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How to monitor tempreture in a Behmor - Probe Placement

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  • #16
    Matt, just tried to directly place some pictures as they are not very big. (beginners mistake)
    But I have to learn how it works or send somebody the pictures by email.
    So you can read here only the mouth-watering announcement.
    Sorry for that
    Peter

    1) what I got as a result: my first records:
    Line A: 1P2B - 330g - probe in original CS position, top left in the back
    Line B: 1P2A - 330g - center bead probe
    the marks FC, SC are not really accurate, as I was trying

    2) Drilling the hole
    3) with rigid probe
    4) bead probe
    5) in empty drum
    6) bead probe in coffee
    7) overview
    8) workplace

    It was pretty easy. The only step which I regard as really critical is the drilling through the axis,
    after dismantling the lid by bending the wire hinge a bit. You have to pinpoint the center very accurate, as the remaining wall thickness is about 1mm. You need to check for symmetry with a slide gauge carefully before starting to drill.
    Once you have started to drill you will not be able to correct anymore.
    If you open the hinge only a bit you even don't need to re-fix it.
    Standard phrase: No guarantee for nothing. Just describing my personal experience.

    Peter
    Attached Files
    Last edited by Peter42; 27 December 2013, 11:01 AM. Reason: trying to upload the images this time

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    • #17
      Here are the remaining images showing the probe inserted through the axis, pointing into the coffee. They images are not very good as the drum reflects the light.

      The probe is not that flexible that it just hangs down by gravity. It is more related to pre-bending of the wire and the probe has its own idea where to go. It should not go too far into the drum, because this increases the risk of finding the holes of the blades or the drum.
      It happend only during testing without beans, but was no problem.

      Peter
      Attached Files

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      • #18
        Wow Peter
        That's a substantial difference in profile!
        I reckon you've really nailed that now - much easier to compare your roasts with other users with corretto's etc that more easily measure bean mass temp. Might even be possible to find a probe with a bend, or use a piece of steel brake line bent to a 45° or 90° angle (once you've worked out where you want the bead to sit every roast) to insert the through to protect it long term? Not sure how you'd fix it in the drum though…
        Great work
        Matt

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        • #19
          Nice job Peter

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          • #20
            For easier handling I am looking for either some flexible hose to strap on - like on the standard probe.
            Or for a thin tube 3mm outside and 1.8 - 2.0mm inside. A sharp bend will not go through the hole, but if it is done with a large radius of ~30cm it could work perfectly. Perhaps the whole in the axis must be increased to 3.5mm or 4.0mm.
            Peter

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            • #21
              Hi. Here is probably my last long update on Peter’s Center Probe, as currently it fulfils all my expectations.

              I bought some small aluminium tubes at the handicraft shop. The idea was di should be min 1.7mm, Da as small as possible. I fould: First: Da=3.0; di=2.5mm. Second Da=2.5mm; di=2.0mm. The small one finally fits perfectly my needs.
              I also bought a 2mm rod (wood) and a 1.5mm rod (steel) to insert them during bending to stabilize and avoid flattening (material as available). I bent the tubes around a 28cm lid or a 18cm pot to get a smooth radius and avoid folding. The pieces I cut off for use in the Behmor are 30cm.

              Results in general:
              The diameter of the hole in the axis should be at least 0.5mm larger than the outside of the tube, because otherwise the friction during inserting the bended tube would be very high and the probe may get stuck. This is also the reason which is limiting the minimum bending radius. You may have to adapt the bending radius a bit during testing for easy handling.
              In the picture the tube is turned upwards just for showing the bend and the red probe cable looking into the drum, as in the normal position the images were miserable.

              The first 3 or 4cm of the final tube should be straight, because otherwise it will be nearly impossible to meet the holes in line. A bevel at the axis helps as well. In normal use you will probably insert the tube with the probe sometimes while the beans are in the drum and maybe rotation and roasting has started.

              When looking on the tube outside the Behmor you see some tape-flags.
              The red flag limits the way to insert the tube into the Behmor and helps to avoid contact between probe and blades. Additionally it indicates the axial position if not fully inserted and shows outside the direction of the bend tip of the tube inside. This could be done by bending the outside end of the tube into the same direction.

              The black tape on the wire limits the way the probe is inserted into the tube and the tip shows up inside the Behmor – outside the tube end. I limited it to 1mm.

              The idea is to pull the probe back into the tube for some cm before inserting the tube through the wall and the axis and push the probe to the end after the tube is inside and in position.
              This way it cannot be damaged and it is faster than if it was fully inside the tube.
              I installed little chain as external support to fix the position of the tube and avoid rotation by mistake.

              Writing this text lasted much longer than doing the whole job this morning. Taking the photo of the tip of the probe needed more than 20 attempts. The camera didn’t like it.

              Unluckily I have currently plenty of roasted beans (even some bought and some presents) so I have to postpone my next roasts. Maybe there will be some feedback of somebody else.
              (Standard footnote: no guarantee, everybody working on his own risk, just recording the spending of my holidays)
              Peter
              Attached Files

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              • #22
                Looking great Peter, thanks for sharing.

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                • #23
                  Real bean temperature measurement inside Behmor drum during roasting

                  As I believe that we can measure the real bean temperature inside the Behmor drum now while roasting, I herewith want to upload those 2 pictures which are related to the start of the work (opening the hinge and drilling through the axis; post #16).
                  They are not that fascinating, but I regard the drilling through the axis as the only critical moment of the whole job because once you started to drill eccentric it is almost impossible to recover. (at least with low budget equipment). And I had no spare drum.

