So I took the Silvia away with us on a three night break, the first time that it had really been used in anger rather than just for testing. It’s a bit of an extravagence but it’s not much trouble to carry it from the car into the accommodation. On the first morning all was well, grinding coffee beans for four cups on an aerospeed wasn’t much of a chore. The coffee was good. The problems started on the second day, there were leaks at the group seal, jets of water were spritzing all over, water was running down into the cup and along the handle onto the floor. No surprise that the coffee was weak. Sometimes the pressure gauge registered about four bar, presumably because of all the leaking water. Things didn’t get any better on the last morning.
When I got home I looked carefully at the setup and didn’t find anything that would obviously cause the leaking but found a few issues which may be of interest;
The ears on the aftermarket bottomless portafilter that came with the machine didn’t quite fit, I could see that they had been filed at some time in an effort to make them fit but were still not right. This made the portafiter hard to locate (hence the misfitting in the picture in my previous post) and perhaps not centralising the basket lip on the seal as the stubs of the filed off ears were stilll protruding a bit. They needed filing to both shorten them to fit the slots and to fit centrally into the grouphead.
The rim of the shower screen wasn’t fitting over the brass block. The metal behind the screen was slightly dished out so instead of the edge of the screen fitting over the block there was a gap, water would flow through this gap rather than go through the screen mesh. I sandwiched the screen between two thick washers and pressed them together in a vice to flatten the screen, It now fits. The old, presumably original, screen that came with the machine was flat. Something to look for in aftermarket screens.
I reduced the OPV to show 9.5 bar on the gauge, which probably translates to about 8.5 at the puck.
I had noticed that the PID was very slow to respond. Placing the sensor of my digital thermometer under a steam thermostat screw next to the PID sensor I noticed that there was a distinct lag between the temp showing on the PID display to that showing on the thermometer. I had fitted a small thin steel washer between the PT100 thermocouple sensor and the top of the boiler, removing the washer got rid of the lag. So the washer was causing the lag and therefore affecting the operation of the PID, slowing down the recovery times after pulling a shot. I had used the autotune to set the PID settings but changed them for some recommended for the Silvia found on the internet. The offset was changed by +2C to get the two sets of temperatures to align.
The next points relate to setting up to use with the aerspeed;
- When used for travelling, it is convenient to use a scoop to almost fill the aerspeed chamber rather than taking a set of scales. This holds about 18g, I had taken a triple basket with me but I now know that this was underfilled. I should take either the 18g double Gaggia basket which fits the standard portafiter or the 18g IMS double basket in the bottomless.
- I tried changing the grind setting to stop the gushing. There is no indication on the aerspeed to show which direction to adjust and I actually coarsened the grind and made things worse. I had marked the handle with a magic marker but that had rubbed off, so I have now stamped the handle.
Hopefully, with this setup I can now fill the aerspeed with beans, grind until empty, tip all the grounds directly into the IMS basket, tamp and pull the shot. Handy when you are away from home and want minimum faff.
So it’s all perfect now, right? Well we’ll see. I’m going to leave it out in the kitchen to make at least one coffee per day until I get the settings right and I’m reasonably happy that it won’t let me down next time I go away with it. Latest coffee was made with 18g beans weighed out, which filled the bean chamber in the aerspeed, grounds tipped into the IMS basket (I knew one of those 58mm funnels would come in handy one day), 25 seconds for 37g espresso, no leaks. I’ll try grinding finer tomorrow but if it stays consistent at that, I’ll be happy.