Hornby class 31

Discussion in '3D Modeling Projects' started by Andy_Sollis, Jan 17, 2020.

  1. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    So you may wonder why is this under the computer aided modelling section?

    sadly, I was a purchaser if one of the first batch of the revamped Class 31 back in the early 2000’s. The first batch, unknown at the time had an issue with the metal used in the chassis where it resulted in a slight swelling or distortion and brittleness. After having laid mine up OK, I came back to it a year or two later (it was in my dads loft after I moved house) I found both the floors under cabs had gone brittle and at one end the full chassis floor had cracked and come away...

    BC3BD8AF-2B93-43B8-A7AC-CF9C7C12490B.jpeg

    the broken parts.
    6C01C995-E068-4AC2-80E4-E7A35414DDF1.jpeg
    missing front of the chassis.
    AD3088E8-311D-4481-89DA-7EAFD8BF1C4D.jpeg
    cracked front of the cab (now glued back up)
    0272C80F-1847-4C78-A87E-B19C5531F7DE.jpeg
    crack on other side of the cab under repair. It should be flush all the way along. This was a weak point due to a panel line behind for the doors.

    As it’s now over 10 years since purchase, Hornby now have no interest as it’s not under a warranty. Earlier customers got replacement chassis blocks.. how long should one of these models last???

    As this loco cost me over £80 when new, I came to the conclusion it was a lot to just now skip, so I’ve set to with the 3D designing to see if I can make this in one of the plastics I print my models in. There will be a lot of measuring and testing, maybe even some costly waste parts if it’s not right first time (it’s not something I can print at home and WILL need an industrial quality printer to make it on.) but I’m going to give it a go and see if I can’t recreate the parts and return the loco to service.
     
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  2. Chatty

    Chatty Full Member

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    Andy

    I am looking forward to seeing how you progress with this project. Please keep us posted.

    Kind regards

    Geoff
     
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  3. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    So, we move on to the next stage, the 3d artwork.

    This is probably one of the most ambitious designs I've undertook since... the last one... (working O gauge crossing gates, OO PAA wagons... er…)

    Anyway..

    Here is the initial floor plan, where the contacts screw to for the head and tail lights. Mine only carried tail lights as the route box lit up in the roof.
    Class 31 1.jpg
    The square indents are where the wire runs go, the chamfered holes are where it screws to the plate below (see next post) and round stubs are either locating posts for parts or where a screw secures. The slots at the front I believe are to locate the cab floor.

    Class 31 2.jpg

    This is the next part and is very much still a work in progress - there are parts to extrude from this and also holes to cut in the middle for the coupling pivot - so this is the next stage I'm working at where the biggest tests will come. it will also have a the buffer beam on the front which again, I will have to design.

    Class 31 3.jpg

    Finally, here are the two parts together - The chassis in the lighter grey and the floor panel in the darker.

    Andy
     
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  4. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Thanks Geoff, It may be a slow burner, but thankfully, I'm not expecting it to cost the earth. It may be around £10 when done, but don't quote me on that.

    Andy
     
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  5. York Paul

    York Paul Staff Member Moderator

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    I suspect Hornby used a zinc alloy to die cast these parts out of, the trade name of which I forget but the metal composition is quite brittle and is also susceptible to corrosive pitting if exposed to water vapour, old Dinky and Corgi cars were cast using a similar zinc , copper and tin composition. I once had a Class 47 and the chassis snapped in half on both sides where the bogie swivel points were. That was quite an expensive loco in its day too... put me off buying their stuff forever.
     
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  6. York Paul

    York Paul Staff Member Moderator

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    Goodness me really ??? Mr S the last one you designed was my Tunnel name boards last night :avatar:
     
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  7. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Hardly tasking that though. This took me 2 hrs, your boards took the time we were conversing, but non the less enjoyable.

    Mazak ?
     
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  8. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    I've sat and made a little progress. Still the V inside the frame for the coupling pivot and the buffer beam to draw.

