firebox stays silver soldered with propane

ive added a new album showing how i do firebox stays with propane illustrating my current project namely a 5"g version of Brighton terrier Stepney.

this method hasnt been covered very well in ME so might encourage others to 'have a go'. 15 mins heat up and silver soldering this afternoon start to finish, though making and fitting the silver soldered rings and fluxing up took much longer! the inner firebox doorplate has to be left off to do it with propane.

there are quite a few pics in the album, so ive only added a couple here.

cheers,

julian

Edited By julian atkins on 26/04/2014 23:27:39

Edited By julian atkins on 26/04/2014 23:28:31

the album link is here

http://www.model-engineer.co.uk/albums/member_album.asp?a=31789

this pic shows how silver soldered rings are fitted hard up against the inner wrapper in the water space as quite difficult to add silver solder inside with the propane torch roaring away inside. then a second pic showing how the silver solder flashes round the stay heads (1/8" dia copper snaphead rivets).

cheers,

julian

Edited By julian atkins on 27/04/2014 00:27:12

this is the part i find difficult in anything less than 71/4, and especially if you get it wrong. I use oxy so hats off to anyone using anything else\!!

Timely post Julian, thanks. I am up to just this stage on a very similar boiler. Allan Crossfield used this method in ME 4354 2009, but nobody else that I have come across. I refer to that article regularly. How did you make the small rings for the stays? Making rings for 1/2" tubes is easy, but winding 1.5mm solder for 1/4" stays? I had toyed with the idea of putting a propane flame on the wire as it approached the mandrel in the lathe to soften it and persuade it to form such tight rings. This is my second boiler. The first was for a Springbok and I used oxy-propane locally with general heating using the Sievert 2944 burner, wielded by an assistant (a reluctant wife on one occasion). One problem was seeing which stays were soldered and which were not once everything is hot and fluxy. I missed some at least once, requiring a whole extra cycle of cool/pickle/flux/heat.

Simon

hi simon,

the rings are wound round 3mm rod by hand. the silver solder rod is silverflo 55 1.5mm rod. i dont anneal it first. i know this is what cupalloys suggest ie annealing it but dont want to affect the composition of the rods by annealing it. it works out ok for 1/8" dia copper snaphead rivets as stays. i do it by hand in the vice with a 3mm drill clamped to the rod. cut off the rings with some pincer pliers.

you can usually see the silver solder flash round the rivet heads quite easily when heated up from the inside.

the outside of the stays are done using a long length of silver solder rod run along each row of stays.

my own method is that used by the late W.A. (Bill) Carter of SMEE fame and superb award winning GNR Atlantic and GWR Dukedog both in 5"g

what is your current loco?

cheers,

julian

The boiler is for a Blowfly. I am making it for a very enthusiastic youngster at my club. I am amazed that you could wind 1.5mm around 3mm rod. I have had 245 snap in cool weather winding 1/2" rings. I will experiment and report back. Also, I adopted Allan's method of using bronze screws, not rivets. I make 5 BA screws from 5/32 Colphos hex, and tap the copper with the tap held in a battery pistol drill. That way I can assemble and disassemble any number of times, which at my level of experience, I need to do.

Today I experimented. I used the lathe, set to screw cut away from the chuck with a 2mm pitch, at 65 rpm. Solder was 1.5 mm Easyflow fed through a bit of wood with a 2 mm hole through it, held in the toolpost. I first tried a 4.5 mm mandrel, with tailstock support, and aimed a Primus burner at the solder between the guide and the mandrel as the lathe ran. I was surprised how little spring back there was, with the resulting rings about 4.7 mm i.d. Too small for 1/4 stays, so I tried a 1/4 mandrel, still using the propane burner. These rings measured 6.7 mm i.d.

Julian, did you solder the inner firebox stays shown above in the orientation shown, i.e., requiring the solder rings to flow up hill to arrive under the rivet heads? I know solder will flow up hill in a capillary gap, but I would have thought that the rings might first soften and lose their spring grip on the stay and slump down before fully melting.

hi simon,

if you have a look at my album on same the set up is shown when being silver soldered ie boiler with firebox pointing upwards, so the stays are horizontal when being silver soldered. also shows the arrangement of thermalite blocks.

you can also see in the album that ive now done the R-H side as well plus that side of the foundation ring.

cheers,

julian

Thanks Julian, that makes more sense, and hence the runs down the rows of stays. Great pictures.