SweetPea super heaters

[firebird]

Hi
I'm well on the way with my build of Sweetpea now but I'm having trouble finding any info re the super heaters. When I built the boiler I included the 2 super heater flues. The flues are 3/4'' OD. I have tried a couple of 5/16'' tubes in the flues but they are a bit tight. I'm assuming I have to solder on a connector for the smoke box end. I have also tried some 6mm tubes and they go in easy.
Any advice gratefully accepted
Cheers
Rich

[SteveW]

Firebird,

If it helps our club's Sweet Pea doesn't use any super heaters. Yes, it has the two big tubes for them and was used to regularly pull a number of loaded carriages on public runing days without any issues of lack of power/pull.

Are you sure you want and need them? They are not without a bit of faff.

[firebird]

Hi Steve

On the SweetPea forum the general consensus is its best to use them. One of the benefits is, apparently, making the loco more economical on coal and water.

Cheers

Rich

[SteveW]

Jun 24, 2024 15:37:46 GMT firebird said:

Hi Steve

On the SweetPea forum the general consensus is its best to use them. One of the benefits is, apparently, making the loco more economical on coal and water.

Cheers

Rich

Would suggest any improvement, given the staggering inefficiencies of these things, will somewhere between purely academic and three fifths of f' all and bring with it all the wonders of lubrication in the face of super heated steam.

Your choice.

[chris vine]

I am not sure that the degree of superheat which will be achieved will have much effect on modern oils??!!

[simon6200]

I’ve done the experiment with and without on a similar locomotive with two 3/4 flues. First ran it for a while without, then added two 1/4” copper spearpoint bronze-brazed elements. The difference was astonishing, especially with only two superheaters.

[firebird]

Hi Simon

That's what the guys on the SweetPea forum say.

They recommend radiant type, the type that go all the way into the firebox which are best made of stainless steel??

Cheers

Rich

[simon6200]

Yes, stainless radiants are the best. I have 4 x 5/16 radiants in my Springbok. But they must be welded by a good TIG welder, whereas I can make copper spearpoints myself. Also, stainless spearpoints must be welded in an open position then heated up and bent parallel. But you can’t get them as close as you can copper elements so might need larger flues.

[andyhigham]

I took a different approach on my Sweet Pea. A single 10mm stainless, threaded on each end tube ran from the smokebox, down the flue, looped round over the fire then back up the other flue to the smokebox.
The superheater loads from the back and fittings screwed on inside the smokebox

[steamer5]

Hi Rich,
Think I’ve posted this before, any way another build option……

www.cheltsme.org.uk/index-superheaters.html?

Cheers Kerrin

[JonL]

I'm very much in the pro-superheater camp. Even just swapping from non-radiant to radiant transformed my William.

[firebird]

Thanks Simon, Andy, Kerrin and Jon

Some good info there

Cheers

Rich

[tenor]

If you leave out the elements, a lot of flue gas takes the easy route down the big tubes while not giving up much heat, so you screw up the amount boiled.
In my experience most designs have over large elements crammed into undersize flues. There is a lot of science in balancing the flow between SH flues and tubes. Evans, Young and LBSC were designing by guesswork.
Martin

[suctionhose]

Jun 29, 2024 12:00:05 GMT tenor said:

If you leave out the elements, a lot of flue gas takes the easy route down the big tubes while not giving up much heat, so you screw up the amount boiled.

Martin

So true! Many moons ago when dad and I were entry level live steamers, we blew an element and decided to try it saturated.

1. No steam and a burnt smoke box until restrictors were applied to the flues.

2. There wasn't much detriment to removing the superheaters indicating that they were of poor design.

3. Much was gained in performance from other sources, mainly valve gear and smokebox draughting, suggesting that the engine was lacking in many respects.

We were falsely lured to believe superheaters were optional. Nothing further from truth!

[johan]

Jul 1, 2024 7:50:27 GMT suctionhose said:

3. Much was gained in performance from other sources, mainly valve gear and smokebox draughting, suggesting that the engine was lacking in many respects.

We were falsely lured to believe superheaters were optional. Nothing further from truth!

Onion peel syndrome: you fix one thing and then the next one become apparent and you fix that etc etc. Typical in cases where you look for efficiency. Each bit does something, but you first have to fix the biggest ones before the smaller ones can be useful.