Sunday, March 20, 2016

Spring and Springs in Alaska

So we are a few days away from the vernal equinox, AKA spring. Strangely, I have been working on some projects that involve springs. And we have a surprise ending.

First we have the spiffy new handle on the dividing head.

This is a spring loaded plunger that pushes the prong into the dividing head and holds it steady. The plunger is pulled back to go to the next hole on the plate. It took quite a lot of messing around to get it right. I kept getting the spring backwards! I had to change springs several times; my supply of springs is limited. So that is one spring.

Next idea I had was a vertically adjustable Dremel holder. My first try looked like this:

The Dremel is held in the chainsaw attachment, already described elsewhere. This worked but it was very sloppy, so I spring-loaded the screws.

It works a lot better that way. The Dremel tends to lever it because this stuff is all Aluminum form Lowe's. A casting would be much better but I'm not set up for that. Bit too much slop. Have to think about that. As it is it is a hand-held Dremel router.

Well, that's three springs. While I was at it I clamped the thing to my homemade pantograph.

This worked surprisingly well. I realize now I have a pantograph with adjustable ratios, depending on where I clamp it. Bonus. It is nice to have a vertical adjustment. I hand-made a set of templates, seen at left. I am holding everything down with two-faced tape. Not ideal, but it works. I m encouraged. Springs are  wonderful.

Finally, "spring" also means a season of the year. The Vernal Equinox is March 21 or 22 depending on a lot of things. This is an astronomical datum. Alaska has its own ideas:

About 10 cm or 4" snow yesterday. Biggest snow of the year. Of course we were (still are) in the El Nino hotspot. No snow to speak of, until yesterday. A day late and a dollar short. No skiing. But it was nice to have the snow, and a fire welcome. Observe Miss Mocha curled up on her tuffet at the right of the picture. Right out of Currier and Ives.

And today the temperature went way up, +6C or so I do not expect winter wonderland to last very long. Spring, one way or another, is here.

Tuesday, March 8, 2016

The 120 tooth saga n the Isaacs clock

The biggest wheel on the Isaacs clock is a 120 tooth monster. As I said before, when I made the pinions I inadvertendly went from module 0.6 to 0.9 and I am unwilling to redo the pinions. I calculated that the biggest wheel on the clock  it would fit on the lathe i.e. I could "swing" it. So it did, but this whole 120 tooth "great wheel" is a monster fully up to Godzilla's standards. I calculated that a 120 tooth wheel would fit the lathe. I had no idea how close that calculation was.

I cut these things out on the bandsaw. Then I turn them down to the exact diameter on the lathe. It is something like (N + 1.76)*M (M is the module and N is the number of teeth, and if anybody is screaming about this remmeber these are cycloidal bears, not involutes). As you can see it clears the little Taig by about 2mm and I had to file it a little to get it to fit!

Next we need a pair of backing disks for  the wheel. I like the kind of board called masonite or its like. It does not matter if it is a lot off-center, its function is to support the wheel in its odyssey on the mill.

Now my dividing head has a height of 50 mm. Unfortunately at Module 0.9, the radius is about  110mm so I am a bit short. What to do? Why, riser blocks.

Above 100 tooth wheel for comparison.

A 100 tooth just barely fits without blocks. So... First I tried putting it on the left side of the mill. Note the riser blocks. Note the clamping. Also note I have not supported the wheel. Two big mistakes in one go. Unsupported Lexan wheels flex and lead at best to inaccurate cuts. At worst to "crunchies" where you wreck the wheel beyond repair. Worse yet, I am "climb milling." the cutter is fed in the same direction as the cutter moves. Sometimes this does not matter. On all the previous wheels it didn't. But this is a huge wheel relative to my equipment. So remove the vise, go to the right side of the mill.

Much better. Now I am "conventional milling" and the cutter moves opposite to the feed. I am still having problems. Stay tuned.