Author Topic: Thermofilter Build  (Read 1950 times)

Offline D4F

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Thermofilter Build
« on: December 07, 2013, 10:03:14 PM »
Brew temperature is a critical component of espresso. Gaggia machines can easily have an 18° F drop of intra-shot temperature even when using a PID controller.  The study below is frequently cited.

http://www.afonic.org/espresso/TempPerfomanceStudy-Gaggia.pdf

Some method of ascertaining group temperature or brew water temperature is needed to establish a baseline and to document changes in temperature with changes in technique and heat. The Styrofoam cup test will give only an approximation of brew water temperature. A better tool is a thermofilter. Several DIY thermofilters have been made, some of which are shown below.

http://coffeegeek.com/forums/espresso/machinemods/588424

AndyPanda’s DIY thermofilter is in the thread below.

http://coffeegeek.com/forums/espresso/machinemods/588430?Page=7

A thermofilter similar to Andy’s will be built using easily obtainable materials and usual household/shop tools. The process will be simplified and documented for use by others.  It is important to note that a single basket is necessary.  A double basket will not work well because there will not be adequate room between the thermocouple exit of the basket and the portafilter sidewall. A K-type thermocouple is used and a reader will be needed.  You may use other appropriate thermocouples or sensors.

The first step is to seal the bottom of the filter basket with a thin layer of JB Weld, leaving only a hole which will allow a flow of approximately 50 ml/25 seconds.

Starting with a single basket, a wire will be used to keep a small opening in the bottom of the basket. The single hole will approximate puck flow of about 50 mL per 25 seconds. This is with a 0.011 inch wire. This size is probably the easiest wire to use and is available at guitar string outlets. Smaller wires are available but more difficult to work with.

Prior to insertion coat the wire liberally with silicone lubricant spray and allowed to dry. This is so epoxy used in the basket not adhere to the wire and allow the wire to be pulled back out.. The wire should be inserted through a hole in the center of the bottom of the basket and taped in place so that it is vertical.  About 1/16 to 1/8 inch of JB Weld epoxy should be layered in the bottom of the single basket and will hold the wire in place. It should look something like this photo.



Offline D4F

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Re: Thermofilter Build
« Reply #1 on: December 07, 2013, 10:04:51 PM »
When the epoxy is fully hardened pull the wire, coat with more silicone and reinsert. The next step is to place a short piece of simple plastic drinking straw around the wire. This will become the pathway for brew water to exit the hole. This is shown in the photo below.

« Last Edit: December 07, 2013, 10:21:31 PM by D4F »

Offline D4F

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Re: Thermofilter Build
« Reply #2 on: December 07, 2013, 10:12:28 PM »
I have built a couple of other thermofilters noted in the thread in OP.  Fortunately, Susan (SJM) wanted a thermofilter and I was interested in a build that was perhaps easier with non-shop tools, so she agreed to help by being the builder.  Photos are hers and she will hopefully chime in. 

If others are interested feel free to ask questions.

Offline SusanJoM

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Re: Thermofilter Build
« Reply #3 on: December 08, 2013, 01:55:08 PM »
Plot spoiler :-))))

This TF is exactly what I have been needing/wanting.
I just ran two tests, with 45 minutes in between to be sure the Classic had stabilized completely, and the tests were identical:  they show that my offset (when my PID is set to 217 degrees) is about 12 degrees and that there is a 10 degree drop in temp from the beginning of the pull (205) to the end (195).

Both these test were run "straight".  I did nothing to add heat to the pull.  I just pushed the brew button and read numbers off of the reader.

Oh bother.   I do think that the TC is reading about 4 degrees low, so that also needs to be factored in when making any adjustments, but....the TF is very cool.

Stay tuned and D4F will continue with the directions for the build.

“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”

Offline D4F

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Re: Thermofilter Build
« Reply #4 on: December 08, 2013, 03:09:00 PM »
It should look about like this after the first JB Weld mix.  You can use other epoxy, but High Temperature epoxy only.  Many epoxy gets soft before the 200F approximate brew temperature.  JB Weld is readily available.

Offline SusanJoM

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Re: Thermofilter Build
« Reply #5 on: December 08, 2013, 03:18:01 PM »
This one
“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”

Offline D4F

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Re: Thermofilter Build
« Reply #6 on: December 08, 2013, 03:49:23 PM »
Let that fully set/harden, probably overnight.  You can get some leveling of the JBW if you warm it until it thins a bit.  Leveling is not so important at this step, but heating will also slightly accelerate the curing process, and you will want to get a feeling of heating so that you can level the last batch of JBW for the top of the puck.

When JBW is fully hardened, pull the wire out the bottom.  You need to be able to re-insert the wire if a coffee ground plugs later, so get a feel for it now.  It will probably take pliers to grip for pulling the first time.  Re-silicone and re-insert and pull and insert a few times until comfortable.

