Viewing 31 posts - 1 through 31 (of 31 total)
  • Ha ha! It only bloody works!
  • Stoner
    Free Member

    Following on from this thread:
    http://www.singletrackworld.com/forum/topic/qu-for-the-electronerds

    I got my hands on a pair of thermocouples for a couple of quid each. Two PCU heatsinks for £10 and a couple of 1.5v motors for £3 each. Two rotor blades for £3.

    So all in it’s cost £15 or so.

    And it works!

    [video]http://www.youtube.com/watch?v=zsE4YtzXZe8[/video]

    At least, the blade goes round, seems to be enough to keep sufficient heat differential across the thermocouple but it doesnt really feel like its moving much air around so I’ll have a go at fabricating my own impeller sometime.


    This is the second version, the first using the metal brackets and one heatsink just wouldnt transfer enough heat to the termocouple.

    The second attempt was much better.

    wwaswas
    Full Member

    good work.

    now, you just need sharper blades and some young children with inquisitive fingers…

    derek_starship
    Free Member

    Perhaps you should visit one of these more often:

    Fresh Goods Friday 696: The Middling Edition

    Fresh Goods Friday 696: The Middlin...
    Latest Singletrack Videos
    IanMunro
    Free Member

    Cool!
    What happens if you try it with the pettlier device sitting directly on the stove top, with the heat sink on top of it?

    FunkyDunc
    Free Member

    How much heat does it actually move in to the room though? Surely you need a much bigger fan?

    organic355
    Free Member

    ROLF ON: can you tell what it is yet? ROLF OFF

    Seriously, what is it?

    geoffj
    Full Member

    Coooooool!

    Stoner
    Free Member

    Ian – i tried it briefly (with an ice cube on the top 😉 ) but the fly leads are too close to the stove to leave there like that without running the risk of damaging them.

    organic, read the original thread, linked in the first post.

    Funky dunc – naff all! So I will try to make a better blade for it.

    cynic-al
    Free Member

    Needs some help with his arithmetic also.

    binners
    Full Member

    derek – it looks to me like he’s been visiting one of those far too often. In fact i suspect he may have been there all day 🙂

    uphillcursing
    Free Member

    I would be tempted to get a solid Aluminium block for the hot side. You will be losing a lot of the temperature differential from the Heatsink doing what it was designed to do.

    uphillcursing
    Free Member

    BTW, Did you measure the Current and Voltage?

    Stoner
    Free Member

    uphill – you’re right, I just didnt have a decent conductive block lying around so used the other sink.

    al – maths was for just the bits I used.

    £10 heatsinks
    £3 motor
    £1.50 blade
    £3 TEC
    so £17.50 if you want me to be accurate 🙂

    Stoner
    Free Member

    I managed to get just over 2v out of it at its peak.

    uphillcursing
    Free Member

    Get a larger diameter airscrew. shifts more air more efficiently. Or a higherKV motor(more RPM/V)less good for this IMHO.

    Saying that, as you increase the load on the motor it will try to draw more current. I doubt the supply is enough to burn out the motor but there will be an optimum point.

    Fun and games…..(insert nerd smiley)

    cynic-al
    Free Member

    Two PCU heatsinks for £10 and a couple of 1.5v motors for £3 each. Two rotor blades for £3.

    £19 there mate. Glad you’re not surveying my investment LOL111

    Stoner
    Free Member

    I doubt Ill be able to find a more appropriate motor – its hard enough to find one that works at these voltages anyway.

    What characteristics would a bigger air pushing screw have? If I want to make my own – i.e. what kind of ratio of surface area to void area? what kind of diameter and what kind of pitch on the blade face?

    Stoner
    Free Member

    Im only using one motor and one blade.

    SO £17.50

    Im glad Im not using you for my conveyance. LOLZZZ!!!111thickysolictorzzzz!!!! 😉

    uphillcursing
    Free Member

    Hmmmm. not my field of expertise

    However, they are usually quoted as having 2 vital statistics. The Diameter and the pitch. Diameter is self explanatory. pitch being how far would it travel forward given one full rotation assuming no losses.

    Model aeroplane sites might be a good place to ask.

    Stoner
    Free Member

    Ill probably just bodge about with some bottle plastic and a glue gun I think.

    uphillcursing
    Free Member

    Google got me this clicky

    Looks like they have ones that are thin to be use at high rpm. and these for lower rpm. What constitutes low/high I do not know but would guess you want this sort of thing.

    Pick your diameter so as to have no cooling on the hot side and at 70p each you can get a few different pitch combinations for some trial and error.

    cynic-al
    Free Member

    But your costs were for 2 rotors WTFparttimers111

    CASE CLOSED YOUR HONOUR.

    coffeeking
    Free Member

    You want to maximise heat conduction in the base (i.e. thin solid block of copper/alu, or take your existing one and wrap it in tinfoil, bottom half only of course) and maximise power dissipation in the top to maximise your delta T across the thermoelectric module (Which is actually a whole heap of thermocouples).

    You want a motor/blade combination that provides an electrical resistance of approximately equal to the electrical resistance of the thermoelectric module, this will give you approximately peak power output from the device.

    HTH

    Stoner
    Free Member

    You want a motor/blade combination that provides an electrical resistance of approximately equal to the electrical resistance of the thermoelectric module, this will give you approximately peak power output from the device.

    I’ll never be able to work that out 🙁

    I was going to wrap the bottom in aluminium tape to help.

    Quite remarkably the thing has kept on running all day long so at least Im getting sufficient delta T (i.e. the top block isnt heating up too much) to keep 1.5v+ output.

    kaesae
    Free Member

    Nice, eh you could power a steam engine with that stove?

    Stoner
    Free Member

    this is next. A sterling engine

    uphillcursing
    Free Member

    Looking at the pics. I would have thought lowering the motor height would get more airflow over the cold side heat sink. That would be my first port of call.

    coffeeking
    Free Member

    🙂 I’ve a full size one of those at work Stoner, running off 3kw of electrical power 🙂 Stirlings are fascinating engines, but VERY difficult to scale.

    Stoner
    Free Member

    uphill – I will lower the motor when Ive made a new blade

    ck – pics please 😉

    coffeeking
    Free Member

    Pics to your profile email?

    Stoner
    Free Member

    that’ll work. ta.

    Id love to make my own sterling engine but there’s no way I could machine the cylinder and piston to tight enough tolerances, so I will probably have to get a kit.

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