Finney7 LSWR L12

Discussion in 'Workbenches, including workshop techniques.' started by Dikitriki, 22 August 2017.

  1. Dikitriki

    Dikitriki Flying Squad


    Chassis is just about ready for the wheels now. I've attached the driving wheels springs to retain the hornblocks. The rear ones are soldered on, the front ones are screw on so I can drop the inside valve gear. I have checked that our new style cranks and 4 eccentrics fit between the hornblocks, and they do with nice clearance to spare; so no problems getting the inside motion in:thumbs:.....other than putting it together in the first place:)

    The front driving axle springs are coil, so I had to solder a plate to the bottom of the casting and sections of angle to either side of the hornguides. The angle was drilled and tapped 14BA.



    and with the overlay on and bearings in place.


    Wheels next, coupling rods and motor, then the inside motion.

  2. Steph Dale

    Steph Dale Western Thunderer


    Just a thought, but if you move your extra stretcher at the front to the bottom edge of the chassis then you won't have to fiddle about with the coupling to get the body on and off.

    The rest of it looks good. The production chassis will have a suitable retention on the main driving axle hornguide, much as you have done it.

  3. Dikitriki

    Dikitriki Flying Squad

    Good point Steph. It's obvious now you mention it!

  4. Dikitriki

    Dikitriki Flying Squad

    Major stage reached.

    The wheels are on.
    The coupling rods have been polished off. The etched oil corks were filed off and 0.5mm brass rod added in their place.
    The washer and nut retaining the coupling rods have been replaced with some etched representations from the test etch. Better than the Slater's washer and nut, not as 3-dimesnional as the cast ones.
    The gearbox and motor are fitted. The gearbox is an SDMP 40:1L and fits perfectly inside the compensating beams and without fouling the compensating rod across the chassis. The motor is one of our new powerful 1525 ones for smaller locos. It is retained by a strap across the chassis just above the gearbox, and has just enough movement for the compensation. There is plenty of room inside the body for this combination.




    I haven't tested it under power yet, but the chassis revolves freely without any binding.

  5. Steph Dale

    Steph Dale Western Thunderer


    Plain rods on your loco surely? The geometry should be robust to swapping them over. Trying both is good for the test build though. :thumbs:

    I'm pleased the crank pin nuts worked, it's worth adding to your comments on them that they're very close to scale thickness. They should be just over 1" thick, which makes the cast ones pretty monstrous.

    Recognising that this is a test build it'll be interesting to see how that 1525 motor works out. They've impressed me enormously but I still wonder if something a touch larger might suit, under the BR power classifications I suspect they'd have been class 3 or 4; ten coach trains were not uncommon.

    I must say, Richard, you are making this look very easy...;)

  6. Ressaldar

    Ressaldar Western Thunderer

    Great work Richard, do the instructions for the gearbox say to leave the cusps on?:)):))


  7. Steph Dale

    Steph Dale Western Thunderer

    Yes they do - several times!

  8. Dikitriki

    Dikitriki Flying Squad

    I shall build the other rods - I misinterpreted a photo. Still, I have made a start on a superheated L12 now:D

    The crank pin nuts work, and were easy to tap, but I'm not convinced by the definition. Cue horrible enlargement....


    I think there is room for a Canon 1833, though the excess spindle will need cutting off. I'll pick one up with a 15mm gearbox at Doncaster.

    If I am making it look easy, it's because the material I have to work with is darned good in the first place:thumbs:

    I am really looking forward to doing the inside valve gear. We have experimented with a printed set of brass cranks.



    In both pictures, the crank on the left is as it arrived, the one on the right has had the edges lightly filed back.

    I was interested to see how the printed brass material behaved. The answer is 'superbly'. Before I did anything whatever - not even any cleaning in preparation - I tinned part of the outside of one of the cranks (60/40 tin/lead) to see what happened and the solder flowed really well straight off. I then smoothed down the flat outside of the cranks - they exhibited very fine 'ripples' due to the production process - on wet and dry; a matter of seconds. Then I took a file to the outside of one set to finish them, and very quickly the imperfections disappeared. In short, it behaved exactly the same as any brass casting, in fact better than most, and requires much less effort in finishing.


