It is not intended to approximate oblong or oval chainrings, but others have seen that as an advantage. It does seem, though, that the square-ness of the chain path when VECTr is in expanded position (lumpiness) will not be as noticeable since larger gears are used on downhill or level roads when the pedal momentum is at play, and crank loads are not heavy.
In more contracted settings, the squareness would be less pronounces, and in the smallest position, non-existent.
That is an interesting comment. I take it you mean it will not work well in snow or cold. I don’t see why you would think so. I expect it would function (sliding parts slide) as well as a derailleur system. Maybe you can explain what you mean.
Wondering about chain wear, it doesn’t support the chain with as much surface area as a traditional setup. Height increases and decreases at different points in the pedal stroke so leverage would change, how would this effect efficiency. Also would it work in mud and grime? Also would it be likely to be lighter, heavier or similar weight to a traditional setup?
Reduced chain wear is not VECTr’s main advantage. But while the five teeth of each gear segment may increase wear on those links because of heavier load, there are six or seven links suffering no wear. The extra-wear on some links will pass around the chain, so overall there is not increased wear, or it is minimal. Think of it this way: VECTr only has 20 teeth which engage the chain, so chain wear will be the same as always running on a 20t ring, but the rider will have the advantage of 24 to 44 tooth equavalent gears.
I’m not sure how that variation in the expanded position will affect efficiency. Some have seen a similarity to oblong or irregular chainrings, and both as and advantage and a disadvantage. It does seem, though, that the square-ness of the chain path when VECTr is in expanded position (lumpiness) will not be as noticeable since larger gears are used on downhill or level roads when the pedal momentum is at play, and crank loads are not heavy.
I don’t see why mud or grime would negatively impact its operation any more than it would the hinges of derailleurs. The chamber that houses the springs for the locking bolts, though, could be closed to keep them clean. I expect it would require little or no more maintenance than traditional setups.
As to weight: the VECTr gear-segement disk weighs 375 g compared with 300 g for the Shimano chainrings it replaced. I am sure that weight can be reduced by at least 20%. The control elements weigh 150g compared with the same for a Shimano derailleur I have. So VECtr would weigh as much or less than a traditional setup. Also, it should cost as much, perhaps a little more to produce (as there are 12 or so pieces to assemble).
So many questions! How many watts/ how much power can it take? It seems that sheering forces on each of the “tooth segments” (specifically the lone segment engaging the chain in the power stroke) would be very high and not distributed along a whole chainring. Also, since each roller on the chain engages and disengages the drive mechanism 4 times as often as on a traditional system, does this increase chain wear? To Larry’s point, it does seem that the sliding mechanism could become clogged by mud or other debris. Would the shifting mechanism be indexed, or is the Vectr system inherently indexed? What width of chain is it designed to work with? 8,9,10, and 11 speed systems all use different width chains. How does it attach to the crank arms? This is a very intriguing idea and a fascinating design. I would love to learn more about it!
As I have done only limited road testing; I have not done any engineering of the design, so can’t answer watts or sheering forces.
I think VECTr dis/engages only as a 20t ring (each tooth in each roller is what matters, not the beginning of a series of teeth), which is less that as 24t to 44t rings. Anyway, this is a question for engineers.
Mud/debris could be prevented with a plastic guard(s).
Shifting is now with a friction shifter, but it would have to be indexed. The current design need a longer cable pull than indexed shifters I have, so that is why I modified an old friction shifter.
Optimal chain width is a refinement that would come with product development. If VECTr is installed front and back, I would thing it advantageous to have a narrower chain.
It currently attaches to the crank arms with 64mm BCD bolts (on a square tapered bottom bracket) but custom crank arms could be fused/forged together.
In the short term, I am looking for partners to help in the product development. If you know anybody, send this along to them. But I appreciate your interest.
Thanks for the response! It is great fun to talk with you as you work through design and engineering issues.
Guards are a good idea to limit debris infiltration.
It sounds like you’ll have to develop your own shifter or modify the design to work with common pull ratios. Currently SRAM uses a 1:1 (approximately) and Shimano uses a 2:1 pull ratio (again, approximately).
On chain width, many single speed or internally geared setups use a wider chain. Narrow chains are advantageous for derailleur systems with narrow spacing between cogs in the cassette. A wider chain might be stronger and less prone to wear.