    Class 31 4.jpg

    9777BE1A-2924-47BA-893E-9E4B07368589.jpeg

    Class 31 5.jpg

    898B7414-83F0-447E-9D24-D06EBF69C279.jpeg

    The legs to the left (that go back to the chassis - I may make over length then anyone who may choose to have a go at this if I'm successful can trim/file them to the correct length they need. Still another 2 holes to locate too where the buffer cowl screws in.

    Andy
     
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  9. York Paul

    York Paul Staff Member Moderator

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    Only kidding Mr S... those boards look the biz and the order is now placed. Mazak was the trade name I believe.
     
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  10. Chatty

    Chatty Full Member

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    Andy

    What CAD program are you using?

    Geoff
     
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  11. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Autodesk 123D design
    - Its an old program bow that has been superseded by Fusion 360 but I cant get to grips with that...
     
  12. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    So the top half is complete, I'm now progressing on to the buffer beam. have to say, it took some doing - but even measuring with the micrometre it seems Hornby stuck to everything being either a full or half millimetre size or thickness, which made it so much easier.
    Class 31 6.jpg
    Lots of small parts to model on here such as the buffer and coupling mounts, vac and air pipe holes and also ETH socket and a few other detail cut-aways,

    Class 31 7.jpg

    But as the main layout is complete, I have been able to test up the final model ready for print - this includes any parts that may be too weak and gives me a final price. At the moment its's actually coming out at just over £10 which I'm a little surprised and disappointed at, but its not available anywhere else.
     
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  13. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    I will obviously need to do a test print myself first to check for alignment and any errors that need correcting. then we can look at the prototype being made available to the public. So at minimum we will probably be looking at April.
     
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  14. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    So after back tracking after finding some flaws in my measurements, I've completed the design work. The front had for some unknown reason become 4mm too large (found when I checked the buffer beam) so was shrunk. Further checks showed that had thrown out the locations of the holes for the screws, so again, remeasure and start again (using a totally different cunning plan and mirror designing to get the correct spacings.
    Class 31 8.jpg

    The two complete panels.

    Class 31 9.jpg

    The two separate panels, the right had one has the shaping for the coupling V to swing - Only upon printing will I know if I have it correct :facepalm:

    Class 31 10.jpg
    And from the underside, showing the rear of the buffer beam and cutaways again for the coupling and the sprung buffers. I sadly lost one of the fine circlips that secure the buffer springs in place.

    So, were on hold now till pay day, when I will press the order button.. I've also change the packaging layout so the 4 panels are stacked as opposed to laid out, which would you believe, save £2 of the printing price. Unbelievable Jeff!!!! (Sorry Geoff).

    And whilst working on my loco today, the other end snapped off. So the full kit will not go to waste.

    Andy
     
  15. SRman

    SRman Full Member

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    Brilliant stuff! :)

    I got a replacement chassis, but would still seriously like to get your replacement parts when you are done, anyway (future-proofing!).
     
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  16. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    I found today I have a very slightly curved chassis now. May get away with it. For £10 or there abouts, it’s worth taking the punt!

    andy
     
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  17. York Paul

    York Paul Staff Member Moderator

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    Excellent Andy ! Its horses for courses I guess...wouldn't know where to start with something like this.:tophat::tophat::tophat:
     
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  18. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Paul, if I can make these cock ups with a micrometer and then typing it on to the computer (the size specs) then I can see how your Ivatt tank kit can go of kilter. You’ve done a splendid job with that, I’m just hoping I can resurrect some of this model...

    Any suggestions for sticking the plastic to the metal? I wonder if it’s worth drawing in a locating pin and then drilling the metal chassis (risky given its fragile state) or just gently grind the broken area back flat with a dremil?
     
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  19. York Paul

    York Paul Staff Member Moderator

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    I'm not sure Andy it depends which plastic you are gluing to metal, if its printed resin plastic then maybe cyano Roket Max is as good as any but you only get one shot in getting right because if you move the setting parts then the glue fails and you have to clean the hardened residue away before regluing which never seems to be as good second time around. I'm very sure you will pull this one off successfully, it just takes a bit of trial and error.:thumbs::tophat:
     
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  20. Keith M

    Keith M Staff Member Moderator

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    Araldite 'Rapid' should do the job Andy, especially if you score both surfaces to give a good key for the adhesive.
    Keith.
     
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