Atlantic's works: Portable layout - Scenic details next

[Pebbles]

From their specification it would appear that these small motors have a rated voltage of 8 volts. There is little reason why they cannot be used intermittently at 12 volts but clearly they prefer to operate with a gear ratio of more than 40:1. The cheap motors I purchased came with two types of brass worm. One type, whilst being single start, is compatible with the old Hornby two start gears while the other type is compatible with the cheap gears being used. Unfortunately you don't get a choice, it's pot luck.

[Atlantic 3279]

8 volts? Interesting!

A trial run this morning with the revised gearing wasn't as smooth and quiet as I'd hoped, but I reckon I may be able to improve on that aspect with a second attempt at boring a final drive gear to fit the 1/8th inch axle. My first effort runs slightly eccentrically.

The revised ratio does seem beneficial however. On duties that previously made the motor get too hot to touch it now remains at a temperature that allows it to be held continuously, although still fairly hot. Loco and tender alone still managed a scale speed around 55mph on the output from a hand-held controller. I doubt that a full 12 volts is being applied.

Molyslip enjoyed a fashion as gear lubricant didn't it? No idea if it is compatible with nylon.

[Atlantic 3279]

Time to return to the well overdue business of illustrating the production of the J6 body castings.

Here's the previously shown part-filled moulding box for the boiler, with part of one side removed to reveal some of the thin shuttering projecting from the firebox end of the master boiler, allowing same to be trimmed down flush with the surface of the set portion of the rubber mould. I tidied up the level of this a little more after taking the picture, so as to get a neat square edge around the top of the central recess. The moulding box was then reassembled, Vaseline applied to the top face of the set rubber, and a further quantity of liquid rubber poured in to form both a core and a cap.

Here's the mould after extraction from the box and as you can see I've cheated by taking the master boiler out to check that all was well before taking any pictures!

Core piece and cap part way out:

Separated fully. No comment.

Here's how the outer mould conveniently opens up for release of the fatter smokebox and its deep base.

First boiler out of the mould, in the rough state:

[manna]

G'day Gents

Amazing

manna

[earlswood nob]

Good morning all

Great info about resin casting.

The J6 should be an easy conversion to the J2, with only larger splashers and wheels needed. Some also had a slightly shorter chimney.
Most of the J2's worked in the Nottingham/Lincolnshire area, with a couple in the West Riding.

The J1 would be a more difficult conversion as it had a shorter smokebox and footplate with the rear drivers slightly more inside the cab. The boiler was also lower as the loco had slide-valves.

Eaelswood nob

[S.A.C. Martin]

Looking good Graeme!

[LNER4479]

We need an 'amazing' button!

[jwealleans]

Is it going to be one of these when it grows up?

[Atlantic 3279]

Not sure about that......

T'other side of the first boiler casting, still "as it came":

After breaking off the flash:

One annoying but not terminal air bubble defect in the base of the smokebox front.

Too much gusto when breaking away the flash at the base of the firebox on this side, but that defect will be hidden by the cover for the control rods on this side of the loco, so it's no hardship, fortunately.

The mould by the way is filled by initially pouring the resin into the outer portion, with that on-end and its seam held together manually. After tilting it in various directions to try to get the air pockets out of any recesses, and rubbing a little resin into the impressions that form the washout plugs and mudhole covers, the core/cap piece is then pushed gently home into position. Resin needs to overflow of course and the mould is then place on a sloping surface so that the boiler shape within is upside down with firebox base highest. Some hand pieces of card are fitted to stop the mould sides from splayiong an a final check is made to ensure that the core piece has gone in fully with the cap aligned perfectly with the outer edges of the outer mould:

Significant shrinkage seems not to be a problem with this pre-coloured G26 resin, as the boiler casting appears to fit the rest of the loco master parts well enough:

In view of the pressing need to get these J6 locos ready for next month's show, I'd told myself that I simply wouldn't bother with brake gear at this stage. As spike Milligan would have put it, "so here it is", along with moulding box also containing mid-steps and front valve covers. alongside is the rubber mould for these small parts.

As the cab has a flat front and no awkward undercuts it is dead easy to make a one-piece mould, leaving the cover sheet to form the cab front. I'm not going to waste space with pictures of that, nor of the moulds for chimney and dome which are dead simple like others I've shown on here in the past. This shows how far I'd got with the body before I started to fiddle around with the chassis again.

I'll be back with more details shortly, but I'd better give this lot a fair chance to upload cleanly first.....

[Atlantic 3279]

Is it going to be one of these when it grows up?

It will need more than twice weekly cycling trips and the odd sausage roll to beef it up into one of those!

Was there anywhere in NSW for a loco to run fast enough to get any real benefit from streamlining?

[Atlantic 3279]

Revised drive layout using cheapo nylon gears providing two-stage 1:48 reduction in lieu of traditional single stage 40:1 Romford steel worm and brass pinion:

The motor worm engages with the 30 tooth part of a 30 / 10 tooth double gear wheel. Displaced upward just behind that wheel, engaged with its 10 teeth, is a 16 tooth intermediate gear. I had to displace it upwards to try to squeeze the primary gear and the final drive gear as close together as possible, otherwise the gear train simply wouldn't fit in. Even so, I had to narrow down the 10 tooth section of the primary gear and the whole of 16 tooth intermediate, just in order to get the 30 teeth of the primary gear on the centre line of chassis. There's no room to offset the motor to one side....

]

Even though I thought I'd worked it all out "just so" I finished up with slight interference between the primary and final gear (also a 16 tooth job), so I took the offending section of the teeth off the final gear!

[Atlantic 3279]

That more or less brings things on to what's cooking at present. Here's the running plate module with central cut-out carefully covered over using 5 thou plastic:

I decided to try a new way of dividing the necessary moulds for the upper and lower faces of the running plate, with the intention of getting the division between the two exactly in line with the lip at the edge of the running plate without any awkward flash or bubbles in the angle under the lip. Step one ion the cunning plan was the cutting out of some contoured pieces of 60 thou plastic to match the curvature of the running plate, plus some shallower beams to support the ends of the running plate, then sticking these to a base for a moulding box.

The running plate module sits on the end beams, between the contoured sides thus, leaving a narrow gap at each edge of the running plate.

]

Ultra careful application of sellotape over the top edges of the running plate, across the narrow gap, and down the sides of the support pieces seals the running plate in place.

Tape on the faces of the buffer beams does a similar job of sealing the ends to the end support beams.

A seal of PVA takes care of the screw holes, leaving a nice dimple.

Before setting off on today's 32 mile cycle torture, I filled the moulding box to the brim with rubber compound. It may cure sufficiently for me to take a look within this evening. The plastic support pieces will of course be removed before the inverted mould receives the second pour of rubber to form its other half.

[LNER4479]

Rivetting stuff - can't wait for the next instalment

[manna]

G'day Gents

Brilliant stuff with the moulds etc.

The C38's probably never had any need for streamlining, it being a good PR exercise only, they were used on the Sydney-Newcastle express's, and the interstate Sydney-Melbourne, and would maybe have run up to the mid 70's (MPH), once over the Blue Mountains and onto the Prairie like flatlands beyond, speed would not be a factor as the track was a bit ! light (probably 60mph Max) and there are so many un-gated level crossing.

manna

[2002EarlMarischal]

Then most exciting aspect of my day, watching this amazing thread!

Really awesome work Graeme.