superheaters

[chameleonrob]

the board has been quite quirt resently so I thought I would air an idea I've had for superheaters. I relitively new to modle engineering (engineering less so) so if this is a bad idea please explain it to me.

To my understanding the most superheat you can get is from the radiant part in the firebox itself, a short straight steam circit is more desireble than a long convoluted one, the regulator is placed either in the smokebox or the boiler making adjustment and maintainance difficult.

The answer I came up with for this was to have the steam pipe go from the dome to the backhead, where the regulator valve would be, very easy and clean access, from here it would go tothe wet header either on the backhead as well or, though a small hole, in the firebox. the hole (or holes if the wet header is outside the firebox) in the firebox ccould simply be an overlarge hollow stay, chauked with something to make it reasonbly air tight but not burn. from there the superheater tubes (maybe doubling back a couple of times) goes via the tubes/flues to the dry header in the smokebox and then to the cylinders.

With this design you would have to be careful with expansion of the superheater tubes both lengthways and though the holes between the backhead and the firebox and of your choice of chauking material. one other advantage is the amount of space in the smoke box is increased dramatically as there is only the dry header in there, not both of them.

let me know what you think.

Rob

[alanstepney]

I dont see any great advantage.
Apart from anything else, how much superheat does one want? All that is required is just enough to ensure that what goes into the cylinders is steam and not water.

In the normal layout, the steam is taken from the highest point, and goes to the wet header, usually in the smokebox. Then up-and-back in the superheater tubes, and straight to the cylinders.
one can play with number, type and layout of the superheater elements to get the desired degree of superheat.
Would your suggested layout give the same flexibility? Would it make it easier to have steam / water tight joints?

If you were trying for a greater degree of superheat, what material would you make the tubes from, and how will you lubricate the engine?

Lots to think about before re-writing the book.

However, the proof of the pudding....

Why not try it and see how well it works?

[chameleonrob]

thanks for the responce, but to set a few things straight; I'm not trying to get a very high degree of superheat, mealy rearanging components into a what seams to be a better comfigeration. the conventional layout with either no superheaters of convection superheaters is probable best, but with radiant superheaters where most of the heat is put in in the firebox, having long pipes to and from the smokebox, especially as it means the regulator is in a very inaccessable position seems an odd way of doing things, plus with less in the smokebox you'll have more space to fit the dryheader.

for me, the biggest advantage is that the regulator is in an easy position for adjustment and on long rod going part or all the way though the boiler

ps looks like i'm not the only one with this idea, model engineer reporter that Peter Gardner wrote an artical in the 2 1/2 gauge association newsletterabout what seems to be a similar concept. If anyone gets the news letter could either post the artical or describe its contence it would be apriciated

rob

[IP]

I'm not too happy about the idea of having hot tubes poking out of the firebox, I admit they would have to be protected but I personaly find that the footplate gets hot enough for my fingers as it is.

I believe that LBSC tried this idea once or twice dont quote me, the idea seems to have departed this station so to speak.

With my Gresley I've used co-axial superheaters but arranged the wet header so that steam passes through the superheaters twice.......I add that the co-axial elements extend all the way to the front of the firebox [ie right up the the backhead]

To date I'm happy with the results.

Regards
IP