Atlantic's works: Portable layout - Scenic details next

[Atso]

Excellent work.

Agreed, can you do some N gauge stuff now please!

[Saint Johnstoun]

I wonder if the slope on the chassis weight at the front is intended so that the same chassis can be used for a Bugatti nose version?

[Atlantic 3279]

I think the safest answer to that is "almost".

[Atlantic 3279]

I should in all likelihood have been concentrating much more solidly on certain hopper wagons today, but I had to do a bit more tinkering with the P2 job. This is how things now stand:

As will be seen, the inner elements of the motion bracket assembly have now been added. In order to get it back onto the chassis once these parts at present I had to break off the cast outriggers that had carried the Lentz valve gear, but I have kept the pieces so that should I have to abandon this conversion (which I now think highly unlikely) I can re-attach them by drilling, pinning and gluing. After careful reference to the Isinglass diagram I have worked out exactly how far back the motion bracket should sit and I have re-positioned the cylinders a little lower than I originally placed them, their tops now being approx. 3mm below the running plate. I've also drilled their rears to take the piston rods, eventually some valve rods, the original Hornby outer slide bars AND the new etched inner slidebars that form part of the A2 derived valve gear conversion set. I've re-used the Hornby crossheads and con-rods, carefully checking that full fore and aft movement of the crossheads is possible before soldering the rear ends of the Hornby slidebars to the new motion bracket. Even with the added inner slidebar layers it is impossible to get the leading crankpins to touch them when the leading wheelset is pushed to its extreme limit of sideplay. This much of the assembly runs perfectly freely after giving careful attention to relative positions of the slidebars and the centre lines of the piston rods. The crossheads of course lack the "foot" or drop link that will be needed to carry the union link of the Walschaerts valve gear. I have ideas on how I might overcome that, in due course. The return cranks, originally set with their small ends more or less on the line of the driving axle (correct for the Lentz drive) now lean correctly to suit the Walschaerts arrangement. Surprisingly, nothing at all clever was require to achieve this: With the return crank screwed firmly in place on the flats on the end of the crankpin it turned out to be possible to just grasp the crank carefully with pliers and then turn it (and the crankpin too it seemed) by the desired amount. Could it be that whilst firmly fitted, these P2 crankpins are devoid of the flats that appear to lock other Hornby crankpins at set orientations in the moulded plastic of the wheels?

I really must concentrate on those wagons now before taking this any further......

[Atso]

I'm enjoying watching how you're putting this together, Graeme. I'll be most interested to see how you tackle the 'S' curve that drops the front of the footplate down to the new cylinders.

Good luck with the hoppers, don't let them take you away from the important stuff for too long!

[Atlantic 3279]

I originally had in mind a scratchbuilt section of front running plate in brass, but having seen Will's use of pieces of Gresley Pacific running plate for the S-curves and having had a quick rummage amongst my project remnant containers I must say I like the idea of following his lead.

[earlswood nob]

Good morning all after a walk in the foggy dew,

I was wondering about the S curves in the footplate.
I may well use the idea when I finally get around to building/converting a P1.
The P2 will look good alongside the P1.
It would also make an interesting double header. The video of double P1 headed train was illuminating.

This forum is such a great place to test ideas, and pick up new techniques.

Earlswood nob

[Horsetan]

The small end of that return crank doesn't leave you a lot to play with.

[Atlantic 3279]

Agreed!

[Atlantic 3279]

Even so, I've managed by diligent effort last night to hang working valve gear on it, although I may go back to that crank and add a second layer. The head of my pivot pin almost passes through the hole! Picture later.....

[earlswood nob]

Good morning all

I will be interesting to see how the valve gear fits.
The P2 motion is similar to the O2. However, I don't think Heljian will supply that yet.
I suspect that it's also similar to one of Thompson A2 variants.
The Comet D49 is very close, but needs a different motion bracket, and the future supply of Comet parts is unknown since the sad passing of Geoff Brewin.

