7mm Mickoo's Workbench - Connoisseur 4F, JM LMS Garratt - Martin Finney 47xx - MoK Ivatt 4MT

Discussion in 'Area 51' started by mickoo, 8 September 2018.

  1. mickoo

    mickoo Western Thunderer

    Little bit of bench time today on the Garratt, brass gets really tarnished if you put it down for a while......

    Couple of shots before the replacement parts.

    Cab.

    IMG_9234.jpg

    Boiler frame/brake hanger stay.

    IMG_9235.jpg

    New cab sides, rear sheet just plonked on for photos, the cab rear sheet needs a big circular hole adding in, the kit would have you add a simple circular sheet strip to the correct diameter to the rear outside face....and leave the middle solid....not happening.

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    A bit better I think, should look okay once the rear wall is secured, door added and roof fitted.

    New boiler frame/brake hanger stay.

    IMG_9240.jpg

    The smoke box base is a disaster, why there are two slots cut in the wrapper I do not know, it'll need some sort of 3D casting printed down there; I'll need to finish the front engine frames with at least wheels to check clearances before working something up.
     
  2. mickoo

    mickoo Western Thunderer

    Couldn't resist, all seems to fit okay, will finish the other riveted strap and rear door tomorrow.

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  3. Lancastrian

    Lancastrian Western Thunderer

    Mick,

    So a micro solenoid to open the front damper ?

    Ian
     
  4. mickoo

    mickoo Western Thunderer

    No..........:p
     
  5. mickoo

    mickoo Western Thunderer

    End of weekend update, most cab work and finishing off the ash pan etches, some small fiddly bits to fit, some brackets and the damper linkages to finish off.

    Test fitted pipework and raw white metal castings around/through the ash pan, it fits where it's supposed to fit. Now it just needs cleaning up, tweaking and final fitment when the rest of the pipes are sorted.

    Cab openings need a strap across the top of the doorway, then the roof can be formed and test fitted.

    Doors to follow later, missed a trick and should of added them to the supplementary etch, not an issue, I'm sure there will be more going off in the future ;)

    I know for certain I'm going to need to add the engine frame doubling plates, four of those is going to take up some real estate and being as they are external, thus visible, really do need adding.

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  6. Dikitriki

    Dikitriki Flying Squad

    Mick,

    Fantastic work - the new firebox etc is superb.

    I wonder whether the two cut outs under the smokebox are to give increased clearance for the flanges on the leading engine unit?

    Richard
     
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  7. mickoo

    mickoo Western Thunderer

    Cheers, I'm rather smug with the etched doors truth be told, such a simple up lift has big visual benefits.

    Slots, that's something I hadn't considered and I really hope not as it'll leave no room for the saddle and steam pipe connections. I did a quick measure and it'd have to be 3'-1" gauge if they were clearance slots :D

    Having said that, it is going to be tight up under there and the pivot is between the intermediate and rear driver so there is going to be rear end swing clearance required. I'm actually more concerned with the rear drivers clouting the inside of the boiler bed plate, than I am them impacting the smoke box.

    Image1.jpg

    The crop does show that the smokebox slots do align with the rear drivers, the crop also shows the external doubling plate over and around the intermediate driver on the engine frames.

    I've got a niggling feeling that the pivot point on the engines will not be fixed, I'm going to have to develop some sort of sliding pivot block with side control; then add discreet pegs to the boiler bed plate that impact the rear inside of the engine frames and prevent the drivers shorting on the side frames.

    An added bonus is O fine gauge which will give a few more mm to play with, but does bring the rims closer to the smokebox base. There's also a real risk of the rear driver rims shorting on the underside of the boiler frame footplate if the engine goes over any humped track of any significance.

    Still, all that is way ahead in the future.
     
  8. Scale7JB

    Scale7JB Western Thunderer

    Great stuff Mick, makes me want a Gladiator U1 more than ever. :rant:

    JB.
     
  9. Sparky

    Sparky Member

    All looking good so far Mick.
    Thinking of the pivot points, there needs to be a measure of `flex` along the length of the whole loco.
    I overcame this by making the the bushes on the front and rear units pivot. It only needs a couple of millimetres, but otherwise, the whole thing becomes one very stiff chassis.
    Clearance for the wheel flanges hasn`t been a problem so much as the rear chassis member on the front and rear loco units catching the underside of the centre unit framing. Needed some judicious fettling each time (I`ve built 3 now :confused:)
    Turns into an impressive machine when finished.
    Poacher Bob
     
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  10. Oz7mm

    Oz7mm Western Thunderer

    There's a Garratt here...............................

    John
     
  11. mickoo

    mickoo Western Thunderer

    Excellent, thanks for the advanced warnings.

    I did wonder how I was going to add some flex in the longitudinal axis, I reasoned to make the front pivot with little or no rolling axis play, then make the rear pivot a sort of gimball affair; thus allowing the rear engine to roll independent of the front and boiler frame.

