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Thread: Debate of the Day: Experimental Chain Tensioner

              
   
   
  1. #41
    Senior Member Stevo's Avatar
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    No I'm not moving that bottom support. I agree with the original builders (the Vertimati brothers) that is where that support belongs.

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    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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  2. #42
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    Quote Originally Posted by Stevo View Post
    No I'm not moving that bottom support. I agree with the original builders (the Vertimati brothers) that is where that support belongs.

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    I should have written MOVE or MODIFY
    Do you mean the cross piece that interferes with the top run of the chain? What I've done in these situations and have seen the factory do to clear the chain is
    (1) angle the cross piece up to clear the chain
    (2) put a S curve in the X piece (use a larger diameter, stronger piece of tubing if you do this)
    (3) if there's room and the chain has a master link, put the X piece between the chain runs
    (4) Like in the photos in post 36, on a swing arm in this case, replace part of the X piece tube with a piece of large cross section(thick) angle iron or bent large cross section(thick) flat bar
    Last edited by Electro Flyers; 6 Days Ago at 1453.

  3. #43
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    Quote Originally Posted by Stevo View Post
    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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    No tensioners. The primary belt from the motor to the jack shaft is tensioned by moving the motor in slots under the motor mounting bolts. The secondary belt (the sprocket in the photos is the front sprocket for that belt) from the jack shaft to the rear wheel sprocket uses the stock slots in the swing arm to slide the rear axle back to tension the belt. With the jack shaft turning concentric with the swing arm pivot, the belts' tensions remain the same through out the swing arm travel. I've noticed some OEM electric dirt bikes use a similar system, but with a chain secondary drive. This bike is waiting for the right motor/controller/battery combination, and of course $, to get finished.
    Last edited by Electro Flyers; 1 Week Ago at 1335.

  4. #44
    Senior Member Stevo's Avatar
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    I now understand your setup better now. I'm trying to keep my drive as close to oem as possible. There is no crossbar on the top run...the only things are the rear shock reservoir and rear break line cross over... which are protected by the idler wheel attached to the frame. The chain makes contact with that wheel on extreme load and compression. There has to be a pivot there in order to protect those other components. You gotta remember this is dirt bike... a lot more travel than a street bike. So I'm waiting for some parts and I will shoot some more video with a few different solutions I have in mind.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

  5. #45
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    OK, so even if the lower support was gone, you still need to limit upwards travel, which means you need an additional element in any case and so the whole cycle reverts.

    Have you considered mirroring the idler that's already in place?

    I'm not certain about it, but I expect that would remove L1 entirely from the chain length calculation and effectively bring your chain pivot point into line with the swingarm pivot meaning that you get zero (or very close to it) net change in system length with +/- ~50deg travel about the aligned position. Reckon that's enough even for a dirtbike... and may remove the need for a tensioner.




    Of course you could likely achieve very close to the same net effect by increasing the stiffness of the pulley you have in your video and taking a link out of the chain...

  6. #46
    Senior Member Stevo's Avatar
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    So I got to thinking about chain derailers on mountain bikes/street bicycles and how the "double-ider" is utilized to remove/control all of the required chain slack in those drive systems. The wheels are spinning (in my head).
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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  8. #47
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    Dunno about that notion dude.
    With the weight of the chain and its velocity at even relatively slow speeds, I expect it'll just be a mess - you'd be better staying as you are at that stage.
    I still reckon you could stand to loose a link in the setup you have, trim it out using the adjustment available, and up the tension on that tensioner a good chunk - it doesn't seem too far from a workable solution as it is.

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  10. #48
    Senior Member Ted Dillard's Avatar
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    ^ What he said.

    Have you checked out conventional industrial solutions? I'd think they'd be a lot more to the point than bicycle products. See this: http://www.brewertensioner.com/tensi...sitioners.html and this, for starters: http://www.roll-ring.com/?lang=en

    I know you like the movies, so here:



    ...also this:



    (complete with Happy Music)
    Last edited by Ted Dillard; 2 Days Ago at 0546.
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  11. #49
    Senior Member Stevo's Avatar
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    That Rollo-Ring is a pretty nifty invention, but I don't think applicable here. And gocart chain adjustment is not the same animal, without 6" suspension travel

    What I really really need to find is a 520 sprocket adapter for the 7/8" keyed electric motor shaft. Nobody makes a solution AFAIK.
    I was going to meet with my local machinist about prototyping one up. I ordered a JT sprocket for a BMW G450X... the inner diameter should fit over the shaft diameter no problem. They are available in 13, 14 and 15 tooth configs.
    Last edited by Stevo; 2 Days Ago at 0954.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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