                  Try to mark the center of the axis as perfect as possible before starting the drilling. This is not the moment for being tolerant. Check if the distance to the edge is the same for all directions with a slide gauge or so. It is easier if you hit on a small drill because it makes a short line. With two or more lines you get a cross or a star and you have the chance to move and adjust it a bit.

                  All the other steps are easy going and cheap and if it doesn't work in the first run you can try it again.

                  Peter
                  ------------------------------------------------------------------------------------------------------
                  -- be an animal: be curious; trust your guts; play the game --
                  Attached Files

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                  • #24
                    Behmor temperature measurement inside drum

                    My curiosity won, as I wanted to have the real verification that it works with the tube. I roasted 330g Malabar (to have another 2 weeks to drink my other beans) on P2A, on 220V although 229V-230V really available. You find the the roast monitor chart enclosed.

                    Comments on handling and test:
                    The tube should be really inserted before the drum starts rotating. The 330g are about the min. amount to be used with this probe tube. Should be more to have more beans above the blades. Handling was without problems. Minor adjustments were:
                    First the tip of the tube was above the beans. I pulled the tube 5-8cm back, bent it a bit more by moving the end slightly down, and re-inserted to touch the beans. The coverage improves during roasting as the volume of the beans increases. In the picture with the yellow beans you see that there are some beans are in touch with,- and running above the tip, but it is not deeply digged in. Nevertheless the measurement seems to work good. With the chain stabilizing the outside end of tube there was no tendency of tube rotating at all.

                    For the chart:
                    The beans are dry, no oily spots, seems to be Vienna - light French ( CS11?).
                    I hit cooling after 18:45. (due to 220V the standard time is 19:00).
                    May be it was 10-15 sec too long as I needed a moment to recognize the change froom FC to SC and had some smoke for 15sec after start of cooling. I still have some difficulties in these evaluations.
                    I will know it in about 10 days.
                    Peter
                    Attached Files

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                    • #25
                      Nice work!

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                      • #26
                        Great job Peter!
                        Matt

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                        • #27
                          Thanks for the detailed work and photos peter. I can't wait to do this modification to my Behmor in the coming weeks.

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                          • #28
                            Jatallo, Wish you good luck as well. And I am keen to get some additional feedback.

                            Meanwhile my lessons learned from two roasts:
                            - use larger batches about 400g+. It is easier
                            ( I'll stick for a while to 330g so that I can compare my curves, as I want to check the influence of some side effects)
                            - before plugging in the square axis, rotate the drum a bit in the normal direction to have the same bean distribution as later (back side at heating: beans are higher).
                            Then it is much easier to adjust the height of the probe - and perhaps bend it a bit more or less - before starting the motor.
                            - when bending the probe after start, there is some friction against the hollow axis. This can cause the Behmor to stop. It is probably the safety feature against damage after blocking. It happend to me, but was no real trouble as it happend within the first two minutes. The restart was no problem and I had an unplanned preheated roast.

                            - the hole in the outside wall shall be enlarged for easier insertion of the bend. It could be done as an oval hole downwards (following the curve).
                            I made a little funnel to easify the the insertion and allow the curve downwards and reduce the heat drifting into the wall - but I don't like the form and size and didn't install it yet.
                            You may get some photos from the next version after installation.

                            The most surprizing thing for me was that with the few roasts I did with the bean mass temperature, I now understand the roast much better, as I had before all the time trouble to distinguish FC (crack) and SC (pitch-sound) and the simultaneous mixture sometimes on my Monsooned Malabar, Decaf and others.
                            Now as I heard it and smelled it in parallel to the known temperature I could get it in accordance to the phrases I read so often about before.

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                            • #29
                              Accurate drilling shouldn't be the trouble any more and it can be done the quite safe way:
                              For drilling without trouble you need a drilling template, and for preparing this you should have at least a cheap version of upright drill rig, but dont't need any big machine. The drilling shall be vertical.

                              A aluminium plate of 20-25mm would be perfect, but a hard wood or multilayer board of 25-30mm would do it as well. Size about 100mm (4 inch) would be nice, but is not really important.
                              - Drill a very small hole through: about 2.5mm 0,1" - somewhere in the middle area.
                              - use a conterbore (if you have) to enlarge the diameter to ~ 10mm (0.4") = a bit bigger than the diameter of the Behmor axis.
                              - Then you drill the half way through the plate the hole with the diameter of the axis. Use a standard steel drill with the v-shape tip.
                              Just after starting check if the large hole starts concentric with the small hole. If not just move one inch to the side and start a next try. If you are not satisfied you have as many chances as you want.
                              If it is wooden board, use a drill slightly smaller than the diameter of the axis. The hole is normally a bit larger than the drill.

                              The idea is that you can put the board onto the dismantled lid of the drum and the axis just fits and disappears in the board, so that when drilling from the other side with the small diameter, you just find the centre.
                              Anyway, - check directly after the very first slight touch of the drill onto the axis and stop if it's not ok.

                              Is a long description, but could be job for a Sunday afternoon.
                              A picture would show it nicer, but currently I don’t have an appropriate piece of wood at hand.

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                              • #30
                                Hey Peter,

                                I just picked up a bluetherm duo for my behmor and am considering doing a mod similar to yours. Are you still pretty happy with the results of yours? I'm trying to figure out which k-type probe to buy. Any suggestions?

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