Thoughts on 'friction' drive?

[peterjd]

As you would know from some of my other posts, I am 'paranoid', with electric assisted bikes at least, about extra weight, particularly when it is badly distributed and when it makes my bikes less adaptable. This is one reason why I like the underlying concept of the (modern) friction drive ie that you can just use the extra assist when you want it eg on hills, hence reduce battery weight and 'friction' penalties. It seems the major problem is performance in the wet. I have wondered whether a wheel rim (or tyre wall) development could mitigate that problem by allowing a gear type of engagement (perhaps on both sides of the wheel/tyre rim) . Has this been tried? Any thoughts? Peter

 

[Woosh]

This is one reason why I like the underlying concept of the (modern) friction drive ie that you can just use the extra assist when you want it eg on hills, hence reduce battery weight and 'friction' penalties.

the main issue of popular conversion kits is the battery. It has to be good enough to give you about 250W of assistance for your maximum regular rides. That depends of course on the type of rider you are, and can be 1 hour, 2 hours or 3 hours.
If you use a small drill battery, 36V 3AH, it is lightweight but may last less than 1 hour and can't realistically help you climb a steep hill.

 

[flecc]

It seems the major problem is performance in the wet. I have wondered whether a wheel rim (or tyre wall) development could mitigate that problem by allowing a gear type of engagement (perhaps on both sides of the wheel/tyre rim) . Has this been tried? Any thoughts? Peter

Yes Peter, the Cybien-Sport e-bike in France, invented and made by a one man outfit. It uses a different rim on the rear wheel which has extended rubber walls on the rim and dual motors that clamp either side. A clever touch is that as the bike reaches the legal 25 kph, the motor clamping automatically releases, leaving one riding a friction free normal bike. The motors were USA sourced. I doubt the Cybien is still made, the inventor will be very elderly now.

Of course toothed gears you suggest would no longer be friction drive, so perhaps self defeating. Personally having seen every form of friction drive fail over the last 70 plus years, I wish people would stop inventing them!

 

[Nealh]

The Revos friction drive works in the rain and they have a short film of their kit on a 10% incline in the wet. The main issue with them is regarding the wheel contact and most are always on.
Kepler on ES thread lives in Australia and he designed his own diy kit FD with a sprung release to allow contact on the move, his drive though was only for dry conditions.

 

[peterjd]

the main issue of popular conversion kits is the battery. It has to be good enough to give you about 250W of assistance for your maximum regular rides. That depends of course on the type of rider you are, and can be 1 hour, 2 hours or 3 hours.
If you use a small drill battery, 36V 3AH, it is lightweight but may last less than 1 hour and can't realistically help you climb a steep hill.

I think that might be rather pessimistic. I sometimes use a 36V 5Ah lithium Bosch type battery with my heavyish Mk 1 Swytch bike and get at least 2 hours running for U3A bike runs of about 15miles of rolling south Leicestershire countryside. Friction/cog drive might be less efficient but lighter bike and lighter use might cover that.

 

[peterjd]

Yes Peter, the Cybien-Sport e-bike in France, invented and made by a one man outfit. It uses a different rim on the rear wheel which has extended rubber walls on the rim and dual motors that clamp either side. A clever touch is that as the bike reaches the legal 25 kph, the motor clamping automatically releases, leaving one riding a friction free normal bike. The motors were USA sourced. I doubt the Cybien is still made, the inventor will be very elderly now. Why so?

Of course toothed gears you suggest would no longer be friction drive, so perhaps self defeating. Personally having seen every form of friction drive fail over the last 70 plus years, I wish people would stop inventing them!

Interesting translation - Michel Orain designer, about 2005

 

[peterjd]

Yes Peter, the Cybien-Sport e-bike in France, invented and made by a one man outfit. It uses a different rim on the rear wheel which has extended rubber walls on the rim and dual motors that clamp either side. A clever touch is that as the bike reaches the legal 25 kph, the motor clamping automatically releases, leaving one riding a friction free normal bike. The motors were USA sourced. I doubt the Cybien is still made, the inventor will be very elderly now.

Of course toothed gears you suggest would no longer be friction drive, so perhaps self defeating. Personally having seen every form of friction drive fail over the last 70 plus years, I wish people would stop inventing them!

I couldn't resist doing a bit of Internet searching. Below is a press release from 2008 (Translation via Google translate with a little editing).

 

[flecc]

I couldn't resist doing a bit of Internet searching. Below is a press release from 2008 (Translation via Google translate with a little editing).

Thanks Peter, very interesting.

I understand he set up a small factory later and produced variants including upright models, but I only knew of his enterprise at a very early stage, virtually a one man business then.

As a design it precisely fitted your mentioning the possibility of driving both sides of the wheel.
.