BR55/G8.1 Locomotive Project

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datman
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Joined: Mon Feb 17, 2020 10:10 pm

BR55/G8.1 Locomotive Project

Post by datman » Wed Feb 19, 2020 4:44 am

Hi,

I am new here.

I am on the long road to build a BR55/G8.1
Trix Br55 Left Side.png
I have not found any plans for a scaled model so I have to create my own from the original locomotive plans I bought of a german site. I have done some 3D modelling at full size to get a feel for the build. I am now scaling down to 1:11 5 inch.
I have plans for Chris Evans Nigel Gresley 5" and also for Clarkson's P8. The Nigel Gresley has a very close dimensions to a scaled BR55 in boiler, cylinder size and also the drive that I can use them for reference in design.

This is drawn full scale
Br55 Chassis Model.png
This is the start of my scaled 3D model
BR55 Frames and Boiler.png
I will be build to scale as much as possible and with as much detail as I can, its all about the detail for me.

I am sure I will ask many questions along the way and will appreciate any help I can get.

Ian
Last edited by datman on Wed Feb 19, 2020 5:07 am, edited 3 times in total.

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Wed Feb 19, 2020 5:02 am

Hi,

I have a few design questions.

Brass has a slightly higher thermal expansion, does that mean its bad to use a brass adaptor ring between the boiler and smokebox?
Would silver soldering the the boiler to the adapter ring to the smoke box be OK? This is what seems to be done. Does anyone bolt on the smokebox?

What sort of spacing do you need between the firebox and the outer boiler shell?
Boiler Firebox section.png
At the moment I have 3/8 (10mm) between the walls.

Thanks
Ian

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Wed Feb 19, 2020 5:14 am

Hi,

I have another question (yes another one) Does the height of the firebox door matter much?
Boiler section 1.png
Thanks
Ian

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Marty_Knox
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Re: BR55/G8.1 Locomotive Project

Post by Marty_Knox » Wed Feb 19, 2020 12:21 pm

I think your crownsheet is way too high. I try to keep the top row of tubes on the vertical centerline of the boiler, with the top of the crownsheet about an inch above center. You will have far more problems with a high crownsheet than you will from too few tubes.

rkcarguy
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Re: BR55/G8.1 Locomotive Project

Post by rkcarguy » Wed Feb 19, 2020 1:19 pm

I've done a lot of cruising of various boiler builds here on Chaski and there is a huge thread here with a myriad of pictures, various designs, pics of some failed boilers cut open, etc etc.
I really don't see a problem bolting on your smokebox in my opinion. I would want the holes "blind" so that there is no potential leak points and corrosion will not occur in the threads. Use high quality bolts made from 400 series stainless with a lot of high temp never-seize and lock washers.
The 3/8" distance of your firebox water jacket isn't much, but that's a tough one in the scale you are modeling. We've seen a lot of boilers where these walls fill full of rust scale so the wider the better. Best bet would be to place 2 drains at the two lowest forward points of your firebox water jacket and flush after each use so scale never has a chance to build up. 1/8" NPT threads should *just* make it if you can't space the walls further than 3/8" apart.

As far as the bolted connection is concerned, you have an advantage with that step up in diameter at the smoke box. You could incorporate the bolted connection into that from either direction and not have the threads enter the tube bundle at all nor have a bolt flange that intrudes on your tube sheet area.

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gwrdriver
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Re: BR55/G8.1 Locomotive Project

Post by gwrdriver » Wed Feb 19, 2020 2:42 pm

Ian,
There are two options to consider - one is to affix the boiler (a solid connection) to the frame at the firebox end. If that's done then some allowance for expansion and contraction will have to be made at the smokebox end, keeping in mind the smokebox must essentially be air-tight.

The second option, the one I choose, is the smokebox should be made to accept the boiler barrel and a solid connection made at that joining point. This structurally connects the boiler to the frame via the smokebox assembly. Any expansion or contraction of the boiler must then be accommodated by a captive but sliding connection at the rear (firebox) end.

In my most recent locomotive project the boiler front tube plate has three threaded studs. The smokebox has a 3-holed plate to receive the studs which are then nutted on pulling the boiler up tight, similar to what rkcarguy has just described. I'll try to add a photo later.
GWRdriver
Nashville TN

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Wed Feb 19, 2020 2:55 pm

Marty_Knox wrote:
Wed Feb 19, 2020 12:21 pm
I think your crownsheet is way too high. I try to keep the top row of tubes on the vertical centerline of the boiler, with the top of the crownsheet about an inch above center. You will have far more problems with a high crownsheet than you will from too few tubes.

Thanks Marty,

Your right, I have read where people have not enough steam space above the water level and the associated issues. Currently it drawn to scale except for adjustment for plate thicknesses. I see 1/2 above crownsheet as a common value for minimum water level, how much steam space do you need above the water level?

Ian

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Wed Feb 19, 2020 5:00 pm

gwrdriver wrote:
Wed Feb 19, 2020 2:42 pm
Ian,
There are two options to consider - one is to affix the boiler (a solid connection) to the frame at the firebox end. If that's done then some allowance for expansion and contraction will have to be made at the smokebox end, keeping in mind the smokebox must essentially be air-tight.

The second option, the one I choose, is the smokebox should be made to accept the boiler barrel and a solid connection made at that joining point. This structurally connects the boiler to the frame via the smokebox assembly. Any expansion or contraction of the boiler must then be accommodated by a captive but sliding connection at the rear (firebox) end.

In my most recent locomotive project the boiler front tube plate has three threaded studs. The smokebox has a 3-holed plate to receive the studs which are then nutted on pulling the boiler up tight, similar to what rkcarguy has just described. I'll try to add a photo later.
Thanks gwrdriver, rkcarguy

I will now bolt on the smokebox similiar to your method.

I will be putting drains in the bottom of the water jacket, this is the same as the prototype.

Ian

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gwrdriver
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Re: BR55/G8.1 Locomotive Project

Post by gwrdriver » Wed Feb 19, 2020 7:34 pm

Ian,
Here are the photos of my smokebox arrangement, and for starters my boiler is 6" diam copper.
The first photo shows the mounting studs, 3 x .250" C510 phosphor bronze at 120°, and will be silver soldered into the front tube plate.
The retainer plate is milled mild steel and fits within a recess in the back of the smokebox shell and will be spot-welded in.
Photo #2 shows the retainer in place.
Attachments
BRING1.jpg
FRONT03.jpg
GWRdriver
Nashville TN

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Thu Feb 20, 2020 1:59 am

Thanks gwrdriver,

My boiler will be 5 1/2" copper tube. I see you have 4 bigger tubes, does the mean you will run 4 superheaters, or 2 running twice to firebox?

Ian

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gwrdriver
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Re: BR55/G8.1 Locomotive Project

Post by gwrdriver » Thu Feb 20, 2020 1:43 pm

I expect to use conventional S'heater elements so I'd expect there would be four.
GWRdriver
Nashville TN

datman
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Re: BR55/G8.1 Locomotive Project

Post by datman » Thu Feb 20, 2020 2:38 pm

gwrdriver wrote:
Thu Feb 20, 2020 1:43 pm
I expect to use conventional S'heater elements so I'd expect there would be four.
Hi gwrdriver,

What do you mean standard? you can get standard 4 way fittings/components for superheater?

Ian

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