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Home Made Hot Air Roaster 0.5 - 3kg

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  • MrJack
    replied
    Yep. You can buy lantern glass (cylinders) for <$15 from a camping store. Otherwise look on ebay for borosilicate glass.

    Leave a comment:


  • Mischa
    replied
    A few lessons learned, going to make a new roaster from scratch i think. Similar design, just a few ease of use modifications.

    Does anyone know the easiest/cheapest way of buying small pieces of heat resistant glass?

    Leave a comment:


  • blend52
    replied
    Originally posted by Mischa View Post
    well i was thinking of getting a few different size drill bits and testing out which size works best. I was planning on putting the jet in the lathe on full speed (2000rpm) and using the tailstock chuck to drill the hole.
    Mischa,.. have a read of this page. It will give you a few tips on using that small drill bit..
    Drilling very small (0.010") holes in brass?

    Leave a comment:


  • Mischa
    replied
    Originally posted by MrJack View Post
    Can you vary the flow at all?

    My design is quite different. It uses a completely conical bed, with a pyrex tube section above to prevent strays and provide visibility. It's 110mm in diameter and is a bit greater in depth. 25mm at the inlet end.
    In that configuration my first prototype would not spout with more than 40g or so, due to the slightly anaemic air source.
    Yeah I've got a triac style motor speed controller, but the motor I've got is insanely powerful. I reckon I could loft 20kg+ with it. Do you have a diagram to illustrate your design?

    Leave a comment:


  • MrJack
    replied
    Originally posted by Mischa View Post
    Thanks for the info!

    The two sections just sit on top of each other, so i can take this roast chamber off and plonk one on thats a different size. I roasted 1kg in this roast chamber yesterday, however it is on the large size for that amount of coffee. I'm thinking that 80 or 100mm square would be better for 1kg, I'm planning to make one of that size tomorrow probably.
    Can you vary the flow at all?

    My design is quite different. It uses a completely conical bed, with a pyrex tube section above to prevent strays and provide visibility. It's 110mm in diameter and is a bit greater in depth. 25mm at the inlet end.
    In that configuration my first prototype would not spout with more than 40g or so, due to the slightly anaemic air source.

    Leave a comment:


  • gazza
    replied
    This what you need and it won't beak the bank, probably cost more for postage.


    Gary

    Click image for larger version

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  • Mischa
    replied
    Originally posted by blend52 View Post
    Any plans/thoughts for a chaf collector ?

    Also ..are you sure you mean 0.3mm jet size ?..
    That is very small for a burner jet, even my little camp stove is bigger than that !
    I have some slightly smaller drill bits ( 0.010" = 0.25mm), and to use them you need a special high speed precision drill press.
    well i was thinking of getting a few different size drill bits and testing out which size works best. I was planning on putting the jet in the lathe on full speed (2000rpm) and using the tailstock chuck to drill the hole.

    Leave a comment:


  • blend52
    replied
    Any plans/thoughts for a chaf collector ?

    Also ..are you sure you mean 0.3mm jet size ?..
    That is very small for a burner jet, even my little camp stove is bigger than that !
    I have some slightly smaller drill bits ( 0.010" = 0.25mm), and to use them you need a special high speed precision drill press.

    Leave a comment:


  • Mischa
    replied
    Originally posted by blend52 View Post
    Most carby jets ( Delorto, Mikuni, etc) are calibrated in "numbers" ..EG: .# 50, #85, #105, etc.
    But those numbers are actually hundredths of a millimeter.
    so a # 50, is actually 0.50 mm diameter.
    A good carby specialist should be able to sort you a #30 ..but good carby specialists are hard to find !
    The threaded fitting may be a bit different to gas fittings though ?
    Tip.. the common Honda 6.5 hp industrial 4 stroke uses a #28 main jet !

    PS.. nice project,
    Is there an optimized design for a 1kg version ?
    Thanks for the info!

    The two sections just sit on top of each other, so i can take this roast chamber off and plonk one on thats a different size. I roasted 1kg in this roast chamber yesterday, however it is on the large size for that amount of coffee. I'm thinking that 80 or 100mm square would be better for 1kg, I'm planning to make one of that size tomorrow probably.

    Leave a comment:


  • blend52
    replied
    Could you use carburettor jets instead perhaps?
    Originally posted by Mischa View Post
    possibly, but when i've searched for them they don't seem to give you the actual size of the jet? it seems to be all manufacturer specific sizing....
    Most carby jets ( Delorto, Mikuni, etc) are calibrated in "numbers" ..EG: .# 50, #85, #105, etc.
    But those numbers are actually hundredths of a millimeter.
    so a # 50, is actually 0.50 mm diameter.
    A good carby specialist should be able to sort you a #30 ..but good carby specialists are hard to find !
    The threaded fitting may be a bit different to gas fittings though ?
    Tip.. the common Honda 6.5 hp industrial 4 stroke uses a #28 main jet !

    PS.. nice project,
    Is there an optimized design for a 1kg version ?

    Leave a comment:


  • Javaphile
    replied
    Originally posted by MrJack View Post
    ...or even just fill it with small objects (i.e. beans) and the behaviour will likely be somewhat different.
    Yeah, I'm looking forward to seeing what kind of a movement pattern will emerge in a 3kg capable cone. I'm thinking maybe a cycle with the beans moving up in the center and down next to the cone.

    We may never find out though as Mischa said he was thinking of making circular ones, not conical shaped ones.


    Java "New toys are so much fun!" phile

    Leave a comment:


  • MrJack
    replied
    They work on flowrate from memory.
    You could probably confirm with the manufacturer or perhaps just measure some at a motorcycle shop?

    Leave a comment:


  • Mischa
    replied
    Originally posted by MrJack View Post
    Could you use carburettor jets instead perhaps?
    possibly, but when i've searched for them they don't seem to give you the actual size of the jet? it seems to be all manufacturer specific sizing. I also thought about using a MIG contact tip but the smallest they go down to is 0.6mm probably in the future i'd be better off just using a sievert burner as they seem to have the greatest range of burners.

    Leave a comment:


  • MrJack
    replied
    Originally posted by Mischa View Post
    I'm happy to make a few for fellow roasters.



    Thats true but in this case its turbulent air coming through any kind of diffuser plate, so it won't behave as if it was unrestricted and non-turbulent airflow.


    Does anyone know where to buy tiny drill bits? I think the jet on the burner is a bit too small, i want to drill it out to 0.3mm or so.
    Could you use carburettor jets instead perhaps?

    Leave a comment:


  • MrJack
    replied
    Originally posted by Javaphile View Post
    FYI Air forced into a cone at the narrow end travels along the sides of the cone and not in the middle.

    To see this in action light a match and hold the lit portion in the middle of the large side of a funnel and blow in the small side. No matter how hard you blow you can't put the match out.


    Java "Fun with Physics!" phile
    A fun phenomenon resulting from low flow and a very short duct (the pingpong ball experiment is fun too).
    Add a section of straight piping onto the outlet, increase the upstream pressure/flowrate, use a flow straightener or even just fill it with small objects (i.e. beans) and the behaviour will likely be somewhat different.

    Leave a comment:

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