An NSR Absolute Block instrument

Discussion in 'Miscellaneous & Oddities' started by Andy_Sollis, Aug 5, 2023.

  1. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    I wonder if @Rob Pulham has any thoughts on this brass post? Repair or replace.. having thought about it, a 3D printed one will be OK with the bell initially mounted upright and the weight pushing down, but when eventually it needs to be hung and the box is rotated 90
    Deg, I’m worried the weight of the bell dome may pull the resin still? If nothing else… it will be a test of the resin!
    (Still trying to match the thread..
    Adrian crafter came back to me on threads for the bell post and the hammer rest…

    “I would have thought from the photograph and knowing how it works, the
    hole in the Hammer Rest would be threaded. The size would suggest 1BA. The
    thread on the top of the Bell Post (pillar) is either 0BA or 1/4" Whit
    judging by the size, most probably the 0BA size as that would be more
    normal.”)
     
  2. Mossy

    Mossy A classic grump Yorkshire man Full Member

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    Andy

    I think you maybe worrying to much about the strength of the resin. After all your not going to be striking the bell with a sledge hammer or are you?

    Mossy (yes still alive just snowed under with a mixture of household and dad can you just jobs)
     
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  3. Walkingthedog

    Walkingthedog Full Member

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    Think I would rather have a metal part than resin. Nothing to do with strength, it would just more accurate. I still think it could be straightened by squeezing it in a vice.
     
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  4. Mossy

    Mossy A classic grump Yorkshire man Full Member

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    I would agree Brian but if all else fails or is a stupid price, then resin would be a cheap cheerful alternative and multiple copies could be on hand in case there was a failure.
     
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  5. Walkingthedog

    Walkingthedog Full Member

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    Good point Mossy.
     
  6. Keith M

    Keith M Staff Member Moderator

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    Could you drill a resin one and use a longer bell post straight through the resin and the wood casing, nut & washer on the back? That way you'd have the appearance and the strength needed. Nowt to lose by attempting to straighten the bent original though I believe brass work hardens so there's always a risk of breaking it, nothing ventured, nothing gained........
    Keith.
     
  7. Rob Pulham

    Rob Pulham Happily making models Staff Member Administrator Feature Contributor

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    Hi Andy,

    I did have a look when you first posted the renders, and I had intended offering my thoughts. But I have had my head down doing the preview video for my Gauge O Guild and evening with appearance, so I had missed the photos of the actual part until this morning.

    Subject to having actual dimensions and the thread size, the whole thing ought to be relatively easy to replicate in brass. Is it possible to separate the stem from the base and the collar that it sits in?
     
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  8. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Hi Rob,
    No I quite understand folk have other things going on, we all seem to be focused else where the last month.

    I’m not sure they actually are two parts? Although the bottom has been drilled and threaded, but Peter has had a similar one and not succeeded in separating. And I would suspect, would it not have had a grub screw or similar to retain if so?

    I have done drawings.. I’ll see if I can attach them. Although I posted above re threads, I’ve not yet had any taps or die to confirm.

    Ive added some photos of the bottoms of the bell post and the wrong hammer rest I was sent (too small and wrong shape) both have the same inside drilled out and threaded. I wonder if this was for securing in a lathe?

    IMG_7181.jpeg IMG_7182.jpeg IMG_7183.jpeg IMG_7184.jpeg IMG_7185.jpeg

    You can see where Peter had tried to grip it and damaged the surface.
     

    Attached Files:

    Last edited: Mar 27, 2024
  9. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    There doesn’t appear to be much in the way of spares. Hence working on these bits first. I still need to make the hammer rest.

    even I could probably do it with someone reminding me on a lathe, but alas, that’s a tool I don’t have.
     
  10. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    The final bit of “to make” items as I can’t seem to get anything close off the shelf is the beading for holding the glass in to the front of the top over the block instrument.

    Peter has found some that had been recovered at some point, kindly sent me a photo and the measurements and also sending a sample in the post, but, whatever it will be a make up part.
    IMG_7208.jpeg
    Turns out it’s more triangular shaped. I was suspecting a flat trim with a rounded top, so it came as a surprise. I’m suspecting the angle to the front matches the chamfer cut on the part the other side of the glass.
    IMG_7209.jpeg
    So, now we know.. here’s to making some small wood strips.
     
