ACS Horiz. boiler Question.

[Bill Hudson]

Sandy,
Was looking over your Horizontal center flue boiler. I noticed on end of the cross tubes was turned down smaller that the tube size. What is the reason for that?  

What is the order of assembly?

Thanks,
 Bill

[sandy_ACS]

     :computer

Hi PD's,

No!! I have not left the planet...DRAT say's Derek!!!!!. :nose    

Just so very busy.

Bill Hudson asked: -

Was looking over your Horizontal center flue boiler. I noticed on end of the cross tubes was turned down smaller that the tube size. What is the reason for that?

What is the order of assembly?

The ends are reduced in size to the make the inner flue assembly a little easier.
As can be seen from sheet 4 of the drawings, the tubes are 5/16" OD and as these are fitted into the main inner flue in a spiral, if they were left full size all the way then they would be extremely tricky to keep in position whilst soldering them in to place.

The holes for the tubes should be approx 2 or 3 thou (0.002" - 0.003") larger than the OD of the tubes, to allow the silver solder to penetrate correctly, if both ends were left at 5/16" OD then the tubes would tend to slip straight through. The reduced end prevents this from happening.

When drilling the holes for the tubes, in the Main Flue, drill straight through with a 9/32" drill and then open up one side to 5/16" (uppermost side with respect to how you orientate the flue for soldering...usually with the funnel uptake at the top).  Then use a coarse round file to ease all the holes to approx the correct clearance.
Which brings me to another point....the bottom of the funnel uptake, where it joins the main flue could also do with a small reduction in the OD, for the same reason..(not actually shown on the drawing....NAUGHTY BOY SANDY      :hmph ). this will make the location of this a little easier, and will prevent it falling into the flue when heated up.

Incidentally, Bill, the protruding length of this stub should be such that the entire flue assembly can just be slid into the main barrel without the end plates in position.

As for the order of assembly......Naturally it pays to make all the component parts first...then dry fit the uptake stub to the inner flue, and check that the flue can be slid in to the main barrel (just)...once happy with the length of this uptake; then place all the cross tubes in place and make sure they are all down to the shoulders (reduced ends), leave the flue blanking end plate off at this time...this is fitted later... use plenty of flux both inside and outside the joint areas and then solder the tubes in place, start at the larger end...followed by the uptake then, if necessary, move the assembly so as to get at the smaller end of the cross tubes....I can usually manage to do all ends without needing to move the job...but this will depend on how you set up on the hearth...I raise the whole lot up on to refractory blocks at both ends...thus I can get at all joints.

USE SILVERFLO 24 for these inner joints. (Higher temperature grade of silver solder)

Pickle the entire inner flue assembly and thoroughly inspect every joint...if any are suspect then re-solder them....once the assembly is inside the main barrel it is nigh on impossible to fix a doggy joint.

When happy with the inner flue soldering...the next job is to get the flue and main end plates into the main barrel.....stand the main barrel on it's firebox end, you will need to place some wood packing under it, thick enough to allow the flue to protrude without hitting the bench...slip the flue assembly in, and when the uptake reaches the funnel hole lift it up through the hole a little and slip the funnel adaptor into place from the outside to locate it.

Take the correct end plate (funnel end) and slip it over the inner flue and, after aligning it correctly with the main barrel, tap it into place with a piece of wood or a rubber hammer, until it is flush with the outer end of the barrel....turn the whole thing the other way up, again resting on some wood, and fit the firebox end plate in the same way. Incidentally, it pays to apply some flux to these joints as you fit the parts....most of it will be pushed inside, but that is no problem.... check that the funnel adaptor is still in it's correct position...adjust the flue and adaptor if neccessary.

Slip the 2 stays through, from the firebox end...a fiddly job,  I would suggest making them about an inch or so over length, which helps when manoeuvering them.... once these are in place apply more flux to the outside of all the joints...stand the assembly on some refractory blocks. on its funnel end....fit the bushes into the firebox end plate and flux well.

Using easy-flo No. 2 silver solder (lower melting point) solder the firebox end first,,, start with the inner flue joint, then move to the stays and the bushes, finally solder the end plate to the barrel.

Allow to cool enough to be able to handle the job then turn the whole thing over...stand on the firebox end..... clean up the area around the bush hole on the funnel end plate and fit the bush with plenty of flux....re-apply flux to the flue, stay and outer barrel joint areas....you can fit the flue blanking plate at this time...just tap it in to the end of the flue...flux well and then solder up this end of the assembly as before...start at the flue and blanking plate joints.. then the bush and stays finally the outer barrel.

