Thanks to all of you who have visited the original VECTr video on YouTube. Our number of visitors has now exceeded 10,000! Check out an updated version of the video here: https://www.youtube.com/watch?v=fVFmUcA6sjc.

 

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So a bike blog, The Retrogrouch, makes passing reference to VECTr while showcasing another device (the Wavetrans) to show that expanding chainring devices are nothing new in the history of bicycle transmissions.  After noting the coolness of its various features, the Retrogrouch asks, quoting the  Wavetrans website:

You know what else is cool about Wavetrans? It’s ‘something . . . that you have never seen before.’ . . . Unless you actually know something about bicycle history, that is. In which case you know that these things go back almost to the beginning of the safety bicycle.

If you’ve read prior posts of this blog, you’ll know that the insight that expanding chainrings are nothing new, is itself nothing new.  I pointed out in a post on August 30 (here) that this had been tried for over 100 years, but that most of these devices tried to expand the whole circumference of the chainring all at once, which seems to be impossible given that the links on a chain cannot stretch.  The realization that changes in the chainring’s radius would have to occur when the chain is not engaging led me along the path to VECTr.  The Wavetrans inventor seems to have made the same discovery.

If you look at the prior designs over the last century, you will notice how massive and complicated they look.  And with mass and complication comes weight and expense.  This seems to have been the demise of the previous admittedly ingenious designs.  Retrogrouch draws this moral from his history lesson:

Something tells me that people today are no more likely to adopt a transmission that’s heavier, more expensive, and more complicated than a derailleur system than they were 20, 30 or even 100 years ago. I just don’t see the Wavetrans (or the VECTr, or any other similar ideas that might be brewing out there today) having any more success than their Victorian-era counterparts, or any of the revivals from the ’70s and ’80s.

The claim that the idea of an expanding chainring has been tried and failed is the most common criticism I have received about VECTr. I am somewhat surprised and disappointed that this is often the first reaction of the more serious bike enthusiast.  I would not have thought this was so conservative and staid a group.  They seem to reject new ideas, or new attempts to make old ideas viable, because they are not the now current standard.  Never mind that what is now old, was once new.

Brass_scales_with_cupped_trays

VECTr is truly worth its weight . .  and worth the wait!

The only really relevant question is whether the new/old device works and is worth what it costs. And cost is measured, for bicycles, both monetarily and in weight.  Prior expanding chainrings failed because they were not reliable enough given their price and weight. Retrogrouch seems to assume that every one must be heavier, more expensive and more complicated than current double or triple crank sets.  That looks to be true of Wavetrans, but not of VECTr.

 

The weight of the current version of VECTr  (in steel) compares quite favorably (500 g) to the triple chainring (Shimano Alivio (in zinc?)) and derailleur it replaced (475 g).  When VECTr is commercially manufactured, I am sure its weight will be reduced.

When compared with other in-line transmissions with regard to weight versus cost, VECTr is clearly superior:

Product MSRP Weight
VECTr $150 – $200 525g (steel)
NuVinci 360 $399 2450g
Patterson Drive/FSA Metropolis $300 1734g
Rohloff Speed Hub $1100 – $2000 1700g – 1825g
Shimano Alfine 8sp $360 1600g
Shimano Nexus 8sp $280 1500g – 2000g
Schlumpf Mountain Drive $700 1080g
Sturmey Archer SRF5  5sp $181 2010g
Truvativ HammerSchmidt $700 1623g

As far as reliability and performance, the jury is still out on VECTr as I am still tweaking and testing the design.  Again, it is supposed to outperform triples in having more gear settings, and in maintaining a consistent chainline.  It is more complicated (six moving parts) than triples (one moving part (the derailleur) and three relatively stationary chainrings). But that should be offset by the greater reliability of preventing dropped chains.

So, no, an affordable, light expanding chainring has not been tried.  VECTr truly is something you have never seen before.

 

On Friday, my lawyers (it seems odd to say that) filed my application for a patent.  This was a long process that started way back with the CABT design.

patent drawingAfter all the design work to simplify an expanding chainring device, I  built the VECTr model and was able to get it working.  I then updated the provisional patent application I had submitted on the CABT (which in the year following its filing had lapsed) and submitted a provisional application on VECTr. This allowed me to claim “Patent Pending” and provided a year’s protection (provided a filed a non-provisional application) to show the working model on this website and solicit feedback, and eventually offer it for licensing to prospective manufacturers.  Since there was enough positive feedback, I thought the design might be commercially viable, so in June I started working with a lawyer I met through an Eagle Scout networking event.  Producing a description of VECTr and its functioning in the appropriately acrane legaleze, along with other possible ’embodiments’ proved a long and tedious process.  I had to apologize to my wife for I learned it really is hard for others to understand the details of VECTr’s workings which I discovered from having to explain it to the lawyers.

