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Thread: Best belt drive ever! (If I do say so myself)

  1. #61
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    Well, im guessing it has that clearance for a reason, maybe prevent the belt climbing on the pulleys teeth.
    I dont know if it would work. have no way of testing that right now. maybe there is another type of belt and pulley profile that does not have this clearance, GT perhaps? dunno

    Best regards
    Fernando



  2. #62
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    Does anybody have a cad drawing of the GT profile belt? I asked this earlier in this thread as to the mesh of the two belts and the reason for choosing a trapazoidal profile versus the superior (especially in terms of backlash and power transmission) curvelinear profiles like GT.

    The reason I'm trying to find an accurate profile drawing is to sketch the involute (is that the correct term?) of the belt teeth as they pull out of the "rack". This would depend on the diameter of the last idler which looks small in the original design and gives me some concern regarding backbending of the belt.

    The main advantage that I can see with a T profile belt is that if will self mesh while a GT type does not (I believe) thus requireing the rack to be either machined or possibly epoxy cast using the belt as a mold.

    Neat idea of turning the drive belt inside out BTW. I really like the whole concept of this flexible rack and pinion design.

    Cheers

    Mark



  3. #63
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    Mark
    if you are referring to the lousy PAINT sketch i uploaded, it was just a concept drawing, nothing is to scale, and as you can see, the belt is less than perfect! heheh

    Of course every idler arrangement should comply with the minimum backbend diameter needed for a particular belt.

    if you are talking about the first original design then, no need to worry, the last idler is small, but the belt is already straight, so no backbend there.

    Regards
    Fernando



  4. #64
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    I was refering to the original servo belt design and the last idler prior to the driven pulley. Not sure on the spec and I guess it depends on each belt but would think the back bend radius would be larger than the smallest rated pulley.

    The concept "tractor drive" paint drawing is a pretty cool version on the original. Although you are relying more on the belt to rack engagement than the original as it is only dealing with the stretch of the belt where as the later has the whole drive force acting on it.

    I like these designs as to me they are a version of a rack and pinion but with better tooth engagement due to the larger number of "pinion" teeth on the belt engaging the driven pulley.

    The acurrate drawings I'm trying to make are of the tooth profile (personally am planning on using GT) so that I can plot the involute of the belt tooth as it leaves and rejoins the stationary rack.

    Cheers

    Mark



  5. #65
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    I dont know if it would help,
    but gates has a 3d model database for all their pulleys including GT2

    http://www.gates.com/designview/form...ocation_id=866

    You can find them there, but you need to register.

    Ill attach an 18 tooth pulley for a 5mm pitch GT2 belt in .stp format which I can open in autodesk inventor, other formats are available in that same page up there.

    Now providing we can sort out the backlash in the motor pulley,
    Can someone come up with a nice neat way of adding a reduction ratio using timing belt and pulleys?

    Regards
    Fernando

    Attached Files Attached Files


  6. #66
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    Thanks for that Fernando

    I already have cad files for the pulleys but I suspect that they are not the mirror image of the belt tooth profile for the same reasons I'm trying to draw the mesh with the "rack". I'll try using this profile just out of interest to see what I come up with.

    Here's a link to my build thread.... about halfway down the page you ca see how I plan to do my reduction gear.

    http://www.cnczone.com/forums/showthread.php?t=53824

    Cheers

    Mark



  7. #67
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    Hello Mark,

    I saw your design, clever, but im afraid that setup might not work if you are thinking of adding the stationary belt to act as a rack, unless you eyeball exactly there the drive pulley should be. There is no adjustment in it to aid in removing the backlash between both belts.
    unless I am missing something.

    Regards
    Fernando



  8. #68
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    Yep your 100% right... at the time I posted that drawing I was still unsure if I would make a mating rack... the design has changed somewhat since then and the motor mount and drive pulley assembly now is adjustable as required by this design.

    If I had lots of spare cash I would get one of those tming pulleys with a planatary gear reduction inside them instead of the belt reduction... bit too expensive at this point.

    Cheers

    Mark



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    Mark,
    YEa i was thinking the same thing, use a planetary gearbox and get on with it... simpler, cleaner, and probably less backlash.

    What kind of timing pulleys with a planetary gearbox inside, i had never heard of them. Can you point me on where to find them?

    Fernando



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    Came across this awhile ago... think they are one off type items not shelf stock and from memory were close to $1000 (don't quote me on that its just a figure that would scare me away even though they are pretty cool)

    http://www.motiontech.com.au/assets/...r%20Pulley.pdf

    They are made by Mectrol this was on the local distributers site. not been able to find the original site yet.

    Scratch that ... just found them. They changed there name in 2005

    http://www.onviollc.com/dotnetnuke/P...7/Default.aspx

    quoted backlash is higher than I remember but still not much given the reduction it gives.



