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Chain line really out of wack with 30 tooth mighty mini

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    #16
    Oh thats pretty cool. Are these sold in packs "chain idler tensioner pulley"? Sounds like something Luna could package with the mighty mini? hehe

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    • paxtana
      paxtana commented
      Editing a comment
      You can find some packs on amazon. If you go with the colored kind you probably want 8mm. Many of the best colors/sizes can be best ordered direct from china via ebay

    #17
    I decided to grind the bottom bracket on the drive side even more to try to improve the chain line a bit more. I left a 1mm gap between the motor housing and the suspension bushing and now the chain is lined up with the 2nd highest gear. I removed 10mm total from the bottom bracket and it's still not centered with the cassette, but the shifting is improving. I'll try this setup for a few weeks and if I like it, I won't order the bling ring.

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      #18
      I decided my best solution was to go to an IGH. My new 170MM Sturmey Archer came today. Now waiting for a 36 spoke rim from Luna to build the wheel. Fingers crossed.
      Sturmey-Archer SX-RK3 170mm Disc Hub
      http://www.sturmey-archer.com/en/products/detail/sx-rk3
      Last edited by Louis; 04-12-2016, 09:02 PM.

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        #19
        Originally posted by paxtana View Post
        A simple solution


        A $5 chain idler tensioner pulley in this position acts as an effective chain guide. Won't bounce up or move too much left or right. The chainline before the pulley was bad enough that it immediately derails in first gear, but with the pulley there it is basically impossible. It also is impossible to fall off when the ebike is doing big jumps, very useful for a true offroad machine.

        You would want it close to the chainring. The smaller the pulley, the closer to the chainring. Multiple brackets can get a pulley into this position and pulleys come in different sizes and colors.
        I can't loose any width by shaving down the BB as the motor is already hitting the rear forks, so this looks like a good solution. Thanks.

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          #20
          Here's something similar to the idler pully. It won't fix a chainline that just derails under any load at all but it really helped prevent chaindrops offroad. (That's the 30T Raceface/adapter/two 1mm spacers). Just rubs a tiny bit in granny gear and top gear both.

          Edit: Probably should have mentioned that's a BBS02.
          Last edited by skymon; 04-24-2016, 07:37 AM.

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            #21
            I recently recieved my mighty mini after shaving my bb down as far as i could. To my surprise it works great. The chainline is not that good compared to the bling ring but i think the long teeth on the mini really help. Im thinking if removing just one of my 10 gears and spacing them outwards. A thought tho, the gear i remove obviously being the exact right width, will it not just fit straight behind the granny gear to act as a spacer??? Anybody tried that?

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            • ebikerman
              ebikerman commented
              Editing a comment
              I tried removing different gears and placing it behind the granny gear, it depends on which gear you remove. I removed the 2nd highest gear and required a 2mm spacer because when I put it behind the granny gear, it made the cassette too thick to lock properly. I removed a gear in the middle of the cassette and it was fine as a spacer.

            #22
            Originally posted by k_oflynn2000 View Post
            I recently recieved my mighty mini after shaving my bb down as far as i could. To my surprise it works great. The chainline is not that good compared to the bling ring but i think the long teeth on the mini really help. Im thinking if removing just one of my 10 gears and spacing them outwards. A thought tho, the gear i remove obviously being the exact right width, will it not just fit straight behind the granny gear to act as a spacer??? Anybody tried that?
            I had two different cassettes apart last weekend. One SRAM 10 speed, one Shimano/SRAM universal. On each, the smallest cog is unique. All the rest have slots to fit over the cassette hub, but not that smallest one. So, no, it probably won't fit behind the granny gear. You would need to come up with something else. Easiest may be a spacer or gear from an old cassette, but anything round, strong, and the right size should work.
            Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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              #23
              I lost 4 teeth off of the Mighty Mini I wonder if it's due to a whacky chain line.

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                #24
                Lostboy,

                Did the teeth snap right off, or is there some evidence of bending first? Can you get a close-up, clear picture of the break, with enough detail to show the texture of the metal? (long shot, I know).

                If you didn't hit each tooth on something and damage it, or break it in one shot, but they just popped off while riding, then it sounds like you may be reaching the fatigue limit of the metal. Side load from the misaligned chain will cyclically load the each tooth in bending, with every chain engagement event, which could eventually cause that to happen. I would expect this to happen only after quite a few miles.

                So yes, a wacky chain line could cause it.
                Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                  #25
                  I'm pretty sure that I didn't hit anything. The MM sits inside the motor housing. The 4 missing teeth are randomly scattered throughout the ring. I'll try and post a pic.

                  Comment


                  • JPLabs
                    JPLabs commented
                    Editing a comment
                    Yeah, I know what it looks like on there; I have one, too. Agree it would be quite hard to hit. Just mentioned it to be thorough.

                  #26
                  I decided to convert my 7 speed back to a 9 speed because I was still getting ghost shifting and I didn't like the feeling of the missing gears when i wasn't using the motor. I ordered a derailleur hanger alignment tool to see if it's an alignment problem. I spent a few hours with the adjustment screws and I don't think any amount of adjustment will fix this problem. Shifting is ok on the stand, but goes all over the place while under load. At first I thought the loose motor mount was the problem, but after I tightened it, the problem was still there so I think the problem is in the rear end. I read that other regular bikes had the same problem even though the derailleur looked straight by eye balling it.

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                    #27
                    I was looking at Derailleur Hanger tools when I found this; seems like a good tip if you don't have the tool:

                    Try this... Thread an axle (use a full wheel with the QR pulled out) into the derailleur hanger... Make slight adjustments to re-tune the hanger till the two wheels are completely parallel.
                    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                      #28
                      A little late to the party but this thread didn't come up in earlier searches. Glad I stumbled on it today tho.

                      I started a similar thread here: http://electricbike.com/forum/forum/...erailleur-swap

                      I'm running the Luna 42T. Had similar ideas to skymon & Mark. skymon's looks heavily modified but I really like Marks wheel concept. What device is that?

                      I was wondering if something like this would work http://www.amazon.com/Truvativ-32-36...le+chain+guide A little hard to find in a 42T but may be an option for the mini's, from $50 - OMG price range . More expensive than what is shown in this thread but less than having to switch over to a IGH system and if it will work, doesn't look out of place. Unfortunately, unlike an IGH system, your chain & rear cogs are still under a lot of stress.

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                        #29
                        I need help here plz. I have scoured the internet but cannot find anything like what paxtana shows in the pic. The roller is easy but the arm/hanger that attaches to the roller & downtube? I can do minor fabricating but that looks manufactured, very clean looking. Sorry I didn't paste pic, I was unable to resize or use "quote".





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                          #30
                          It looks like he just used a couple of Adel clamps to fab the roller holder.

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