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Nigel's Workbench 25 January 2014 - On Members Workbenches. - More Practical Help - Your Model Railway Club
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 Posted: Sun Jan 26th, 2014 12:29 am
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BCDR
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Background


I used to model in 7mm scale16.5mm gauge narrow gauge(O-16.5), but dismantled my layout (Brymbo Ironstone Works at Hook Norton) and sold most of my stock and track 2 years ago to focus on 4mm scale EM gauge and HO. I was left with 2 sorry looking half-started kits that I bought at a 7mm Narrow Gauge Society meeting at least 6 years ago - a WD Baldwin 4-6-0T pannier from WW1 and a Bagnall 0-4-0 industrial saddle tank. White metal kits, both from Wrightlines, and from the 1980's. Both were for sale as "kit complete but has been started". I did consider putting them on eBay, difficult to sell because of the postage (they are heavy), which would be more than I would get for them, a sure recipe for incurring seller’s fees without a sale. So, I thought, why not a small 7mm narrow gauge diorama for the condo? These kits are not for the fainthearted, and definitely not for a beginner to kit building.


Counting the bits most of the kits were there for both locomotives, although some white metal castings were missing from both (one guide plate for the piston rod in the Baldwin, one top cylinder cover plate in the Bagnall). The rear jacking buffer was also broken on the Baldwin (it did say complete….). It is rather difficult to get spare bits for these models since Kay Butler sold Wrightlines unless you can catch Adrian Swain (ABS Models), the new owner, at a show. I live in Canada and the US and always seem to be in the UK when there is not a narrow gauge show. I decided that I could improvise and even cast new parts if necessary from the ones that are there (something I have never tried, but I am up for the challenge). It looks like somebody with soldering experience started both of the kits, but that somebody else took over using epoxy and then gave up after making a number of errors.


When the kits are built they will form most of the motive power for a small 7mm scale narrow gauge diorama (I hesitate to say layout). The plans are currently for something 13' long x 15” wide and in 2 sections. It will have to be stored in a closet when not in use as space is a bit restricted in the condo. More about that in a future post.
 
The Baldwin 4-6-0T


 
Background. The British War Department ordered 495 Baldwin 4-6-0T Class 10-12-D locomotives for use on the 60 cm narrow gauge rail system used for transporting materiel from staging depots up to the vicinity of the front lines in WW-1 (the “Trench Railway”). After that, the armored diesels and gasoline engines took over. Built from standard parts they only saw 2 years of use and were sold afterwards as war surplus to various railways worldwide. Ten ended up in England and Wales – the Ashover Railway, The Welsh Highland Railway, the Snailbeach and District Railways, and the Glynn Valley Railway. The Wrightlines kit is based on the 2 Baldwins that ran on the Snailbeach and District Railways, a part of Colonel Stephens railway empire. Rebuilt by Bagnall in 1918, they were delivered to the Snailbeach in 1923 and ran as Nos. 3 and 4. They were re-gauged from 60 cm to 2’3¾” by the simple expedient of moving the tires out on the wheels, in which state they ran for some 10 years before being re-tired. Presumably with much thicker flanges, which would have posed some interesting issues for the checkrails and frogs? They stopped running in 1946 (tubes) and were both scrapped in 1950.


 
The kit. The Snailbeach and District Railways gauge is conveniently almost16.5mm in UK O-gauge (7mm to the foot). The instructions in the kit are dated 1984, are typically brief, and concerned primarily with the frames and the valve gear, plus minor corrections to some of the etches (remove 0.5 mm here, 2 mm there). The body is white metal (known to be carcinogenic in the state of California and so presumably this applies elsewhere, so I wear gloves), the frames are brass and the etches are N/S. I thought they were brass at first, but a polish with 800-grit paper brought them back to what they should look like. There is an assortment of rivets and pins for the valve gear, plus various AB nuts and bolts and screws to keep it all together. The kit doesn't have a cab floor, backhead or any brake gear, so a fair amount of scratch building is going to be required.