    Cheers

    Mark



  11. #71
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    Pretty innovative.
    Although other than saving some space, i dont see much advantage to a planetary gearbox ($500 aprox) fitted with a timing pulley on the shaft ($30)

    I think its cheaper to go with the planetary gearbox and stock pulley.

    Regards
    Fernando



  12. #72
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    For the questions regarding backlash in the motor pulley and the belt. In one of Mikes documents, he writes that he gets his T5 timing belts from Brecoflex. Brecoflex offers 3 times of timing pulley tooth profiles. They come in Normal ("lots" of tooth clearance), SE ( reduces tooth clearance), and Zero (No tooth clearance).

    I believe it is safe to say Mike Everman uses zero clearance pulleys to achieve zero backlash in his system.



  13. #73
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    I have gotten some quotes from Brecoflex for AT-5 and AT-10 - 25mm wide series belt and pulleys - standard and zero clearance.

    The zero clearance pulley are about 2 - 3 X the price, but I perhaps worth it in terms of potential performance.

    The other interesting aspect is for DIY to consider staying with the metric 12mm shaft vs the US size - it is easier to obtain consistent shafting and bearings while "knowing less". I realize that more knowledge is better than less, but sometimes easy is good as well.

    I am hoping that this belt setup being worked up here does become available for diy soon. I looked, but the setup now is more commercial oriented - which is ok, just beyond my budget.



  14. #74
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    Harryn,

    Could you tell us if they quoted directly to you?
    What was their quoted price for your requested products... you can PM me if you feel uncomfortable posting quotes here.

    Best regards
    Fernando



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    PM me also if possible Harryn. I'm still undecided if I will stick with T5 or use GT 8mm instead.

    Thanks



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    Could someone please post sources for belts that would allow teeth in teeth with least play? I see Mr Bell uses polyurethane ones.


    Konstantin.



  17. #77
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    http://www.brecoflex.com
    is the only one i have seen that offers zero clearance pulleys.

    I had never heard of it before Lazyman commented on it.



  18. #78
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    Quote Originally Posted by fer_mayrl View Post
    Harryn,

    Could you tell us if they quoted directly to you?
    What was their quoted price for your requested products... you can PM me if you feel uncomfortable posting quotes here.

    Best regards
    Fernando

    Hi - I don't really want to contaminate this thread with OT, but you can see the info I obtained in my build thread - post 15 - 20.

    http://cnczone.com/forums/showthread.php?t=38940

    Technically, they quoted to my company, but I am the owner so it works out ok. I just realized that the quote is now more than 14 months old, so who knows what the price is now.



  19. #79
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    Wow, two pages since my last visit. I better check if my alerts are going into spam!
    My apologies, questions going out to me, and me asleep at the wheel.

    Here's an attempt to address questions to me in one response:
    Yes, the "tractor tread" continuous belt is offered on ServoBelt, for cases where the debris or contamination is so bad that we must mount the static belt on the bottom or side of the chassis. Otherwise the dynamic belt drapes. All the idlers and tensioning idler on Fernando's sketch are not strictly necessary. You'd use some idlers if you wanted to control the loop enough to fit covers over it all. The main downside of this is reduced life, though less expensive to change out the belt.

    We recently concluded a life test of the BrecoFlex belting, and the standard grade did approximately 18 million starts and stops (approx 60 lb accel/decel forces). We are now embarking on life test with a higher flex version of the same belting, that has the same ultimate tensile strength. We will have two going, one with low payload and high speed, one with 200 lb accel/decel forces (which is the upper limit we impose on T5x35 wide).

    As to backlash in the motor pinion, the "zero clearance" version from Breco-Flex is um, not. There was no difference between it and a carefully prepared and plated standard profile. For the most demanding positioning, we pay special attention to this, and it is our "special sauce". On our rotary stages, we have the pinion and bull-pulley custom hobbed.

    Back bend diameter on the inner idlers is per Breco-Flex recommendation.

    There's some new propaganda on our site, the pdf of the tech-sheet on the servobelt page is the final print version.

    We are currently building 90' and 22' long ServoBelts with dual carriages. I'll post some pics soon.

    Mark, looks like you're doing a nice build. I look forward to pics! We too are doing a belt pre-pass to get 3-4:1, mainly for inertia matching. We're also doing a T10. You should be OK with the GT2-8.

    Here's some common configurations.

    Attached Thumbnails Attached Thumbnails Best belt drive ever! (If I do say so myself)-sb233-90w-820g-x-sb233-90-820gl   Best belt drive ever! (If I do say so myself)-sb344-90s-2200g-x-sb233-90-820gl   Best belt drive ever! (If I do say so myself)-sb233-45w-460-sb344-90w-760c-sb344  
    Mike Visit my projects blog at: http://mikeeverman.com/
    http://www.bell-evermannews.com/ http://www.bell-everman.com


  20. #80
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    Not sure if anyone gets it or not but there is an article about this in Feb Design News (www.designnews.com) pa 38. Exact same product just interesting seeing it in print.



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