I did some simple temperature testing today and transcribed the data by doing a direct optical connection to my print-out device . (ie took video and drew some graphs )

My method was simple and probably introduced some erroneous data points- I removed the screw in the middle of the dispersion screen and held the tip of a TC in the flow of water, as close to the metal as I could get without touching it. I didn't restrict the water flow in any way, so it put out 40ml every 10 seconds, for a total of 160ml in 40 seconds.

1st 17 minute warm-up, no flush

2nd 1 minute rest after first shot, no flush

3rd 30 minute warm-up, no flush





I can post the videos if anybody is interested.

Henry

I just wanted to report that I've found a strong plastic-y taste in the water from this machine, even after flushing fresh water into the HX EDIT turns out fresher water doesn't have this taste... I couldn't distinguish it from regular water.

In case anybody was planning on making one of these, I do not recommend using nylon tubing as I did here. Even though it is rated for higher temperatures and pressure then it is being subjected to it is still giving up enough of itself that I can taste it in the water.

I'll be using my other machine until I can replace the nylon HX with copper tubing.

Henry

Wow, very cool. Awesome project. I love seeing things like this; it makes the engineer in me very happy. Good work!

Thanks!

Henry

hbuchtel wrote:I do not recommend using nylon tubing as I did here. Even though it is rated for higher temperatures and pressure then it is being subjected to it is still giving up enough of itself that I can taste it in the water.

My Techno uses Teflon tubing as sold by McMaster-Carr and metal instant tube fittings. I've never gotten any taste from it, and I do check periodically, by pulling a blank shot, letting it cool, and tasting it against fresh water.

Best,
David

Nice. That is what I did as well, pulling one shot using water that had sat in the HX all night, one shot after flushing all the water out of the HX and letting it come back to temp, and, after they cooled, comparing the two to a cup of fresh cool water.

The first cup was very unpleasant, and the second cup seemed to contain the slightest hint of the plastic taste... but it could have been my imagination.

Perhaps my mistake was choosing nylon rather then telfon? Or maybe the quality of the material was not very good? Depending on how the copper tubing works out, I might order some of the teflon tubing from McMaster and have it sent over here.

Thanks for your idea,

Henry

Well, I broke my promise about not using this machine till I replace the tubing... I have to flush all the contents of the HX out before using it though, which is a pain.

I wanted to share this video I took today. I did the "Schomer" type of temperature reading method, ie locking in the PF with a tc sitting on top of the coffee.

The results were pretty impressive, you can see by about six seconds the temp had stabilized at 86/87C (flicking between the two) and stayed there for the rest of the 33 second shot.
If you listen carefully you can hear me saying something brilliant to my wife

Unfortunately I haven't calibrated either my PID or the other readout device, so I don't know what the actual temperature is. A couple days ago I was pulling shots at 93C (PID) which didn't taste too hot, and now at 91C it doesn't taste too low, so I guess it isn't too far off.

I've got the next version all planned out (in my mind...), I'm just waiting for some $%^& time to get it made!

Henry

hbuchtel wrote:In case anybody was planning on making one of these, I do not recommend using nylon tubing as I did here. Even though it is rated for higher temperatures and pressure then it is being subjected to it is still giving up enough of itself that I can taste it in the water.

Yeah, you have exactly backwards. The whole point of heat exchangers is to transfer heat! You want the most conductive metal available INSIDE the boiler. If there's a temperature gradient inside the boiler, you probably want the inlet at the hottest point and the outlet at a cooler point to maximize heat transfer and temp stability. (If you were going for maximum temperature on the outlet water, you'd put the inlet in the coolest area and outlet in the hottest part of the boiler.)

OUTSIDE the boiler, the Nylon tubing deserves a little more thought. Any heat that transfers out of the tubing is wasted heat/energy. If taste is an issue, stainless steels are lousy heat conductors, but they're much more difficult to bend then copper or Nylon because they're so much less ductile.