In answer to your points:
1) I don't know the patent situation with the Brompton rear fold, but since many others use it, for example Birdy and Ori, there may not be a problem.
2) I don't think belt tension is a problem. If the pivot is at the rear of the BB and slightly higher than it's centre, the fold would slightly slacken the belt. i don't see that as a problem, the belt tension would return once unfolded. The pivot position could be designed to minimise that slackening. Also an external-to-belt roller could be incorporated in the design so that it only contacted the belt in the fold, keeping the belt engaged onto the sprockets when carried.
P.S. I think the Airnimal Joey pivot is just below the BB.
1) I don't know the patent situation with the Brompton rear fold, but since many others use it, for example Birdy and Ori, there may not be a problem.
2) I don't think belt tension is a problem. If the pivot is at the rear of the BB and slightly higher than it's centre, the fold would slightly slacken the belt. i don't see that as a problem, the belt tension would return once unfolded. The pivot position could be designed to minimise that slackening. Also an external-to-belt roller could be incorporated in the design so that it only contacted the belt in the fold, keeping the belt engaged onto the sprockets when carried.
P.S. I think the Airnimal Joey pivot is just below the BB.
OK, now I think I understand better what is going on:
Look at the Airnimal Chameleon video, 0:38:
http://airnimal.eu/technology/the-fold/#.U1VanPmSzT8
You can see the pivot point is such that the whole "assembly" of the BB and the rear triangle rotate. Since the BB and the rear triangle are rigid together, I believe there is no problem with the tension.
Instead, if the rotation only occurs for the rear triangle but not for the BB, such as for the Brompton:
then by all means, a tensioner is needed, and a belt would most likely do not work.
To sum up:
It is not necessary to have the swing arm pivot = BB in order to have a belt with no tension problems. The pivot point can be different from the BB, but what is necessary is the BB and the rear triangle turn around together when folding.
Does this sound correct?
Look at the Airnimal Chameleon video, 0:38:
http://airnimal.eu/technology/the-fold/#.U1VanPmSzT8
You can see the pivot point is such that the whole "assembly" of the BB and the rear triangle rotate. Since the BB and the rear triangle are rigid together, I believe there is no problem with the tension.
Instead, if the rotation only occurs for the rear triangle but not for the BB, such as for the Brompton:
then by all means, a tensioner is needed, and a belt would most likely do not work.
To sum up:
It is not necessary to have the swing arm pivot = BB in order to have a belt with no tension problems. The pivot point can be different from the BB, but what is necessary is the BB and the rear triangle turn around together when folding.
Does this sound correct?
Yes, you posted when I was still typing my comment, so I only could read what you had written after I posted my message. Thanks!
I can only think of asking on social media online, it's possible that a cycling enthusiast in the engineering or CAD field might be inspired to dabble. One problem is that many of those interested in the cycling subject wouldn't be interested in the electrical aspect, so it may be necessary to deal with that in kit fashion
The professional route would be too expensive.
Are you sure a ready made commercial product wouldn't satisfy your needs? Perhaps starting with a commercial bike and modifying it to suit your special requirements would be a more practical and economic approach.
The professional route would be too expensive.
Are you sure a ready made commercial product wouldn't satisfy your needs? Perhaps starting with a commercial bike and modifying it to suit your special requirements would be a more practical and economic approach.
Yes, flecc, your argument makes a lot of sense. In fact, this is the path I am following right now: I am starting to build a couple of e-bikes (which are based on standard 26'' bikes).
If everything goes all right, I will start moving towards my goal, first building say a 20'' mini velo with a foldable handlebar and pedals (but no foldable rear triangle), and not with a frame box, but with a standard main triangle, and a triangular, plastic-like box screwed into it. I believe this can be done in practical terms even by myself.
And so on.
And of course, in every practical build I will discover many new things that now I have not come up with, and even I have not imagined, because only real, practical knowledge leads to real knowledge.
And probably in a few months' time, my ideal bike will be very different from the one I have outlined in this thread.
But I believe it is usually a good idea to start trying things. For example, it would be great to have a collaboration with an engineer who can build CAD models, because once one tries to build that in practice (with real measurements, etc) one realizes of things that before, one had not thought about. And this realization pushes knowledge forward. So, my idea to create CAD models is not so much to have finished models in say two months' time, but just as an exercise to learn. Possibly, the final, "real" model will take two years to finish. In the meantime, of course, I have to build several "intermediate" e-bikes, with as many different motors / controllers / batteries / ... as possible, just to learn.
Having said that, I believe the bike I have described so far makes a lot of sense for European urban usage.
If everything goes all right, I will start moving towards my goal, first building say a 20'' mini velo with a foldable handlebar and pedals (but no foldable rear triangle), and not with a frame box, but with a standard main triangle, and a triangular, plastic-like box screwed into it. I believe this can be done in practical terms even by myself.
And so on.