 
Motor. The original kit was designed to take the XO4 or ECM type 3 motor with a 40:1 gearbox, both of them monsters and visible in the cab and under the boiler as they were intended to drive the middle axle and wheels. There was an excellent article several years ago on this locomotive kit in "Narrow Gauge and Industrial Review”, covering how to re-motor with a large Mashima can and a multi-stage gearbox, with the motor sitting in the boiler and the gearbox driving the rear wheels. This article was in many ways the inspiration to get on and build the thing. This kit has no backhead or cab floor because of the original motor design, so some scratch building will be required. The backhead probably needs to be removal to allow dismantling. Luckily, I have a bag of 7mm scale back-head valves, dials, pipes, etc.in the spares box, so a reasonable representation should be possible once I do some research on the real thing.


 
Frames. The frames had been soldered-up along with the top-hat bearings. Ken Wright used a belt and braces approach in the design, cylindrical frame spacers held in place with screws, and small flanged plate spacers soldered-up in various places. The holes for the screws will require some additional countersinking. First problem encountered in the rebuild was the bearings. Ken Wright in the instructions called for bearing holes 9/64” in diameter, and for the bearings to be soldered-up only after adjustment of spacing for the connecting rods and running in. When I put the connecting rods on the wheels they seized-up, so the bearings will have to be desoldered and the holes opened-up very slightly (or even elongated according to the instructions, which says a lot for the precision of etching back in the 1980’s!). I will probably need new bearings as well. The second problem is that the connecting and motion rods are very “underweight” and need some additional thickness. A double thickness of N/S using scrap from the etch should do it.


 
There are half-etch representations of the frame cutouts. It would look a lot better with real cutouts, so the first job was to desolder the frame spacers, separate the frames, and using a jeweler’s saw, fine blades and needle files open up the frame cut-outs. Tedious, but I think it was worthwhile – lots of daylight under the boiler. The frames are meant to accommodate that XO4 motor, the locating hooks at the end that engages the cab bunker floor were retained but where the XO4 motor would have sat they were reduced in height so that they would be under the new cab floor. Some means of anchoring the cab floor to the frames is required. There is a hole for a bolt in the spacers, so a nut will have to be soldered to the floor. I haven't soldered anything yet as the bearing spacing has to be sorted out.







Frames and wheels as found in the kit. Note the large frame spacer to the right where the motor is supposed to sit. 






 
Frames and wheels after surgery. Note the height reduction to the left of the flanges to allow a cab floor to be fitted. 



Wheels. The wheels are old Romfords and the flanges will need reducing. All insulated, so no live chassis (which I prefer). I'm leaning towards plunger pick-ups, as wipers will get in the way of any brake work (that is still in the planning stage).


 
Body. The basic bodywork had been done (very badly, and nothing was square or vertical), with the parts put together with poor quality epoxy. It was never painted, and age and epoxy oxidation (along with white metal oxidation) had taken their toll. The whole cab assembly was rather creaky, with most of the joints having failed, and the pannier tanks were at an alarming angle. No sign of any soldering work except for the front footplate (nicely done and which I left alone), so the whole body went into a tin of paint stripper for a month. The one I use is a "green" stripper that is a methylene chloride-based gel, which is an excellent solvent for dissolving epoxy glue. It is green in color, which I suspect is as close to  ecologically green as it is going to get. If the instructions on the can say it will strip epoxy paint it will dissolve epoxy glue, it just takes a bit of time and patience. [See footnote[1] if you use this method with a painted white metal kit].


 
After pulling out the larger castings I poured the contents of the tin through a fine mesh strainer to catch the small bits (safety valves, water filler covers, etc.), gave everything a good scrub with washing-up liquid and a new hard-bristle tooth brush (freebie from the dentist, why on earth would you want to use an old one? The bristles are worn for starters). Final polish was with a suede brush (fine brass wire), and I started to plan the approach to the rebuild. I always clean the surfaces to be soldered-up 5 minutes beforehand to make sure white metal oxidation is kept to a minimum.


 
Sub-assemblies. The body builds into a series of sub-assemblies. The bottom half of the boiler with the saddle tanks, the top half of the boiler and the front cab sheet, the front footplate, the future backhead which will have to be removable to get at the bolt holding the boiler top to the front cab sheet, and the sides and back sheet of the cab. The roof will be held on by spring wire to allow access. One of the nice thinks about 7mm scale is that you can get your fingers or pliers in to do things with sub-assemblies that would be impossible in 4mm scale.


