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  1. #11
    Quote Originally Posted by birchy View Post
    OK, OK! I'll put the lump hammer down for now!

    I have got one 14T pulley to give me a 3:1 ratio (42T) on the Z axis, so might have to change that to an 18T or bigger. My thinking is that even if we had 1 or 2 degrees of rotational backlash in the pulleys, this would still not be enough to cause a problem if using ballscrews?

    Here is a simplified, why backslash in reality will not happen with these belts
    Imagine 2 pulleys on a horizontal plane with a belt mounted. When tightened the belt, all the teeth from 6 to 12 o'clock on the left and from 12 to 6 on the right will preload.

    Now imagine the belt start to move clockwise driven by the left pulley. From 9 to 12 o'clock is where the backslash will happen, but from 6 to 9 will be still preloaded. At the right pulley the same. From 12 to 3 backslash and from 3 to 6, tooth engaged.

    So at any time at least half of the engaged teeth are without backslash.

    Hence the tooth strength together with the tension plus the pulley size , if enough will not permit backslash.

    18t pulley is what i use on my machine, changed from 14, he he. For other reasons though.

    Yeah, for the Z it shouldn't be a problem.

    When i changed belts even when the pulleys were tightly fitted they gave me problems, especially the small ones connected directly to the motor shafts. They were backslashing by slipping on the shafts even if i used 3 grub screws on each. And only under heavy loads so it took me a lot of time to figure the problem. A little "super" glue eliminated this.

  2. The Following User Says Thank You to Boyan Silyavski For This Useful Post:

  3. #12
    Quote Originally Posted by birchy View Post
    EDIT: Just a FYI, Bearing Station - Adhesives, Bearings, Belts, Chains, O Rings, Oil Seals, Pulleys & Sprockets are generally a bit cheaper and have a "price match guarantee", however they don't offer a machining service.
    I have used them before a few times and to be fair they have been ok. BUT this last time they let me down badly with regards to delivery times in that I ordered 8 20t pulleys on the 5th August and despite 10 -12 phone calls which they promise to return with an answer, they never do. I have now got 7 of the 8 and they are telling me that none of their supplies have got any more and its not their fault. I now have rung Belting-on-line and they have plenty.
    I personally will not be using them again. Clive
    Last edited by Clive S; 01-09-2013 at 08:00 AM. Reason: Wrong date

  4. #13
    vre's Avatar
    Lives in Athens, Greece. Last Activity: 06-03-2019 Has been a member for 5-6 years. Has a total post count of 35.
    I have servos with 19mm shaft and i want to retrofit a lathe (1.6m between centers) .
    I want a pair of timing pulleys with 1:3 reduction for Z axis and a pair of timing pulleys with 2:3 reduction for X axis.
    What kind timing pulleys/belts will be best for that application that they have NO backlash and good quality/performance ?

    Also all car engines have inside timing pulleys ( What Is a Timing Belt ? - AutoZone Car Care - YouTube )
    So you can extract for free timing pulleys from old broken car engines if you go at car repair shop and search at scrap engines.
    I have extracted some timing pulleys from broken engines but i don't know the type of pulleys to order matched timing belts.
    Where can i find a chart with specs with all types of pulleys to identify that i have extracted from car engines ?

  5. Oof! And get ready for it... the deep dive on belts and pulleys, everything you every wanted to know and more:
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  6. #15
    I'm very lucky in that my local bearing and seal supplier also do toothed pulleys and belts, it was there that I saw the steel wire reinforced belts, they have them in stock in stock too.
    You think that's too expensive? You're not a Model Engineer are you? :D

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