Author Topic: Superheaters for model loco  (Read 1563 times)

Offline ChuckKey

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Re: Superheaters for model loco
« Reply #15 on: January 08, 2017, 04:38:25 PM »
You dont by chance have a reference to Jim's article do you? Be interested to have a read, 954C is pretty HOT!.
Last place I worked we ran 100 bar steam at 525 C so Like Dave said, you paint wont last long!

It was originally a paper read to The SMEE, and later published in Model Engineer, March-April 1966 (which is the year before my library starts), but also reported in 'Model Locomotive Boilers: their design and construction' by Martin Evans, MAP, 1969.

I have quoted it wrongly. That temperature was of the superheater itself, not the steam, which was up to 620F, and which admittedly sounds more like it. This is still a somewhat higher degree of superheat than is usual in full size (the saturated steam temperature being higher at the higher full size working pressures). He reports that after 9 years and 1000 miles hard running, using a high-superheat grade of Shell Valvata cylinder oil, the pistons were withdrawn to replace the graphite packing. The cast phosphor bronze cylinders and drawn bronze pistons were found to be in excellent condition. (Nothing is said about the packing though.)
« Last Edit: January 08, 2017, 04:45:28 PM by ChuckKey »

Offline steamer

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Re: Superheaters for model loco
« Reply #16 on: January 08, 2017, 04:59:02 PM »
OK ....sounds more like it....100 bar  ( about 150 psi) is at 377F   round abouts......  so 620 would be 243  degrees of superheat....

Still....hard on everything and you MUST use internal lubrication with a suitable oil.....and mechanical injection   ( Lube pump)

...and forget paint....gonna get smoked right off...

Dave




"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Steamer5

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Re: Superheaters for model loco
« Reply #17 on: January 09, 2017, 10:33:03 AM »
Hi Chuckkey,
 Thanks for the reference, my copies don't go back that far either, I'll have to check out the club library, think they have ME issues back that far. Yes the temp sounds better.

Dave,
 7 feet! Who delivered the popcorn,  :lolb:

Julian
 Sorry for kind of hijacking your thread, I hope you have found the banter....er... discussion on superheaters of interest. Keep us posted on how you get on making yours. Getting my stainless ones to fit turned into a mission, easy a making the wet header bush, had to do it twice, melted the first trying to silver solder the tubes in! Then the gentle tweaking to get the tubes to be central & the bush to fit & seal to the boiler bush took awhile to sort. Hope you have better luck!


Cheers Kerrin
Get excited and make something!

Offline Barneydog

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Re: Superheaters for model loco
« Reply #18 on: January 23, 2017, 11:09:44 PM »
Got a bit of a plan. My son in law has access to some offcuts of stainless tube but the smallest is 15mm diameter so he bringing me a couple of feet. Plan is to lay the tube in the superheater tube through the the boiler and above the fire. Input from the regulator will be a copper tube through a cap of some kind into the stainless tube and then just lay in the stainless to within half an inch or so of the fire end. A cap of some sort on the end to turn the steam back. A short copper tube at the other end to direct the steam to the cylinders. Displacement lubrication supplied with wet steam from a globe valve on the manifold to add lube just before the cylinders. Any obvious problems? May just be worth a go just to see if it works. Benefit will be ease of construction and copper tube can be bent easier to align with fittings in the smokebox. Stainless outer tube should avoid any sagging tubes in the firebox.

Julian

Online Jo

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Re: Superheaters for model loco
« Reply #19 on: January 24, 2017, 08:01:08 AM »
It was originally a paper read to The SMEE, and later published in Model Engineer, March-April 1966 (which is the year before my library starts), but also reported in 'Model Locomotive Boilers: their design and construction' by Martin Evans, MAP, 1969.

Page 252, 18th March 1966 tests carried out on a LBSC designed Minx: There were a number of substantial changes from the original design including the Stainless steel superheater sticking 7" into the firebox. Super heat tests were conducted at 270 deg F, 320 deg and 307 deg.

Jo


Usus est optimum magister

Offline Alex

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Re: Superheaters for model loco
« Reply #20 on: January 25, 2017, 05:27:13 PM »
This is one of those things which gets into a superheated argument - apologies for the pun.

I'm against superheaters for models - not that they don't do *something*, but that we don't need them.

1) I've got one locomotive in which the superheater flue is plugged solid, and it runs just fine, until more of the remaining tubes get clogged with ash. (the olde LBSC non-radiant superheater, gunked in)

2) I've got another that the original owner removed the superheaters - for what ever reason.

3) A friend with a Sweet Pea had superheaters leak, so removed them, and does not notice the difference.

As mentioned above, lubrication of superheated steam is an issue, from my days licensed as a full-size locomotive guy, ISTR that an issue was lubricating oil burning ("carboning" was the term) in the piston valves, and steam oil lubrication was one of the scientific issues to resolve of the day.

Last thing! Look at the Raritan design - no superheater, no lubricator! Just squirt in some oil at the beginning and end of the day - so easier to make, and maintain.

Whatever you do will be what you do, and will not be the "wrong" direction. Have fun!   

Offline Barneydog

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Re: Superheaters for model loco
« Reply #21 on: January 25, 2017, 09:15:07 PM »
Many thanks Alex,
My plan is to build a superheater and fit it. The pipework in the smoke box will be such that it can be removed and either another superheater fitted or a bypass pipe fitted to give plenty options. This gives the options of non superheater or various designs to determine design and/or necessity.
Lube will be adjustable displacement type feeding in after superheater to the cylinders. Steam supplying the lube will be non superheater.
Both these should give me full flexibility for steam and lube. Also gives the opportunity to build a selection of superheaters and try them.

Regards

Julian