Well, that long, laborious process concluded Friday with the filing of the patent application.  Now I expect there will be a longer, more protracted process as the patent office reviews the applications, and requires clarifications.  I will keep you posted on the progress.

Last week, I blogged about working on the mechanism within VECTr that will multiply the relatively short distance (4 mm) that a Shimano index shifter pulls to the greater distance (11 mm) of the VECTr settings. This is a critical part of the VECTr gear that will make it compatible with existing index shifters, such as a Shimano 7-setting shifter.

This morning, I was able to make this mechanism work! The working model in the video is rough, but it gets the job done with the shifter…

https://www.youtube.com/watch?v=7OhGLS7lhSk

This week, I have been working on the mechanism within VECTr that will multiply the relatively short distance (4 mm) that a Shimano index shifter pulls to the greater distance (11 mm) of the VECTr settings. This is a critical part of the VECTr gear that will make it compatible with existing index shifters, such as a Shimano 7-setting shifter.

Index Mechanism 9.30.15

Work in progress

The latest version of my expanding chain ring idea is called VECTr, short for Variably Expanding Chain Transmission. How does it work? Find out here: https://vectr-gear.com/how-it-works/.
The key to the design is the simple locking mechanism which performs two functions: (1) holding the gear segments in the desired radial position while they are engaging the chain, and (2) unlocking from that position and moving to a new one when the rider moves a gear shifter.  The current design has a simple pin going through the gear segment and into a locking notch on the base of the device.
Sept 25 2015
Simply by being rotated as the rider pedals, the pin hits a curved control plate, gets unlocked, and slides along the contour of the control plate moving the gear segment to a new position.  When free of the control plate, a spring pushes the pin back to lock the gear segment in place so it can transfer power once again.
As you can see from previous posts, simplifying the design was not a very simple process.  I have found that the first, or most obvious (to oneself), way of solving a problem is seldom the simplest.  I tried to envision what I wanted my device to do, imagine a means of doing it, and then try to eliminate as many parts as I could while allowing the device to function.  The result of this long, meandering process is VECTr.
VECTr is a simple design that really works. The video on my website shows a very basic working model to illustrate proof of concept. The next step in this process will be to develop an actual prototype that can be safety tested. But, there is a little tweaking here and there that remains to be done. VECTr is patent pending and has attracted over 9,500 views on its You Tube channel, and has received some very positive feedback so far.
Now you know the long and winding path that led to VECTr. From here on out, this blog will feature updates on this work in progress. Share your thoughts on VECTr, and join the ride!

After realizing that the Continually Adjustable Bike Transmission (CABT) model was just too cumbersome to be appealing, I could not let the idea go. I still thought the problem of an expanding chainring system should be solvable, but it would take a new approach.  As my wife will gladly tell you, I am often guilty of over thinking things and making them more complicated than they need to be. So, I ditched the CABT design and started over from scratch.

I tried to think of the simplest way to get the gear segments both to be adjusted (i.e., change radial position) and  to lock into that new position. First, I decided that having gear segments slide along straight arms radiating from the center of a circle was the simplest way to for them to change radial position. (This is far simpler than my use of spiral-shaped gear segments being moved by a pin sliding within them, which thereby changed their radial position).

The other problem was how to allow them to lock into position while engaging the chain, and unlock and change position when the bicycle’s rider wishes to change gears. I got rid of the threaded screws that changed the position of the gear segments in the CABT model. I went through several designs for the locking mechanisms and tried building and testing them, using simple materials and working in my garage.

Initially, I thought the gear segments could be locked by means of a toggle which fit into a notch on the edge of the radial arms. I tried simple pivoting brackets, and an elaborate scissoring mechanism:

sketch 1

Toggle locking mechanism

The another design involved having pins pinch the radial arms when depressed by the force of the chain:

sketch 6

Pin locking mechanism

Neither of these seemed like they would work sufficiently well, and they were too complicated. So, I thought it would be most feasible to have a pin perpendicular to the plane of the base plate serve as a locking mechanism.  I thus had to figure out a way for this pin to move in and out as directed by the rider:

sketch 2

Perpendicular pin locking mechanism

Next, I tried a design inspired by clothespins:

sketch 3

Clothespin-inspired locking mechanism.

After that, I tried having the toggle swivel when making contact with the control plates, which would raise the locking pin from its notch:

sketch 4

Swiveling toggle locking mechanism

As many designs as I came up with and tried to build, they all seemed too complicated and/or heavy to be commercially feasible:

button-pin photo

Not it either!

It wasn’t until I thought of putting the locking notches within the groove along which the gear segments slide that I made the step which led to VECTr in its current design:

sketch 5

The penultimate design