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Dema.RAL tamper discussion

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  • #91
    Re: Dema.RAL tamper discussion

    Originally posted by 644345424F360 link=1227148434/88#88 date=1271313096
    Hey that sounds great but could be a bit complex to design without infringing the Espro patent  :

    I think it would be cheaper to use the Dema.RAL in conjunction with a Click-Mat.
    Click-Mats dont work that well with tamper stands.

    It could be made simpler than the Espro by just having a spring mechanism using a 10N/mm rate spring with 11mm of preload and 1mm of alllowed movement between the tamper shaft and the disc. Then as soon as the shaft began to move independantly of the disc, you would know that you had reached 110N of force (assuming that the length has been set long enough not to bottom out) and when the shaft and disc lock again then you would have reached 120N of force on the puck. Both points should be pretty easily detectable so you only have a small range of error if you tamp until the shaft/disc assembly begins to compress.

    I feel that adjustability of the force isnt necessary as the key is consistency but by allowing for the preload to be adjustable, you would be able to vary the force range indicated by the tamper (of course, adjustment would add further complexity/cost).

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    • #92
      Re: Dema.RAL tamper discussion

      Hi Kannage.
      The problem in the past has been the selection of the spring. The spring that I have decided to use has a wire cross section diameter thin enough to maintain a preloaded force of 10 to 20 N thus only requiring a mass load of 1 to 2 kg (9.8N = 1kg) to initiate and maitain this load over the full length of the stroke, what this does is place the operator in control it allows them to "Feel" what is taking place.
      The spring I use has a "nominal" load rate, if I was to use a spring with a toleranced load rate the cost of the spring would be 5x the cost, due to sample load testing the springs before and after heat treatment .
      All the designs I imagined were simple enough at first glance, but when you throw in the most inportant variable "The end user" its a whole new ball game.

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      • #93
        Re: Dema.RAL tamper discussion

        Fair enough. It took years for Harrison to produce consistent enough springs for him to win the Longitude prize.

        Im guessing, then, that one of the reasons you investigated adjustable force designs was to allow for dialling in vs spring rate tolerances.

        Could an elastomer be used instead of a spring?

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        • #94
          Re: Dema.RAL tamper discussion

          Have just finished making a coffee with my new Vibrant Green Demaral Tamper and shes a beauty!

          Ill post photos later, but Ive taken them with Petes new flash (pun intended!) Digital SLR and have no idea where the cable is to transfer them on to the computer, so theyll have to wait until he gets home from work tonight.

          I really love the feel of this tamper and, on initial use, have absolutely nothing negative to say about it at all.

          I was extremely lucky (or it was fortuitous and preplanned because Angelo had some knowledge of Mavers...if so, thanks Angelo!) that the tamper was set to the perfect level already so I didnt need to adjust it at all. I did my normal dosing - one thing Ive got really down pat with my technique and fortunately straight index finger to level off - and away I went with the Demaral.

          I had one of the nicest pours out of my Maver so far, I have to say.

          Well done, Angelo, on what I think it a great design for us numpty home baristas who are too short to do a straight forearm tamp unless they stand on their tippy toes!

          :-*

          Cheers
          Di

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          • #95
            Re: Dema.RAL tamper discussion

            Originally posted by 486F796B73000 link=1227148434/93#93 date=1272599656
            Ill post photos later, but Ive taken them with Petes new flash (pun intended!) Digital SLR and have no idea where the cable is to transfer them on to the computer, so theyll have to wait until he gets home from work tonight.
            If your PC has a card reader or you have a plug-in card reader you can take the card out of the camera and plug it into the PC.

            Dont tell Pete I told you if you stuff it up :

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            • #96
              Re: Dema.RAL tamper discussion

              Thanks Rusty - I gave that a go but it keeps on coming up with Card Reading Error, so I figure I better leave it alone for the moment, considering the camera is almost worth as much as my Maver!

              Cheers
              Di

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              • #97
                Re: Dema.RAL tamper discussion

                Originally posted by 406771637B080 link=1227148434/95#95 date=1272601512
                considering the camera is almost worth as much as my Maver!

                More to the point - your life is worth more than both

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                • #98
                  Re: Dema.RAL tamper discussion

                  Okay, here are my two babies...(excuse my GP - I probably should have given him a quick polish beforehand...its amazing how you dont notice something until you have it in close up!)





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