3D Printed Lima Gear Replacement

Discussion in 'Workshop Benches' started by gormo, Dec 19, 2022.

  1. gormo

    gormo Staff Member Administrator

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    G`day Folks,
    I have had a Lima Express Parcels rail car for approximately 30 years now and in the last couple of years one of the small gears near the wheels failed.
    I have not seriously tried to source a replacement online, although they are probably readily available, so the rail car was placed in the pile with my other fixer uppers.
    The subject of the broken gear came up in conversation when I was talking to ChrisM a couple of weeks ago and at that time he offered to try and print a replacement for me.
    I probably did not emphasize strongly enough just how small the gear wheel is, so I probably shocked Chris when the part finally arrived at his door via the post.
    It was discussed further over the phone and Chris was keen to have a crack at printing it , just to see if it could be done.
    Chris tells me that the final product was testing the limits of his apparatus due to it`s small size and thickness.
    The original gear was carefully measured with digital calipers and the measurements transferred to a working drawing which allowed the part to be printed ( Resin )
    So this is the final product below and six of them arrived at my door today.......so I now have 5 spares.
    Thanks for the time and trouble Chris........the part is now fitted and working and there is a video below showing how it was fitted to the rail car


    IMG20221219164328.jpg




    :tophat:Gormo
     
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  2. Vinylelpea

    Vinylelpea Full Member

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    As as I mentioned on you tube, great to see these models given a new lease of life. My Bachmann shunter is still going strong with 3d printed gear. :thumbup:
     
  3. gormo

    gormo Staff Member Administrator

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    Yes I agree Phil,
    The older stuff is a bit more bomb proof than the new fine scale, delicate models.
    The new stuff is good to look at and it runs and sounds nice, but needs very careful handling so the little bits done get damaged and fall off.
    I have a limited budget, so I have to make do and hopefully improve the older models that can occasionally be had on FleaBay.
    :tophat:Gormo
     
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  4. paul_l

    paul_l Staff Member Administrator

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    Nice one Gormo and Chris, welldone on fixing a geriatric loco - any good with replacement knee's :avatar:

    Paul
     
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  5. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Won’t they be a little brittle? Not something I’ve ever considered?
     
  6. Chris M

    Chris M If 2 wrongs don't make it right ... try 3 Full Member

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    Hey Gormo,

    Great to see the gear worked. Be interested to see if the loco can pull a large consist up your grades without any issues. I thought you might be interested in how I set up the gears for printing.
    My first attempt had the wheels sitting flat on the print bed but they failed miserably.:faint:
    What did work was placing a fine support under each tooth (as shown in the pic).

    Gear 12 Tooth (Lima).jpg

    The only other issue is "will the gear last"? I think resin rubbing against plastic (nylon?) should be OK but I guess time will tell.
    Anyway ... great to see the Lima running again.

    Chris
     
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  7. Mossy

    Mossy A classic grump Yorkshire man Full Member

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    Chris, it sounds like a job for this newish ABS like resin. I'm waiting for a fat man with a large bear and an odd mode of transfer for mine to arrive fingers crossed.
    I'm hoping to use it for parts which are fragile and/or in places where they are easily damaged. Hopefully more news in the New Year.
     
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  8. paul_l

    paul_l Staff Member Administrator

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    Hi Chris

    Nice work, I'd also suggest putting a 0.1 or 0.2 mm fillet on the bottom printed edge of the gears, this has the effect of moving the supports in from the edge so less chance of the effecting the gear mesh.

    Paul
     
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  9. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    Bear? Beer? Whiskey!!! Brandy!!
    Or Beard! :cheers::cheers:
     
  10. Mossy

    Mossy A classic grump Yorkshire man Full Member

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    So pedantic, us old OAP's have fat finger disease, yes beard
     
  11. gormo

    gormo Staff Member Administrator

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    Not as far as I know Paul, you may have to get a new knee printed in Switzerland, a friend of mine has just had two done over there.
    :tophat:Gormo
     
  12. Vinylelpea

    Vinylelpea Full Member

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    Yes the 3d prints can be brittle, but also have a small amount of give before they break. I have used a 3d printed gear in my Bachmann split chassis shunter. Done a too distruction test lasted 45mins before falure. It wasn't the gear that failed but the 3d printed axle part at the wheel failed. About 3 months on the newly fitted part is still going fine.

    Phil from Australia
     
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  13. gormo

    gormo Staff Member Administrator

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    The great unknown at this stage.?.......will it last.?....well there`s only one way to find out and that is try and break it.
    I intend to give it a good run today at some stage and that will do two things.
    One ...it will effectively run in the new gear and Two...it may show if it is wearing or going to break.
    The other thing I will do is load it up with a train, even though this rail car would not normally pull a train, and see if that will break it....:scratchchin:
    :tophat:Gormo
     
  14. Andy_Sollis

    Andy_Sollis Staff Member Moderator

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    That is very encouraging!! Not something I’d thought of in resin..

    Maybe in some of the other prints offered by shapeways, such as the nylon etc..

    How are they with any lubricants?
     
  15. Chris M

    Chris M If 2 wrongs don't make it right ... try 3 Full Member

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    Hi Andy,

    You could never print this gear with an FDM printer ... it is just too small. So resin is really the only option with the current 3D printer technology. Lubricants should help and Gormo did add lubricant after installing the gear ... so we will see.

    Chris
     
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  16. gormo

    gormo Staff Member Administrator

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    G`day Folks,
    The rail car was running at moderate speed this morning for about half an hour.....fifteen minutes in each direction on the flat.
    I then attached ten wagons to it to try it up the incline, bearing in mind that when it was damaged and unladen and only driving on one axle, it couldn`t make it up the slope and would reach a point where it would sit and spin the wheels without moving forward.
    I filmed this mornings run to show the results.



    :tophat:Gormo
     
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  17. ianvolvo46

    ianvolvo46 Staff Member Moderator

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    :cheers::thumbup:
     
  18. Vinylelpea

    Vinylelpea Full Member

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    I use a food grade silicone grease. Seem to be fine. I use water based resin.
     
  19. paul_l

    paul_l Staff Member Administrator

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    For those interested, here is a video on the relative strength of the resins vs filament - spoiler alert the ABS like resins maybe the answer for the future.



    My HR Passenger tank uses some 3D printed gears and is doing better than the brass gear on the worm / wheel.

    Paul
     
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  20. Echidna

    Echidna Full Member

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    Dear Gormo, and others,

    the DRCs were only ever intended to hau equal to one or two vans, or one bogie vehicle, so the model is replicating the prototype in this instance !

    Regards, Echidna.
     

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