small overhead crane question

Discussion in 'Structures' started by skyraider, Nov 7, 2018.

  1. skyraider

    skyraider Member Frisco.org Supporter

    If any of you have any experience with block and tackle or hoist mechanisms, I'd appreciate your input. I'm building a Durango Press small overhead crane kit. Photos are attached. NOTE: if anybody decides to build one of these, contact me first to avoid several headaches that aren't covered by the instructions.

    It's a hand operated hoist. You pull on one side of the long chain loop to raise a load; you pull on the other side if you have to get the hook back down with no load. The photos don't seem to accurately depict how the chain would be "threaded" in order to make it operate correctly. The two photos of completed models aren't mine. They are shots I found while doing research attempting to figure out how to build the model.
    There's a small pulley on the same side of each large gear. The chain should use these pulleys, but doesn't seem to in the photos.

    If anybody can steer me in the right direction on how to thread the chain, I would appreciate it.

    Paul Moore
    durango single hoist 2.jpg durango single hoist.jpg DurangoPressOverheadCrane.JPG IMG_4359.JPG
     
    Joe Lovett likes this.
  2. klrwhizkid

    klrwhizkid Administrator Staff Member Administrator Frisco.org Supporter

    Paul, I don't believe they have an accurate representation of what would be workable;
    There would be a loop of chain that is manually operated. That loop would be connected to the outer circumference of a large pulley. There would be a smaller gear that would part of that large pulley. The smaller gear would drive either a similar size gear (for spacing needs) or a larger diameter gear (for mechanical advantage. The larger diameter gear would have a smaller gear attached to it that would then drive a large gear that has a pulley attached to it onto which the chain passing through the block would wind. Just think in terms of Drive to driven:Large to small to gain mechanical advantage.

    At least that is what it looks like they were attempting to represent, but I think the designer did not really understand the concept.
     
    Sirfoldalot and skyraider like this.
  3. skyraider

    skyraider Member Frisco.org Supporter


    Keith,

    Thanks a ton. This morning I spoke with the model manufacturer's owner and he pretty much said the rigging is just for modeling representation. There's lots of stuff missing to make it truly realistic. They just used whatever castings they already had for gears and pulleys. What you said is absolutely correct.

    As a result, I finished it with the rigging it has and didn't attempt to do anything additional. This tiny model took more time for what I got out of it than anything else I've ever built! It also required more head scratching than just about any other model I've attempted. It needs details, and a little more weathering and more cinders and dirt to make the base fit the area so there's no gap under the base. It will eventually have a flat car under it with a couple of people unloading it.

    Paul
    IMG_4363.JPG IMG_4368.JPG IMG_4371 copy.jpg IMG_4372 copy.jpg IMG_4373 copy.jpg
     
  4. Sirfoldalot

    Sirfoldalot Frisco.org Supporter Frisco.org Supporter

    BOY! I'm glad that you two sorted that out! I could see what was needed to make it prototypical, but wasn't looking forward to trying to put it into writing. Keith - you did a fantastic job .. :)
     
  5. skyraider

    skyraider Member Frisco.org Supporter

    It's a lot easier to just ask a question than type it, isn't it? Keith and Sherrel, Friday I called the manufacturer to see if there was something I was missing. There's not. Durango Press's products are usually a model of a specific prototype. This crane is just a representation of a small overhead crane. As a result, it is missing several components to the rigging. They used off the shelf castings that they had already made for other models and just threw some stuff in a box and called it a crane. For most folks, it's sufficient.

    One more shot. I think this is where it will be. It is near a grade crossing so something could be lifted off of a flat car, the car moved forward, and a truck backed under the crane for offloading. Or the opposite could be done. This week I will create a sling and have the crate- or something else--suspended by the crane. A couple of workers will be added. IMG_4378 copy.jpg

    Paul
     
    Last edited: Nov 12, 2018

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