Building a NSWGR CPH Railmotor

[Deeja]

I am dedicated steam man, however there are times when steam is too much effort (Like loading all the ancillary equipment, tools, blower, coal etc) into the car when on holidays, or when you can’t run steam (total fire ban days), so I decided I want an electric or liquid fuelled motor 'play thing'. A number of design 'rules': It shouldn’t be too large, be as self-contained as possible, be able to run on fire ban days, be a proper scale model of something – not just a powered box, and preferably not too many compound curves, which ruled out some diesel models which have compound ‘cheek bones’ or hoods at the ends – I didn’t think my sheet metal skills were up to that, and do not have many woodworking tools apart from hand tools. So it was decided, after much scouring of photos, plans and thoughts of “How on earth would I make this or that” when looking at photos etc.

So it was decided that a NSW railways CPH railmotor would fit the bill. These are from the 1920s – definitely the steam era – and 42ft long, seemed just right for a 5"g model. Plus there are still quite a number preserved on heritage railways, museums etc, so access to a real full size one is possible if needed. They also have a certain charm about them.

See photo of prototype below


So I set to work during COVID lockdown and started sketching in CAD what to do. I obtained some 24V/150W motors which are small enough to axle hang yet big and powerful enough to handle the railmotor + 1 driver load. It is not a locomotive in the traditional sense and doesn't need to haul a great load. The prototype only had 1 axle powered so I reasoned 1 powered bogie is sufficient. Having axle hung motors also leaves the interior available for batteries, controller, electric vacuum pump, radio control gear (at a later date), on board battery charger, etc.

The basic design is a chassis as close as possible to the original's steel truss frame, and to make a skeleton from 6mm square steel and have a laser cut wooden body skin from plywood as the outer shell. I drew both the steelwork and wooden body panels at the same time as it is surprising how closely they inter react. I have used laser cut and scribed ply previously to make some covered wagons – see photo below.



Last week the steel parts arrived from the laser cutter for various body parts, bogies, drive train etc, and I now have enough to keep me busy for many months! The body panels will be ordered later when the main superstructure is more advanced. After all it is almost the last thing required, and also the most visible on the finished model, and as we all know the detailing is what takes a lot of the time.

This is not intended to be a quick ‘get me running a quickly as possible’ build, but to build a scale electrically powered model, and is expected to take quite a few months. I will post updates as I make progress, but do not expect an overly quick time scale. I would also welcome any comments and questions you may have. I know there are quite a few here on Oz, but I look forward to comments/suggestions from you UK based modellers.

Now back to the workshop to do some more.

[peteh]

I assuime you have also looked at Jim's build ? modeleng.proboards.com/thread/13762/building-nswgr-railmotor-401

[Deeja]

Yes I have. I decided I didn't want an all wood body as I wanted to be able to sit ON (with suitable seat) as an option so had to be strong enough. Intend to use a 1-bum truck with foot pegs on the railmotor. As as I said I have next to no woodworking equipment. But that is an interesting build nonetheless.

[Jim]

The CPH will be an interesting model and a nice addition to the growing number of non steam models.

Like you I decided that much as I love the Britannia I needed something that could be easily transported by a less than energetic senior cit while at the same time giving me lots of fun on the track.

Jim

[Deeja]

One of things about the CPH is that the body ends are square in the middle and angled on either side. From the drawings this angle calculates to 15.25°. I used 6mm for the headstocks and wondered how I could bend, accurately, the side bits to precisely this amount. Firstly I made a triangular 'jig' from 3mm sheet using Pythagorus to get an accurate angle. I then carefully hacksawed part way through the headstock to about 3mm deep square across where the bend was needed. I then bent them in the vice while heating with the propane torch until they were 'soft' enough to easily bend, and of course they bent only on the cut line. I got them as close as I could while trying not to burn fingers, and when cold gently tapped them to final position using a straight edge and the jig. When all done I TIG welded the back to fill up the saw cut and regain full thickness, and cleaned up the weld by filing. See photo. Note the black tape is only to hold things in place for the photo. When lined up against some of the laser cut parts with the same angle, I managed to get the ends within 0.2mm and was quite happy with that.