 
The cab. I started by soldering-up the cab sides and back sheet up using 100°C solder and the iron at 25W (the lowest it will go), the trick is to heat the solder, not the white metal, and get it to follow the flux. I use liquid no-residue organic flux, and made sure the surfaces to be soldered were bright metal (no white metal oxidation) and grease-free. I use 95% IPA (not the stuff that comes in pint glasses) as it gets rid of grease and dries rapidly. The front sheet is designed to be fixed to the cab sides top and bottom using solder and small screws, not the epoxy glue that the previous owner had used. This will have to wait until the backhead and floor are in place.





The cab. Note the large hole in the floor to accommodate the motor. Needs a bunker front and doors as well.

The boiler and pannier tanks. I removed the casting webs from the top and bottom of the inside of the boiler (mini-saw and a half-round file) as this is where the new motor will go. The walls of the boiler are 2mm thick, so the webs are superfluous. The nut for the bolt holding the boiler through the saddle to the frames at the front was then soldered in place. A trick I learned about recently was to rub graphite (I use a 4B pencil) over the bolt, thread it though the nut with the nut in place, put a dab of flux around the nut, and solder-up. This way the graphite keeps the solder from sticking, and the bolt does not end up soldered to the nut. Not pretty, but that nut is not going anywhere.

 

Boiler flanges - before and after.

The smokebox door was fixed in place to the bottom half of the boiler with CAA glue (5-15 second gap-filling) as it was a bit tight space-wise to get the tip of the soldering iron in place. I would have liked to solder the saddle tanks to the bottom of the boiler but again just a little bit too tight, so gap-filling CAA glue was used. I will go back and put a couple of tacks of solder along the bottom where they are out of site just to make sure.



Bottom half of boiler with smoke box door.



Top half of boiler with cab front sheet bolted on and boiler fittings (propped on for the moment). 




Major sub-assemblies on frames. Taken before I opened the frame holes.

That is it for the moment. Next up when I get back to the real workshop at home is sorting those bearings, the flanges on the wheels, putting some meat on the connecting and motion rods, and building a backhead. I have a trip to the UK coming up, and I plan on visiting the “Buzz” narrow gauge railway to get some shots and dimensions of the backhead of their restored Baldwin. In addition, write to Adrian to see if he has spare parts available before I enter the wonderful world of white metal casting (in the garden shed and wearing a mask!).

[1] Leaving a painted white metal kit put together with epoxy for a month in paint stripper results in a rather gooey mess which traps small parts. Strip the paint first by painting with the stripper and putting it an airtight container overnight, remove the paint, and then dunk in stripper until the epoxy dissolves. The stripper can be reused several times.



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©Nigel C. Phillips
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 Posted: Sun Jan 26th, 2014 05:35 am
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Marty
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Fascinating and enjoyable read... And a couple of useful tips too. Organic flux for heavens sake...whatever next.

Keep it coming.

Cheers

Marty



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Marty
N Gauge, GWR West Wales
Newcastle Emlyn Layout.
Newcastle Emlyn Station is "Under construction"
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 Posted: Sun Jan 26th, 2014 08:11 pm
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BCDR
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Hi Marty,

Thanks. The organic flux contains weak organic acids - malic or succinic acids for example to etch - a high boiling point ester (think rosin) to prevent re-oxidation, and an alcohol to make it flow (IPA or ethanol). Not so aggressive as phosphoric or hydrochloric acid, and it really is no clean, meaning no corrosive residue. Getting rosin residue off requires strong spolvents. Developed for the electronics industry, which uses automatic machinery. 

It does require clean and non-oxidized metal, hence the prep 5 minutes before soldering. The only drawback is that solder needs to be applied immediately after fluxing, otherwise it evaporates. I still wash and brush-up before painting. I get it from DCC Concepts - just down the road from you in Naval Base (at least I think it's organic, smells like it). Buying it by the gallon is cheaper (although having used 50 mL in 2 years a gallon is a bit too much to keep around as it's getting into HazMat quantities).

Nigel



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