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  1. #91
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by BaronJ View Post
    Hi Bob,

    Have you thought about the insulation that is used on the walls of camper vans ?

    Its a 5 mm thick synthetic foam rubber that is self-adhesive on one side and a 2 mm thick metallised plastic bubble bonded onto the other. Its rated to 150 C. I've loads of it from when I did my van, I'll take a picture later.

    One thing that I will say is that once you have stuck it on it doesn't come off easily, even with the heat of direct sunlight on the van walls.
    Thanks.

  2. #92
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    Hi Bob,

    Some pictures of the insulation I referred to earlier.

    I used this stuff on all the walls, roof and floor of the van and then did the lining out with plywood and wool carpet. It really keeps the heat out and suppresses the noise from outside. Net result is a cool van when its hot outside and nice and cosy when it gets cold.

    30-09-2019-2.JPG 30-09-2019-1.jpg 30-09-2019-3.JPG
    It is 8 mm thick overall, with a strong adhesive on one side that grabs on contact, so you do have to be careful when applying it. The other side is a layer of nitrogen filled plastic bubbles with a metallised plastic film glued on top. The idea is that it reflects the heat or cold back into the van. Its rated to withstand 150 C.
    Best Regards:
    Baron J.

  3. #93
    BobL is offline Member: Blue and white apron brigade
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    Thanks for the info. It looks like the van insulation would be perfect for the sides but I am less concerned about the sides as I am about the top which unfortunately has a much smaller gap. Some of the gaps at the top are 5mm or even less so I would have to cut around these spots. This is why I went for the thin (~1mm) silicone sheet. So far it seems to be doing its thing and has stabilised the temp enough for my liking for the moment. There are still the odd temperatures fluctuationsthat cannot be explained by the usual boiler cycling but I have moved onto another coffee related project which I will post about as soon as I have something to show.

  4. #94
    BobL is offline Member: Blue and white apron brigade
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    Coffee machine is going well but here I'm reporting on a coffee related experience that coffee nerds may be interested in.

    Today my uber coffee nerd mate arranged for us to get access to a "coffee lab" containing a wide range of coffee making equipment and testing gear to test out some of our ideas. The lab is owned by a major roaster that my mate used to work for. To give you an idea of the gear involved the coffee machine we were using was a 3 group head Synesso ( $20k+) the grinder was an automated Mazzer Robur Electronic (~$3), and the auto tamper was was about $2k. With all this gear being able to be automated we could consistently fix some variables to be automatically reproduced and could then test, for example, the overall extraction using a Coffee specific Total Dissolved Solids (TDS) meter ($1.5k).

    We were given a bag of fresh coffee and spent over 2 hours making about 2 dozen coffees. The coffee was all ground the same way and weighed into the portafilter using digital scales. The coffees all looked amazing to me but all bar 2 coffees ended up down the sink as I had already had 3 double shots before arriving and we were served a different coffee on arrival.

    Today was just a play around day to get a handle on the gear for future testing of some other ideas. One thing we check out was how the extraction (amount of coffee extracted) depended on tamper force and it turns out it is not dependent on tamping pressure at all. In fact "no tamping at all" and just a level filter basket produces the same extraction as coffee tamped with 30kg force. We also checked out the reproducibility of the TDS meter - it reads to 0.01% but the reproducibility is something like about 0.3% extraction for typical extractions of 20%. Not as good as we hoped for but it should be enough for what we want to do.

    Taste interpretations are of course a a different matter but we don't get too much into that. It's basically good, so-so or not good.

    We are going back again in a couple of weeks once we decide what else we are going to test. I will try to remember to takes some photos next time

  5. #95
    BobL is offline Member: Blue and white apron brigade
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    More coffee nerdy frippery. . . . . stop here if you are not into "frippery" - go and find something more useful to do with your time

    One of the aspects of making espresso that seems to get a lot of attention is the tamping of freshly ground coffee into the portafilter/ basket. In my previous post I suggested that tamping was not necessary in terms of % coffee extraction, although taste is possibly another matter . What is desirable is an even distribution of the ground coffee in the basket otherwise the water will not pass evenly through the same distance/volume of coffee leading to "over extraction" of some of the coffee and "under extraction" of other. To this effect some baristas tap the portafilter with the tamper or onto a table while others use a highly over priced "distributor" to sweep the coffee grounds out to fill the basket evenly. Auto tamping is carried out with various manual and (semi) automated devices some of which cost more than $1k!

    While watching a vid of all this it got me thinking about using vibration to more evenly dIstribute and pack the coffee into the filter basket. I have a mind the time when I used to work at a concrete slab factory and later as a high rise form work labourer when we used vibe to settle wet concrete inside form work. It's very quick and produces a very compact layer of settled material.

    By way of a pre-test I got out one of my old 1/3rd sheet vibration sander, tipped it upside down and put a portafilter filled with coffee on the pad and turned it on. The coffee just went everywhere so I tried it again this time with the tamper just sitting on top and it distributed and tamped the coffee to as firm as hand tamping in less than a second. Of course being untouched by human hand the process is quite reproducible.