I also used the same jig for lining up to cut the ends of the buffers to the same 15.25° - the only way the buffers can be straight. Only the rectangular base is yet to be soldered on before buffers ready for painting.

[Deeja]

A bit more progress has been made on the CPH over the Christmas period. Sometimes slow due to the warmer humid weather 'down under', and it is 'holiday season'.

I have drilled and machined where necessary parts of the main frame and welded a lot of the bits together.



Starting to look like a chassis now!
It has been all TIG welded and the thicker cross beams will support the batteries, and provide some rigidity to the frame. The rounded parts of the chassis visible under and near the end of the photo are for clearance over the traction motors and transmission. The chamfered ends of the cross beams are weld prep ready for the side frames. These aren't on yet as there was shortage in the under bench store of the correct size, plus being in a holiday period and COVID restricting movements, the trip to the steel merchant hasn't occurred yet. On the smaller side sub-beams, I put tabs to slot into the 6mm sq holes in the main frame (also 6mm thick), but made the tabs 7.5mm long so they protruded 1.5mm on the inside which I then fused to the main frame. These sub-beams are also welded to the main frame top and bottom as well as the inner end. The side frames will be added as soon as possible. I also tapped a number of holes in these sub-beams to attach the various under floor bits like (dummy) battery boxes, air tanks, plumbing, foot rest mounts etc later. Easier to do it when they are separate bits of metal(!) even if some of the holes are never used.

The buffers have also been completed, and prototype buffer for comparison

and now already to fit.

Work has also been continuing on various other bits and below is a test partial fitment of the bogie side frames and horn blocks. More work to go yet but getting there.

[Deeja]

A lot more work has been done on my CPH railmotor, but not a lot of visible progress, mostly work on many of the bits - particularly bogie parts.
Below is a a photo of the main frame progress. The frame itself has been undercoated and the base of the body bolted onto the frame. Undercoating was necessary to contain the surface rust as it has been VERY wet and rainy so far this year (1700mm to end of June compared to 860mm whole year average) and you just have to look at something and it rusts!



The "1" and "2" are to distinguish easily No.1 and No.2 ends as being a symetrical design it easy to get confused.
The raised bit near the centre of the frame are the door guides for sliding side doors. It is ready to add the verticals to support the top of the body frame. Note I have made the body frame removable and the bolt ends can be seen poking up into the (unseen) interior of the body. Once completed this probably won't be necessay to remove the body from the frame, but very useful during construction.

A lot of work has been done on the bogie parts, and assembly will be next, including working equaliser beams, springing etc. Photos of the bogies in due course.
Work is continuing of the roof, and interior mechanical and electrical bits such as battery holder for the traction batteries, placement of circuit breaker, switchgear etc, and working out how to accommodate the on-board battery charger, etc

[Jim]

Like you I put a large 1 and 2 on the frames and the two power units so as not to get the No1 and No2 ends muddled up especially given my talent for getting hopelessly muddled.

Your proposal to fit an onboard battery charge sounds interesting could you give us more details in later posts?

You're making a superb model of the CPH, Deeja.

Jim

[Deeja]

Thanks for your comments Jim.
Am currently working on the body frame. I now looks like a railmotor except without the body panels. And yes, the 1 and 2 certaily help.

Certainly more details and photos soon. I have a modern electronic multi-stage 12V/10A battery charger (actually 2 - 1 for each battery) and they fit nicely crossways within the body. The charger is about 60mm thick and I can 'stack' the chargers edgewise on top of each other so it takes up minimum body length internally. I am putting a Euro style mains input socket, like the one on the back of a computer, inside the body near the sliding door so I can just plug in a power cable when required. And the wiring suitably installed to keep the mains and battery voltages separated, and fingers impossible to touch the mains. None of this "Oh I forgot the charger" or similar, just load and go. I did not want or need to pack all the ancilliary bits and pieces every time like you need for a steamer, except perhaps for an extension cord. The chargers can be left permanently connected to the batteries.

I am using 2x 12V/50AH deep discharge batteries for the traction batteries, and a 24V->12V converter to power the auxiliaries for the 12V Aux supply.

