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Thread: Check my maths?

  1. #1
    Part of the furniture ajvx01's Avatar
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    Default Check my maths?

    If my main engine pulley is 116mm and my blower pulley is 35mm does that mean when I shift at 6000rpm the blower is spinning at 19885rpm?

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    I dont maths but 116/35*6000 equals fast.

    Roller bearings wont like it but factor the time spent at that speed before being sad otherwise every alternator ever would cry after 18000 rpm.

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by guy incognito View Post
    I dont maths but 116/35*6000 equals fast.

    Roller bearings wont like it but factor the time spent at that speed before being sad otherwise every alternator ever would cry after 18000 rpm.
    Not really as the vortech has a max rpm of 52000 so really I need to adjust the pulley sizes to get some decent psi..?

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    So spin that bitch. Just stay in the efficiency range of the impeller.

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by guy incognito View Post
    So spin that bitch. Just stay in the efficiency range of the impeller.
    I'm just not sure how.. I want the blower at about 40000 rpm for my maths on hp but with a main Gilmer pulley of 116mm I'd need a blower pulley of 6mm? Surely my maths is wrong?

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    Do you ever leave? EH179's Avatar
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    Your maths is good.

    Are you stuck with 6000rpm limit because if you went to a 200mm engine pulley, leave the blower pulley there and a 6500 limit you can nearly double the current blower speed.
    200/35 =5.714 X 6500 = 37,142 rpm.

  7. #7
    casual poster conrod0's Avatar
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    Try either of these calculators

    Pulley Calculator. RPM, Belt Length, Belt-Surface Speed, Animated Diagrams Metric


    https://www.blocklayer.com/pulley-belt.aspx


    Quote Originally Posted by ajvx01 View Post
    If my main engine pulley is 116mm and my blower pulley is 35mm does that mean when I shift at 6000rpm the blower is spinning at 19885rpm?

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by EH179 View Post
    Your maths is good.

    Are you stuck with 6000rpm limit because if you went to a 200mm engine pulley, leave the blower pulley there and a 6500 limit you can nearly double the current blower speed.
    200/35 =5.714 X 6500 = 37,142 rpm.
    Thanks mate, my concern is that if I do that, do I risk over spinning all my other accessories like water pump, alternator etc? That and where would I look for somewhere to make custom Gilmer pulleys?

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    Part of the furniture ajvx01's Avatar
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    That's great thanks mate!

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    With gilmer style pulleys it's easier to count the teeth and work out the ratio that way. Your 116mm pulley is likely about 39 teeth and to get your 40000 rpm blower speed @ 6000rpm you'd need something around 6 teeth (which would give you 39000rpm @ 6000rpm) but I doubt you'll get one that small. To achieve what you want you'll probably have to go to a bigger crank pulley for the blower only and run the accessories on a separate belt (v-belt?)

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by hq308 View Post
    With gilmer style pulleys it's easier to count the teeth and work out the ratio that way. Your 116mm pulley is likely about 39 teeth and to get your 40000 rpm blower speed @ 6000rpm you'd need something around 6 teeth (which would give you 39000rpm @ 6000rpm) but I doubt you'll get one that small. To achieve what you want you'll probably have to go to a bigger crank pulley for the blower only and run the accessories on a separate belt (v-belt?)
    Thanks mate, my issue is I really only want one belt..

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    Find out if you can get different gears for the blower

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by guy incognito View Post
    Find out if you can get different gears for the blower
    That's a great idea that I hadn't even thought of!

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    Hi,

    With your maths you have forgot about the internal step-up ratio.

    E.g. a Vortech V2 has an internal step-up ratio of 3.6:1 (max speed 52,000 rpm)

    You will need to check the exact ratio with the model you have, but most of the street/strip models are around 3.6:1 step-up ratio.

    Your maths has only calculated the blower pulley speed (116/35 x 6000 = 19,885) now you have to times this by the step-up ratio of 3.6:1 (19,885 x 3.6 = 71,588).

    Looks like you are spinning it too fast. To slow it down you need a larger blower pulley and/or a smaller crank pulley.

    Hope this helps.

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    Part of the furniture ajvx01's Avatar
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    Quote Originally Posted by SRH11 View Post
    Hi,

    With your maths you have forgot about the internal step-up ratio.

    E.g. a Vortech V2 has an internal step-up ratio of 3.6:1 (max speed 52,000 rpm)

    You will need to check the exact ratio with the model you have, but most of the street/strip models are around 3.6:1 step-up ratio.

    Your maths has only calculated the blower pulley speed (116/35 x 6000 = 19,885) now you have to times this by the step-up ratio of 3.6:1 (19,885 x 3.6 = 71,588).

    Looks like you are spinning it too fast. To slow it down you need a larger blower pulley and/or a smaller crank pulley.

    Hope this helps.
    That helps a lot! Thanks, I was hoping I'd missed something like that..

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