Steel-to-Ali equivalency calculator

  1. Browser Happiness is an even fillet.

    Messages:
    412
    Location:
    South Lincs, UK.
    Fellow forum members, is there a rough rule of thumb one can use for working out an equivalent size of ali tube to use in place of steel for lighter weight? I'm making up some one-off cleaning tools at work and they need 3 metre handles, and even using fairly thin-wall tube (I decided on 1.22mm wall x 34.93mm dia so it doesn't flex too much) means the handle will weigh nearly 3 kg, and this has been suggested as being too heavy, so I thought an ali handle screwed to a steel head would do the trick, but I didn't want to get ali that was too thin and potentially bendy/flexy.
    If there is such a thing as a rough rule, please can you let me know :)
     
  2. Parm

    Parm I only give advice if I know

    Messages:
    5,235
    Location:
    Towcester
    Cant help you with any rules of thumb as such but at a clients site they were having issues cleaning sugar dust from high level metal work. They tried home made ali tools with some degree of success. Problem was that they got knocked about and generally didn't last very long.

    After much head scratching and research they settled for titanium tube with a threaded ali head on to which tools could be fitted. I think they also tried expanding foam inside the tube to limit the amount of flexing
     
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  3. mike 109444

    mike 109444 Member

    Messages:
    3,778
    uk Bristol
    Like Mr Parm can't help with direct experience but if you look around for the guys that clean office windows, they use a VERY long extending pole with hose attached for the higher windows. You might find it easier/cheaper obtaining some of them (the polls that is! No not the Polish guys either!! :laughing:)
     
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  4. hotrodder Member

    Messages:
    4,598
    SE England
    Rough rule of thumb is that aluminium is ~ 1/3 the stiffness of steels and ~1/3 density. Titanium is about 1/2 the stiffness and density of steels. The elastic modulus/stiffness (Young's Modulus) barely changes for different alloys i.e. even flavours of aluminium that are 'stronger' than mild steel are still ~ 1/3 stiffness even if it takes more force to permanently bend them

    For most stuff stiffness of the product is also a function of design which is tweaked to take advantage of the different properties. Bicycle frames for example... steel vs aluminium vs titanium all end up with different tube diameters and wall thickness with ali most noticably using larger diameters

    http://cleaningspot.co.uk/acatalog/ungernLitewaterfedpolecatalogue.pdf is about window cleaning pole systems, stiffness and the materials used
    For a length of tube used as a 3m handle then if 1 3/8" x 18swg steel tube is gonna be just stiff enough then increasing the dia in ali would increasae the stiffness more quickly than the weight given it's lower density. Don't think you'll find 18swg ali tube above 1 1/4" dia, 1 5/8 x 16swg (41 x 1.5mm) should weigh ~ 1/2kg per metre according to the Aalco catalogue i'm looking at. You'll have to do your own stiffness calcs or punch some numbers into something like http://www.engineering.com/calculators/beams.htm#tube
     
  5. voipio Member

    Messages:
    410
    Cambridge, UK
  6. penfold

    penfold Ambassador plenipotentiary

    Messages:
    2,055
    Location:
    Argyll and Bute, God's own country.
    If wobbliness/flex is to be avoided carbon fibre tubing might be justified, very light too.
     
  7. norlander

    norlander Member

    Messages:
    3,421
    Location:
    Europe, mocycling paradise
    Look into budget priced fishing poles (not rods) the first three sections might do you, maybe the first two. Not sure about attaching the cleaning head.
    Wrapping the tubes in gaffa tape may help as reinforcing.

    Be careful if you go that route, carbon fibre splinters are nasty, and reckoned by some to cause additional problems, might want to check with HSE maybe.

    The sections fit into each other if you need to break the tool down for storage or adjust length.

    If that works, you could become the firms pole star.
     
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