And of course, in every practical build I will discover many new things that now I have not come up with, and even I have not imagined, because only real, practical knowledge leads to real knowledge.
And probably in a few months' time, my ideal bike will be very different from the one I have outlined in this thread.
But I believe it is usually a good idea to start trying things. For example, it would be great to have a collaboration with an engineer who can build CAD models, because once one tries to build that in practice (with real measurements, etc) one realizes of things that before, one had not thought about. And this realization pushes knowledge forward. So, my idea to create CAD models is not so much to have finished models in say two months' time, but just as an exercise to learn. Possibly, the final, "real" model will take two years to finish. In the meantime, of course, I have to build several "intermediate" e-bikes, with as many different motors / controllers / batteries / ... as possible, just to learn.
Having said that, I believe the bike I have described so far makes a lot of sense for European urban usage.
Perhaps you could find an apprentice or student who is working with CAD and who could use your project as practical experience towards their careers. I am using a couple of trainee marine engineers to help me renovate my narrowboat and they appreciate the hands-on experience it gives them.
Wouldn't a faux bar be a way to include rear suspension, while allowing at the same time a singlespeed belt?
A faux bar suspension has, or better, it may have, such as the Kona Cowan DS:
the pivot point coinciding with the BB:
(reference: http://en.wikipedia.org/wiki/Bicycle_suspension)
As a consequence, the rear wheel is pivoting around the BB, which leads to a constant tension for the belt.
It seems a standard four bar has a patent by Specialized:
http://www.bikeradar.com/gear/article/buyers-guide-to-mountain-bike-suspension-part-2-28438/
but the report does not say the faux bar has a patent (of course, the fact the report does not say that, does not imply a patent does not exist).
So, with a faux bar where the BB coincides with the pivot point, if one could separate the shock from the rest of the rear triangle with a kind of handle or switch (at the yellow point of the picture above, where the yellow seatstay connects to the red piece), the rear triangle could be rotated towards below the main triangle (as a Brompton / Ori), while keeping belt tension intact and allowing the usage of a shock, right?
Edit: a commençal absolut sx, with a single pivot (no faux bar) has also pivot point = BB:
Edit 2:
List of bb pivot frames:
24 Bicycles Flextoy
Blackmarket Killswitch
Commencal Absolut SX
Cove G Spot
Dartmoor Shine
Descendence Lovemachine
DMR Bolt
Doberman Le Pink
Edge Blade
Edge DH 1
Fire Eye Match
Kona A
Kona Bass
Kona Cowan
Lenz Milkmoney
Macmahone Kingdom
NS Soda Slope
Oneghost Wakazashi
Solid Flair
Specialized P.Slope
Tank Hone
Tank T-Works
http://singletrackworld.com/forum/topic/kona-basscowan-ds-any-good-for-xctrail-use
A faux bar suspension has, or better, it may have, such as the Kona Cowan DS:
the pivot point coinciding with the BB:
(reference: http://en.wikipedia.org/wiki/Bicycle_suspension)
As a consequence, the rear wheel is pivoting around the BB, which leads to a constant tension for the belt.
It seems a standard four bar has a patent by Specialized:
http://www.bikeradar.com/gear/article/buyers-guide-to-mountain-bike-suspension-part-2-28438/
but the report does not say the faux bar has a patent (of course, the fact the report does not say that, does not imply a patent does not exist).
So, with a faux bar where the BB coincides with the pivot point, if one could separate the shock from the rest of the rear triangle with a kind of handle or switch (at the yellow point of the picture above, where the yellow seatstay connects to the red piece), the rear triangle could be rotated towards below the main triangle (as a Brompton / Ori), while keeping belt tension intact and allowing the usage of a shock, right?
Edit: a commençal absolut sx, with a single pivot (no faux bar) has also pivot point = BB:
Edit 2:
List of bb pivot frames:
24 Bicycles Flextoy
Blackmarket Killswitch
Commencal Absolut SX
Cove G Spot
Dartmoor Shine
Descendence Lovemachine
DMR Bolt
Doberman Le Pink
Edge Blade
Edge DH 1
Fire Eye Match
Kona A
Kona Bass
Kona Cowan
Lenz Milkmoney
Macmahone Kingdom
NS Soda Slope
Oneghost Wakazashi
Solid Flair
Specialized P.Slope
Tank Hone
Tank T-Works
http://singletrackworld.com/forum/topic/kona-basscowan-ds-any-good-for-xctrail-use
Last edited:
From the point of view of having a belt, a separatable suspension frame of that type would allow the belt fitting.
But the fold seems to me to be an inconvenient one, breaking at both sides where the suspension link pairs to the spring/shock unit.
This sort of frame (Tonaro Bighit) but with BB centred pivot would allow the fold separation at one point above the spring/shock unit.
But the fold seems to me to be an inconvenient one, breaking at both sides where the suspension link pairs to the spring/shock unit.
