Sunday, October 30, 2011

How the Pedals failed

One (hopefully) last data point on pedalpalooza.

I ordered a triangle head screwdriver online after striking out at Radio Shack,  and promptly took apart the dead pedals, and one live right pedal.

Removing the black end cap reveals a circuit board and LEDs, which lifts up off of a bayonet mount 

There are three gears.  The one with the visible screw head is the end of the drive shaft (pedal)  The large one in the foreground has two tiers,  one in back with 18 teeth, and one in the front with 35.  The smaller cog mates with the pedal spindle, and the larger one mates with the generator spindle (the metal one on the left), creating current.

Bayonet mount for the circuit board on the right

When I removed the intermediary gear on the two pedals which no longer work, it became obvious why they don't work anymore- a section of teeth on the smaller cog are sheared off.  

When I took apart the right pedal (which has never been installed)  the circuit board is handed, but the other parts are basically the same, just a mirror image.   I took the center gear out of the good pedal, and put it in the bad pedal and reassembled it and the generator and the  circuit board and LEDs are perfectly fine.

So,  if only I could get replacement gears I could at least fix the one bad pedal whose threading I didn't mangle.  A cursory search though shows that it's not that simple.  I could probably get them custom made, but finding one with exactly the right diameter and number of teeth on both the top and bottom, the right bore for the spindle and the right height "stock" would be a real challenge.  I found a very technical post on getting custom gears cut for repairing a iRobot Roomba, and it sounds like the tooling is pretty expensive ($300)  and only starts to make sense if you are making hundreds of them.

I may contact Pedalite and see if they would sell me replacement gears.  Their customer service has been really good,  so they might do it.  It means that I would have at least one more left pedal that would still be operational, and a right pedal that's never been installed,  and I could put both of them on another bike- which might be good if I start riding Minerva more.  It's also possible that if they have a lot of failures of this gear they could/ should consider making it out of metal instead of plastic.  It would probably cost a few cents more, but maybe they'd consider it in order to make a more durable long lasting product.


  1. Just my thought, why not make an epoxy cast of the gear then fill with that low melting point aluminum. It may work and may not, if you have a small propane torch which I am sure you do, you can melt the metal, epoxy or J.B. weld is cheap. Tip: use a release agent, silicone spray, maybe even cooking spray.

  2. It seems rather foolish of a company to make generator light pedals where the internal clockwork mechanism isn't fabricated out of metal. A rather cheesy cost saving measure by the manufacturer, gravely shortening the longevity of the product, which does a grave disservice to the consumer.

    Would any buy these pedals if they knew the innards were made of flimsy plastic destined to fail quite quickly?

  3. I wonder if you could find somebody that has a 3D printer. They live for moments like this, like the guy with the pickup truck.

    They're found in computer science departments, engineering departments, and hacker/Maker hangouts all around.

  4. You could almost certainly get someone to machine or die cut a gear for you out of aluminum fairly cheaply...

  5. You wouldn't have access to a 3D printer would you? You should be able to CAD it up in 3D and print away. I have no idea how strong it would be, or what it would cost, but it would be an interesting experiment.
    Yep, I wonder what people are thinking when they make plastic gears, I've stripped the plastic gears in two of my father's fishing reels over the years.

  6. The other thing to consider is ditching the pedals and installing regular pedals with reflectors. Approaching cyclists from the rear in a car often times the reflectors are more noticeable than lights. The idea is to supplement with lights, of course.

  7. MIT has a 3D copier and I have these pedals, though mine have failed on the right side.

  8. @Anon11/1

    I wonder if they make the 3D copier available to semi-outsiders. The Scientist is MIT affiliated, but doesn't like to ask for special favors, especially for something as trivial as bike pedals. I need to ask my coworkers in the Industrial design side, I'm sure they know all about the best ways to prototype a small part.

  9. Tried to e-mail but couldn't find one - thought you might be interested in this infographic as a bicycle aficionado. :)