    Though given the rotary bunker protruding into the cab, it may pay to gimball the front pivot instead.

    MD
     
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  12. Scale7JB

    Scale7JB Western Thunderer

    Would the MOK bogie gimball thing work?

    JB.
     
  13. mickoo

    mickoo Western Thunderer

    Yes it would and something like that is what I have in mind :thumbs:

    Just need to machine it up and work out some sort of retaining method that allows the engine to be separated from the boiler frame easily.

    I may gimball the rear end as well but add side bearing pads, they will prevent roll but allow pitch movement of the engine.
     
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  14. Lancastrian

    Lancastrian Western Thunderer

    Mick,

    I've modified two of Dave's bogie pivot pins for the Schools class(s) so that I don't have to use the cir-clips.

    [​IMG]

    Top turned down a few thou, then drilled and tapped to accept a 12BA bolt. This allows the bogie assembly to be dropped out without having to try and remove a cir-clip which is difficult to get too under a frame spacer. The frame spacer has a hole drilled to allow the removal of the bolt through the top. The nut and washer allow a degree of adjustment for the springing.

    Ian
     
    Last edited: 25 August 2020
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  15. simond

    simond Western Thunderer

    Mick,

    you need to pivot (yaw) at both ends, rock (pitch) at both ends, and roll (roll) at one end only.
    In building my much smaller (0440) Garratt, I took some inspiration from Giles and Phil who are ahead of me in many ways...
    I would tend to allow roll at the front unit, and prevent roll between the rear unit and the boiler, as you suggested, as the clearances are less.

    atb
    Simon
     
  16. Lancastrian

    Lancastrian Western Thunderer

    Mick,

    Just had another thought, you could also invert the MOK bogie pivot assembly if space is an issue.

    Ian
     
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  17. mickoo

    mickoo Western Thunderer

    Ian, cheers, whatever option I choose it has to be accessible from below, from above would leave big holes in the front and rear decks.

    I need to, at a bare minimum, partially make up a set of frames with the pivot stay tacked in to visualise how it all might work.
     
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  18. mickoo

    mickoo Western Thunderer

    Cheers, that sounds pretty much how I was planning to do it, just need to make sure reality meets expectations :D
     
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  19. mickoo

    mickoo Western Thunderer

    Good news, the H38 etches arrived before the weekend :thumbs:

    Hopefully make some good progress in the next three days, it's a back log project so it'll leapfrog the Garratt to completion.

    Not sure why the etches are coated in Marmite :eek:

    There's basically three large sub assemblies, chassis, exterior body works and interior, the bogies have already been made by a third party so just bolt on. There's a few items to 3D print, namely gas tanks and battery boxes, nothing too untoward.

    The roof is a preformed alloy affair, it requires some form of fixing and of course, roof fittings to complete.

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    The only elephant in the room was forming the curved sides over such a long length, yes there are those that can do this with whittled tree branches and moss underlay, but for the inept like me, a set of rolling bars would be required.

    There are essentially two types of rolling bar, those used by modellers to form boilers and such fine hand crafted ornaments and those used to roll battle ship bilge plates by men in stove pipe hats. In short you go from too small for the job (coach side) to bloody enormous, guess which ones I bought :p:eek:

    To be fair, most suppliers only stock 12" or 24", one other I found does do 12", 16" (about 17mm too small for a coach side), 20" (order by request) and 24". An ideal size would of been 18".

    Being as time is sort of critical then it'd have to be 24", measurements were duly made, spaces cleared in workshop, etc, etc. What I failed to account for was the additional combined 16" of overhangs for gears, arms and other gubbins.

    IMG_9257.jpg

    Quite clearly just too bloody big, exceedingly heavy and not cheap. Still, they only need to roll two coach sides and interiors to perfection and they will have been worth while. Clearly they cannot live indoors so will have to be wrapped up and moved to the garage and quite frankly are only really any good for coach sides and maybe larger items unforeseen in the future.

    I'll now have to get another smaller set for the workshop, again these will be pinch rollers and the trusted pyramid rollers will be stood down, good as they were, their imperfections (some the result of the inherent pyramid design) were being to niggle me.

    In better news, the new vice was much better suited to it's new environment :thumbs:

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    I've existed with a small watchmakers vice I believe it's called, great for small pieces but no scope for larger fold up etches like cabs or long deep pieces like footplates, I needed something with a bit (lot) more throat clearance, a woodworkers vice would be ideal, but like bending rolls, seem to come in only two sizes, too small, or way too big.
     
    Last edited: 29 August 2020
  20. richard carr

    richard carr Western Thunderer

    Nothing wrong with that vice Mick, it looks just like mine.

    I do find that those jaws are pretty useless, some aluminium angle works far better for me.

    Richard
     
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