Am I Crazy?

Forums Mountain Bike Forum Am I Crazy?

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    • #242277

      I had a random thought earlier for a potential redesign for MTBs…but I don’t know if it’s a dumb idea or not.

      Before I get to it, let me just say I live in New England and there rocks (and rock walls) everywhere. As a result, my bikes have taken many good whacks and my pedals and crank arms have the scars to prove it. Aside from the pedals, my derailleur is the part that takes the most abuse from rocks. I’ve broken and replaced countless derailleur hangers (not so bad) and a few derailleurs (not so good).

      So, anyway….earlier today, while looking at random bike photos, I saw one where the derailleur seemed to hang very low and while imagining the complete destruction I would subject it to, I thought to myself, why hasn’t anyone come up with a MTB derailleur that sticks up instead of hanging down? Is there something about bike mechanics that would not allow that to work? Is there further redesign that could make it work? Are you shaking your head in disbelief that you’re reading such an idiotic thought? lol

    • #242279

      There is too much tension on the top of the back gears. The derailleur would be stretched straight and the chain slack would just be hanging out the bottom.

      Now if you had your chain pull from the bottom of the rear gears then all you would need is an internal hub with a reverse gear and you would be in business.

    • #242315

      Okay, well I guess I’m crazy. haha Ah, well…

      Still, if some enterprising mechanical engineer came up with a derailleur and drivetrain design that would work efficiently while moving the derailleur up and further out of the way of obstacles, I’d give it a try.

    • #242333

      You could always go with a Pinion or Rohloff. Or go single speed.

    • #242409

      I really don’t see how it could work. With your chain traveling in a clockwise direction (when looking at the right side of the bike) having the rear mech anywhere other than before the chain interfaces with the gears wouldn’t be able to push/pull the chain from one gear to the next.

      I guess more exposed rear mechs with longer cages is just just going to be the reality of things with 1x12s showing-up on more bikes next year…

       

    • #242412

      The only way I can see it working is if there was a gear system in the BB that reversed the sprocket direction so the rear was driven from the bottom instead of the top. But this would be as bulky and weigh as much as a Pinon gear box. I really think at some point in the future Pinion type transmissions is where bike gearing will go.

      • #242415

        As with coming up with any new idea to fix any problem, gotta think outside of the box and look at root cause.  Rather than focus on the derailleur, focus on why we have them to begin with.  A chain and need for gearing!  Loose the chain, loose the derailleur.  Time for a light weight shaft drive with a gear box up front. 🙂   Light weight hollow tech alloy  (or ceramic/alloy combo) ring and pinion at the wheel with a hollow ceramic drive shaft… and if the pinion is placed correctly, you could not only eliminate rear end pedal bob, but even counter act it.  Image what kind of rear suspension travel we could have then!  Another problem solved.  Hmmm… I could see this on downhill bikes…

      • #242480

        This is where my thinking fell short, I was locked into thinking about traditional drivetrains. Maybe the OP was on to something, the train of thought just stopped a station or two short (like mine).

      • #242482

        FYI: there was supposed to be a smiley after the last comment. The “train of thought” line was meant to be a setup for a self-deprecating joke.

    • #242504

      I think the shaft-jacking effect on a shaft drive would complicate pedal bob even more than it already is. Anyone that has ever ridden a shaft drive motorcycle can attest to the strange behavior of the rear suspension under load.  I would expect a trans in the BB with belt drive to be more effective. That is how many motorcycles have gone.

      • #242514

        Alvin, you’re right about the shaft-jacking effect.  Direction of shaft rotation, and placement on the ring (upper half versus lower half), would either raise or lower the rear of the bike under power.  I had a Honda Nighthawk many years ago that was horrible at raising the rear when applying full power with a modded motor.  We actually came up with a (very expensive and complicated) mod (more like a hack) for it that re-positioned the pinion.  Then the problem reversed… it did wheelies too easily.  Suspension didn’t work well either, but that’s another story.

        But yeah… BB trans with a belt drive! Imaging the weight savings of a belt drive for a bicycle… and quiet too… 🙂

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