This section will cover what you'll need to do to build the THAM and also address assembly and shimming.
Section A:
Start with the Pulley Brackets
These pulley brackets were actually fun to make although the first one took me close to 45 minutes as I had to design it along the way while working with the metal. It's possible I over engineered things a bit and I'll be looking for a complete off-the-shelf solution in future designs. Please let me know your ideas.The pulley wheel and the hitch pin were used so all was not lost.
Here is a photo of the pulley I used in the project that I picked up at ACE. I tried in vain to use the pulley as-is but was forced to literally hand make new pulley brackets to accomodate the design requirements mentioned to reduce cable binding.
In Image 5 below you see the single piece of flat steel from ACE measuring 3' x 1 1/4" which was plenty to build the 3 brackets needed.
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| Image 5 |
First I measured and constructed a bracket out of paper to provide a template for the overall length needed for the first bracket. Then I simply cut the length and using leather garden gloves began to bend the steel around the EMT. With the help of my vice, channel locks, vice-grips and ball-peen hammer, I worked the steel into submission...at times beating on it. The metal is softer than you think and if you take your time, you can easily work with it.
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| Image 6 |
Here's another view (Image 7) of the bracket under construction. It took several fittings to get it right as I was learning on this first one.
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| Image 7 |
Notice in Image 8 below the gap I left for the pulley wheel.
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| Image 8 |
Pulley wheel being fitted to the bracket. Key point, don't drill holes in the bracket at this point. Remember in the design section how I mentioned that the top pulley on the 1 1/4" & 2" EMT needed to be positioned just inside the tube? Again, this is so the cable as it comes up and makes the turn around the pulley is not scraping against the lip of the EMT.
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| Image 9 |
So now you have to remove the bracket and started measuring how big of a slot you need need to cut into the EMT so the pulley wheel can protrude inside just a bit when installed.
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| Image 10 |
Trace around the wheel with a Sharpie (Image 11) and then carefully cut out the metal. I used a reciprocating saw loaded with a metal blade to speed things up but you could also do this with a hack saw.
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| Image 11 |
After making to cuts down the EMT, grab the metal to be removed (Image 12) with the channel locks and simply bend it back and forth to break it off. File all edges.
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| Image 12 |
Again, test for overall fit (Image 13) to see if the slot is big enough for the pulley. This photo shows the 1" EMT sitting inside the 1 1/4" EMT.
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| Image 13 |
If everything looks good, mark the pulley bracket with a Sharpie to drill the hole for the pin that holds the pulley wheel in place. After you get the pin and pulley in place (and have tested everything again for fit), file all edges. I used a bench grinder to round the corners on the brackets so they matched the wheels. I also filed down the lips of the wheels themselves to eliminate a potential binding point in the EMT for the inner piece that will be travelling by this pulley. Image 14 below shows the first bracket in place.
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| Image 14 |
And here in Image 15 below you can see the slot that I cut when constructing this first pulley bracket. You won't have to make the slot as long as this photo shows. As the design calls for a 2nd pulley below the first, I mistakenly made the first slot too long. The second pulley will not have to protrude into the EMT at all.(see original design diagram as well as Image 16). Make your slot just a bit longer than the pulley diameter.
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| Image 15 |
Below in Image 16 you can see the first two sections of EMT ready to go. The upper piece shown is the 2" EMT that sits at the bottom of your entire assembly. The double-bracketed EMT is the 1 1/4" diameter piece. I attached the brackets with JB Weld opting for their slow formula (not the 5-minute version). I chose the slower curing formula (let it sit for 24 hours) because this stuff is really tough and was perfect for this application. When using the JB Weld, be sure to completely coat the metal surface with it. I made my brackets with a tight fit to start with so that actual amount of JB Weld used was not that much.
Also, I painted everything with
Rust-Oleum Galvanizing Compound Spray Paint.
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| Image 16 |
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| Image 17: J-B Weld & Rust-Oleum |
I chose to pay a little more and use stainless steel aircraft cable instead of the galvanized cable in order to avoid corrosion. The aircraft cable was available at
Orchard Supply Hardware (OSH).
