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Thread: Bucket Cooler MkII - advice required

  1. #1
    Sleep is overrated Thundergod's Avatar
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    Bucket Cooler MkII - advice required

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Ive almost finished my new cooler.

    Pics to come later.

    Its a bucket in a bucket powered by a vacuum cleaner motor with a flat bottomed wire mesh sieve on top.
    On/Off switch is from a dead Taurus (Aldi) Heatgun.

    Test run appears to show more suction than my old Sadie-powered version; but to be fair the hose connection hole had developed a large leak.

    Problem:

    The vacuum motor driving this unit has a slide switch to vary the power.

    At the moment Im running on half throttle.
    Starting up at full throttle gives the bucket a hell of a jolt as the motor is only a tight fit in a hole in the bottom of one bucket (in other words not bolted in).
    Starting at minimum or half is acceptable.
    Indications from my test run are that I may not need full power for effective cooling. Live testing will confirm.

    Any idea how this slide switch may work and what it does to the power consumed and the motor?

    Is minimum adding electrical resistance to slow the motor?
    If yes is this a bad thing in the long run or of little consequence.
    Each use is only likely to run for a maximum of 2 minutes (way less than the vacuum cleaner was designed for).

    Im trying to decide if I need to make the slide switch accessible from the outside or just leave it set and inside the cooler.

  2. #2
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    Re: Bean Cooler advice required

    Hi TG,

    depends on the motor type but *as the motor will be AC rather than DC the control method is a little different to just adding a resistor like you can do with a DC motor. Basically it doesnt just convert the reduction in power to heat like a resistor would do so dont worry about it or any heat generated to much. It is a more complicated answer if needs be but what you have planned wont cause any problems. :)

    Thought about it just a little more and iff anyone is planning on running any AC motor for extended periods at below 30-40% speed then there is a potential cooling problem for the motor but that means 10 minutes plus (at least). There is derating factors etc but to tech for here.

  3. #3
    Sleep is overrated Thundergod's Avatar
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    Re: Bean Cooler advice required

    Thanks beanflying.
    Ive decided for the small amount of time it will be running, compared to a full power vacuum cleaning session, Ill run it at full throttle.

    Here are some pics.

    Theres another air outlet on the opposite side as well.

    The second one shows the motor looking in from the top.
    The rubber surround was reversed from its original position on top to underneath to dampen any vibration and also help seal the hole a little.

    The last picture shows the sieve mounted into the bucket lid.
    I will not lock it in place, merely let it sit on top for easy transfer of the beans after cooling.






  4. #4
    Senior Groupie LindaD's Avatar
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    Re: Bean Cooler advice required

    Quote Originally Posted by 013D203B313027323A31550 link=1232439433/0#0 date=1232439433
    flat bottomed wire mesh sieve on top.
    TG that setup looks great *[smiley=thumbsup.gif]

    What sort of sieve is that and where did you get it?. It almost looks like a sieve you use when panning for gold. *:)

    -Linda

  5. #5
    Sleep is overrated Thundergod's Avatar
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    Re: Bucket Cooler MkII - advice required

    Thanks Linda.

    I did enquire about gold panning sieves but they are bloody expensive.

    I got it for $5 at my local Asian "Junk Shop".

    My stainless steel colander in my original version didnt have enough holes for my liking and it was extremely hard to drill more.

    This one being wire mesh seems to breathe so much more freely.

    I almost cant wait to roast my next batch of beans so I can test it out.


    Cost:
    Sieve $5
    Buckets $4 ($2 each from the local Haloumi cheese manufacturer)
    Switch $0 (from dead HG)
    Praise from Linda - Priceless

  6. #6
    Mal Dimal's Avatar
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    Re: Bucket Cooler MkII - advice required

    Youve got to be a bit careful with using vacuum cleaner motor/blower assemblies TG as generally, they are not designed to run ad infinitum with an unrestricted intake, or the motor running flat-out continuously. The motor would soon overheat, brushes burn out, bearings fail, etc. This is all due to the motor running in an overloaded condition, i.e. the blower just pushes too much air through. Normally, they have some form of restriction on the suction side in the shape of filters, bags, etc before the air reaches the blower intake.

    A simple way to get around this without the need to involve electronics, etc is to just manufacture a simple restrictor plate and fit this over the intake of the blower. Something around 50-60% of the original cross-sectional area would work ok. You could then just leave the speed controller set to maximum or ask a knowledgeable electronics friend to bypass it it for you. Because of the myriad possibilities in how this device is designed, Id hesitate to make a recommendation from afar.

    Anyway mate, let us know how you get on.....

    Cheers :)
    Mal.

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    Re: Bucket Cooler MkII - advice required

    This was my pickup (no longer used) before the Hottop built in cooler It is a test sieve used for grading soil and rock samples. I was sitting it on a tiltable fan that was used to keep the smoke away while roasting then swung vertical with the sieve on top. So shiney ;)


  8. #8
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    Re: Bucket Cooler MkII - advice required

    @ Mal

    Thanks Mal.

    Im afraid my poor old non engineers brain doesnt understand your explanation.
    Wouldnt a restriction to the air intake cause strain on the motor as it struggles to overcome the restriction?
    Less airflow would mean a warmer motor.

