wturber
1 MW
This is a bike that I started about five years ago. It is more about scratching an itch than being practical. That said, the intention was that it should be practical and that it would be used regularly. The itch was that I thought the whole idea of a Stoke Monkey was a neat hack. But when I looked into doing one for myself, the left-side drive and the need to turn the pedals with the motor put me off a bit. If only you could have a right side drive with a freewheeling crank. Then you could send power from the motor or the pedals to the back wheel - independently or in concert with each other. A side benefit is that with the motor no longer driving the cranks, you could implement a torque sensing bottom bracket.
The Stoke Monkey was outdated five years ago. And that's why I got a good deal on the Crystalyte motor and mount from Grin. And yes, the Stoke Monkey is even more outdated today - which frankly, increases the appeal to me.
The plan was to make a cargo bike using an xtracycle Free Radical. Yep. Something else that is outdated. Xtracycle no longer makes either the Free Radical or the more modern Leap. I bought my Free Radical from some gal in Tucson. It was in sad shape.
I liked the Trek 820 bikes because they were steel and had fairly robust tubing. I found on on Craigslist. It had a suspension fork and I'd decided that I wanted a solid fork on this bike. This bike would seldom need to go much faster than 25 mph. And with a long wheelbase, suspension isn't as important. I found a Surly fork at a bargain price on Craigslist. I bolted it all together and it seemed like it would work.
I was in no rush, and piece by piece I stripped and repainted the bike, Free Radical and fork. The color scheme grew from the red Stoke Monkey motor. The name came from the story told by Richard Feynman about "Cargo Cults" after WWII. I ordered a Cycle Analyst, motor controller and other bits and pieces from Grin.
The next order of business was the right side drive. It uses a White Industries freewheel intended for use in cranksets of gas powered bicycles. ACS makes a left side drive single speed freewheel, the "SouthPaw" that ratchets in reverse and mounts with reversed threads. Great. But how can I mount that on the Stoke Monkey/Crystalyte hub? I noodled many options and eventually found myself hacksawing the threads for mounting the freewheel off of the Crystalyte cover. I carefully filed that surface nice and flat with a file and then mounted a right side bottom bracket bearing cup in place of the removed threads. I had read somewhere here that BB cups used the same threads as freewheel mounts. And this proved to be true.
Mounting the cup accurately was a challenge. I solve it by 3D printing drill guide jigs. The jigs fit snugly into the center hole of the motor's cover plate and bearing cup. This let me drill the needed holes with pretty good precision. I'm not sure if it really matters, but I added some side plates to engage the flats of the bearing cup and used toughened epoxy to bond both of these to the motor cover plate. Will this be strong enough? I hope so. I'm limiting the system to 1000 watts of batter draw so as to not tempt fate. After all, those screws are tapped into aluminum.
I never had a clear vision of where and how to mount the battery. Also, retirement, Covid, and many other things provided distractions and the bike hung partially completed for years. Three things occurred that pushed the project over the line. First, Battery Hookup had a smoking deal on some 48v 550 watt hour "shark tank" batteries. So I bought three at a bargain price. Then Grin started selling their Fischer AG torque sensing bottom brackets for a stunningly low $60. But the final thing was that I locked my IronHorse ebike to a trailer used by Bob's Free Bikes (where I volunteer) and one of the volunteers borrowed the trailer and drove it home - dragging my bike on asphalt for about a mile or so. While the bike held up surprisingly well, it was definitely out of service. So given the choice of resurrecting the IronHorse or finishing Cargo Cult, I chose the latter. And so, the project was finally completed.
The Stoke Monkey was outdated five years ago. And that's why I got a good deal on the Crystalyte motor and mount from Grin. And yes, the Stoke Monkey is even more outdated today - which frankly, increases the appeal to me.
The plan was to make a cargo bike using an xtracycle Free Radical. Yep. Something else that is outdated. Xtracycle no longer makes either the Free Radical or the more modern Leap. I bought my Free Radical from some gal in Tucson. It was in sad shape.
I liked the Trek 820 bikes because they were steel and had fairly robust tubing. I found on on Craigslist. It had a suspension fork and I'd decided that I wanted a solid fork on this bike. This bike would seldom need to go much faster than 25 mph. And with a long wheelbase, suspension isn't as important. I found a Surly fork at a bargain price on Craigslist. I bolted it all together and it seemed like it would work.
I was in no rush, and piece by piece I stripped and repainted the bike, Free Radical and fork. The color scheme grew from the red Stoke Monkey motor. The name came from the story told by Richard Feynman about "Cargo Cults" after WWII. I ordered a Cycle Analyst, motor controller and other bits and pieces from Grin.
The next order of business was the right side drive. It uses a White Industries freewheel intended for use in cranksets of gas powered bicycles. ACS makes a left side drive single speed freewheel, the "SouthPaw" that ratchets in reverse and mounts with reversed threads. Great. But how can I mount that on the Stoke Monkey/Crystalyte hub? I noodled many options and eventually found myself hacksawing the threads for mounting the freewheel off of the Crystalyte cover. I carefully filed that surface nice and flat with a file and then mounted a right side bottom bracket bearing cup in place of the removed threads. I had read somewhere here that BB cups used the same threads as freewheel mounts. And this proved to be true.
Mounting the cup accurately was a challenge. I solve it by 3D printing drill guide jigs. The jigs fit snugly into the center hole of the motor's cover plate and bearing cup. This let me drill the needed holes with pretty good precision. I'm not sure if it really matters, but I added some side plates to engage the flats of the bearing cup and used toughened epoxy to bond both of these to the motor cover plate. Will this be strong enough? I hope so. I'm limiting the system to 1000 watts of batter draw so as to not tempt fate. After all, those screws are tapped into aluminum.
I never had a clear vision of where and how to mount the battery. Also, retirement, Covid, and many other things provided distractions and the bike hung partially completed for years. Three things occurred that pushed the project over the line. First, Battery Hookup had a smoking deal on some 48v 550 watt hour "shark tank" batteries. So I bought three at a bargain price. Then Grin started selling their Fischer AG torque sensing bottom brackets for a stunningly low $60. But the final thing was that I locked my IronHorse ebike to a trailer used by Bob's Free Bikes (where I volunteer) and one of the volunteers borrowed the trailer and drove it home - dragging my bike on asphalt for about a mile or so. While the bike held up surprisingly well, it was definitely out of service. So given the choice of resurrecting the IronHorse or finishing Cargo Cult, I chose the latter. And so, the project was finally completed.
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