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Thread: Wood pulleys?

  1. #1
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    Default Wood pulleys?

    Hi guys/girls,

    You will have to forgive my naive questions here as I a newbie to wood working in general.

    I have an application that requires the use of two v-belt pulleys that are non standard diameters. I am having trouble finding aluminium pulleys that will give me the required ratio......so.... I thought that I may be able to get a couple of wood pulleys lathed up to satisfy the requirement.

    I have a couple of questions.....

    1. Is wood strong enough to be used as pulleys? More so the pressure on the sides of the v-belt groove.
    2. How much "meat" would you need around the groove to make it reasonably strong?
    3. What wood would be appropriate. I assume a hard wood would do the trick, but have no idea.
    4. How much heavier would a wood pulley be compared to a metal one?
    5. do you think heat is the number one concideration?

    Thanks in advance for your help.

    Cheers

    Paul

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  3. #2
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    Cliff.
    If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.

  4. #3
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    It would probaly be just as easy to get them turned up out of aluminium.
    Particulraly if they have to transmit power to the shaft.
    Check out the local engineering shops nearby, especilay if you live in a mining of farming community.
    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  5. #4
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    Hi Soundman,

    Yep, tried to source an aluminium pulley through the local engineering mobs. You would not believe the price they want just to lathe up a couple of pulleys.

    I think it is the cost of Aluminium stock. Obviously they need a fairly chunky piece of it to wittle away......

    If wood can perform the function, it would definately be the cheeper option.

    Cheers

    Paul

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    Quote Originally Posted by rotorque
    I have an application that requires the use of two v-belt pulleys that are non standard diameters. I am having trouble finding aluminium pulleys that will give me the required ratio......so....
    Paul, can you use four pulleys on three shafts to get the final ratio you need?
    1:1.2 then 1:1.15 should give 1:1.38 (if I've got the maths right)

    ian

  7. #6
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    Hi Rotorque,

    I have made a number of custom pulleys from wood, knocking together kinetic artworks (basically wanky machines with an electric motor that do bugger all! ).
    For smaller ones, some with multi "V's", I've had good service from spotted gum. I made a custom turning scraper with the exact V needed for the belts I had, but careful work with a standard V tool and maybe a basic gauge/template will do it.
    For larger ones I've used Formply, that hardwood ply used by concretors, but any good quality thick ply would work. The problem really is the thickness of the outer edges remaining after lathe work. They don't look pretty in that area, and sanding after on a good disc sander will help. As you know the belt doesn't have to sit right down the walls of the V, so allows for clean up.
    Thick MDF works for test pulleys, cheap and quick, but won't last.
    Just thinking, if you wanted a really impressive looking pulley that would last, try somehow laminating a sectioned hardwood rim onto a ply disc then lathing the rim to shape! Might go and try that myself !
    As for the heat buildup, I haven't found it to be an issue....although not absolutely sure it couldn't happen:eek: . I have made many sets of spotted gum bushings over the years, directly running steel shafts into holes bored through, and they'll last for years. Serious. Some windmills still run hardwood (red gum) bushings in their main workings, new 'uns. Reasonable speeds and the friction produced may not be that big an issue, but certainly test your machine first.
    Good luck.
    Andy Mac
    Change is inevitable, growth is optional.

  8. #7
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    Hi All

    Maybe a simple question, how would you attach the pulley to the shaft,I have thought of using a steel/ brass sleeve the you can tap and use a set screw or would a collar work the best.

    Regards
    Solly

  9. #8
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    Quote Originally Posted by Rhino_Bhejane
    ..Maybe a simple question, how would you attach the pulley to the shaft,..
    Just glue and/or screw it to a regular pulley.
    I glued my big one onto a truck flywheel that was already mounded on the shaft.
    The intermediate one on the lay shaft was glued to a smaller ali pulley.
    Cliff.
    If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.

  10. #9
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    Mounting the wooden part to an existing smaller pulley works well, that way the grub screw and sleeve are there, and even old pulleys with broken V's can be reused. Another option is to glue a block of timber in the sleeve area, and/or a welded flange with a nut and bolt.


    Cheers,
    Andy Mac
    Change is inevitable, growth is optional.

  11. #10
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    Thanks guys,


    Great info. I was thinking of using a steel sleeve, similar in shape half a cotton reel and pressing this into the core of the pulley. I can then bolt through the top flange of my sleeve (cotton reel) and the pulley. I will need to run a lubricated bearing through the steel sleeve for one of the pulley set ups so want to be able to interference fit this bearing.

