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  1. #11
    Quote Originally Posted by m_c View Post
    You don't have to retension timing belts on cars, and the latest ones last 150,000miles or 10 years with no maintenance.
    And given quite a few run with fixed tensioners, stretch isn't a concern.

    Every car i have had has always got some form of tensioner on the timing belt, in most cases its a idler pulley under spring tension (auto belt tensioner).

    You could argue this just keeps the belt tight against the pulleys, but i have noticed a slight difference in length when i have changed them in the past. But whether you would get this much on a router to cause major problems, who knows.

  2. #12
    Quote Originally Posted by deannos View Post
    But whether you would get this much on a router to cause major problems, who knows.
    I do and no it doesn't.!! Been using belts on my machine for years and they haven't stretched to the point I can see or measure. Had a hand in few belt drive machines and none of them suffer from belt stretch and they are spot on accurate and super reliable.
    Must say doesn't work out much cheaper than ball-screws after you've bought all the belts,pulleys etc Unless like John S you can hob your own and have time.!

    Was surprised to find the Jobs 5 axis machine I've been trying/about to buy connects to the ball-screws with 25mm timing belts and the moving head(X axis) on that thing must weigh 7-800Kilo. The bed(Y Axis) alone must weigh 200K and this thing was designed for machining titanium and precision moulds for Mclaren F1 to super fine tolerances.! So they wouldn't be fitting them on this quality machine if they stretched to any detrimental amount.! (That said they are probably something special and cost £500 each. . Lol)

  3. #13
    Belts offer numerous advantages for driving ballscrews, the stretch is almost invariably negligible there since the belts are very short. However if you're using belts to replace ballscrews (i.e. the subject of this thread), then the stretch will be a factor - otherwise belt driven machines would be good for machining more than just soft materials.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  4. #14
    Quote Originally Posted by Jonathan View Post
    Belts offer numerous advantages for driving ballscrews, the stretch is almost invariably negligible there since the belts are very short. However if you're using belts to replace ballscrews (i.e. the subject of this thread), then the stretch will be a factor - otherwise belt driven machines would be good for machining more than just soft materials.
    Oh here we go.!!! . . . My machines is nearly 1500mm wide so thats over 3000mm long belt and stretch hasn't affected it yet.! This belt has been on machine probably coming up 2yrs, the first which I damaged had been on over 2yrs and hadn't stretched in that time.!

    It's all relative to the machine and work load and I know, Again thru experience, that this size machine doing the kind of work John intends then it will be a very very long time before belt stretch even remotely comes into the frame.!! . . . Yes they clearly will stretch over time that's a given but ball-screws wear-out and I know a good quality belt will last just nearly has long has any Chinese ball-screw.!!

  5. #15
    We're talking about different things. I'm not talking about the belts stretching over time (since as you say that just doesn't affect us). I'm saying when you apply a force to a belt it will stretch then spring back when you remove the force. So I agreed that when driving a ballscrew with a belt there's no problem. However I thought John S was asking about using the belt instead of a ballscrew? I.e. long open belts on either side of the gantry to push it along...
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  6. #16
    Hello,

    What do you think of using T5 Timing Pulley for my router?

    I'm using HGW 20 Hiwin Block, 1605 ball screws, 4Nm step motor and I'm thinking of use Timing Pulley running at 1:1 ratio.

    30 teeth pulley.

    Thank you

  7. #17
    Quote Originally Posted by C.AlveSilva View Post
    What do you think of using T5 Timing Pulley for my router?
    You could do but the motion is 'smoother' with HTD pulleys and T5 may have more backlash, not sure.
    Last edited by Jonathan; 10-09-2012 at 07:54 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  8. #18
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    Quote Originally Posted by deannos View Post
    Every car i have had has always got some form of tensioner on the timing belt, in most cases its a idler pulley under spring tension (auto belt tensioner).
    Not everything does though, and I normally deal with vehicles that don't.
    You could argue this just keeps the belt tight against the pulleys, but i have noticed a slight difference in length when i have changed them in the past. But whether you would get this much on a router to cause major problems, who knows.
    The normal difference you'll notice between new/old is flexibility. If you were to put them on a proper belt measurement jig, there would be neglible difference in length.

  9. #19
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing Has been a member for 9-10 years. Has a total post count of 1,834. Received thanks 192 times, giving thanks to others 5 times.
    Quote Originally Posted by Jonathan View Post
    Belts offer numerous advantages for driving ballscrews, the stretch is almost invariably negligible there since the belts are very short. However if you're using belts to replace ballscrews (i.e. the subject of this thread), then the stretch will be a factor - otherwise belt driven machines would be good for machining more than just soft materials.
    Stretch/Elasticity during use will be a factor, but loosening the belts of when not being used is going to have a neglible effect.

  10. #20
    Quote Originally Posted by m_c View Post
    Stretch/Elasticity during use will be a factor, but loosening the belts of when not being used is going to have a neglible effect.
    Agreed..
    The manufactures do say you should check the tension after running for a little while as they stretch a bit when first installed then 'settle down'.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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