fire box stay's

Hi a silly question with 5" Tich fire box boiler stay's do they need to be thread and screwed in then silver soldered in or the copper rivets located with a good fit then silver soldered.

I have googled photos and it looks like a mix of screwed and held in place with a spring washer then soldered what is the best way to go about this.

thanks Kevin

Copper rivets silver-soldered into position is the current preferred option. Screwed and nutted stays were preferred at the period when LBSC was writing as it allowed the use of (relatively) high-temperature solder ('Comsol' ) as a sealant in the event of leaks.

Suggest that heads are placed on inside of firebox, small countersink on outside of structure on side where heat is to be applied where stem of rivet is to be silver-soldered. I would not make the fit 'good' with no qualification as you write, as you need to allow the sliver solder to flow along the stem of the rivet through the hole. Of course one man's 'good fit' is another's 'rattling good fit' in the world of model engineering! A couple of 'nicks' made with a file around the good fit hole will allow silver-solder flow to both sides of the stay. Basically you want a ring of silver-solder on both sides of the structure where the rivet passes through after silver-soldering.

Cut excess length of rivets when boiler tested and thus all silver soldering fully completed.

Regards,

Phil

Edited By Weary on 18/02/2018 08:52:22

I seriously hope you haven't fixed the firebox and/or the boiler backhead in place yet ?

Hi thanks for the information all I have done is a dry fit on all the boiler parts next job is to make sure I have enough gas thanks

thanks again Kevin

Leave the rivets well over length so you can get some heat into them, then cut off after pressure test. If you can't get long enough rivets you can use bronze bar. I've seen it recommended that a nick from a chisel can be used to stop them falling through, which is all the head is doing on a rivet actually, the silver solder gives it all the strength it needs

To add to Duncans good advice, leave them long if you are using a 'big' propane type torch, if you happen to be using an oxy fueled torch they need to be short or they heat up much quicker than the surrounding metal, boil the solder and burn out the flux. An alternative to a chisel nick and the method I use is to give them a squeeze in the vice, right on the end, works a treat! Good luck.

The advantage of the rivet head on the inside, it affords some added protection to the silver solder joint from the products of coal combustion.