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Thread: Debate of the Day: Experimental Chain Tensioner

              
   
   
  1. #31
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    Stevo: that idler pully - is that just to take the chain over the top of the center stand support bracket?

    ...if so, is just cutting that out altogether an option?
    Can't imaging that chain tensioner (and the maintenance and noise that will come with it) is any better value than an abba stand...

  2. #32
    Senior Member Ted Dillard's Avatar
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    Quote Originally Posted by Spoonman View Post
    is any better value than an abba stand...
    DID SOMEBODY SAY ABBA????



    (oh god i'm so sorry. hell, it's friday and i haven't even started drinking yet... i probably better put up bail money right now.)
    Power in Flux: The History of Electric Motorcycles
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  3. #33
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    Quote Originally Posted by Ted Dillard View Post
    DID SOMEBODY SAY ABBA????


    (oh god i'm so sorry. hell, it's friday and i haven't even started drinking yet... i probably better put up bail money right now.)
    That's it Ted. I'm going solo the next album. I think you're going to start drinking because you're worried about how to incorporate, and explain this complicated chain formula in the next edition of your book.

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  5. #34
    Senior Member Stevo's Avatar
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    Listening to Abba tunes will definitely lead me to drinking...

    I'm more of a visual guy, but I know the importance of math, so thanks Spoonman for your effort!

    The idler is a preventative measure... without it, the chain will chainsaw a hole through the frame cross support in shortorder.
    There was originally a stationary idler on the top run above the swingarm pivot, mainly just to prevent the chain from rubbing the rear shock reservoir. I'm thinking of utilizing this as another "corner", which I suspect will control the slack... see new illustration :
    IMG_20180914_104607.jpg

    I suspect pushing upwards on the chain would be better than pushing down on the chain, or removing this chain tensioner idea altogether, as it was oem style. It just seems like there is a lot more slack now than there was before with the new motor install, which I believe is due to the increase in L1 in Spoonman's calculations.
    Last edited by Stevo; 14 September 2018 at 1059.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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  6. #35
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    Quote Originally Posted by Stevo View Post
    It just seems like there is a lot more slack now than there was before with the new motor install, which I believe is due to the increase in L1 in Spoonman's calculations.
    In the case of this arrangement, an increase in L1 will have a disproportionate impact on the chain slack on account of the narrowing effect it has with respect to that window of travel in the swingarm before the chain starts to get deflected by the idler pulley - so yes, the increase in L1 will most certainly be the source of the problem alright.

    I really would be considering moving or refabricating that crossing brace in the frame to be honest - it *is* the best solution even if it's a good bit of work. You'll end up with a quieter, more efficient, and lower maintenance drivetrain as a result.

    I don't expect it's actually doing a whole lot more than carrying the center stand, particularly given the proximity to the swingarm throughbolt.
    The bike would also have likely originally had a couple of engine mounting through bolts not too far away from that location as well so I reckon its importance as a structural member is limited.

    If you're worried about it then just weld in a new one 4-6" forward of it, or if you want to retain the support at the corner then maybe something in a 'U' shape such that the actual cross-tie is still closer to the motor and hence not fouling the chain.

  7. #36
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    Quote Originally Posted by Spoonman View Post
    In the case of this arrangement, an increase in L1 will have a disproportionate impact on the chain slack on account of the narrowing effect it has with respect to that window of travel in the swingarm before the chain starts to get deflected by the idler pulley - so yes, the increase in L1 will most certainly be the source of the problem alright.

    I really would be considering moving or refabricating that crossing brace in the frame to be honest - it *is* the best solution even if it's a good bit of work. You'll end up with a quieter, more efficient, and lower maintenance drivetrain as a result.

    I don't expect it's actually doing a whole lot more than carrying the center stand, particularly given the proximity to the swingarm throughbolt.
    The bike would also have likely originally had a couple of engine mounting through bolts not too far away from that location as well so I reckon its importance as a structural member is limited.

    If you're worried about it then just weld in a new one 4-6" forward of it, or if you want to retain the support at the corner then maybe something in a 'U' shape such that the actual cross-tie is still closer to the motor and hence not fouling the chain.
    Ditto on the cross brace mod or move for chain clearance. Looks like a steel frame-easy to weld. Although it looks like you've done a fair amount of aluminum welding. Something like this a good mod: SSA52206.jpgSSA52207.jpgSSA52204.jpg

    In this case, this is a top view of a section of a swing arm round tube replaced by a bent piece of heavy section flat bar. The tube was in the way of a jack shaft sprocket mounted concentric with the swing arm pivot for an ongoing E-bike project. For strength, keep the piece that replaces the tube fairly massive. Although massive, you'll only add a small amount of weight for a small replacement piece.
    Last edited by Electro Flyers; 14 September 2018 at 1347.

  8. #37
    Senior Member Stevo's Avatar
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    It's hard to visualize from the pics how the belt travels through that jackshaft and drive pulley. Since it's a belt drive, there must be a tensioner somewhere in that design.

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  9. #38
    Senior Member Stevo's Avatar
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    I disagree with both of you about not needing the cross support. The next place up the frame that cross supports right and left chassis sides is at the top rear shock mounting point. I already welded a cross support 6" forward to support the battbox bottom mounts. There is no centerstand....it's a dirtbike.

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  10. #39
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    Quote Originally Posted by Stevo View Post
    I disagree with both of you about not needing the cross support. The next place up the frame that cross supports right and left chassis sides is at the top rear shock mounting point. I already welded a cross support 6" forward to support the battbox bottom mounts. There is no centerstand....it's a dirtbike.

    Sent from my Pixel 2 using Tapatalk
    I'm not suggesting you REMOVE the cross support. I'm suggesting you MOVE or MODIFY it. If the chain is rubbing on the cross support, is this because of the large rear sprocket? If so, you could put a fixed idler on the top part of the chain to keep the chain from rubbing on the cross support. Because it is on the main load side of the chain, it will be subject to heavy loads, possible making a lot of noise and early failure. As I recall, you wrote there was an idler in this position originally to protect part of the shock. What I am suggesting is that if you are confident in your welding and fab skills, you could move the cross support or modify it to clear the chain so that no idler is needed. If there are other rub points those too could be moved or modified

    I successfully do this kind of stuff all the time. If you don't feel like you have the skills to do this properly, don't do it. Maybe, you could find someone else to do the work.
    Last edited by Electro Flyers; 15 September 2018 at 1238. Reason: Added MODIFY

  11. #40
    Senior Member Stevo's Avatar
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    As you say, the main load side of the chain is the top run (witness the video of chain tightening on acceleration.) The bottom run may see light load on Regen, which is programmed to pretty low levels, almost insignificant, hardly noticeable. I don't see the bottom idler or the cross member being the issue, as the bottom chain tensioner controls the bottom run's slack without any issues whatsoever. It's the top run that's proving to be the headache.

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