OT- Would this V belt pulley setup work?
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    Default OT- Would this V belt pulley setup work?

    The blue pulleys are all the same 6" diameter.

    The red pulley is 4" diameter, and so is the green pulley. The green is pulley is a smaller 'v' groove on the same pulley as the blue one. In other words, it is a 2 groove pulley made from a solid block of metal we'll call the RW pulley.

    The pulley at the bottom is the driving pulley and is going 3000RPM.

    So... all the 6" pulleys will spin the same 3000RPM. The red pulley will spin faster by the ratio of 6/4. Will the blue pulley R spin at 3000RPM or will it want to spin at the green 'W' pulley speed? Or will there be instant and constant 'disagreement' on the RW pulley and the belt starts slipping and smokin'?

    Note that the belt can't just go to the X pulley from the C pulley in a straight line as it will contact the W pulley diameter; it has to go over the pulley.pulley.jpg

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    the belt starts slipping and smokin'?
    And if you get the belts tight enough, nothing will move at all.

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    You need idler pulley in there on that dual groove location in the center. Either W or R has to be a idler and allowed to turn at a different rpm than the other because the belt speeds are the same, but pulley diameters are different.
    Last edited by Doug W; 11-20-2019 at 01:22 AM.

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    Can you go direct from green pulley to X pulley? So green pulley is driving X

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    I'm a bit dense..but what is the purpose of the belt over the green sheave..it has almost 'zero' wrap and will transmit almost 'zero' horsepower. For me..being dense, it would be much easier for you to explain what you're trying to achieve from which sheaves.

    If you put an imaginary line from the center of the green sheave out to its edge and rotate that sheave 360 degrees I think you'll see that the blue attached sheave rotates exactly the same as the green attached sheave, so in that case, there would be no smoking and screaming.

    Stuart

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    From my observation it looks like the belt will be traveling at a faster speed over the green pulley than the green pulley is turning. The belt isn't really slipping since it's driven, and the pulley isn't exactly slipping either. I think the only thing you will get is some smoke from the friction of the belt running at X surface over the pulley. From your explanation it looks like the belt will be traveling 50% faster than the pulley is spinning.

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    I feel like info is missing to make this make any sense. Is there a reason that RW pulley needs to be two different diameters? (such as something out of diagram that right belt wont clear if it is on a 6" pulley)

    With the limited info I would have guessed that the only reason that W pulley exists is as an idler position for the right belt. Is that correct? I really read the last line of the original post as: need W pulley so that belt doesn't rub on W pulley..just remove W pulley? What all is being driven on each shaft? Just make RW pulley the same diameter on both belt grooves, and this setup would then work as I am seeing it, so what is preventing same diameter that is not shown on this diagram?



    EDIT: The 6" drive pulley runs the belt at 4712.x fpm @3000rpm, so regardless of driven pulley size all the belts are moving at that speed across them. Now I am thinking it works as it is drawn up..it hurts my head to think about it too long. I am thinking that it does indeed work as it is drawn, but possibly only because C pulley and R pulley are the same diameter.

    EDIT2: I had to visualize RW pulley as two separate pulleys, it wont work. W pulley is a 4" pulley spinning at 3000rpm, therefore it wants a belt surface speed of 3141.x fpm, but has a belt traveling over it at 4712.x fpm so it will be fighting the belt. I suspect there would not be much "fight" speed wise as RW pulley will surely spin at closer to 3k rpm due to the belt wrap being 3.5 times what it is on W pulley, but the right belt will certainly have friction with W pulley. I imagine dragging a V belt through a pulley at ~1600 fpm will not make for a happy set up.

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    If you can't go directly from C to X because of clearance issues make W an idler pulley to sit on face of R. Or... make W and R the same diameter.

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    Quote Originally Posted by GregSY View Post
    The blue pulleys are all the same 6" diameter.

    The red pulley is 4" diameter, and so is the green pulley. The green is pulley is a smaller 'v' groove on the same pulley as the blue one. In other words, it is a 2 groove pulley made from a solid block of metal we'll call the RW pulley.

    The pulley at the bottom is the driving pulley and is going 3000RPM.

    So... all the 6" pulleys will spin the same 3000RPM. The red pulley will spin faster by the ratio of 6/4. Will the blue pulley R spin at 3000RPM or will it want to spin at the green 'W' pulley speed? Or will there be instant and constant 'disagreement' on the RW pulley and the belt starts slipping and smokin'?

    Note that the belt can't just go to the X pulley from the C pulley in a straight line as it will contact the W pulley diameter; it has to go over the pulley.pulley.jpg
    You would need a idler pulley between C&X to deflect the belt below or above W pulley as it won't work the way you have in your diagram.The way it is now the belt between C&X will slip on W and go up in smoke.

