the steam dome... I would suggest you reconsider this since it will help prevent carry over of water droplets into you steam line and also gives you the perfect location for attaching a pressure gauge.

I hope this helps you with the build, however, if there is anything you need more help with then either ask here on the forum or PM me.

Best of luck.

Regards.

Sandy. aka sandyC.  ;D

« Last Edit: October 24, 2016, 11:25:10 PM by SandCam »

Offline K.B.C

  • Full Member
  • ****
  • Posts: 166
Re: boiler stays
« Reply #24 on: October 24, 2016, 11:42:03 PM »
So...  af campbell and sandyc argyll scotland.. 2- desperate characters indeed, between the two of them there is a wealth of information which they unstintingly give help to those making a boiler .

Dave  when you have the end plates in and ready to solder I would recommend that you drill some small holes around the circumference of the shell, 4- will be enough and insert some copper rivets to hold the plates in place, they don't require to be riveted, leave a very small countersink on the outside of the hole , flux the copper rivets and solder the lot in place, when finished and cool file of the ends sticking out.
There is nothing worse than if when soldering in the end plates and they slip even if they are a tight fit.
I use 3/32" copper rivets to hold in the end plates.

I hope this helps.

George.
Your never too old to learn.

Offline daveclm

  • Full Member
  • ****
  • Posts: 22
Re: boiler stays
« Reply #25 on: October 25, 2016, 10:28:57 AM »
hi sandy
i thought they where you designs.  i think the holes are to sloppy to just solder the stays in. would i be ok to put 1/4 stays in, turn the ends down to fit the holes i have drilled, or drill the holes to fit the 1/4 stays. will change it to fit the dome. sorry to be a pain in the backside.
thanks dave.


Offline SandCam

  • Full Member
  • ****
  • Posts: 136
  • West Coast of Scotland UK
Re: boiler stays
« Reply #26 on: October 25, 2016, 10:37:25 AM »
hi sandy
i thought they where you designs.  i think the holes are to sloppy to just solder the stays in. would i be ok to put 1/4 stays in, turn the ends down to fit the holes i have drilled, or drill the holes to fit the 1/4 stays. will change it to fit the dome. sorry to be a pain in the backside.
thanks dave.

Hi Dave,
Yes if the holes are oversize for the 3/16" stays then just fit 1/4" ones, no need to turn down the ends... just use the same method for forming the mushroom heads and solder them in.

Keep Happy.

Sandy. ;D

Offline daveclm

  • Full Member
  • ****
  • Posts: 22
Re: boiler stays
« Reply #27 on: October 25, 2016, 11:20:09 AM »
thanks all for the help.

Offline daveclm

  • Full Member
  • ****
  • Posts: 22
Re: boiler stays
« Reply #28 on: October 29, 2016, 10:57:49 AM »
hi sandy
after what you said about the centre flue should be 1.75 dia and should be 10swg, i was thinking to remake the centre flu, but on the drawing it says to use 1.75 16swg. if it should be 10 swg i will remake it. got the stays sorted and the steam dome, all solder in.

thanks dave.

Offline SandCam

  • Full Member
  • ****
  • Posts: 136
  • West Coast of Scotland UK
Re: boiler stays
« Reply #29 on: October 29, 2016, 01:53:02 PM »
Hi Dave,

Oops... It would appear I have slightly misread one of your previous posts... my apologies, however...

Quote
the boiler tube is 106 copper 1.6mm 16g bought from kennions, dia is 31/2", centre flue is 1 1/2" 106 1.6 16g tube, the end plates are 106 3.2mm 10g i known a bit over board on thickness i allready had it

You did state that the current flu was 1.5" dia x 16swg and that the end plates were 10swg... I read it as the flu being 1.5" dia x 10swg, since that was what you had available.

The reason I mentioned this in my post was mainly that the plan calls for 1.75" dia for the flu not 1.5" dia ... The 10swg was my error.

It would now appear to be that the flu is actually as per the plans so please disregard my previous comments about this and the implications it would have made for the burner etc.

The use of 10swg for the end plates will do no harm whatsoever other than make the boiler a bit heavier.

It is good to see that you have upgraded to the steam dome... it will certainly help limit the carry over of water droplets in the outgoing steam.

So your flu is fine so just go ahead and use it.

Once again my apologies for my misreading of things... must go back to specsavers and complain. :Argue: :Jester:

Keep happy.

Sandy. ;D
« Last Edit: October 29, 2016, 01:56:29 PM by SandCam »

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal