I think we can lose count of how many FD's in the 10 years have come and gone.
Imagine how I feel about them after watching at first hand over 70 years, every conceivable variant of them failing in the market, most failing technically as well. The first of many I fitted in the trade was 73 years ago, a Sinclair-Goddard Powapak. Nothing to do with Sir Clive, he was about to leave primary school at the time, but years later he too failed with two bicycle motor friction drive designs.
And I'm not just speaking of driving on the tyre, one clever design drove a special rear wheel rim with rubberised sides. Yet another very different bicycle friction drive was the Tongxin Nano hub motor, which used to break the friction ring that was driven by rollers.
Every time I see yet another friction drive motor announced with claims to have solved all the problems, I sigh, wondering why people don't do their market research first. If they did that they'd learn that there is nothing new under the sun, every option really has been tried before, and failed.
I only opted for the Revos as it only added 2.5kg to 10.3kg lightish gravel bike.
There is a small market for such a physically light and occasional usage motor, but not really big enough to sustain a long term business, as all of them find out very soon.
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