Smoke box door internal clamp

I am building a 5" gauge LMS tank engine with a 'clamped' smoke box door. Due to the small size of the clamps these will not be functional but instead be dummies. I need to come up with some way of securely clamping the door from the inside of the smoke box. This latch/clamp can then be accessed using a tool through the chimney. Does anyone have any suggestions on the best way to tackle this? Thanks Dave.

I wonder if you could use some form of bayonet fixing - a few lugs on teh door that enter matching slots in the smokebox front ring but set at an angle, poke the door lugs into the slots the give the door a part turn to lock it into place, the dummy clamps may give you something to grip it by when turning.

Thanks Jason, that is worth consideration - the only drawback I can think of is that the door hinges would have to be made as dummies to allow the door to be rotated when locking/unlocking.

David,

What kind of clamped door is it? For example, I have seen engines with say 6 clamps round the periphery of the door in addition to the normal central handles. If it was that type, I would imagine that the central clamp would be adequate for a model.

Phil H

This problem was cleverly addressed on an LMS 3F by a Mr H A Taylor in an ME article in the early seventies. Access to the clamp was via the chimney. The edition should be possible to locate via the ME online index.

Michael

Many years a go I saw a neat trick the builder of a twin sisters made the smoke box number hinge up to reveal a cap headed bolt, this screwed in to the normal style cross bar.

worth thinking about. Paul

A pair of neodymium magnets?

Not a lots of forces on a smokebox door.

Hello David,

I've built three LMS 4Fs in 3.5" gauge all with clamp type doors, I built the door and the seating ring all in one piece with four dummy clamps and only two in the twelve o clock and six o clock positions were used to secure the door. the clamps in that case held the entire door sealing ring hinges etc the bolts used were 8BA with 9BA heads. The method does give a reasonable appearance to the door when finished and undoing a couple of bolts to clean the smokebox I don't find a problem.

If you contact me via my e-mail address I can send you a number of photographs of the system i used.

Regards,

Bob

Magnets don't like the heat, but I have no idea just how hot the door would get. They'd probably be OK up to around 100C.

According to Wikipedia if you get UH grade magnets they are rated up to 200C.

This page explains it, sort of...

can you tell me the exact issue number, I've got lots of MEs from 71, but they are in the attic, so it won't be quick!

I can't work out how to get a pdf into the albums, so send me a pm with your e-mail address and I'll send it. However, don't hold your breath it looks about as easy to use as finding Schrodinger's cat. Paul Rushmer's flip up number plate idea looks more viable to me, or even a number plate held on by magnets, but you'd then have to etch the number plate in a magnetic material, steel or nickel

Just found this thead: I'm building an LMS 2-6-0 Crab that has the clamped smoke box door bin trying to think of away round the problems this may lead to a solution my club has a set of back issue for ME so will look them up.

Stew

Stewart, If you pm me your e-mail address I can send you a copy of the scan.

Why not a central locking arrangement as used on most boliers on portable steam engines and traction engines ?? . You can still have extra "dummy" clamps around the perifery if required.

Ref temperatures in smokebox: Temp of steam at 50 psi = 175 deg C and at 100 psi = 200 deg C (approx) The hot gases passing thru the boiler tubes will be hotter than this.

I know nit picking, but steam at 50 psig has a temperature of 147 C at 100 psig it is 170 C. as you say the gasses in the smokebox will be hotter.

The centre clamp would look really out of place on a Crab, best solution is a centre bolt hidden under the number plate