On the issue of roller engagement, I believe that each time a roller engages a new tooth it rolls slightly as it settles into the new valley. You could try marking a roller to see if it rotates as it travels around the expanding gear. On a traditional chainring rollers don’t rotate after they first settle into a valley. This may or may not be an issue with the system.
Do you have any ideas about how to manage chain tension if VECTr is installed front and back?
I’ll be thinking about people in the industry who might be interested. This could be a big hit with the recumbent crowd.
I’m curious about who the target user is. I think the overall design is interesting and could see it as a viable option in the city-bike/commuter bike market. I could see this being a potentially nice setup on a bike that is designed to be ridden frequently but not typically under the strains and stresses of a “performance” road or mountain bike. It would also allow for a sleek chain guard on bike with front shifting which is difficult now on a commuter with 2 or 3 chain rings and the accompanying front derailleur.
Also, I think breaking into the market as an after-market drivetrain would be very difficult. As a complete bike I could see some promise but I think it would be a tough sell as an aftermarket piece. Stick with it, though.
Would it be smoother with more than 4 expanding sections? Eight perhaps? Harder to make but it might be smoother.
Also, could you do something similar at the rear? You could change the gearing ratio and go bigger both at the front and rear ro give you more space on the rear cassette.
The unevenness of four contact points has been the biggest criticism so far. As it is, it does not feel all that lumpy, and only in the most expanded position, but for some, that is a huge drawback. It could have more gear segments, but then there would be a greater increase in effective teeth between each setting (now the gearing increases in 4-tooth increments).
I envision the final product to be on both the crank and the rear which, as you say, would give a greater range in gear ratios, be much lighter without the rear cassette and derailleur, and overall more streamlined.
I wanted to create a variable gear chainring for mountain bikes to get rid of the rear derailleur which is still incredibly vulnerable. Never got as far in figuring out how to make the actual shift happen, and I really like the idea! Could even make a switch for on the fly oval 🙂 I think current off road bikes need some sort of gearing at the BB area and not relying on a frame accepting a gearbox would be a huge advantage. Ground clearance would be an important factor though. I’d definitely want more segments for a smoother ring but I do see the drawback in increasing steps between gears. Best of luck with this!
VECTr - Variably Expanding Chain Transmission 
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It looks like it functions like a square chainring and the pedalling force appears to be correspondingly notchy – kinda like Biopace.
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It is not intended to approximate oblong or oval chainrings, but others have seen that as an advantage. It does seem, though, that the square-ness of the chain path when VECTr is in expanded position (lumpiness) will not be as noticeable since larger gears are used on downhill or level roads when the pedal momentum is at play, and crank loads are not heavy.
In more contracted settings, the squareness would be less pronounces, and in the smallest position, non-existent.
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Definitely not a Winter or snowy conditions mechanical system that will work smoothly
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That is an interesting comment. I take it you mean it will not work well in snow or cold. I don’t see why you would think so. I expect it would function (sliding parts slide) as well as a derailleur system. Maybe you can explain what you mean.
LikeLike
Wondering about chain wear, it doesn’t support the chain with as much surface area as a traditional setup. Height increases and decreases at different points in the pedal stroke so leverage would change, how would this effect efficiency. Also would it work in mud and grime? Also would it be likely to be lighter, heavier or similar weight to a traditional setup?
LikeLike
Reduced chain wear is not VECTr’s main advantage. But while the five teeth of each gear segment may increase wear on those links because of heavier load, there are six or seven links suffering no wear. The extra-wear on some links will pass around the chain, so overall there is not increased wear, or it is minimal. Think of it this way: VECTr only has 20 teeth which engage the chain, so chain wear will be the same as always running on a 20t ring, but the rider will have the advantage of 24 to 44 tooth equavalent gears.
I’m not sure how that variation in the expanded position will affect efficiency. Some have seen a similarity to oblong or irregular chainrings, and both as and advantage and a disadvantage. It does seem, though, that the square-ness of the chain path when VECTr is in expanded position (lumpiness) will not be as noticeable since larger gears are used on downhill or level roads when the pedal momentum is at play, and crank loads are not heavy.
I don’t see why mud or grime would negatively impact its operation any more than it would the hinges of derailleurs. The chamber that houses the springs for the locking bolts, though, could be closed to keep them clean. I expect it would require little or no more maintenance than traditional setups.
