In the last post, I said that I had been focusing my attention on a 5-arm 110 BCD version of VECTr that used the same idea for the locking pin as the version in the video.  That basic idea consists of the locking pin moving laterally when contacting the control plates to unlock the gear segment, and being pushed along the contour of the control plate into its new radial position as the crank turns.  I had said that I had been trying to get this to work, and the fact that I was trying, meant that I was unsuccessful.


Old version of control plate mechanism, with long sweeping outside plate (on the left).

Well, it’s a funny thing about tinkering that sometimes ideas strike you while trying to do something else. When I was working on the laterally locking pin design last spring, I was indeed unsuccessful, and so went back to the drawing board (or CAD program) and came up with perpendicularly drawn locking pin design.  And in the fall, I was trying to get this new design to work, when, seeing some parts from the old design on my desk, I wondered again why it wouldn’t work.  So I reassembled them, but tested them with the control plates for the new design, and what to my wondering eyes should happen, but the hybrid of old and new worked (sort of).  I discovered that it wasn’t the lateral locking pin that was the problem, but the control plates (which seemed necessary for the version in the video and had worked there — see image to the right).



Instead of the long sweep for the outside control plate, the new design had two simple angled control plates, but they seemed able to unlock and re-position the gear segment of the old design, but not as smoothly as they should.  So, as a result, for the last few weeks, I have revived the old design and tested various shapes for the control plates.

20170127_113644Finally, I found that by modifying the inside control plate from the old design, it would contact the locking pin on the gear segment at an appropriate angle to unlock it and slide it to the desired radial position.  (It took much trial and error to find the appropriate angle — a better understanding of geometry and the physics of friction might have led to a good design, a priori, but what can you do . . . .)


Gear segment being moved to the outside of the expansion arm by contacting the new inside control plate.



The gear segment in the new outermost position with its locking pin released to lock the gear segment in place.


So, this is (hopefully) the last major hurdle to finalizing a truly functional design.  I know of many smaller hurdles and tweaks that will be necessary, and I will probably discover others, but I feel good that VECTr is getting closer to the marketable stage.

Further Refinements

Posted: January 6, 2017 in Uncategorized

While the original video of VECTr garnered positive feedback and interest, there were many questions about its operation as well as suggestions for improvement.  (You can see a representative sample in the comments on various pages of the this website.)  Easily, the number one criticism was that the expanding chainring design has been tried and found commercially wanting.  As I continue to point out, there have been many expanding chainring designs that have not had sustainable commercial success, but the differences among them probably account for their varying degrees of profitability.  Trying to find the simplest, most reliable design producible for the least cost is the true challenge in design in general, and specifically in the expanding chainring transmission game.

20170102_173953There were concerns specific to the VECTr design which I have spent my time trying to address.  The first had to do with the smoothness of the operation.  It has always been an aim of the design process to make a device which is compatible with current bicycle standards, and so I made a four gear segment mechanism which could be fitted to the 64 BCD fittings of a MTB crank arm.

It was noted, however, that this made the operation of VECTr appear “lumpy” and uneven, and viewers thought it would make for an uncomfortable ride. Yet, increasing the number of gear segments would increase steps between the gear ratios, and thus limit the range of settings for the device.

20170102_174309aAlso, the design of the locking/adjustment mechanism of the gear segment consisted of three pieces for the sliding motion, plus a pin/bolt and spring for the locking motion, in addition to the actual chain-engaging gear segment.  These were all held together with simple blind rivets, which I knew were none too strong, and probably would not hold up to the stresses of actual road use.  In working up some cost estimates for the manufacture of VECTr in that iteration of the design, it became clear that it would be difficult to entice a manufacturer to license the design, or for me to make them out of my garage.  I thought, too, that simplifying the design of the gear segment mechanism would decrease the weight and offset the additional mass of added gear segments.

20170102_174008The result of rethinking these issues led me to design VECTr with five expansion arms (fitted for 110 BCD cranks) and five gear segments which would slide within narrower channels, still having notches on one edge into which a locking pin would fit.  In a prior blog post I detailed how I had to call upon my trigonometric acumen (latent and seldom used as it was) to work out the proper spacing of the notches for the five arm design.

20170102_174223In this new design, I replaced the three-piece sliding parts with simple bolts (which also took the place of the rivets) and the locking bolt sliding with the rest; it would be biased into locking position by an external elastic band or other small spring.

I spent much of my time working on VECTr this past year (when I could work on it) trying to get this design to work, as well as working to make the control mechanism compatible with a Shimano indexed shifter.  I detail some of that work in a prior blog post, too.

Given that I say that I tried to get this new design to work is a pretty good indication that it was not successful.  I will have to let you know the insights this process gave me that led me to the current design, which I think shows even greater promise.

Not Dead Yet!

Posted: January 2, 2017 in Uncategorized

drawingDespite the dearth of posts on VECTr, progress has been proceeding, albeit in fits and starts. (I have been making some major transitions in my day job, too,  over this time.)  Encouraged by the interest in the original video of VECTr’s operation (which now has over 12K views), I sought to refine and simplify the design so as to make it more feasible for me to conduct a first run at manufacturing it commercially.  I also tried to take into account suggestions for making it more compatible and smoother in its operation.  In the weeks ahead, I will be detailing the improvements I made, designs I tried, and challenges I encountered in these past intervening months.  I will also be giving updates on the state of the current design and progress in testing it, hopefully continuing to move toward the point of making a salable product for widespread use.  Stay tuned for further updates!

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:


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.


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…