Allow to cool again...then stand the boiler in a horizontal position....clean up the areas around the dome (turret) hole and safety valve bushes...fit these in place, make sure the dome (turret) is the correct way round and again check that the funnel adaptor is still in the correct position... apply plenty of flux to all these joints and this time also flux the inside joint where the funnel adaptor and the funnel uptake meet.... solder up these top joints staring at the dome (turret) then the safety bush followed by the outside joint of the funnel adaptor...then very carefully the inner joint between the adaptor and the uptake...make sure you don't get any lumps on the inside of the adaptor...or you will have fun getting it off.

After pickling the whole boiler...cut off the extra length from the 2 stays and deburr with a small file and coarse emery cloth.

WELL DONE.......have a beer..or three....your ready for pressure testing.


       

I hope this helps.

Best regards to all.

Sandy :computer  :vacat  :yeah  

[Bill Hudson]

Thanks Sandy,  

Now to find some copper tubing.  Copper (in small quantities) is hard to find here.  The scrap price is so high that people are stealing it from almost any where, some one even went into our parks and opened the access plates to the high power path lights and stole the bare copper ground cables.

How much can I fudge on the tubing sizes (up or down) and still be with in the design of this boiler since I am the mercy of the scrap available?  

I am wanting to try my hand at building a boiler and I do not have any specific chore for it at this time.  
I do have a foot length of 3" NSI-61 heavy gauge copper tube .084 wall. Some of the label stamp has been cut of so I can't tell if it said water or boiler. Would I be asking for problems to use a lighter gauge for end plates or do they need to be the same gauge as the boiler shell?
I have a 26" long tug boat kit I would like to build an engine and boiler for but I think this tube is too large and too heavy for that purpose.  Instead I was wondering if I could build a little boiler to test engines with from that piece of tube?

Bill

[sandy_ACS]

   :computer

Hi PD's.

Bill.......yes copper (and all of it's alloys) is getting more expensive and more difficult to purchase in sensible quantities over here as well.
Most of the trade guys are complaining that the Chinese are buying up all they can lay hands on, including all the scrap, which is driving the price up and up......over 36% in the last year alone, on top of a 28% rise the previous year.....silver solder has also followed this trend...it is now almost 3  times the cost it was 2 years ago.....which all means....boilers are going to get far more expensive. :twisted:  :twisted:  :  :  :shock:  :shock:

OK,

Nothing hard and fast about the tube sizes, within reason.

The 3" piece you have will make a good main barrel, however, if you retain the 42mm dia flue this will give somewhat lower water capacity unless you make the main barrel (and inner flue) longer...say 7" instead of 6".  Or you could reduce the flue OD to say 1 1/2", but you will need to adjust the burner (outer dia.) size to suit....also the water tube lengths etc.

The end plates should not be less than 16swg (0.064") thick or they will bulge out with the pressure, and since it is difficult to add any more stays, in suitable locations, this should be retained. They can, of course, be heavier, however this makes flanging more of a chore.

The water cross tubes can be increased to 3/8" OD if this is easier to source, however, try and maintain the 20swg (0.036") wall thickness.
It is feasible to use 22swg (0.028") wall thickness for either OD, however, this will make the amount of reduction possible on the small end a little more critical....only take off about 0.008" from the wall thickness, and adjust the hole in the flue to suit.

If you increase the tube OD then adjust the tube spacing to maintain the same tube to tube clearance.
The only critical dimension here is the distance from the outer end of the flue (burner end) to the OD of the first tube.....this distance is to give sufficient clearance between the burner and the tubes.....other than this... adjust as you see fit.

I would not recommend reducing the water tube OD to anything below 5/16" as this will interfere with water flow.

The flue OD can be reduced to 35mm (1 3/8") with a 3" OD barrel......my new 3" boilers use this size, naturally, if you go this route, then the lengths of the cross tubes etc will need to be adjusted accordingly.
Keep the wall thickness at or slightly above 0.060".

The only critical materials are those for the stays, (these must be phosphor bronze), but can be slightly larger in OD if this is easier... just watch the clearance alongside the inner funnel uptake..

Dome and bushes can be from Phosphor bronze (horrid stuff to tap threads into though), Colphos 90, SAE 660 or even gunmetal....BUT NOT BRASS.

A good source of most of the smaller sizes shown is the local plumbing supplies merchant.....42mm OD is a standard plumbing size as is the 28MM used for the funnel uptake .
The water tubes can be made from 8mm or even 10mm central heating type small bore copper tube.
It might pay you to track down a local plumber/heating engineer, who may have some suitable off cuts he would be prepared to sell, or even give you.....although at todays prices...I think the former is more likely.

Finally Bill, a smaller version (say 2 1/2" OD x 5" long with a 28MM (1 1/8") flue and a 22mm (7/8") funnel, would make a perfect boiler for your 26" tug...with an engine having 5/16" bore x 3/8" or 7/16" stroke.

Have fun.

Best regards.

Sandy.  :vacat  

[Bill Hudson]

Sandy,

I think you are a very generous gentleman..Thank you for your advise and input.

Bill