Chimney Liner ID??

[ron]

Hi Everybody
I'm in need of your sage advices regarding chimney ID. Mr Evans states a chimney liner for Simplex of 2" long X 1 3/16" OD X 1/16" wall thickness brass, silver soldered into the smokebox. This size of pipe doesn't seem to be available and I don't have a big enough piece of brass to turn it from solid, the nearest I have is 1 1/8" OD X 1/16" wallthickness copper pipe, is the bore critical enough that 1/16" less is going to make a difference or should I cut down the length of the copper pipe and silver solder in a strip to bring it out to 1 3/16" dia, any other ideas welcome.
Ron

[havoc]

Essential in this case is to check that the relation between chimney and blower/exhaust stays the same. So if the chimney becomes smaller in diameter, then the blower/exhaust will have to come closer. Or you need to make the opening of the exhaust smaller.

[abby]

You could roll one from a piece of brass sheet , or I could cast you one , but not for about 2 weeks.

[baggo]

Hi Ron,

I don't think reducing the diameter of the chimney liner by 1/16" will make that much difference but as suggested, you may have to alter (increase) the height of the blast nozzle to take this into account.
You can get a rough idea by drawing out the arrangement on paper assuming that the steam exits from the nozzle at an overall angle of 17°. The height of the nozzle should be such that the steam cone hits the inside of the chimney liner at it's narrowest point i.e. the start of the parallel bit. In theory the liner should have a slight taper outwards towards the top of the chimney rather than stay parallel but articles I have read suggest that this is not critical. The important bit is that the exhaust steam cone does not hit the liner too high or too low and that the cone is truly concentric with the liner.

Draughting is all a bit hit and miss anyway and you'll probably have to play with different diameter blast nozzles until you find the right size for your particular engine and the coal that you are using, as well as how hard the loco is going to be worked.

John

[Shawki Shlemon]

In my opinion the chimney should be able to handle the gases coming through fire tubes therefore I would choose 1.25" tube and leave every thing else the same .

[baggo]

Hi Ron,

I've just had a look at the drawings in the ME articles and the length of the brass tube that the blast nozzle sits on is shown as 3-29/32" from the centreline of the horizontal exhaust pipes. I am sure this is wrong and would place the blast nozzle far too high in the smokebox. I reckon it should be more like 2-5/8". Have you got the full size drawings with this dimension on?

John

[ron]

Hi John
It's given as 2 15/16" excluding the nozzle on my drawings, that's the size I've made it to, I suppose it's easier to shorten than lengthen it if necessary.
Shawki, that's a good point, I hadn't considered of the products of combustion I was too busy concentrating on what effect it would have on the blast, I will try and purloin something somewhere of the right size, 1.25 is too big, it would leave the finished chimney a bit thin walled there isn't much extra meat on the casting.
Abby, thanks for your kind offer, if I can't find anything suitable I'll try expanding the copper tube I've got with a silver soldered strip first of all.
Ron

[baggo]

Thanks Ron, I'll make a note of that

[ron]

I've found an old bit of thickwall stainless pipe 1/16" bore, probably 316 or 321 grade, so if I can manage to turn the OD down to 1 3/16" I'm in business, I hate turning stainless
Ron

[ron]

Hi John
Didn't have much choice, stainless was the only big enough bit of metal I could find other than some cast iron, the bore was 1 1/16" [just testing you were paying attention ;D]
Anyway it's made now and the chimney casting bored to fit.
Ron