    As mine runs now all the airflow cools the motor; this will obviously change when I add hot beans.

    Any way, I dont see it running more than 2 minutes at a time once a week.

    The motor was free so well call it an experiment and see how long it lasts.

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    Re: Bucket Cooler MkII - advice required

    Thundergod,

    A series motor (like in a vacuum cleaner) will run at an excessive speed without a load (restriction in the air passage). The load reduces the speed to a "more normal" rate of rotation where bearings run more happily and where the windings arent trying to exit the motor due to centrifugal (or as "modern" physics calls it centripetal) force.

    I still cant understand how things leaving the centre are effected by centre seeking force ::)

    But whatever the physics explanation - a series motor designed to rotate at a very high speed - without the benefit of any load - will try to self destruct..... and thats the important bit!!

  10. #10
    Mal Dimal's Avatar
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    Re: Bucket Cooler MkII - advice required

    Yep,

    What JB said.... I dont think a vacuum cleaner motor/blower would "fly apart" as such though, most likely burn the motor out or the brushes before that would happen. Basically, a vacuum cleaner is a Series Wound Motor, also called a Universal Motor, driving a single or multiple stage Centrifugal Blower. It is the air being drawn into the blower that provides the "suction" that we all associate with so-called vacuum cleaners.

    The series wound motor that JB refers to above, has a theoretical infinite speed when no load is attached to the shaft. In this situation, the motor would indeed self destruct as it rapidly and continually increased in speed. Centrifugal Blowers on the other hand, will continue to move more and more air through them as the shaft speed increases, at an almost exponential rate until such time as the limits of the blower design are reached. What this means with respect to motor load, is that as the series motor continues to accelerate, the load from the blower causes an exponential increase in motor load in proportion to the quantity of air being moved. At some point, equilibrium will be attained but with no restrictions either to the suction side or the exhaust side of the blower, this will usually be at some point above the full load rating of the motor which will result in the eventual failure of the motor.

    As you know, most vacuum cleaners use some form of filtering system, bag collection system, etc and this provides the necessary "throttling" required to limit the motor load so that it stays within its designed rating. Take the motor/blower assembly out of the machine though, and all that designed and intended restriction to the throughput of the blower has been removed and this will result in an increase in load of the motor, probably beyond what it is rated to run continuously.

    To overcome this situation, you need to provide the requisite restriction to the air-flow that was once provided by the vacuum cleaners filter/bag/cyclone system and the easiest and most effective way to do this is to just fit a restrictor plate over the intake/exhaust as I described above. It is usually much easier to fit this plate over the intake though and that is why I suggested it. Hope this brief explanation has cleared things up a bit mate and not muddied the waters even further.

    All the best :)
    Mal.

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    Re: Bucket Cooler MkII - advice required

    *
    Very nice Thundergod. [smiley=thumbsup.gif]

    I dont know much than I need (for floor cleaning purposes) about vacuum cleaners but, as it was free, how can you lose? *

    My hubby helped one of his apprentices build a small forge fire for home a couple of years ago and they used a second hand commercial vacuum cleaner as a blower. *I know it gets a lot of use (as hes very keen on making Damascus steel knives at the moment) and its still going strong.

    Look foward to hearing how it goes - Carrie *:)

  12. #12
    Senior Member Koffee_Kosmo's Avatar
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    Re: Bucket Cooler MkII - advice required

    Good one TG
    If the motor fails I would use an exhaust fan

    I use an exhaust fan on my cooler and found it to work without fault

    KK

  13. #13
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    Re: Bucket Cooler MkII - advice required

    @ JavaB Thanks for the explanation.

    @ Mal I found a new bag in the box. I suppose I could restrict it with a piece of that.
    However, the beans themselves will cause some restriction when dumped into the sieve.
    As I said initially, live testing will confirm some things.

    @ CarrieK Stay tuned.

    @ Koffee Kosmo Everyone uses an exhaust fan; Im different.


  14. #14
    Mal Dimal's Avatar
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    Re: Bucket Cooler MkII - advice required

    No worries TG.... :)

    Used motor/blower assemblies are probably a dime a dozen from appliance repair centres so if one gives up the ghost, should be cheap and easy to get replacements. Id imagine if you had a choice, probably try to get units that had a previous life working in a shop-vac or similar. Theyd most likely use a higher rated motor..... Anyway, time will tell ;)

    All the best,
    Mal.

  15. #15
    22a
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    Re: Bucket Cooler MkII - advice required

    Nice work TG. Ive got mine set up in a very similar way. Works a treat too, although it sounds like a jet engine when I turn it on. Luckily youve already avoided the (magnificently stupid) design flaw that I had originally of not drilling an exhaust hole. I had assumed the air would simply flow out the bottom, which was open. I ended up with a bean-cooling hovercraft zooming around my kitchen floor.




  16. #16
    Sleep is overrated Thundergod's Avatar
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    Re: Bucket Cooler MkII - advice required

    Behmor Coffee Roaster
    Quote Originally Posted by 79792A4B0 link=1232439433/14#14 date=1232477970
    I ended up with a bean-cooling hovercraft zooming around my kitchen floor.
    ;D

    You should have told me earlier so I could have tried for myself before cutting the holes.



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