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    Aren't C, X and R all the same diameter. If W is attached to R, regardless of its diameter, it's turning the same speed as C and X so there should be no slipping and smoking..right?

    Stuart

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    Quote Originally Posted by atomarc View Post
    Aren't C, X and R all the same diameter. If W is attached to R, regardless of its diameter, it's turning the same speed as C and X so there should be no slipping and smoking..right?

    Stuart
    It is the same RPM yes, but a different surface speed. Think of turning a part on the lathe, you need to speed it up as part gets smaller to keep the same surface speed.

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    W may be a loose pulley,set on its own bearings on the same shaft.I used to make up A/C compressor mounts for old classic cars,and used some very strange arrangements to get all the belts in.

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    Quote Originally Posted by GregSY View Post
    The blue pulleys are all the same 6" diameter.

    The red pulley is 4" diameter, and so is the green pulley. The green is pulley is a smaller 'v' groove on the same pulley as the blue one. In other words, it is a 2 groove pulley made from a solid block of metal we'll call the RW pulley.

    The pulley at the bottom is the driving pulley and is going 3000RPM.

    So... all the 6" pulleys will spin the same 3000RPM. The red pulley will spin faster by the ratio of 6/4. Will the blue pulley R spin at 3000RPM or will it want to spin at the green 'W' pulley speed? Or will there be instant and constant 'disagreement' on the RW pulley and the belt starts slipping and smokin'?

    Note that the belt can't just go to the X pulley from the C pulley in a straight line as it will contact the W pulley diameter; it has to go over the pulley.pulley.jpg
    Make "W" the same 6" diameter as all the blue sheaves.

    Still a shitty design, but at least it is cheaper and more durable than making "W" an idler.

    Either of which will work

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    Thanks all.

    Yes, I thought of making W a 6" diameter and that's what I'll probably do. It's not an especially shitty way to do it...at least it's done in a lot of OEM applications that way so for whatever that's worth...


    W can't be an idler - there is no room for it. I mean 'zero' room. It also must be there because if you draw a line from X to C, it contacts the axis of the RW pulley. The drawing is not perfectly clear on that but trust me, there is no way to do it. If the center of RW were .5" diameter, it would clear but in the real world the various pieces used require that the minimum diameter of the RW pulley - where it slides over the pump shaft it is driving - be 3".


    The other solution would be to move X down to allow a straight shot at C but...the whole point of this exercise is to move X up a given amount.

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    It will work as long as the green pulley is mounted on a bearing so it acts as an idler. I assume the intent is to mount both pulleys on an existing shaft. In that case why not just make both pulleys the same diameter?

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    As above, there is no way to make the smaller pulley an idler due to space constraints. And I do plan to make the R and W the same diameter.

    It would be 'better' if W were smaller as it is only there to allow the belt a pathway, and the smaller it is, the more 'wrap' the belt sees going around X. But in practice, it won't make much difference if it is 6" instead of 4".

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    Quote Originally Posted by GregSY View Post
    As above, there is no way to make the smaller pulley an idler due to space constraints.
    Whomever told you that was uninformed.

    An idler, common shaft, takes no more space than fixed. It simply has a bearing in the hub where solid material would have been. Not an uncommon item in any way. Look at any sheave for a hoist. Automotive industry has several in ordinary parts-bins.

    There are no brackets, tensioners, anchors, anti-rotation goods, swing arms etc. needed for an idler in this application.

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    You're overlooking that the ID of the pulley must be 3" to slide over the pump snout. So an idler bearing would need to be 3" ID and 3" OD given the 4" pulley has a V groove depth of 1/2".

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    Quote Originally Posted by GregSY View Post
    You're overlooking that the ID of the pulley must be 3" to slide over the pump snout. So an idler bearing would need to be 3" ID and 3" OD given the 4" pulley has a V groove depth of 1/2".
    Vee belt? What's a Vee belt? This for a museum display?

    Check the depth and width of a PolyVee or MicroVee for the power to be transmitted.

    Everyone else did.

    Long time ago.

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    I have plenty of experience with serpentine belts...and they're not as great as the magazines would have you believe. Biggest issue is they really need a spring loaded 'constant' tensioner unless you are driving only one load, and a small load, off them. A spring loaded tensioner becomes its own slop-mess when you don't have the resources of an OEM. Plus, they take up space and are an extra component.

    I've had some otherwise successful setups with serpentine belts using non-spring loaded tensioners that just would not work between cold and hot temps. I mean...they'd work but inevitably would slip and squeak on start-up or fast accel. If you tightened them more to stop that...there was too much tension in the belt. So I popped lots of hood on lots of cars and sure enough...the only time you'll see an OEM use a screw or cam tensioner is when there is one small load.

    A V-Belt doesn't have those issues. And it doesn't require a reverse rotation water pump which can be an issue on engines that were never made with one. Let us All praise the V-belt!!!


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