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Ore Bridge Model - Chapter 2
In the previous posting, I had partially assembled the ten 4-inch interior cross-braces, and was preparing to join two sets of three 12-inch sections of brass L-girder stock together for the top horizontal beams. Then I remembered that I need a half-height (2") cross brace for the back end. Here is the semi-finished short brace:
ob_model_short_inner_brace.jpg
Here is my first use of styrene: I chopped off twenty pieces of Evergreen .020" strips at 1/4 by 3/16 inches to be used as gussett plates for the center of each "X" brace, plus another two at 1/8 by 3/16 inches for the half-height support frame. Then I cemented these to the centers of the X-braces on each side:
ob_model_brcs_with_gsst_plates.jpg
Before I attempted to attach the brace frames to the top beams, I knew I'd need something solid to keep them positioned at a perfect 90° angle and the same exact distance between each other (27/8 inches). So I decided to cut some scrap 2by4 sections to be used as jig blocks. Since I didn't want the wood sticking to any stray epoxy cement, I shaved off the bottom corners:
The first cross brace frame had to be attached extra firmly, so I soldered it. Then I verified a perpendicular joint using a draftsman's triangle:
My next step was to mix up some J-B Weld 'steel' epoxy, which I dabbed on the top corners of each brace frame. I pressed these firmly onto the L-girder with jig blocks in between:
ob_model_braces_in_position.jpg
After waiting 20 hours for the epoxy to cure, I removed the jig blocks. At this point I still have not permanently cemented the X's to their frames, so I removed them to slip out the wood blocks more easily:
...and here is what the assembled section looked like in its normal position:
Immediately behind the last 4-inch brace frame, I cut tiny notches into the vertical sides of the L-girders so they could be sloped downward:
ob_model_notch_in_last_brace.jpg
I positioned the short brace frame 27/8 inches beyond the last 4-inch tall frame, but as of now I have not yet cemented it:
Next, I'll have to finish the bottoms of all the brace frames. This is where I'm at as of 10/23/03. -KJL
