Fortieth week

About in-cylinder length
I did a long pump session this week where I first pumped for 30 minutes, took a five-minute break during which I did some edging, then I pumped for another 30 minutes. During the whole session I kept the pressure at about 5 inHg. The funny thing was that I measured my in-cylinder length at the end of the first 30 minutes, and then again at the end of the second 30 minutes - and the result was about 3 mm shorter at the second measurement.
And here I have believed that the in-cylinder length have a slow and steady increase during a pumping session. This is apparently not always the case, at least not for long sessions where I can feel some tiredness at the end which might affect in-cylinder length.

The day after I did a short 10 minutes pumping session at 6 inHg, and after ten minutes the in-cylinder length was the same as after 30 minutes at 5 inHg. That is not surprising since the pressure was slightly higher.
But a few days later I did another 10 minutes session at 6 inHg (albeit the first two minutes was at 7 inHg), measured at the end of those 10 minutes and - surprise! - it was 2 mm longer than it had been before the break at the long session or after 10 minutes at a steady 6 inHg.

So the in-cylinder length seems to be more related to amount of pressure than time spent under pressure. Might be a subject worth exploring further...

* NOTES for week 40 *
* Monday morning: Pump, 5 minutes at 6 inHg.
* Monday night: Pump, 2*30 minutes at 5 inHg with a 5 minutes edging pause. 20,0 cm (7.87 in) in-cylinder length at the end of the first 30 minutes, and actually 3 mm shorter at the end of the second 30 minutes.
* Tuesday: Pump, 10 minutes at 6 inHg. 20,0 cm (7.87 in) in-cylinder length.
* Thursday: Pump, 10 minutes at 6 inHg.
* Friday: Pump, 10 minutes at 6 inHg, first two minutes at 7 inHg. 20,2 cm (7.95 in) in-cylinder length at 6 inHg. Afterwards MSEG 13,7 cm (5.39 in).

Note: All pumping this week done with new "Mr B" pump and 2" cylinder. See photo in my album.
In-cylinder lengths are measured with a ruler outside the cylinder.