Firehole doors

[Lisa]

This may seem a bit of a silly question, but I haven't had much to do with copper boilers since the 80's as all of dad's 5" loco's, and my previous foray into 7¼" gauge all had Briggs steel boilers. So...

How do you attach the firehole door to the backhead?

Briggs boilers have a dry wall firebox, thus attaching the firehole door was simply a matter of drilling holes wherever one wished to bolt things on. This is obviously not possible with a copper wet walled locomotive firebox.

My thoughts thus far are:
Threaded over-long stays.
Attach it to the cladding.
Blind threaded bushes, soldered either onto, or into, the back plate.
Don't attach it - Blowfly's designed firehole door has a bracket bolted to the cab floor.

[uuu]

Mine has blind bushes soldered into the backhead.

Wilf

[92220]

That's how the firedoor frame is fixed to the backhead on the 9F - tapped bushes silversoldered in to match the mounting bolt holes.

[Shawki Shlemon]

Generally I have used blind bushes silver soldered in the back plate , I have also used the last suggestion like the blowfly on small engines .

[Nigel Bennett]

I've used bushes tapped through - but the bushes were silver-soldered to both plates of the firebox, as hollow stays. I've also seen an extended firehole ring, which sticks out of the backhead. The firehole door assembly attaches to that.

The above presumes you haven't built the boiler yet. If you drill and tap the backhead directly with a smallish thread size (say 6BA or M3) and fit the firehole door with bronze screws with Loctite 542 or similar, that should be good enough.

[Deleted]

Better still, fit studs as full size practice. That way, you don't disturb the threads in the boiler if you ever have to take the firedoor assembly off. Make the studs a tight fit and also use Loctite if you want to, but the studs should self-seal where the thread runs out.

[dem132]

Interesting topic, couple of differing views over the years. Good practice recommends the blind bush to be used (my DY black five boiler I've asked for 4 blind bushes around the fire hole). But old LBSC practices etc, was to drill and tap into the back head. My Maid of Kent has this method. I personally don't like the idea of drilling into the copper and tapping it. Of course use bronze screws, it was a right surprise when I discovered that who ever done my MoK boiler and used steel screws! I would favour attaching the fire hole door to some cladding on the backhead and make the fire hole ring align with the fire hole on the boiler. If blind bushes weren't present.

[Jim]

I fitted a backing plate to the cladding to give a solid foundation to the fire hole door mechanism that opens and closes the two sliding doors. Once fitted the backing plate closes the gap surrounding the fire hole in the boiler and the cladding. I did it this way because i hadn't thought about about fire hole doors at the time I was setting fire to everything as i silvered up the boiler.





The plate is either 1/8" < 3/16" brass I can't remember now, but from what I had on hand the important bit is it does the job intended.

Jim

[Cro]

I have done the same as Jim for the 9f but I have 4 bushes silver soldered into the plate that the bolts screw into.



The boiler originally had blind bushes fitted though which is what I would noramlly do at point of making the backhead.

Adam

[jma1009]

Hi Lisa,

My early locos had tapped holes in the copper backhead for phos bronze fixings to secure the firehole door arrangements. Never a problem, but things have moved on, and now we use blind bushes etc silver soldered to the boiler for new contruction. As I have never fitted backhead cleading, the methods of Jim and Adam havent applied.

In the case of my last 2 boilers, the firehole assembly has been fixed to 4 of the backhead stays made of generous size and the stays blind tapped for the fixings.

Cheers,
Julian

[nonort]

If you dont fancy putting either threaded holes in the boiler or blind bushes why not use a method I have seen elsewere. Fix the door assembly to a thin wall tube then use a ring nut inside the firebox of the boiler?

[92220]

Not seen that one, but it would certainly work as long as the inner and outer plates are parallel - or very nearly so.