ATSF 4-8-4 3751 class

alister Mar 14, 2021

  1. alister

    alister TrainBoard Member

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    Still a little rough, just trying to get the proportions right. A lot of work to do smoothing everything out.

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  2. alister

    alister TrainBoard Member

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    Just applied some paint to see how bad it is, the second dome needs some work! The casting wasn't good - using old resin. I should really get some new stuff :)

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  3. alister

    alister TrainBoard Member

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    Found some drivers of the right size.

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  4. alister

    alister TrainBoard Member

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    Well that driver is just a little too big to keep the wheelbase within it's limits. I have cut up the mechanism from a Spectrum J 4-8-4 (severely modified)
    I will probably need to cut a little more off it.

    Picture showing light modification
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    Shell as it was - note the razor saw in the background
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    Chopped shell
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    Modified mechanism

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    Shortened Shell

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  5. alister

    alister TrainBoard Member

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    Just a note about the build, this is the original 3751 class 4-8-4 Northern which is shorter than the 2900, 3776 and 3765 classes and has 73 inch drivers not 80 inches and the model bears no real resemblance to the current restored 3751 in California.
     
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  6. alister

    alister TrainBoard Member

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    I've reassembled the mechanism to see how the shell sits. The mechanism needs to be shortened a little then possibly lowered some more.

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  7. acptulsa

    acptulsa TrainBoard Member

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    Looking at it that way works for modeling purposes. But if one were to set the historic record straight, one would say, same engine. She was thoroughly hot rodded in 1938, at the age of ten. So thoroughly that they basically hoisted the boiler and drove a new cast frame in under it.

    E.D. Worley said, officially they were the same engines, but to the yardmaster, the superintendent, their crews, and to anyone who looked at them before and after, they became different engines.

    Usually hot rodders change the engine out first. This class was the opposite. The boiler got a new, much longer smokebox attached to the front, but otherwise the class' boilers is about all that stayed the same.
     
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  8. alister

    alister TrainBoard Member

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    Yes it was heavily modified but if you look at the diagrams in Frank Ellingtons Steam Locomotives of the Santa Fe, A former shopman's scrapbook you will notice that the boiler lengths are a little different as well and those diagrams are what I'm basing my builds on, hopefully they are correct. If not I'll lengthen the boiler back to original Bachmann length and build a custom brass mechanism with the bigger K4 drivers, this will push out the driver wheelbase length but it looks really good.
     
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  9. acptulsa

    acptulsa TrainBoard Member

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    The 3751 Class unquestionably had/have shorter boilers than the 3765, 3776 and 2900 Classes. I don't have my copy of Iron Horses of the Santa Fe Trail in front of me to check the before and after railroad mechanical department tracings. Sorry. But my understanding is, the 3751s kept their original boilers (and very little else) over the years. That's why they were the road's only Northerns that couldn't operate at 300 psi.

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    Note the main differences are the sand dome and the smoke box length. The original smoke box placed the stack immediately ahead of the tubes.

    The boiler proper and tubes may well have been lengthened some, though. I'm not sure I'm seeing two full feet of extra smokebox length. But two feet was needed to keep the stack and cylinders ahead of four new box drivers each six inches larger. I do think I'm seeing about an extra foot of boiler proper and flues between the number boards and the smokebox seam...?
     
    Last edited: Sep 19, 2021
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  10. alister

    alister TrainBoard Member

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    Cool, this is the type of feedback that is gold. It's fairly difficult to get exact measurements etc when you live about 20000 kilometres from the country where your chosen locos are :D It's by posting my progress that I get to find out how close or not that I have come to getting it right. Looks like I'm going to have to get E.D. Worley's book too.
     
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  11. BigJake

    BigJake TrainBoard Member

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    Extending the boiler forward into the lengthened smoke box would have been difficult. I don't think a flanged seam would have worked well as a boiler extension, so the forward boiler diameter would've had to be reduced and carried forward inside the smoke box, thus compacting and complicating all the front-end tubes and manifold plumbing. And a bigger boiler likely would have needed a bigger firebox.

    Surely the original was already superheated, so the extra smoke box room for that plumbing up front is not likely needed.

    Like you said, it was probably just to get the cylinders (and therefore, their manifolds/plumbing) further forward to stay in front of the enlarged drivers.

    Is that part of a feedwater heater they added up front, forward of the shortened stack? Perhaps the extra space made installing one an easy improvement in efficiency. Whether that increased efficiency would allow the same firebox to run a bigger boiler, I'm not sure...
     
  12. acptulsa

    acptulsa TrainBoard Member

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    That's probably the same stack. The old photo shows the extension up, while in the post-restoration shot, it's down in low bridge mode. Yes, that's the Worthington feedwater heater in front of it, replacing the original Elesco and freeing up the pilot beam for pumps.

    A bigger boiler doesn't necessarily need a bigger firebox. A bigger diameter might create problems getting enough heat in all the extra tubes, but greater length mainly just soaks up a smidgeon more heat, improving efficiency.
     
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  13. alister

    alister TrainBoard Member

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    I chopped the mechanism and started adding putty to the shell

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    Attached Files:

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  14. alister

    alister TrainBoard Member

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    Gettin old sucks, just lost a mechanism spacer! ping on the floor in nowhereland. I've ordered 5 from Bachmann so I'm sure it'll turn up now. So much for getting it running today!
     
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  15. Shortround

    Shortround TrainBoard Member

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    That's how it works for me. :oops:
     
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  16. acptulsa

    acptulsa TrainBoard Member

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    Funny, I didn't have to get old before that started happening to me.
     
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  17. alister

    alister TrainBoard Member

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    I ordered some new parts from Bachmann for this and other projects, Bachmann duly sent the package to me but funny how things go awry. Whilst in transit USPS suspended all deliveries to NZ, so it got to San Francisco then did an about face and was sent back to New Jersey!. Oops! So now I have to wait for things to settle before my package with the needed parts can restart it's 20000 km journey again!
    I blame Murphy, darn silly law.... :)
     
  18. badlandnp

    badlandnp TrainBoard Member

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    Murphy. Yes, he is a close cousin of mine. Nasty fella. Don't much like him. Nope.

    :LOL::eek::eek:
     
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  19. MK

    MK TrainBoard Member

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    :ROFLMAO::LOL::D:)

    No joke, governor of New Jersey is Murphy!
     
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  20. alister

    alister TrainBoard Member

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    Wow that is a coincidence! Who knew!! Not me :LOL::ROFLMAO::whistle:
     

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