This sort of frame (Tonaro Bighit) but with BB centred pivot would allow the fold separation at one point above the spring/shock unit.
I cannot understand your comment, flecc. Would you mind to provide more detail for me to understand that, please?
If the suspension links pass both sides of the frame seat tube and the spring unit is ahead of that, to achieve a fold Brompton fashion means separating the suspension links on both sides.
The Tonaro style frame avoids that problem, since there is no seat tube in the way. The spring unit could be detached at one point for the rear frame to swing around the BB pivot point.
The Tonaro style frame avoids that problem, since there is no seat tube in the way. The spring unit could be detached at one point for the rear frame to swing around the BB pivot point.
Mmm I either do not understand you, flecc, or I do not agree with you. What I mean is the following:
Look at the picture:
There is the rear shock, which is in grey. Then, the suspension link (in red), which links the rear shock with the seatstay (in yellow). Please note the suspension link has a joint at the seat tube (in blue).
What I would like is some kind of lever, at the (yellow) point of the joint between the suspension link (in red) and the seatstay (in yellow).
Then, one would have, on one hand, the rear shock and the suspension link (in red), still together, and both together still with the seat tube (through the blue joint). And on the other hand, and already physically separated, the combination seatstay + rear wheel + chainstay + BB. Please note the BB coincides with the pivot point.
So, once these two parts are physically separated, one could rotate the rear wheel towards below the main triangle. The rear shock and the suspension link would remain at their position.
Do you agree?
Look at the picture:
There is the rear shock, which is in grey. Then, the suspension link (in red), which links the rear shock with the seatstay (in yellow). Please note the suspension link has a joint at the seat tube (in blue).
What I would like is some kind of lever, at the (yellow) point of the joint between the suspension link (in red) and the seatstay (in yellow).
Then, one would have, on one hand, the rear shock and the suspension link (in red), still together, and both together still with the seat tube (through the blue joint). And on the other hand, and already physically separated, the combination seatstay + rear wheel + chainstay + BB. Please note the BB coincides with the pivot point.
So, once these two parts are physically separated, one could rotate the rear wheel towards below the main triangle. The rear shock and the suspension link would remain at their position.
Do you agree?
Yes, now I understand exactly the point you mean. However, it might mean separating on both sides, two points, unless you have the red yoke joined at one point at the rear above the wheel.
What I had in mind with the Tonaro style frame was that a true Brompton fold with the whole rear triangle rotating becomes possible, with only one detachment point on the shock to undo.
Either way will work though.
What I had in mind with the Tonaro style frame was that a true Brompton fold with the whole rear triangle rotating becomes possible, with only one detachment point on the shock to undo.
Either way will work though.
It seems as if the Kona Cowan DS has been designed for my usage, on purpose. Look that the point of contact between the seatstay and the chainstay (a yellow dot) shows the seatstay and the chainstay are not a single piece of metal, but two pieces linked with a screw or something similar.
As a consequence, probably a belt could be passed through there, only by unscrewing the screw.
And the sliding dropouts probably allow to use a belt, because the distance between the dropout and the BB can be chosen (a bit) by selecting the exact point at the sliding dropout to fix the rear axis.
In fact, if I can find a Kona Cowan DS, it seems I only have two points of contention:
1. Can I create a kind of lever to separate at will the seatstay from the suspension link?
2. Can I use smaller wheels than 24'' / 26'', which are the ones originally intended for that bike, without altering handling too much?
As a consequence, probably a belt could be passed through there, only by unscrewing the screw.
And the sliding dropouts probably allow to use a belt, because the distance between the dropout and the BB can be chosen (a bit) by selecting the exact point at the sliding dropout to fix the rear axis.
In fact, if I can find a Kona Cowan DS, it seems I only have two points of contention:
1. Can I create a kind of lever to separate at will the seatstay from the suspension link?
2. Can I use smaller wheels than 24'' / 26'', which are the ones originally intended for that bike, without altering handling too much?
Ingenuity should take care of point 1, and I don't think smaller wheels will severely affect the handing, The wheelbase remains the same. The steering with a smaller front wheel will be a little faster, but that will be offset by the longer than normal wheelbase for a small wheel bike, this having the effect of slowing steering. The two could well balance out.
Did you see what looks like a new OEM version of the 8fun crank drive at the show?
http://www.bike-eu.com/Home/General/2014/4/Electric-Bikes-Worldwide-Report-Edition-2014-Published-1508717W/
8-Fun crank drive offerings seem to be facing tough competition this year from a few well established Chinese motor companies like MPF, XOFO and MXUS, their products are cheaper - sometimes by as much as 20%. In the early days, the BBS01/02's compatibility with standard BB shells scored against the TCM which require slightly larger BB shell. This exclusive advantage is now gone. The unit that shemozzle refers to requires a special frame mount and will put 8-Fun straight into Bosch's territory - I can't see 8-Fun winning that battle.
I doubt they have developed it for the global market when they have such a huge market on their doorstep.
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