Scratch build - LNWR Precursor Tank - Scale7

[adrian]

Good to see you getting chance to do some modelling Adrian.

Well that aged well. Pressures of work and other issues just left me drained in the evening so I never had the energy to pick this up. However just before Christmas I decided I had to get moving on it again. A few recent posts have shown a little more interest in pre-grouping and Precursors so I thought I would post my updates over the next few weeks.

The front, middle and rear parts of the side frames were clamped together with tool maker clamps and using a ruler across the top to make sure they were straight from front to rear before soldering them together. It was only at this point did I start to appreciate how damn long this tank loco is going to be!

I then set about making some more of the intermediate frames spacers. Also behind the buffer beams a mounting plate to enable the bodywork to be attached to the chassis.





Also additional brackets for behind the buffer beam - cut from a strip of nickel-silver, riveted along the edga and then folded.


Once all the parts were ready I started soldering together the chassis - no photos I'm afraid of that stage however no complex jigs used. It was assembled on a flat glass plate and as the hornguides were fitted rather than "alignment axles" I just used two length of brass square bar and careful checking with an engineers square.

 

[adrian]

So I now have a rolling chassis - with CSB suspension.

I have decided to make the buffer beam part of the chassis rather than the bodywork. I just think it'll make it easier to keep the bodywork straight and flat, the loco lends it to this arrangement for me just because it has a very thin straight side valence. Other designs with deeper side valences I might have done differently but for this loco it seemed an appropriate arrangement.

 

[SimonT]

Adrian,
glad to see you back modelling. I too had a 2023 full of other matters and have just started again. Good, isn't it!

The axleboxes look interesting. Presumably a 3D print in an ABS like resin. Do they have a brass bush inside like the original S7 insulated axleboxes? Were the horncheeks set with a jig or were they a muck about with the iron until they felt right?
Simon

 

[adrian]

The axleboxes look interesting. Presumably a 3D print in an ABS like resin. Do they have a brass bush inside like the original S7 insulated axleboxes? Were the horncheeks set with a jig or were they a muck about with the iron until they felt right?

Sort of - but nothing fancy.

The "axleboxes" are more like CSB cradles for miniature ball races.

Then for the hornguides I just soldered one side vertical checking with a square - this is illustrative only. I then used one of the Slaters insulated axlebox as a spacer to solder the other side on.


I then have a little steel peg to fit in the axlebox so I can use the coupling rods to space out to match the dimensions and solder in the hornguides for the other axlebox.




The slot in the frames are actually slightly wider than the hornblocks to allow the flange on the bearings to be slightly recessed which lets me get the frames a nice width and close to the wheels.

 

[simond]

Very nice, and I may shamelessly copy you!

How will you collect the power? presumably not through the ball bearings?

 

[SimonT]

Adrian,
thank you for your full and generous explanation. I might have to will give it a try.
Simon

 

[Brian McKenzie]

Excellent work there, Adrian - but I'll echo what concerns @simond. A large O scale exhibition layout in Chicago totally slogged out the ball bearings in their locos - admittedly after doing a high mileage and with current hungry Pittman motors.

 

[adrian]

How will you collect the power? presumably not through the ball bearings?

No - as the Slaters wheels are insulated there is a "cunning" plan for small plunger pickups from the tyres, hence the small location hole visible in the last photo behind the hornguides.

 

[paulc]

Sort of - but nothing fancy.

The "axleboxes" are more like CSB cradles for miniature ball races.View attachment 234272

Then for the hornguides I just soldered one side vertical checking with a square - this is illustrative only. I then used one of the Slaters insulated axlebox as a spacer to solder the other side on.
View attachment 234271

I then have a little steel peg to fit in the axlebox so I can use the coupling rods to space out to match the dimensions and solder in the hornguides for the other axlebox.
View attachment 234270

View attachment 234269

The slot in the frames are actually slightly wider than the hornblocks to allow the flange on the bearings to be slightly recessed which lets me get the frames a nice width and close to the wheels.
View attachment 234267

View attachment 234268

Aaahhh you 3D guys keep coming up with these great ideas . Is the bearing glued into the printed hornblocks ?
I may have to try CSB on my next loco build , are those just handrail knobs that the wire slides through on the frames ?

 

[adrian]

Aaahhh you 3D guys keep coming up with these great ideas . Is the bearing glued into the printed hornblocks ?
I may have to try CSB on my next loco build , are those just handrail knobs that the wire slides through on the frames ?

Hi,

Eventually the bearings will be glued into the hornblocks but not just yet. The fulcrum positions are just a SWAG at this stage until the loco is finished and weighted. The cunning plan is that once complete I can print off a new set at the end of the build and adjust the height of the fulcrum hole if the ride height needs rising or lowering. Although I suspect I'll get towards the end and go f**k it, they are close enough and leave them as they are.

The chassis fulcrum points are nothing more than a length of 1mm nickel-silver wire bent into a P shape with a small set of round nose pliers. They are then soldered into holes drilled into chassis and filed flush on the outside. It would work fine if just a peg for the fulcrum point but by making them captive like this means that I don't need to fit stays across the bottom of the hornguides to stop the axleboxes dropping out. The CSB wire holds everything in place. On the real loco the springing was a mixture of either dual or quad coils underneath the horn guides so I was going to have a go practising my 3D modelling and printing for those items and stick them on later.

 

[simond]

I like the hornblocks, and I very much like the idea of reprinting them to fine tune the ride height. Very sharp, sir!

 

[adrian]

I only started to appreciate the length of the loco when I cut out a sheet of nickel-silver for the footplate - I'm going for all in one length option here.


The first task was to cutout a central area to clear the drivers, there's more to cut out later for the area behind the smokebox but I'll do that later when I have something to work with. This was simply to get it clear of the drivers and the frames to get it to sit flat. I could then solder on some brass angle to form the valance.


I then wanted to get the side tanks built and soldered on so it would keep the footplate straight, it's rather flexible at this stage. Strips of N/S were doubled up and soldered together so that I'd have a matched pair of sides, top, front and rear.

The front of the tank needs a cutback for the boiler and the top needs narrowing down the side of the boiler. Which led to a pause on this whilst I cut and rolled a boiler.

Tack soldered together

and then a couple disks to hold it circular so that later on I can cutout a section to fit the motor through.

That then allowed me to work out what needed cutting back on the side tanks.

Soldering together the tanks - just tack soldered together for the moment whilst I sort out fitting of all different body components.