Posted Sun Aug 19, 2012, 1:12pm Subject: Re: DIY PortaFilter - ThermoFilter Inexpensive Basket Thermofilter
This basket thermofilter was very easy to make and maintain. I have had it plug once with a coffee ground in the hole. Fairly easy to remove with the original E string wire. Solution is to clean the machine before using the thermofilter. Use a cleaning agent, remove the screen and back flush. I rarely see a left over grind if I clean first.
When I originally made the TF, I lost the wire and hole. I broke off a soft wire in the hole. I had marked the approximate spot and then gently opened the area with a countersink tool. I was able to find the hole and thought all was good. I ran basket in the machine and got 90 ml in 25 seconds and found that a second hole, one over, had blown out from removal of epoxy with the countersink tool. I got the E string and mixed a small JB weld patch and re-epoxied the holes up and the wire in. I then had a 70 ml run in 25 seconds and decided that I had opened the hole with a needle a little too much. I did a third attempt, patched with wire in, and pulled the wire without any attempt to expand the hole and back to 50 ml in 25 seconds. This TF was easy to build, and to correct mistakes.
A K thermocouple and reader can be inexpensive if you dont mind the order and wait from China, $5.77
Probably NOT good enough for government work, but works well enough for the home user.
I have continued to use the basket thermofilter. No problems and easy to use. This has helped me to adjust and understand the temperature in the Gaggia classic. A little critique. I think that for the expense, lack of, and ease of build it was very worthwhile. I have had a chance to see a few others in action on YouTube and of course found nothing like the real thing, the Scace. Mine and some of the others are slow to respond. I think that ease of build and maintenance came at a little sacrifice of responsiveness. Putting the thermocouple in a copper tube made replacement and other use easy, but blunt the response with added mass and shielding of the thermocouple.
the concept of making the puck of a DIY thermofilter with raw sintered metal beads was proposed. I am not sure of the density/thermal mass of the beads. Epoxy and HDPE are fairly low thermal mass as coffee.
The other problem to face when making a thermofilter is to make it with the correct or variable orifice, and a cleanable orifice. The orifice is in essence a single basket hole and can be clogged with one grain of coffee.
Posted Tue Mar 26, 2013, 7:57pm Subject: Re: Styrofoam Cup Method
I have decided to add a Styrofoam Cup explanation in this thread dealing with temperature measurements. The photo shows the cup with an instant digital thermometer inserted. You cannot do it well without digital instant. Those are available for about $10 or less. The cup is cut short and to about the diameter of the basket so that it fits in the group. I run the test about 3 - 4 seconds, about 30 - 40 ml. To repeat the test wait about 5 - 10 minutes to re-equilibrate. Be careful, the water should be about 200F and you want it all in the cup, not on you.
In use I preheat the cup and thermometer to about 200F so that it reads very quickly. Just before I run the test I pour hot water in the cup, dump and run the test. If you do not preheat and you wait a couple seconds for the steel probe to heat and conduct, the temperature will be falling as you read it. If you pay attention to detail you can get reasonably reproducible temperatures, though the method still is an approximation.
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 7,774 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Vene. A1, La Cimbali M32 Grinder: Azkoyen Capriccio, Major Vac Pot: 40s era Silex Drip: Msl. Com. brewers Roaster: gave it a try, decided no
Posted Wed Mar 27, 2013, 6:19am Subject: Re: Styrofoam Cup Method
Remember the Scace device was developed by a person in their home/garage. Anything that can regulate the flow to simulate the flow through the coffee and has a thermometer and a way to measure pressure will work, less room for water will help be a bit more accurate with water temp.
I have seen a needle valve used to adjust the flow of water. A naked PF and a back flush disc should be able to be modified to install a pressure gauge, a needle valve and a temp probe. It may not be slick looking but as long as it does not leak, it will get the job done.
In real life, my name is Wayne P. Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!
Feed the newbs, starve the trolls and above all enjoy what you drink!
I had a little problem today, but an easy fix, a reminder that this is an easy DIY home project. I put a little too much stress on the center post and it broke loose. The fix was easy. Already done for the photo the central JB Weld was removed from the basket and the post. Easily chipped out with an Exacto knife point centrally and filed off of the post by putting the post in a drill press and using a file. It was an easy fix to JB Weld/Epoxy it back in.
I have an improvement for the next one. The 0.011 hole is easily plugged with a 1/4 scrap of duct tape and does not leak.
Flow is affected by r^4 where r is radius. Pressure and flow conditions assumed constant.
Current flow is about 50ml and I would like about 30ml as an additional test point or I wish 60% of current flow. That gives a radius, or diameter, of 88% current. 88*88*88*88 = 59.97 60% of the current 0.011 hole is 0.0096 and there is an option for 0.009 and 0.0095 in guitar strings. I would build the next one with 2 (or more) size wire holes and plug the unused for testing. Actually it would be easy to use 0.009, 0.0095, 0.010, and 0.011 spaced about 90 degrees apart. Attached photo shows the pinhole at the end of the shadow of the center post and that fits with in the cutout of the puck, for flow. Easy to make it with more holes and duct tape off. Easier than an adjustable valve.
If you use coffee as your puck, you can obviously adjust flow as usual, but from what I searched, the thermocouples fatigue and break. Not a problem as most of the K thermocouples will work just twisted back together. Solder has its own conductivity so is not a good joiner or the wires. The wires can be arc'd/sparked together or twisted. The difficulty is to plan for R and R of the thermocouple from the basket, so the copper tube and simulated puck. If you epoxy it up, the hole sizes are noted above.
I also thought about a probe to the screen, perhaps between the diffuser and screen. Ideally you could bore the group and have a threaded removable insert to hold the thermocouple and make replaceable. I have blown a tube out, as RobCups noted with the thermocouple, and realize the pressure :)
I finally got a chance to change the thermofilter flowrate. I used a 1/8" drill bit and finger twisted it in the old 0.011" hole to get a small place to epoxy. I found a 0.009" diameter wire and placed it through the bottom of the basket as a pull wire. The wire was coated with silicone spray and allowed to dry before insertion. JB Weld to the inside of the basket where drilled out with the wire inserted. Allowed to harden and the wire pulled. This gave a flow of water at 25ml/25sec to simulate a double.
I would have used a 0.0095" diameter wire as calculated above for about 30 ml but it is not readily available. I found the wire for $1.25, a guitar string, but the music stores did not have the 0.0095" and it would be a special order.
Use looked like the prior video, and more described here
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