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  11. chigley

    chigley Full Member

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    wickes homebase etc finishing strips, they keep that type of edging

    Ken
     
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  12. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    I’d already checked B&Q and the local timber merchant.

    father in law has now made me some out of Sapele which I’m hoping will match in. Cost me nothing as come from some scrap off cuts.
     
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  13. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    The sample piece of wood has arrived, but looks like it got snapped in the post in to 4 bits. Oh well. I’ve managed to glue it. Now to cut my strips and see if I can recreate the shape.
    IMG_7250.jpeg

    I’ve also finally managed to get in the lock for the bell box, so can look at a key. However I still need to work out how to re do the catch part that they lock over.
    IMG_7251.jpeg
    in the end I’ve had to drill the screws as it appears the ends had been peened over or milled. I managed to free one a few weeks back, but a screw 2 was not having it. I’d charged my drill yesterday and thought I’d just give it one last tickle. There was a small gasp of horror when the drill bit suddenly gripped something and stopped and then went again. Seems it had bit in to the screw and actually undid it for me. I was then worried I may have drilled away the thread in the brass back plate, but upon swapping the screws over side to side, they both bit back in and hold it secure.
     
  14. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    The last few days have been spent cleaning up items on the original lower half of the block instrument internally. There are a number of metal wiper contacts and metal terminal blocks that mary together to produce the contact system behind the rotary dial in the lower door.
    IMG_7617.jpeg
    here we are part way through. Hopefully you can see the difference with the colour of most of these, the verticle one that sits on a square of what appears to be Bakelite has come up nice.
    Some bits may be revisited as not all have come up that well… the old soak in coke doesn’t seem to like this metal.
    Anyway, like BR, we’re getting there!

    IMG_7618.jpeg
    the lower left plunger was looking rather grubby so I decided to loosen the three bolts that secure it and slide it out. For some reason it was dull and green tinged. I decided to use some metal polish to clean it up but it didn’t do much. It also had a rub of Coca Cola (none diet or cherry version) but again didn’t do much.
    IMG_7619.jpeg A while back I purchased some metal polishing mops. Not quite what I was expecting as they are more gritty than the white ones.
    IMG_7683.jpeg
    I have no idea as to the reasons for the red green yellow and black colours, but the black one seems to polish up the metal quite well.
    IMG_7681.jpeg
    IMG_7682.jpeg

    Refitted and looking much better (photo doesn’t actually do it justice! It’s almost mirror finish on that front flat surface. I nearly wondered about doing a quarter segment like they do with buffers!

    finally, re the bell box, Peter has tonight found and offered me a replacement post for the bell. This will save some time and cost of materials and getting a new one turned up. So we are just now looking at the hammer rest to the recreated. IMG_7685.jpeg
     
  15. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Today’s failed focus has been on trying to separate the main plunger on the front which connects to the selectors and comutator inside.
    IMG_7689.jpeg

    As it starts, a screw in the end knob, which then twists off the shaft by thread.

    on the main handle part is a screw, once removed this allows the circular area to also unscrew and slide back over the shaft.
    IMG_7687.jpeg
    somewhere in there is a big hefty spring. But it needs to come forward, but that’s all held from within. The black area seen below is the rear of the window with the Train on Line/Line Blocked/Line Clear labelling which needs to also be restore.
    IMG_7690.jpeg
    moving inside the door there are 4 screws in this collar, although it’s not yet clear what they are holding. IMG_7688.jpeg Although the commutator is shown in place here, it’s just the large central screw securing it to the brass disc behind.
    However this is my stumbling point as the brass disc needs to come off.
    IMG_7692.jpeg all I can find is that it’s on a pin, which I’ve knocked out - but alas, nothing else moves. That disc seems to be well secured to the square shaft!
     
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  16. chigley

    chigley Full Member

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    It's good to see you trying to keep the originality of it Andy
     
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  17. Rob Pulham

    Rob Pulham Happily making models Staff Member Administrator Feature Contributor

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    Hi Andy,

    Try getting some white vinegar and giving the stubborn parts a soak overnight in that. I have had great results on all sorts of metals - a bonus is, it's not sticky like coke.
     
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  18. chigley

    chigley Full Member

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    Filling an old seized engine with coke is cheaper:avatar::avatar::avatar:
     
  19. Walkingthedog

    Walkingthedog Full Member

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    Blimey can you get coke cheaper than white vinegar?
     
  20. chigley

    chigley Full Member

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    Tescos etc own brand
     

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