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Torsion-box workbench with parfguide hole-pattern

Post author By admin
Post date November 24, 2019
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(Built a few months ago, but better blog late than never..)

Here's a 1600mm-by-930 mm workbench built from two sheets (1220mm x 2440mm, 4-by-8 metric feet) of 15mm plywood. It's a torsion-box design with the top and bottom sheets separated by 240mm. The sides have rounded openings that create storage-bays for tools etc. The top has 20mm diameter holes drilled using the parfguide-system (it uses pythagoras 3-4-5 triangles to get the holes reasonably accurately positioned). The hole-grid is 10x17 so there are 170 holes in total. Assembled using pocket-hole screws.

Here's a rough sketch of the dimensions. The dimensions were chosen to fit my workshop, so that it could be built from two 1220mm-by-2440mm sheets, and the dimensions rounded to fit the 96mm-by-96mm parfguide hole pattern nicely.

The pieces needed can be cut from two sheets of plywood, resulting in two top/bottom pieces, two long-sides, two short-sides, and four internal dividers. I only used two of the dividers.

sketch of how to cut the pieces from a sheet of plywood.

There are a lot of torsion-box or "Paulk workbench" builds out there, here are some links:

Jay Bates, modified Paulk bench
Ron Paulk, Paulk work bench
The naked carpenter, Modified Paulk workbench

Tags plywood

woodworking

UJK precision mitre gauge fence on Makita 2704 table-saw

Post author By admin
Post date November 23, 2019
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Axminster sells this UJK mitre gauge fence, which replaces the stock mitre gauge/fence on my table-saw. The small coin-sized guide at the front needed a bit of filing to fit in the slot of the Makita.

The button was filed down a bit to fit the slot.

Tags axminster, makita, ujk

CNC woodworking

Laser cutting

First try at using the 50W CO2 laser cutter at the Iso Omena library. Material is 4mm Birch ply (K-rauta). I didn't have time to optimize the speed/power settings, so the edge-finish is quite burned, and a flame appears from time to time. There was a 3M tape-film (?model?) available, which when taped over the plywood-to-be-cut should reduce burning and flaming - but I didn't have time to try it.

Workflow: DXF files exported from CAD, the into Adobe Illustrator, set all linewidths to 0.01mm, then save as PDF, then print from Adobe Acrobat to the Epilog printer-driver, set speed/power for the material, send to the machine, set the (0,0) coordinate (top left) for the job, and press Go!

Tags CO2, cutter, laser, plywood

Time and Frequency

~800Hz wide clock-transition in 88Sr+

Post author By admin
Post date November 8, 2019
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Here's the latest preliminary result from the VTT MIKES 88Sr+ ion clock (in case you missed the live-stream!):

-C2 component of the clock transition at 445 THz in 88Sr+

This shows a ~2 kHz slice (left axis, double the 1 kHz shown, because we plot the input frequency of a double-pass AOM) of the optical spectrum around 445 THz, where we expect to find the -C2 Zeeman component of the clock-transition in 88Sr+ (a secondary representation of the SI second). The right axis shows the probe-pulse length in seconds, where we see only a few percent excitation (z-axis) at short pulse lengths, but a clearer signal up to >10% at longer probe pulse lengths of 40 and 50 ms.

It ain't pretty, but considering the carrier is at 445 THz, this noisy and broad looking 800 Hz wide peak is still a measurement to a relative level of 2e-12. When fully operational a line-width of <10 Hz (2e-14) is expected.

Our experiment now has one metglas magnetic shield. This particular Zeeman component (-C2) has a sensitivity of 11 kHz/uT, so the observed linewidth of 800 Hz could be caused by a low-frequency AC magnetic field with an amplitude of 30-40 nT or so. We think the remaining DC-field is around 1.6 uT (down from 66 uT without the metglas shield).

Among other improvements, next is building a second metglas shield, to reduce AC fluctuations in the magnetic shield even further. Stay tuned...

Tags strontium

Time and Frequency

Trapping again

Since about July 15th our single-ion experiment has been in maintenance-mode, but today again some trapping!

The central 'pale blue dot' is a single 88Sr+ ion trapped between the inner electrodes (cylindrical) which are driven with a ~400 Vpp ~16 MHz sine-wave to create a Paul trap. The outer conical electrodes are grounded. The window-reflections of the 422nm cooling laser create the larger circular spots in the top half of the picture. A single laser-cooled 88Sr+ ion emits around 10 million photons per second, making it easily visible on 1s or longer exposures with a DSLR. Sigma 105mm/F2.8 macro objective with a short (13mm?) extension-tube.

Live stream:

Tags ion, strontium

Uncategorized

Mowing season end

In 2018 the automower worked for 516 hours. By October 2019 the count is at 960 hours, so it has worked 444 hours during the 2019 season.

The outer shell is removable - so all the grass clippings can be cleaned off...

Time for a winter break, back to work in May 2020.

Tags automower

Orienteering2019

Iltarastit Paloheinä

The last Iltarastit event for this year. A bit wet in the forest after all the rain lately. I did have my garmin-watch but it somehow managed to forget this run completely - so a hand-drawn route instead.

Tags iltarastit, paloheinä

Time and Frequency

uBlox F9T qErr correction

Post author By admin
Post date October 11, 2019
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Here's a test of how to correct the 1PPS signal out of an F9T with the qErr-value from the UBX-TIM-TP message.

When the time-interval-counter is configured with start=reference-clock, stop=uBlox, the qErr is applied with a + sign to the measured time-interval - resulting in much smoother data for averaging times up to tau=1000s.