Tensioner Redux

Discussion in 'Motorized Bicycle General Discussion' started by stilldoc, Nov 4, 2009.

  1. stilldoc

    stilldoc New Member

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    My stock tensioner broke so I'm giving this a try. The roller is from Tractor Supply and has been discussed on this forum but mounted on the seat post.

    [​IMG]

    I'm using it bolted down, but it could also be configured to swing loose and attach to a spring.
    Once I'm satisfied with the position, I will anchor the bracket to the chain stay with a self tapping screw to prevent rotation into the spokes.

    (Looking at the photo while previewing this message, I think I might try facing it the other way, toward the back wheel, to get the bolt heads away from the chain)
     
  2. stilldoc

    stilldoc New Member

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    Okay. Don't try this as it's pictured above. The roller bracket metal is not strong enough to withstand the torque created when starting the bike. Mine wound up like this:

    [​IMG]
    [​IMG]

    I'm lucky it didn't rotate into the spokes.
    :-||
     
  3. 2door

    2door Moderator
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    People underestimate the pressure applied to the chain under load; which is why so many have had the tensioner bracket come loose and be pulled inward, into the spokes. I've never tested the force on the chain at that point but it would be an interesting figure to know so we could pass along that information to new builders. Keep us informed on how your bracket idea is working. I'm glad the bracket is all that was damaged with your experiment. Thanks for sharing the photos.
    Tom
     
  4. BarelyAWake

    BarelyAWake New Member

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    I just wanted to say thanks for the follow up on this 'un - it's helpful to hear the problems as well as potential "solutions" and far too many of us forget to mention when somethin' goes south.

    Looks like it's still a good 'un tho, if with just a stronger plate and/or a spring... you gonna mess around w/it more? If so - keep us posted ;)
     
  5. stilldoc

    stilldoc New Member

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    I like the bearing roller. It's smooth and quiet, so I think I'm going to try to find a way to attach it directly to the stock tensioner bracket with a grade 8 bolt. What I'm trying to accomplish is to develop a solution that doesn't require welding (since I don't have a welder) and uses easily acquired parts.
     
  6. BarelyAWake

    BarelyAWake New Member

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  7. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

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    Most engine kits these days have the good bearing rollers in them! ;)
     
  8. stilldoc

    stilldoc New Member

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    Here's the latest rendition. It requires a 6mm bolt, a spacer, and washers.
    Holding so far. I'll update the thread if it fails.

    [​IMG]

    brnot
     
  9. stilldoc

    stilldoc New Member

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    Holding up so far. Several startups and rode about 25 miles today.
     
  10. 2door

    2door Moderator
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    Glad to hear it. Thanks for keeping us updated. Use caution however. You've already seen what can happen so keep a close watch on the bracket and make sure it doesn't move on the chainstay. You don't want all that steel to get pulled into your spokes.
    I see a small hole in the stay. Is that from an earlier mount?
    Tom
     
  11. stilldoc

    stilldoc New Member

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    Tom,
    You're right, that is a hole from an earlier mount. I was hoping to use it again but the width of this rubber roller dictates placement further forward away from the hub in order to clear the spokes.

    Right now I have it tightened down pretty firmly with some grade 8 bolts. I thought about just dropping an internal tooth washer between the bracket and the chain stay as an alternative rather than drilling a second hole. It would damage the paint but not potentially weaken the frame.
     
  12. stilldoc

    stilldoc New Member

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    Just an update. No problems with this setup so far.
    I think adding the grab strips between the chainstay and tensioner bracket has worked well to prevent rotation without drilling a hole in the frame. It also allows for adjustment if necessary.

    I'm not sure of what type of metal the strips are made. I'm a little concerned about the possibility of rusting. Another option is to use an internal tooth washer. I've included a photo of both.

    [​IMG]

    cvlt1
     
  13. AaronF

    AaronF New Member

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    Nice setup there.How is it holding up for you? Do you have the part # for the roller wheel?
     
  14. Creative Engineering

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    stilldoc,

    Your frame appears to be of the same type that is shown in the pics below. i.e. a typical coaster brake beach cruiser type frame with long drop-out slots.

    Naturally these long slots were not designed into the frame so that we could mount an engine and keep our drive chain at the correct tension, but why not take advantage of it?

    Simply put your kit tensioner on the pedal side...or rig up a spring loaded tensioner like is shown in the pic.

    Jim
     

    Attached Files:

  15. stilldoc

    stilldoc New Member

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    Aaron,
    I haven't had any problems with it yet. Hasn't moved or bent.
    I think the roller is a good off the shelf, locally available option to a replacement stock roller. It might reduce some noise as well. It does require some modification to attach to a stock tensioner bracket.

    Here's the link to the part at TSC:

    Baja Motorsports Chain Tensioner Assembly - 5510238 | Tractor Supply Company
    .
    .
     
  16. AaronF

    AaronF New Member

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    Good deal!I noticed you had a problem with the bracket bending on your first start off.I'll probably take the bracket off and mount the roller the same way.Thanks brnot
     
  17. stilldoc

    stilldoc New Member

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    Jim,
    I think that's a good solution. I had the stock tensioner on the pedal chain and it worked okay but I became worried about failure upon use of the coaster brake which could be catastrophic. I've always thought that the ability to stop is more important than the ability to move. The spring tensioner setup shown in the photo would eliminate that problem. Do you know where to get it?
     
  18. AaronF

    AaronF New Member

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    Here is one similar to that,hope it helps.NEW Single Speed Chain Tensioner AKA Singleator 200-001 - eBay (item 370292689104 end time Dec-17-09 21:32:40 PST)
     
  19. Creative Engineering

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    Aaron,

    That's the part. That's a good price too!

    The single speed beach cruiser frames don't have the M10 X 1 threaded hole, so I made an adapter.

    Jim
     
  20. Finfan

    Finfan New Member

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