Years ago Shimano developed a short-lived drivetrain with the "freewheeling" function in the crank, not rear cluster. As such, the rear mechanism only permits reverse movement as a safety feature if the front becomes jammed. Since Bafang BBS mid-drives have a freewheel mechanism in the crank, this freewheel should be acceptable for these mid-drives. Anyone see a problem? BTW, they are for sale on ebay.
Shimano "Freewheel"
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Chalo
100 TW
Shimano Front Freewheeling System ("FFS") was, like the label says, a system. It had a special crank with the freewheel in it, plus a rear thread-on gear cluster that didn't turn freely. This unfree-wheel component did however contain a stiff one-way clutch that would turn if for instance something became jammed in the chain.
All these parts are old and unsuited for index shifting. There's enough drag in the freewheeling chainring of a Bafang mid drive to cause unwanted behavior in the derailleur and chain if the rear freewheel doesn't turn freely, such as if you use a Shimano FFS gear cluster. The derailleur cage will be pulled forward, when coasting, and slack chain spooled over the top of the rear sprockets.
There's nothing to be gained by using an FFS cluster, and in most cases it's a very bad idea to use a thread-on freewheel with a mid drive, rather than using a rear cassette hub. Extra chain tension will worsen the chronic axle bending and breakage that originally caused cassettes to take the place of freewheels.
All these parts are old and unsuited for index shifting. There's enough drag in the freewheeling chainring of a Bafang mid drive to cause unwanted behavior in the derailleur and chain if the rear freewheel doesn't turn freely, such as if you use a Shimano FFS gear cluster. The derailleur cage will be pulled forward, when coasting, and slack chain spooled over the top of the rear sprockets.
There's nothing to be gained by using an FFS cluster, and in most cases it's a very bad idea to use a thread-on freewheel with a mid drive, rather than using a rear cassette hub. Extra chain tension will worsen the chronic axle bending and breakage that originally caused cassettes to take the place of freewheels.
years ago, there was a lot of experiments with crank freewheels. A rolling ramp or sprag-clutch is quieter and more expensive than common pawls, but on industrial conveyor belts, they seem to be very strong.
I'll look to see what I can find about the Shimano freewheeling crank being sold on its own.
I'll look to see what I can find about the Shimano freewheeling crank being sold on its own.
Chalo and Ron, thanks. I purchased this inadvertently since I had never heard of the "FF" system, but will return it. Chalo, thanks for the warning of what could occur with a "BB". The thing that was interesting was that it had been manufactured in Japan. TNC, just go to ebay and put Shimano FF System into your browser and you should see all the parts associated with this drive.
Oh my!...LOL! That's unique. The youtube vid on disassembly and service really revealed how it worked. I thought an old quote from Sheldon Brown kind of summed it up..."a solution looking for a problem". Bottom bracket gearboxes and fully enclosed rear hubs can be impressive and perhaps the ultimate solution to cog sets and rear derailleurs, but it's kind of logical why this Shimano BB freewheel didn't really take off. Thanks for the info on this system.
markz
100 TW
White Industries freewheel are expensive but lasts much longer then even the "Heavy Duty" freewheels that are listed on some websites like Sickbikeparts.com
https://www.electricbike.com/hpc-revolution-mid-drive/
Halfway down where it says The Bottom Bracket Freewheeling Crankset
https://www.electricbike.com/mid-drive-build-part/
3/4 down title Bottom-Bracket Drives, links in article go nowhere.
Check out and do a search on ES to see how Luna's offerings stack up.
https://lunacycle.com/parts/?sort=featured&page=2
My cyclone-tw freewheel crank rusted out pretty quickly but never failed, but never rode it very long either. The bolts rusted making it very hard to replace gears due to different metals on the bolts, low quality metals being used, no anti-seize used.
https://www.electricbike.com/hpc-revolution-mid-drive/
Halfway down where it says The Bottom Bracket Freewheeling Crankset
https://www.electricbike.com/mid-drive-build-part/
3/4 down title Bottom-Bracket Drives, links in article go nowhere.
Check out and do a search on ES to see how Luna's offerings stack up.
https://lunacycle.com/parts/?sort=featured&page=2
My cyclone-tw freewheel crank rusted out pretty quickly but never failed, but never rode it very long either. The bolts rusted making it very hard to replace gears due to different metals on the bolts, low quality metals being used, no anti-seize used.
