The crackle finish black round thing is the counter weight that came with the EQ-1 mount. Unfortunately, it was not quite enough weight to counterbalance Baby:
I needed about another pound. If I had a chunk of round aluminum lying around, I would have used it. But I had a block of aluminum. I was pleased to see that my math skills and knowledge of aluminum's density (2.7 g/cc) were sufficient to cut a 15 oz. block, square it, then drill an 1/2" hole for the axis.
How to hold it in place? The lazy way would be a 1/4"-20 bolt in a threaded hole, but the bolt would have marred the axis each time I tightened it. So I tapped 1/4"-20 through the side to the bore hole and looked for a piece of acetal rod that I could turn down to .2". This would go between the end of the bolt and the shaft.
No luck on acetal. I did find a .125" diameter brass rod in my odd scrap collection. No turning required. No risk of scarring the axis. Just dropped a short piece down the hole and put in the bolt.
When I took off the factory counterweight to install the new one, I discovered it used the same technique, and like my design, it was not captive: when I removed it, the rod slid through to the bore hole, but it was long enough to not fall out the bore hole. I am about to run to the pharmacy, so I will buy a 1/4"-20 thumbscrew at Star Merc, and probably cut a longer brass rod so that it does not fall out the bore hole when I remove the counterweight.
Counterweight perfectly balances Baby.
I found some knobs with 1/4"-20 threads to replace the hex head bolt pictured above. I had hoped for a knurled head thumbscrew, but this multiple lobed knob provides much superior locking over any hand tightenable bolt or screw.
Next time you need to thread a long deep hole, think about figuring out how much length of thread you need, add a bit more, and only tap that much.
ReplyDeleteYou can drill the rest of the hole as a clearance for the fastener, and the time needed and the risk of breaking a tap are reduced.
The finished counterweight looks nice.