In this week’s Patent Patrol, we check out an innovative chain retention device from Praxis Works. Rather than rely on special tooth shaping or other mechanical interfaces, the chainrings use magnets to discourage the chain from jumping off. We dive deeper, to find out if magnets could be part of your drivetrain’s future.

Praxis Works magnetic chainring patent

This isn’t the first non-traditional chainring from Praxis, who partnered with MRP for their Wave Tech tooth profiling, following a dispute with SRAM (who began cracking down to protect their narrow-wide chainring design). We just came across a Praxis patent for a new alternative – magnets.

The magnets could vary in shape (seen as thin bar magnets in the embodiment above), but are intended to be oriented evenly around the circumference of the ring. The vast majority of chains are made primarily of steel, which would be attracted to the magnets – discouraging a dropped chain over rough ground.

It’s interesting to note that the drawings are shown with standard narrow-tooth chainrings, rather than combining the magnets with their Wave Tech design. This is because the patent language calls out that this retention device could be used with multiple front chainrings (requiring narrow teeth) – and actually details the possibility of frame-mounted magnets to assist with shifting.

Now for the questions. Will it ever see the light of day? How much weight will the magnets add? And – does it work? We’ll stay tuned for further development and updates.

Hat tip to Gregory T. for alerting us to this patent.

 

 

12 comments

  1. J'Anky Teal on

    That’s pretty slick. I do wonder how much crud a magnetized chain would attract and retain, and if that would cause wear and drag. There are places I ride where there’s enough iron in the dirt that it sticks to Osprey bite valve magnets.

    Reply
  2. Joe Bond on

    Jesse Pinkman approved.

    Seems like one could DIY this by epoxy resin gluing magnets from obsolete hard drives to chainrings.

    Reply
  3. mudrock on

    Why rely on rare earth metals, the mining of which is an environmental disaster, when the current tech works fine? Also, when the chain rotates off the ring at the bottom, I wonder if the drag of separating the chain from the magnet has any affect.

    Reply
  4. Jon on

    The magnetic force will be providing drag on the chain. It might be a small amount of drag. I wonder what happens if you back pedal when there is low chain tension like when you are in a 10T rear? Will the chain wrap around the front chainring?

    Reply
  5. Hurricane on

    If it does retain the chain so that you wouldn’t need a separate chain retention device, wouldn’t it also retain the chain as where you would suffer from the old term “chain suck” where the chain sticks to a dirty chain ring and gets wedged up into the chain stays?

    Reply
    • Greg on

      My big issue with this is that with any decent chainring, once the chain is on the ring, it’s not going to bounce off. It’s the part of the chain that is not yet on the ring that has the ability to start landing to the side of the teeth. I see no way in which the magnets would help direct that. I believe that the magnetic pull is inconsequential once the chain is a tooth-height distance from the ring. Once it’s below that, the tooth is doing all the work anyway.

      Reply

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