    The eccentrics are our own machined examples. The only thing I don't know is whether Steph put a reamer through the axle holes and centre popped the hole for the wire through the eccentrics, or that's how they came.

    michl080, Wagonman, Pencarrow and 8 others like this.
  9. Steph Dale

    Steph Dale Western Thunderer

    That's an easy one to answer - the crank axle parts are exactly as supplied, in all cases. Hopefully we should have some more on this topic to show at Doncaster...

    Rob Pulham likes this.
  10. adrian

    adrian Flying Squad

    Now you see me being a bodger would just turn the rods around, even easier as a four coupled loco as they wouldn't even need to swap sides.

    The printed brass does look promising for certain components. Do you think it'd be able print fine detail accurately? i.e. rivet detail.
    Peter Cross and simond like this.
  11. Dikitriki

    Dikitriki Flying Squad

    I did think about turning the rods round:). However, 3 things mitigate against that. 1) My mindset! 2) Steph had asked that I build both sets of rods anyway to test the geometry 3) ...and the clincher, there's no bosses on the back.

    I don't know about detail on the brass printing. My first thought was that it didn't lend itself to really fine detail, as the surface finish mitigated against it, and clean up may be difficult.We won't know until we try, but it lends itself to bigger, flatter items like the crank axles which enables one-offs without going to the trouble and expense of moulds.

    Rob Pulham and Len Cattley like this.
  12. Scale7JB

    Scale7JB Western Thunderer

    Brass printing looks like it might lend itself to rods too..

    And they'd be accurate for the centres..?!

  13. Steph Dale

    Steph Dale Western Thunderer


    I promised you a dome, and this evening I've had time to do it. As a bit of vanity I even did the safety valves...

    20180515 L12 dome.JPG

    Backhead next :)

  14. Dikitriki

    Dikitriki Flying Squad

    Good stuff, though there's an odd looking 'crease' showing on the top.

    On to the inside valve gear. The first stage is the cylinder ends, slide bars and motion support bracket. The valve rods and crossheads have to slide smoothly without any resistance.





    The unit is screwed to the chassis cylinder spacer which has to be tapped 6BA.


  15. Steph Dale

    Steph Dale Western Thunderer

    Hehe, it's not a crease; it's a shadow! ;)

  16. Dikitriki

    Dikitriki Flying Squad

    First stage of the crank axle.


    Top is the right hand side looking from the middle of the loco to the inside of the right frame.
    Bottom is a similar view of the left hand side.
    There is a peg through the eccentrics and into the crank web to hold everything in its correct orientation. You just need to make sure that the axle can be withdrawn cleanly before soldering.

    Not cleaned up as there is some more microflame work to do. The black is chemical blackening. I put it on the eccentric outer bearing surface and the inside of the strapping hole so that if there is any stray solder seepage, it is not going to lock everything solid. It will all get polished up later.

  17. Dikitriki

    Dikitriki Flying Squad


    Next stage:

    The left and right units were fed onto the axle, making sure that the quartering was correct. The outside crank only was soldered to the axle, first one side, then the next. This gave me the chance to make sure nothing had moved as the units did revolve reasonably freely. I now had a solid unit. the cranks were drilled through crank and axle and pinned 0.8mm. The pins had to be forced in. At this stage, there is no chance of me dismantling the axle. On the otherhand, it's probably not going anywhere either. This is the stage I am at at the moment.




    Very messy, but no point in cleaning up. The last build operation is to solder the pins in, and feed some solder onto the inner crank/axle interface. Then a good wash and brush up. The drilling of the cranks is probably the most nerve-wracking part of the job - it's pretty much plain sailing from here.

  18. JimG

    JimG Western Thunderer


    I was thinking that that could be an operation fraught with problems, especially with a small diameter drill which could wander quite easily. Is there any possibility that pilot holes could be provided in the castings?

  19. Dikitriki

    Dikitriki Flying Squad

    Hi Jim,

    I'm sure pilot holes could be provided, but equally there will be people who silver solder the cranks and don't see the need to pin, so won't want the pilot holes.

    Stage 2 completed; the axle has been cut, the reinforcing pins between the crank webs removed, surplus solder removed, and the whole thing cleaned up. The eccentric straps revolve freely and all is well :)



    Now to put it all together to make sure it works.

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  20. SimonT

    SimonT Western Thunderer

    I suspect that pilot holes would be futile as the ridges between layers would probably grab the rotaing drill bit and snap it. I understand that 3D printed aero-engine components such as turbine blades still have the cooling holes spark erroded. We could try though!