Earlswood nob

[Atlantic 3279]

The A2/2 valve gear conversion set certainly fits, as it should if all is mutually to scale. It could all be done instead by modifying just a Comet V2 set as I did on my first A2/3 conversions, but it is certainly easier to work from rods that are already the right lengths and a motion bracket that has the correct pivot holes designed-in. I've still had to source a combination lever and union link from Comet V2 etch remnants, likewise some trimmed down rod ends that I used to make the drop-link below the crosshead. That involved drilling out the cast pivot point that held the con-rod little-end onto the original Hornby crosshead. I then put a pin through the new droplink, then through the crosshead and con-rod, soldering the pin the to the con-rod and trimming off the inner end neatly. It retains plentiful clearance over the leading crankpin and coupling rod. As the drop link is not held rigidly vertical by my method of attachment, I cheated slightly and soldered its joint to the union link solid at about 90 degrees. The drop link is so short and its freedom of angular movement so little anyway that it is barely possible to see that it is actually pivoting at the top rather than the bottom. The valve gear works satisfactorily. Nothing catches or gets knotted up! Having built a three-layer version of the expansion link the need to ensure that its top does not foul the underside of the motion bracket stretcher was emphasized - the link is too fat to simply push it tight up against the inner face of the outer bracket and thus let its top waggle around in fresh air, outboard of the stretcher ends. It has instead to be filed a little to get perfect clearance.

Running a few circuits on Grantham yesterday demonstrated that my valve rod is a little tight in the cylinder casting and this results in the valve gear rocking the cylinders slightly. That can be sorted out. Also, with load now imposed on the previously idle return crank, the tendency for the retaining screw on the crankpin to be freed off by running if not fully tightened is quite noticeable, likewise the tendency for the crankpin itself (which I previously twisted to the correct new orientation) to be pushed/pulled to the wrong angle by the leverage on the return crank. A bit of suitable Loctite, cyano or epoxy may need to be applied with care.

I've only erected the valve gear on one side so far, but I now know that I can proceed with roughly the same methods on the second side.

[earlswood nob]

G'day all

Thanks for showing the valve gear. I know so little of the Thompson Pacifics, that I was unsure of the A2 variant that had similar valve gear to the P2.

I look forward to the finished model as I think Earl Marischal (without external deflectors) is one of Gresley's best lookers.

Earlswood nob

[Atlantic 3279]

After a thoroughly enjoyable day with the usual suspects around the Grantham layout on Saturday, then a (not) relaxing Sunday sorting out an electrical fault in a piece of equipment vital to my "proper" professional role (which would have cost around £4000 to replace and which has been "abandoned" for service/repair purposes by the cynical original manufacturers who want to blackmail us all into keeping up with the latest models) I was eventually able to return to the model making theme this evening.
Following due consideration I altered the stretcher modification on the P2 motion bracket, substituting a corner-piece of etch waste for the original "straight piece with bits nibbled out". The reason was, that having firmly established where the motion brackets have to fit, my original stretcher adaptation did not allow removal and re-fitting of valve gear and cylinders without either dividing those two items or disconnecting the wiring from the pick-ups to the chip socket. The revised arrangement allows the cylinders and motion to remain in one organised chunk during fitting or removal, with no need to disturb the wiring at all. This image shows the result from the right side of the loco which still awaits its valve gear.

I've also sorted out the previously mentioned rocking tendencies of the cylinders, finding it due to two causes. Firstly, as suspected, my original valve rod was a bit too thick to suit the very simple means I'd used of connecting it to the combination lever - end of rod bent over to 90 degrees, slotted through hole in lever, bend increased to 180 degrees and nipped up quite tightly. This was denying the combination lever full freedom to pivot to the necessary angles. A thinner valve rod fitted into the available space between the valve crosshead guides without requiring such tight bends to link it to the lever. It works a treat. Second cause of cylinder rocking was just a fraction too little slope at the underside of the rear ends of the slidebars. The tops of the con-rods were touching the slidebars in this area at one point in the upper half of their movement. A spot of filing of the slidebars overcame that. I can now proceed in a confident manner with the valve gear on the right side of the loco!

[will5210]

Excellent work as usual Sir.

My 'Earl' is now almost complete from the waist up with a little bit more lining to do tonight, then varnishing & fixing the deflectors over the weekend.

I must admit to being bit daunted watching your valve gear conversion (not least because I have to look up each component's name whilst reading it through) as I've never tackled Walschaerts before, but hopefully it'll be ok in the end if I take my time & follow your lead.

Cheers