It you cut the wire on the end that goes through the epoxy you may have trouble.  Wire cutters slightly crush and flatten the wire.  If you have to use a cut end, deburr it or remove the crush so that it is round.  I held the end of the wire against a Dremel sanding drum or grinder and turned the tip over, sharpening it if you will.

Offline SusanJoM

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Re: Thermofilter Build
« Reply #7 on: December 08, 2013, 04:20:32 PM »
Let that fully set/harden, probably overnight.  You can get some leveling of the JBW if you warm it until it thins a bit.  Leveling is not so important at this step, but heating will also slightly accelerate the curing process, and you will want to get a feeling of heating so that you can level the last batch of JBW for the top of the puck.

When JBW is fully hardened, pull the wire out the bottom.  You need to be able to re-insert the wire if a coffee ground plugs later, so get a feel for it now.  It will probably take pliers to grip for pulling the first time.  Re-silicone and re-insert and pull and insert a few times until comfortable.

It you cut the wire on the end that goes through the epoxy you may have trouble.  Wire cutters slightly crush and flatten the wire.  If you have to use a cut end, deburr it or remove the crush so that it is round.  I held the end of the wire against a Dremel sanding drum or grinder and turned the tip over, sharpening it if you will.

Okay, okay, that pour was messy it's true.  Tough crowd :-)))  I didn't have a heat gun at that stage in the process....

As for that wire, two things:

I made a loop at the bottom end after discovering in a previous attempt how very hard it can be to pull out.  Then I used needle nose pliers and wound the loop and the wire around them before pulling.  Also I had applied silicone a couple of times and sharpened the end of the wire.  It worked.
In the pictures you can see that the basket is supported on the rim of a short glass.  The loop of the wire and a bit of blue tape are supporting the wire so it doesn't just fall back out.  It took a bit of fiddling to find the right depth, but if you just put the basket into the vise the wire will ....slip slide away....
“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”

Offline D4F

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Re: Thermofilter Build
« Reply #8 on: December 08, 2013, 04:40:02 PM »
You can tape to the bottom of the basket and then twist the tape, corner of the tape, 90 degrees and tape to the upright wire.

Here is an earlier different build photo showing the vise as holder and the wires were taped to the bottom.  Build as in the thread

     http://coffeegeek.com/forums/espresso/machinemods/588424


Offline D4F

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Re: Thermofilter Build
« Reply #9 on: December 09, 2013, 12:55:18 PM »
The following photo shows hole placement.  The ink dot is where you don't want the hole. The actual drilled hole could probably be anywhere between the hole shown and below the dot. You can place the hole where you think it will be most easy to drill, yet not on the sidewall that will be parallel to PF wall where there will not be room.  That hole was drilled with a 3/32 inch fresh sharp drill. You may need to make a slight indent to get the drill started. A vise is strongly suggested for holding the basket.
« Last Edit: December 09, 2013, 02:30:46 PM by D4F »

Offline D4F

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Re: Thermofilter Build
« Reply #10 on: December 09, 2013, 02:17:32 PM »
Here is what can happen if you use a double basket. A double basket could probably be used if the wire was fixed in the center with the first mix of JB weld. Next the thermocouple hole on a double basket could be drilled from the bottom, out toward the sidewall. The thermocouple could then be fitted from the bottom into an arc into the central straw similar to what is done with a single basket. 

Offline SusanJoM

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Re: Thermofilter Build
« Reply #11 on: December 09, 2013, 02:44:41 PM »

The one that DF4 just posted a picture of looked really good until I put it into the portafilter and watched all of the water come up around the sides.  The exiting wire caused just enough of a disruption in the seal to make the whole thing useless....:-((((

And then we went back to the drawing board and started over with the single basket.....
“Thousands of candles can be lighted from a single candle, and the life of the candle will not be shortened. Happiness never decreases by being shared.”

Offline D4F

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Re: Thermofilter Build
« Reply #12 on: December 09, 2013, 10:19:38 PM »
Another photo showing the deburr tool, though others may work. There should not be sharp edges at the basket edge.  Toothpick shows the approximate thermocouple path and elevation at the "puck" center.

Offline D4F

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Re: Thermofilter Build
« Reply #13 on: December 09, 2013, 10:25:14 PM »
A Teflon coated K thermocouple was used.  They are inexpensive and fine for this application.  Fiberglass insulation tends to fray and unravel and is a little less desirable to work with. 

Offline D4F

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Re: Thermofilter Build
« Reply #14 on: December 09, 2013, 10:34:38 PM »
Note the change from the last photo to this.  Some of the Teflon and insulation have been stripped back to give a bit more bare wire.  The JB Weld need to adhere to the wire and seal off the insulation and Teflon so that water does not dissect.  Epoxy and most else will not adhere to the Teflon or insulation.  The thermocouple was also formed to a smooth arc to help stop bending especially at the basket edge. 

 

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