Sherline Mill - Z Axis Reinforcement (Flying Buttress)

For years I have been searching for a retrofit style reinforcement for the flimsy Sherline Z Axis.

Its not flimsy but anyone who has one has probably looked at it and realized that at the upper ends of the travel it couldn't possibly be as stiff as at the bottom. If you run these machines enough you begin to see that the vibrations from machining are resolved mostly in the Z axis.

I run both a hand crank and a CNC version and the real goal here is to develop this idea for the CNC machine.

I have made my 2" increase in Y travel to both of my machines which allows me much greater freedom in mounting work to the table.

I tend to run the 1.25" extension on the spindle mounting all the time. This increases the moment arm between the tool bit and the Z Axis Moment of Inertia.

The box section I fabricated here moves the Moment of Inertia probably the same distance again further from the tool bit BUT increases the overall stiffness.
It would be fantastic to do a comparative FEA on the two versions, I can provide all of CAD data!

I used a 2" x 1.5" x .125" alum. rect. and added 0.125 x 1.5" strips on the sides. The flying buttress is the only way to stiffen the Z Axis because the Z Axis backlash locking lever reaches around and you need good hand access to it.

I had to drill two holes in the Sherline base and two in the steel Z Axis ways.
For the CNC machine I want to make this out of steel but I'm going to try out this one for a while before getting into that.

The more elegant solution would have been 2.25" x 1.5" x 0.125" rect. but that is a rare item indeed.
I'm thinking about a water-jet solid block of alum. too.

04.15.15
Went ahead and made the steel version for the CNC mill.
Should get at least 3 times the stiffness as the alum version.
It looks a little Steampunk but it is extremely stiff!

I added a couple of fasteners to the design to pick up the loose ends.