Turntable speed calibration tool

I do a lot of (vintage) turntable repair and revision. So last step is always calibrating the turntable speed(s) a.o. More general accurate turntable speed is important for vinyl lovers and has to be checked regularly.

Nowadays one can use apps on a smartphone by using its accelaration sensor. Efficiënt apps are "RPM" and "RPM Wow & Flutter".

To have a correct speed reading, the phone should be placed in the center ot the platter where mostly the spindle is sitting. You could always put your phone on top of an 45 rpm puck (for "single" or 17" record) but then still the phone could slip away. The upper surface of an 45 rpm puck isn't that big after all.

So I designed a cradle and cilinder to place the phone in the center over the spindle. The diameter of the cilinder is quite sufficient to fully support a smartphone and keep it in place.

The cradle with its brackets is based on my own current smartphone, which is about 8 cm wide, 17 cm long.

The base/cilinder and the cradle fit by slots so things stay in place not comprimising the speed measuring...

Standard infill will do. I've printed mine in PLA+ with .2 resolution and 20% infill (FDM). No support needed with a well calibrate printer.

You can print both elements together or if doing so separate be aware of the shrinkage of your filament to make sure the slots of the bottom cilinder will fit the holes in the cradle. Clearance is only about 2 mm.

Position the cradle flat on the bed surface. Best way to make sure the slot holes are accurate on an FDM printer.