Op 2 en 3 juli jongstleden kwam Ola Eiken uit Noorwegen over om de situatie in Overschild eens grondig te inspecteren. Het moest Overschild worden - maar waar in Overschild, dat was nog geen gelopen race. Het zou ook in het oude schoolgebouw (De Pompel) kunnen. Maar uiteindelijk gaf het gegeven dat er een kruipruimte onder de school zit de doorslag: die laag lucht kon de metingen beïnvloeden.
Dus werd het onze molen. In samenwerking met de Hogeschool Delft zullen diverse methingen worden uitgevoerd. Hieronder ter informatie de brief die aan de secretaris van het dorpshuis "De Pompel" werd gestuurd (Gert de Vries) en aan onze molenaar - Lex van der Gaag.
Dear Lex van der Gaag and Gert de Vries,
I am the Norwegian visiting Overschild 2nd and 3rd July, searching for a suitable location for measuring gravity with high precision. Gert first kindly gave me a look in the school building, and the day after we all looked into the old windmill. Thank you very much for helping me and for accessing these sites.
Since then I have consulted with my colleagues, an we believe the windmill is the best location, due to the concrete floor resting directly on ground (while the school building has air beneath the floor). We have recently also agreed on the windmill site with NAM, the client.
I hope the windmill can be accessible for gravity measurements. The plan is, as I mentioned during my visit, to measure absolute gravity during a 24-hour period in the week 7th – 11th September. So the question is whether the floor of the windmill can be accessible for a day in that week. We will need 220 V electricity (not much), which I understand can be connected from the neighboring building. I enclose a picture of the apparatus to be used. It is called «FG5» and will be operated by a technician from Delft University.
Starting 12th September we will do a two-weeks campaign of measurements at about 90 sites in the greater Groningen area with a smaller instrument, and we would like to do repeated measurements at the location in the windmill, to tie values from the two instruments. These measurements will only take about 20 minutes each time. The instrument is smaller than the FG5; about 50 kg altogether. If possible, we would like to measure for 20 minutes every day or every second day in the 2-weeks period.
I hope it can still be possible to use the great location of the Overschild windmill for gravity measurements, and to have a cooperation with you.