Completion of body frame next, then bogies, install the electrical bits and pieces, then roof (another challenge!). I also want to test run/debug etc before I put the body panels on.

David

[Jim]

Thanks for the update Deeja from what you say you've certainly got the electrical side of things nicely under control.

Like you I've used 2x12 volt 50 amph deep cycle batteries to serve the 2 power bogies.

Look forward to see more about this build as it progresses.

Looking really good

Jim

[Deeja]

A bit more progress on the bodywork framing for the CPH.

The top (and bottom) 'rims' were laser cut from 3mm sheet with 6mm sq cutouts to fit the 6mm sq vertical body ribs. I had to touch up these cutouts by filing as the laser cut was slightltly undersize at around 5.8 to 5.9mm, but this now means the ribs fit neatly with almost zero slop. These cutouts can be seen on the photo a couple of posts above.

I TIG welded the vertical ribs on the ends so that they are level with the 'rims' top and bottom with no filler material being used, just the base metal fused during welding. Weld penetration is about 2mm which fits nicely with the 3mm material at top and bottom and leaves zero to minimal welding lumps to file off for clean up. See below.



The frame has also been painted and with buffers and coupling hooks fitted looks the part. The floor added with the battery tray in final location can also been seen.

[Jim]

You're doing a cracking job there Deeja. When completed you will have a very fine model of the CPH that was so familiar on country branch lines.

Jim

[johnd]

Great job, watching your progress with interest.
Seems a shame to cover that really nice girder frame work with a board, but as on most of our builds the most intricate work is often covered from view.

[Deeja]

Thanks for your comments Jim and johnd.
Yes I agree it is a shame to cover the framing, but it is still visible on the inside when the (yet to build) roof is lifted. And yes, a lot of our detail work is hidden but that's the hobby.

It also struck me that the prototypes were built with wood framing and individual boards for the body work, later covered in smooth panelling for the CPHs. Just about all boxy freight wagons and earlier passenger cars were constructed this way - steel frames and wooden bodies, so I am largely following prototype but using steel framing.

[dalboy]

A great start to this build. I always enjoy watching and reading on other peoples builds. I know THIS is mainly a wooden build of a tram but still worth a look

[Deeja]

dalboy, tram link doesn't work

[uuu]

Try this: LINK although it looks you might have to register on the site to see the contents.

Wilf

[Deeja]

It's been a while since my last update, but work has had a break due to the never ending rain and some holidays.
I had been thinking of how to do the roof, and get as accurately as possible the 3D curvature and differering profiles laterally and longitudinally. So I decided I would laser cut the profiles and form a frame as a removable roof. I have started welding it together, with a progress shot below.



The painted bits are the body frame and the unpainted bits the roof assy. I decided to put some rectangular nicks in the roof trusses so I could insert steel wire/rods to support the roof. A short trial piece in the photo is to check fit etc. I am using soft 2.5mm dia steel wire (as used in agricultural fencing - cheap, long and readily available) and it can be easily bent at the 'corners'. It will be covered in bronze fly wire mesh carefully tied (sewn?) on with fine copper wire to the rods and then fibre glassed over the top. The roof is already fairly stiff and with all the wire rods welded in place and finally fibre glassing will form a rigid removable roof panel.

Work has also continued on the bogie bits and pieces, and the internal arrangements for controller, sound, battery charger, wiring etc so it can all fit and be maintainable in the future. No use in cramming it in and not be able to get at it.

[steamer5]

Hi Deeja,
Looking good!
When I built Toby I used 2 skins of thin ply over the roof frames glued 1 to the other & clamped down, I used ply frames, but the Toby’s roof doesn’t have curves at the end too, just side to side. It did however make for a nice strong roof!

Cheers Kerrin

[Deeja]

Kerrin,
Yes 2 bits of ply are very strong. My floor is actually 2 sheets of 6mm marine ply glued together. 2 reasons. 1) 1 piece still bends easily, at least far enough to not maintain dimension in relation to other bits, and 2) the lower piece sits down between the lower body frame base and sits on the sub-frame, with the top piece filling out the floor right to the walls. It also suits the scale floor height at the doorways. Just a rigid non-bending floor 12mm thick.
David