Well the construction took several years, from the choosing the box, the type of plugs/sockets (2mm instead of the common 4mm), designing the front panel and sending it for fabrication (at this place as they do have linux support, for an idea of how incredibly long it took, the front panel was done in 2014).
At the circuit part, I made some "variations"... for the power supply I wanted a mains input and a linear regulator for each polarity. So I used a standard transformer, rectifier and LM337, LM317 regulator with +15V and -15V outputs.
In the circuit I changed all operational amplifiers for the LF411 and LF412. In the polarity indicator I used a dual colored LED (red/green), with this I could save one extra hole in the front panel. For the sinus generator I got a AD639 as I couldn't afford the space for the pots and diodes. Eventually I got the AD534 for the multiplier, but it appears that the ones remaining in ebay are made of unobtanium...
For the integrators I used pots as input resistors so that I could adjust the time constants.
After sourcing all the components, the construction took two weeks on several pcb pre-drilled boards (one of these, another of these and for the power supply another).
This is the final result:
With the box open you can see the power supply (transformer in white PCB), the measuring card (brown PCB inside the box, contains basically the second page of the schematics plus the multiplier and sinus generation) and on the right you can see the integrator capacitors and the adders.
The question now is what to do with one... well doing a "fall of object without drag" is quite interesting and easy, doing other ballistic experiments is also interesting... See the presentations at the Analog Computer Museum.