Overhead Crane – I

Synopsis
A while back I was working on Branstetter Hardware with the intent to build an overhead crane to transfer between the loading dock and either/or truck and rail. Since that time the design has evolved some – such that it became more and more a 3D printing project. I’ve decided to pull out of the design portion of the Branstetter Hardware thread and stick it here by itself since this has become an ‘Overhead Crane’ project and not just part of the Hardware build.

At some point I may move more/all of the crane portion from the Branstetter Hardware build .. or not. Time will tell I suppose.

Source Info
drawingProbably the greatest source for me for such things as this is Google Books. In a book titled “The construction of cranes and other lifting machinery1 by Edward Charles Robert Marks, published 1904 we have, if nothing else a great source for inspiration. Chapter XII, Overhead Traveling Cranes, the first drawing provided that inspiration for me.
pinionRussel Greene pointed out that I had flipped the crane travel gears .. that the smaller pinion gear needed to be on the shaft with the larger gear on the wheel shaft.

I zoomed in to the drawing .. and yep .. he’s right. Green is the chain pulley and red the gears. I drew a line at the top of the shaft gear, one below at same distance and one at the bottom of the large gear. Obvious once it is pointed out!

Earlier Design
working_2Using that rather weak drawing as a guide, I came up with my early design. Here, everything was based on using stock Evergreen structural shapes .. Evergreen #276 3/16″ I-Beam for the main beam; Evergreen #266 3/16″ Channel; Code 55 rail. This was my starting point .. at that which basically stalled when I found that it exceeded my abilities .. and so it sat there looking at me for a good while.
Some Numbers
From the book:
The movable bridge consists of one or two cross girders, according to the load and span, secured to end carriages each of which is mounted on a pair of wheels. For loads not exceeding three or four tons, and a span not greater than 16ft. or 18ft., the cross girder may consist of a single rolled iron joist of I section. The span is the distance measured from centre to centre of rails. A 3-ton traveller, for a 15ft. span, should have a 12in. by 6in. rolled iron joist – that is to say, a joist 12 in. deep, with two equal flanges 6in. wide, and a weight of about 56lb. per foot; this will allow of ample margin for strength and stiffness. With a rolled steel joist of the section named the weight need not exceed 45lbs. per foot.

My version measures 78mm/3″ (148″ full size) between centers of the rail, or a little over 12ft. full size The cross-girder is made from Evergreen #276 3/16″ I-Beam. The I-Beam is relatively over-sized but works ok. The flange width is .093″. Scaling up this gives me a flange that would be 18″ x 4-7/16″. Just a WAG on my part says that the slightly narrower but taller I-Beam should substitute for the 12″ I-Beam in the text.

Early Renderings
rendered1Here’s an earlier rendering of the carriage. The angles at the top will surround the Evergreen #276 I-Beam.

I hadn’t closed off the ends of the journals in this rendering yet. Looking at this I decided to make the Journals separate prints and close off the ends. That way the wheels could be slipped up between the channels, the axle inserted and then then journals to secure everything.

rendered2Here, I made the journals separate pieces. There is a short stud with a flattened side that locks into the matching hole in the channel.
rendered3A sectional view of one of the journals. On the left is the mesh as created to 3D print. The right view I filled in everything as if it had been sliced in half.
rendered4Here I put everything back together. The Evergreen beam is at the top, journals are in place as is the wheels (you can’t see from this angle) and a bit of the gearing.
rendered5A look from the end shows a lot more .. wheels, gears, pulley
rendered7Finally the pulleys, gears and journals arrayed on sprues for printing. I have successfully run the meshes through MeshLab and NetFabb and have good meshes. The rendering has the sprue in gray and parts in brass .. this is simply because it renders nicely in these ‘false’ colors.

  1. The construction of cranes and other lifting machinery By Edward Charles Robert Marks []

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