gscace wrote:If you really want to do this right, buy a probe from Omega or someone similar, use an Omegalok connector, and rather than installing the probe in the bolt that is relatively high on the body of the group, install the probe so that the sensing element is just above the dispersion plate, at the very end of the water passageway before the water hits the plate.

I have two metric omegalock fittings on order, but I do not expect them to fit, but figured I would give it a try. I may even go as far as machining the GH and tap an opening into the chamber like the photos Dan posted.

You know, I am glad this little gizmo has generated the amount of discussion and improvising based on the original 'proof of concept' that I made. I have learned more from the discussion of the device and debates about other methods of achieving the same type of data but at a more precise level than I did from building the little gadget. After all, wasn't that the underlying purpose behind Dan's contest, to promote the development of better espresso? I am still hoping to win a grinder (which is why I went through with the idea to start with) but time will tell.

I am having a blast learning about the more technical aspects of espresso, keep in mind I have only owned my own machine for eight months (got my first around December) and have already gone through 4 machines (I still have my lever machine so only two are out of service).

Strugs wrote:Step one complete. I just picked up a TC meter and a Type J TC wire. I am having my buddy at work run a couple of my A6 bolts through his drill press and seal the TC wire through the bolt with metal epoxy.

i would strongly suggest you use type k instead of type j. j has an iron wire and it will rust on you.


--barry "don't ask me how i know"

barry wrote:i would strongly suggest you use type k instead of type j. j has an iron wire and it will rust on you.


--barry "don't ask me how i know"

Actually, that was a typo. I meant K.

The bolt has been drilled. JB Weld is now curing, so my FrE61nkenstein mod should be good to go tomorrow night.

HB wrote:Greg, I assume you won't mind then if I post the pictures you sent me (rescaled)...


External front view


Probe exit above dispersion screen

Did you measure the difference between this location and the E61 channel? Obviously the dispersion screen location is more accurate measure of brew temperature, but I am wondering if the channel is good enough for purposes of repeatability.

In my first iteration I tried installing a probe into the e-61 well above the point that folks are considering. The temperature I was measuring was the temperature of the water flowing in the convection loop set up by the hx and group. This was not close to brew temp, so I learned my lesson and made the measurement as close as possible to the coffee cake. Agreement between my thermofilter and the probe shown in the pix is much better. Putting the probe near the cake gives a much better answer with regard to flushing requirements.

-Greg

HB wrote:

Abe Carmeli wrote:So, you are facing an unknown: how would it be influenced by the grouphead, especially when grouphead temp varies considerably pending on idle time and flushes.

In theory, a properly tuned thermosyphon holds the grouphead temperature (average) pretty darn close to the target brew temperature. Many people seem to be under the impression that the grouphead temperature is all over the map depending on usage. I've not done anything like Bruce's isothermic modeling, but it seems to me that if you're doing your flushes correctly (i.e., clearing the HX of overheated water and then bringing the group back to temperature from its transitory spike), the grouphead will pretty much "take care of itself." Now if you (stupidly) did half-flushes and waited a little bit several times in succession, I would expect the average grouphead temperature to rise.

Of course, some measurements with the Cannonfodder and Scace Devices on the same machine using a dual logging thermometer would answer this question definitively. However, it is fun to speculate about the results in advance.

Agreement between my probe inserted into the water passage and the thermofilter are very good during brewing.

You touched on a very important point with e-61 groups that is not well understood. The thermosyphon loop operates under certain conditions, and under others, may not operate at all, or may operate backward. for example, if the machine is idle for any length of time, the thermosyphon loop runs in the normal direction. If you flush the group and fill the hx with cooler water, the relatively higher density of cool water in the hx makes the thing run backward since the water in the group is hotter. And if the relative densities are the same, the thermosyphon will shut off. This may or may not correspond to the desired brewing temperature. The dynamics are pretty interesting - to me anyway. One sidenote to this is that the need for a fairly large temperature difference between the group and the water source in order to get the thermosyphon to work means that the thermosyphon group is not the best choice for a double boiler machine where one hopes that the boiler water temperature and group temperature are similar.

-Greg

lino wrote:That's not your average E61 in that picture. What make is it?

Actually, may not even be a "real" E61 as it apears not to have a expansion chamber. Also, that's the first E61 group I've seen with a flat top and a rough lower casting..

Is it Elektra?

ciao

lino

Astra Gourmet - electric solenoid is on bottom.

I am keeping a log of my experiments on my WWDP web site:

http://strugs.ca/thermal_obsession.htm

I will update it as the project develops.

the thermometer in the foam cup should be angled downward so the tip is at the lower 'corner' opposite where it enters the cup. the business end of the thermometer is the last inch, and when it's angled downward, that portion gets saturated quickly.

btw, someplace i have an analysis of the thermocup technique. i tied a small thermocouple to the thermometer and datalogged the results.

Hi Barry,

I started out using the angled thermometer approach, but I found that after about a dozen uses, the excessive heat of the water would make the styro start to degrade, which allowed all of the water to escape through the hole in the lower part of the cup.

I found that using the horizontal thermo worked ok, as I was not looking for an accurate temperature, just a repeatable reference point to shoot for just prior to making the shot.