This mod looks really neat!

Unfortunately, I do not have access to a machine shop. Has anyone tried using the aluminum water cooling blocks that are used for water cooling systems on PC's? Some of the blocks that I found on google are only $30 - while they may not have the same volume as this one, maybe they will still do the trick...

xEggbert

They will certainly increase the water temp, but the question is how much ?
If one wants to build a heat exchanger the temp of the boiler needs to be much higher than for the single boiler.
Therefore I went for a chamber that holds enough water so that the temp is stable during the whole extraction.

I don't have a gaggia (or anything, yet) but has anyone tried using an immersion heater in the reservoir yet? I don't know if it would fit, but it seems like a good pre-heating method. I searched the forums, but didn't find anything.

I like the machined block though.. great results, it appears... see my next post.

That graph is great for showing change from 10 seconds in... but how about absolute temps?

I ask because it appears as if both methods give the same temperature result at 10s, and I don't believe that that is really the case. Also, it appears as if the slope is greater at the beginning when using the heat block, indicating that the starting temperature is much lower. All of this would be much clearer if we saw the absolute temperature values, or did variation from maximum temp vs time, or variation from zero time

great work though!