Saturday, December 29, 2007

Simple machines for building complex machines...

So, the holidays are past, and Merry Christmas to me, I'm now the proud owner of a Harbor Freight metal cutting bandsaw. This is a tool I've wanted for a long time, and was finally able to rationalize purchasing after a) it went on sale, and b) I agreed to coach the neighbor's son in the Robot Ramble competition for the Science Olympiad 2008.

We'll be re-using a lot of the components from some of my old battle-robots, like the motors from Centrifugal Enforcer, the batteries and ESCs from a pneumatic flipper-bot I built for Steel Conflict (but never did a build report for), and a few other gear motors, etc. I've got lying around in my stores. That said, there will be some fabrication, namely a new chassis, a lifting arm, and a gripping mechanism, all of which will require cut aluminum and steel.

I purchased the 130lbs+ beastie from my local HF warehouse, and got help from their staff loading it into the Subaru. Unloading was facilitated by a combination of gravity, a skateboard, and enough muscle power to nudge things in the right direction.

Assembly, however was going to be a different story. Step 4 in the assembly process reads "With a second person and appropriate lifting apparatus, set the saw base onto the saw stand and affix with hex bolts..." etc., etc.

Basically, the operation means setting a massive hunk of cast iron, motor, and steel, something like 95% of the weight of the tool, on top of the stamped metal "legs" that form the base.

This is one of those engineering arrangements that's strong once you have everything bolted together, but isn't conducive to supporting one corner of the machine while you lift the other bits into place. This was looking sketchy to say the least.

I didn't have access to a second person, but I could certainly arrange for an appropriate lifting apparatus, so after 20 or 30 minutes of scrounging in the garage and piecing things together, I'd managed some poly rope, carabiners, and pulleys. I lashed these to the joists of my workshed.

Mix in some nylon straps from the completely over-engineered hoist I'd built for the hardtop of the Miata @ my old house....

Adjusting the length of the nylon straps allowed me to compensate for the relatively ass-heavy nature of the tool. Lifting a few inches to test for balance then setting it down for adjustments took just a few tries. Eventually I was able to lift it to a working height and bring the base underneath for attachment.

After that is when the typical Harbor Freight adventure began, as the instructions were apparently for a different version of the tool. The stand that was supposed to bolt to the outside of the machine bed was clearly designed to go inside of the bed. The bolts I was instructed to fasten to "threaded holes" in the machine bed were of a barely-adequate length and the holes were not threaded (nuts supplied instead). Due to the wonder of Chinese tolerance keeping, I needed to substitute a bolt of my own as one of theirs was too short. Oh, and then there was the crusted cosmoline. A judicious application of white gas, WD-40, and an elbow-grease powered scraper cleared the beds and mating surfaces of hardened rust preventative. The best part, though, was all of the pulley-related parts I had to remove in order to install the pulley cover. (Pulleys go on last, yet came pre-installed).

In the end, though, with some care adjusting the clamps and feed adjuster, I have a functioning band saw that cuts my extruded aluminum channel very cleanly and squarely. I'll test on steel as soon as I get the chance.