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The Hinged Plate for the Metal Brake.

The design I am going with for the small metal brake

The design I am going with for the small metal brake

The old statement is: “Why are babies small?” Answer: ” So they don’t have very far to fall while trying to learn to walk”.  The point of the statement is:  When trying to do something new it is always best to try to do it in baby steps;  small falls hurt a lot less than big ones.   Read, study, watch, learn, and then try something small.

I have been thinking through the goals of the sheet metal brake I talked about in the post “Thinking my way toward the ideal sheet metal brake.“.  The biggest goal is to learn some new skills and be able to make enclosures for electronics. I have a complete playlist on my youtube channel of metal working machines.  Many of those are advertisements for “the big boys”.  We are playing, so machines in the thousands of dollar ranges are not in the budget.  Also not in the budget is metal fabricating machines like milling machines so I can build my own brake.  So, where I am is cheap & dirty, one-of, experimental version – proof of concept design.   Just like that baby… I will probably fall on my butt and on the world wide web no less.   But what the heck… it is all fun.   “To do is to be” – Socrates.  (Much better than: “Do a doobe.” – Fox dumb joke.)

Picture of a door hinge I salvaged from an outside door I replaced.

Picture of a door hinge I salvaged from an outside door I replaced.

 

Anyhow, back to the problem at hand. I intend on making this out of hard wood, because I own wood working tools that can do the job and I don’t own metal working tools.  Back when horse drawn carriages and wagons were the transportation used, wheels were made out of wood.  An iron or steel band was placed around the outside edge to serve as a tire and take the wear.  This did two purposes.  First, it was expanded by heat and  once it was cooled and shrink fitted on the wheel it held the spokes and wood pieces tightly together to hold the wood in place and in compression.  The second purpose was to have a hard surface for the wear and serve as the tire.

I fully expect that I will have several problems with the wood on the hinged piece.  First it will probably wear.  If I have the wear problem I will do what they did with the wagon wheels and put a layer of sheet metal over it.  Second, there is a chance it will tend to bow because wood does not have the strength of steel.  I will simply build a brace on the back.   The third problem may be that I have big problems with the screws holding the hinges.   I have ideas, but I will cross that bridge when I get to it.

Ideal Hinge Location.

Ideal Hinge Location.

One of the concerns I have of the DIY (Do it yourself) versions I saw on youtube is the alignment of the hinges. I really have no idea how to fixture those to weld them and line them up correctly. However, I do have door hinges available, salvaged from an outside door I replaced. The door hinges have 1/4″ (6.34 mm) pins, about 1/2 the size of the pins used by the DIY videos. However, my brake is much smaller and my hinges divide the shear stress into five segments and not just one or two points like the home-made hinges did.

Alignment of the hinge in relation to the joint between the hinged panel and the unhinged panel was a concern for me.  I spent some time thinking and drawing some pictures with misalignment to see what would happen.  I was surprised.   The picture with the caption “Ideal Hinge Location” shows my method of finding out.  The yellow circles show the hinge and hinge pin.  The white lines to the right are the fixed panel and those to the left are the hinged panel.   The red dashed lines show the panel rotated at 45 degrees and the green dashed lines show it at 90 degrees.   As usual I did not scale the drawing  before I started so the length of 8 is just a reference that had a good even number and showed how much the hinged panel moved up, down, in and out when it was rotated about the hinge pin.   This will be important in the next drawing.

Effect of mis-aligning the hinge.

Effect of mis-aligning the hinge.

The next drawing with the caption “Effect of Mis-aligning the hinge” is very busy but shows some interesting things.  Remember you can click on the picture and see it larger and then use your browser back arrow to return to the text.  The interesting and unexpected thing to me is that moving the center of the hinge pin horizontally caused both a vertical and horizontal movement once the panel was rotated by 90 degrees.  Once I think about it it is obvious why this happens, but I would have never thought about it without testing it.  Fox’s rule:  “It is a whole lot easier to test on paper than it is to find out in real life.”

Now that I know a little about how critical the alignment is, it is time to determine where the center of the hinge pins are located on the salvaged hinges.  To do that I imported the photograph of the end view of the door hinge into CAD.  I zoomed in on the picture and drew lines on four sides of the inside of the circle formed by the metal around the pin.   I then drew diagonals to find the center of the circle and drew a circle to see how well my fit was.  Actually I was surprised at how well the fit was doing it this way.  The camera was not exactly centered on the hinge pin so it was a little guess work on choosing where to draw the lines.

Finding the centerline of the hinge pin.

Finding the centerline of the hinge pin.

Once the center was found I drew a horizontal like through the center to find the centerline in relation to the hinge leafs. I will have to mortise the hinges like it was done on the doors. However, differently than the installation on doors I will have to “hog out” a clearance for the hinge pin and metal wrapping around the pin.

Now that I have planned it…. I gotta do it.  That will be a future post.

Gary

 

 

 

 

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The hinged plate for the metal brake” by Create-and-Make.com is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

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