    To further explore this possibility I have made the following apparatus.
    Remember this apparatus is for testing, any working product would need to be much more compact and possibly even built into the coffee grinder.

    It's basically a sprung table that firmly holds a portafilter handle and basket. A tamper is just paced on top to prevent the coffee flying off everywhere and to provide a counter weight. Two small vibrators (DC motors that rotate small offset weights) will be attached to the underside of the top and connected to a micro controller to switch the motors on and off so control length of time of vibration. An on board accelerometer connected to the MC will measure the g-forces. Other variables examined will be vibe frequency (motor RPM), motor directions, amplitude of vibe etc.

    VT1.JPG

    Underside.
    VT23.JPG

    The whole thing is made from 4 and 5mm ally plate and SS screws (because that is what I had in the desired sizes), a real working product would need to be all in SS. The bayonet plate that enables the portafilter (PF) to clip onto the underside of the table and apply firm pressure to the 5mm thick rubber gasket is so that it can be held firmly while being vibrated. The current bayonet plate suits my coffee machine but as we will be taking this into the roasters coffee lab I will need to make another plate to suit their machine's PF..

    This approach is unlikely to be the way any final product will be made/used. Once the optimum vibe parameters are determines I envisage setting up a shallow rubber covered vibrating plate onto which the coffee filled PF with tamper on top is just placed/held on top which automatically switches on a vibration source.

    I wanted to call this "vibrotamp" but my colleague prefers "vibroset" as in "vibe settling".

    I am leaving this in the electronics section because I have prototyped the micro controller and its now working - just need to get it into a suitable box for working with. I will post about this soon. I am also making the MC setup into a generic vibe measuring device so that I can use it on machinery and don't have to risk constantly using my mobile phone or iPad as a vibe measuring devices.

    I told you it was going to be nerdy frippery - and it is only going to get worse.



    .

  6. #96
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    Hi Bob,

    That's why we are called "Experimental Engineers"
    Best Regards:
    Baron J.

  7. #97
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    I wonder if an adequate effect could be achieved by just holding the portafilter down on a vibrating rubber pad, or rubber-covered forks?

  8. #98
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by RustyArc View Post
    I wonder if an adequate effect could be achieved by just holding the portafilter down on a vibrating rubber pad, or rubber-covered forks?
    That’s exactly where I’m eventually headed but I’m doing the above to test things out first.

  9. #99
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    Hi Bob,

    If you want small vibrators, grab a defunct Sony game controller ! There's usually two different size ones in them. They run at 5 to 8 volts. I've tried one at 12 volts and had to disconnect the supply voltage to catch it ! It bounced all over the bench. Also some mobile phones have them as well, but they are very small. You can alter the frequency by adjusting the voltage.

    HTH.
    Best Regards:
    Baron J.

  10. #100
    BobL is offline Member: Blue and white apron brigade
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    Thanks BJ. I’ve researched vibe motors and played with some small one used for haptic feedback such as are used in mobile phones and various game controllers. Some of these are very powerful but I have a feeling they will still be too small for this purpose. I’ve played around with a 12V motor from a cordless drill but it drew between 5 and 17A (@ full rpm) from a 12V car battery. I’ve ordered some cheap ($5) vibe motors on line that nominally operate between 6 and 12V but given I’m only running them for about 3 s at a time I’m hoping to run them over a wider range than this. These draw between 250 & 500 mA so this is up to 1A for 2 motors. The mains V sheet sander I was using was rated @ 140W but it was not transferring much vibe onto the PF. It will be a suck it and see experiment.

    Have also experimented with a loudspeaker and square wave as a vibe source. It also sort of works ( between 6 and 30 Hz ie good motor speeds) but appears quite inefficient

  11. #101
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    Hi Bob,

    I suppose that it depends upon the distance or amplitude of vibration that you need along with the frequency.

    I've used the big Sony one with a half size rotor, (little one is same shaft size) to create a crude ultra sonic water bath. It worked quite well, but I was only playing about at the time.
    Best Regards:
    Baron J.

  12. #102
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    Interesting idea Bob.

    I would think you will need the weight on top of the puck whilst vibrating to get compaction.

    Given coffee grains are so light, I suspect without weight you would have a lot of air in the puck.

    Easy variable to test.

  13. #103
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    One of these shaker speakers comes to mind:
    https://www.ebay.com.au/itm/Dayton-P...frcectupt=true

  14. #104
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by RustyArc View Post
    One of these shaker speakers comes to mind:
    https://www.ebay.com.au/itm/Dayton-P...frcectupt=true
    I've looked into these sorts of things and may even go back to them in the future. They typically have reasonable efficient frequency production in the normal hearing range (20Hz to kHz) however preliminary testing shows the vibe I'm finding that works is in the 3 to 30 kHz range which is why I'm initially using a $5 mechanical oscillator (motor) rather the EM vibe sources. The other thing is that these speakers require a power amp which ads significantly to the cost.

  15. #105
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    Quote Originally Posted by BobL View Post
    preliminary testing shows the vibe I'm finding that works is in the 3 to 30 kHz range
    OK - that's much higher than I imagined. I was thinking you could just plug the speaker into an AC transformer and use 50Hz.

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