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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; 4 Weeks 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; 4 Weeks 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
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  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; 4 Weeks Ago at 0546.
    Power in Flux: The History of Electric Motorcycles
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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; 3 Weeks 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

  12. #50
    Senior Member Stevo's Avatar
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    Today I had time to shoot some video of the new chain installed by Richard's suggestion of removing the shock to see how the chain slack changes with rear wheel travel and no chain tensioners installed. The chain is at it's tightest length when the suspension is fully extended, and gets much more slack as the wheel moves upwards. The first part of the video is at HWY speeds of 65 mph, the second part is during fast acceleration runs over big ass potholes and roots. I wanted to see how the chain behaves with big suspension compressions. My experimental chain tensioner has been modified to push upwards on the chain instead of downwards as before, but I didn't have time to video that test run yet. The only chain tension being used on this video is the bottom run, which has a chain tensioner pushing up.


    From my own analysis, and since I posted this thread in The Fight Club! please feel free to add your own critique, is that with the chain adjusted at the bottom of the shock stroke, there continues to be a considerable amount of chain slap on the top run. The bottom run looks smooth as butta. I like it. But the top run has too much chain slap for my liking. There is a protective roller located on the bike frame that you can't see in the video, to keep the chain from hitting the shock reservoir. I noticed some chain damage to it on inspection. I'm gonna try and get some video of it from a different view. The next video should be interesting. I gotta go make a gopro mount now, but first, back to fighting....

    One potential fight is the belt vs chain argument. Another potential fight could be the 520 vs 525 vs 530 chain size argument. I chose 520 chain over belts. I wanted to keep as close to OEM as possible. It's easy to get rear sprockets made but man is it PITA to get a front sprocket! Nobody makes what I need! Travis can get a 10 and maybe 11 tooth in 520, but I think a smaller sprocket would compound my chain tension issue.
    Another fight can be over sprocket choices. I got a 15t Martin on the drive now. I like the acceleration and the throttle feel at low speeds. A 14t has waaaay better acceleration. Exhilarating acceleration is how I would describe it. But it's also scary, as the back wheel can break loose by twisting the throttle The 15t will too, but it has a better feel to it. A more controlled feel, but noticeably slower to top speed, which is around 80ish, the 14t will take it to 85ish. A 13t??? I didn't try!
    Last edited by Stevo; 2 Weeks Ago at 1019.
    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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