    Ian:
    You hit the nail on the head...... that's exactly what I am up to. In fact the set up has a vertical shaft driven through a right angle gear box. This "master" drive shaft will turn a small 3 belt multi vee-drive pulley, through to a larger pulley (ratio to be worked out). This second larger pulley is mated with another smaller pulley (similar size to the master pulley) running back over the top of the master pulley to the "slave" drive shaft, the one that needs the reduced RPM. Clear as mud.

    In essence, there are three shafts.

    Probably the only other question is what sort of power I can run through these pulleys. I need to apply 130 Horse power (100Kw or 2500Nm) at the main slave drive shaft...... I can't see a problem if the attachments to the pulleys are appropriate. I don't think it is the wood that is the week link in this case. Can anyone give difinitive answers on this?

    Cheers

    Paul

  12. #11
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    The British (and all other) Navies used wooden blocks and sheeves for 400 years and did OK, as I remember.

    I have a vague recollection that they used one particular European wood for the running rigging. I seem to remember they found a better one 'in the tropics' may have been Ironwood???

    Suggest you Google it. I've a small reference library at home on Nautical stuff and I'll have a look. Hopefully I'll find some drawings which I'll scan. That would give you an idea of the proportions and tolerances required.
    Bodgy
    "Is it not enough simply to be able to appreciate the beauty of the garden without it being necessary to believe that there are faeries at the bottom of it? " Douglas Adams

  13. #12
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    That is serious horsepower.
    With that in mind I think you are better advised to used metal pulleys
    Regards, Bob Thomas

    www.wombatsawmill.com

  14. #13
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    Look if the sheaves are big enough & beefy enough and you have some way of fastening to the shaft securely, you would be surprised what you will get away with.
    My big bro is a windmill doctor up north and most cretainly all the decent mills run hardwood bearings and they last for many decades as long as the lube is kept up to them. The forces on these bearings is quite high.
    Consider the sail of a 40' mill in a stiff wind on hardwood bearings.
    The prefered timber varies on location the timber of choice in the north is cooktown ironwood.
    The sheaves in blocks on sailing ships is a diferent thing all together but yes they were most certaily timber. The prefered timber (i seem to recolect) was lignim vitaie.

    BTW what are you doing with 100+ horsepower? Is this a chalenger to the big blue lathe?

    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

  15. #14
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    I need to apply 130 Horse power (100Kw or 2500Nm) at the main slave drive shaft...... I can't see a problem if the attachments to the pulleys are appropriate. I don't think it is the wood that is the week link in this case. Can anyone give difinitive answers on this?
    Paul, I think I can.
    130 Horse is car engine type power, and not a small 4 cylinder either.
    2500Nm is the sort of torque you use to get a 70 ton off road mining truck moving. Looking at the Caterpillar site, you need an 18 litre (or 1100 cubic inch) 500 hp diesel engine to get that sort of torque.
    You sure about those power and torque figures?

    If so I don't think I want to be anywhere near your wooden pulleys when you start it up!

    ian
    Last edited by ian; 21st October 2005 at 12:16 AM. Reason: spelling and grammer errors

  16. #15
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    Hi Ian,

    Your patially correct...... The 130 Hp is from a Subaru engine (2.2 ltr to be exact.... ah, you say, now I know your secret). The 100Kw is just a conversion of the HP.

    The 2500Nm is the torque measured on the output shaft...... torque calculations have to take into account the power and the minimum RPM of the output shaft etc etc so is only relavant to the application at hand..... An example, say, is the tractor. When applying a large force to the axle of your tonka truck, whilst rotating slowly (low gear) there is conciderable torque required to get the old girl going. My application has relatively low inertia and higher RPM...... She'll be right mate.

    You will have to forgive me, as I am always the optimist. This sort of power is not all that great, and the engineering principals of pulley systems are relatively basic.

    RPM is relavant, and so is side load. These factors, I believe, are potential failure modes. But.... Due to the tensile strength of the belt systems, alot of the centrifical forces on a pulley are countered by the tension on the belt, sort of holding the whole thing together. The side loads on the shaft are taken into account by the strength of the material itself, in my case they will be metal. The one that worries me is the groove wall strength, this is where the choice of wood becomes important.

    From doing other research on the side, it is pointing to using a ply. Probably marine, or similar. I have been told that due to the cross graining on multiple laminates, the strength exceeds even hard wood that is not cut appropriately with regards to grain.... It's getting quite technical which I am finding fascinating..... I may be a woodwork convert.

    Reading the above, I'm pretty good at convincing even myself......

    Cheers

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