As to weight: the VECTr gear-segement disk weighs 375 g compared with 300 g for the Shimano chainrings it replaced. I am sure that weight can be reduced by at least 20%. The control elements weigh 150g compared with the same for a Shimano derailleur I have. So VECtr would weigh as much or less than a traditional setup. Also, it should cost as much, perhaps a little more to produce (as there are 12 or so pieces to assemble).
LikeLike
So many questions! How many watts/ how much power can it take? It seems that sheering forces on each of the “tooth segments” (specifically the lone segment engaging the chain in the power stroke) would be very high and not distributed along a whole chainring. Also, since each roller on the chain engages and disengages the drive mechanism 4 times as often as on a traditional system, does this increase chain wear? To Larry’s point, it does seem that the sliding mechanism could become clogged by mud or other debris. Would the shifting mechanism be indexed, or is the Vectr system inherently indexed? What width of chain is it designed to work with? 8,9,10, and 11 speed systems all use different width chains. How does it attach to the crank arms? This is a very intriguing idea and a fascinating design. I would love to learn more about it!
LikeLike
As I have done only limited road testing; I have not done any engineering of the design, so can’t answer watts or sheering forces.
I think VECTr dis/engages only as a 20t ring (each tooth in each roller is what matters, not the beginning of a series of teeth), which is less that as 24t to 44t rings. Anyway, this is a question for engineers.
Mud/debris could be prevented with a plastic guard(s).
Shifting is now with a friction shifter, but it would have to be indexed. The current design need a longer cable pull than indexed shifters I have, so that is why I modified an old friction shifter.
Optimal chain width is a refinement that would come with product development. If VECTr is installed front and back, I would thing it advantageous to have a narrower chain.
It currently attaches to the crank arms with 64mm BCD bolts (on a square tapered bottom bracket) but custom crank arms could be fused/forged together.
In the short term, I am looking for partners to help in the product development. If you know anybody, send this along to them. But I appreciate your interest.
LikeLike
Thanks for the response! It is great fun to talk with you as you work through design and engineering issues.
Guards are a good idea to limit debris infiltration.
It sounds like you’ll have to develop your own shifter or modify the design to work with common pull ratios. Currently SRAM uses a 1:1 (approximately) and Shimano uses a 2:1 pull ratio (again, approximately).
On chain width, many single speed or internally geared setups use a wider chain. Narrow chains are advantageous for derailleur systems with narrow spacing between cogs in the cassette. A wider chain might be stronger and less prone to wear.
On the issue of roller engagement, I believe that each time a roller engages a new tooth it rolls slightly as it settles into the new valley. You could try marking a roller to see if it rotates as it travels around the expanding gear. On a traditional chainring rollers don’t rotate after they first settle into a valley. This may or may not be an issue with the system.
Do you have any ideas about how to manage chain tension if VECTr is installed front and back?
I’ll be thinking about people in the industry who might be interested. This could be a big hit with the recumbent crowd.
Mike
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Really interesting design, nice to see people thinking outsiode the box – good luck
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Thanks for the encouragement!
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I’m curious about who the target user is. I think the overall design is interesting and could see it as a viable option in the city-bike/commuter bike market. I could see this being a potentially nice setup on a bike that is designed to be ridden frequently but not typically under the strains and stresses of a “performance” road or mountain bike. It would also allow for a sleek chain guard on bike with front shifting which is difficult now on a commuter with 2 or 3 chain rings and the accompanying front derailleur.
Also, I think breaking into the market as an after-market drivetrain would be very difficult. As a complete bike I could see some promise but I think it would be a tough sell as an aftermarket piece. Stick with it, though.
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Thanks for your feedback. I am beginning to be inclined to agree with you. I will explore that market more. Thanks again.
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Would it be smoother with more than 4 expanding sections? Eight perhaps? Harder to make but it might be smoother.
Also, could you do something similar at the rear? You could change the gearing ratio and go bigger both at the front and rear ro give you more space on the rear cassette.
LikeLike
The unevenness of four contact points has been the biggest criticism so far. As it is, it does not feel all that lumpy, and only in the most expanded position, but for some, that is a huge drawback. It could have more gear segments, but then there would be a greater increase in effective teeth between each setting (now the gearing increases in 4-tooth increments).
I envision the final product to be on both the crank and the rear which, as you say, would give a greater range in gear ratios, be much lighter without the rear cassette and derailleur, and overall more streamlined.
Thanks for your feedback.
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I wanted to create a variable gear chainring for mountain bikes to get rid of the rear derailleur which is still incredibly vulnerable. Never got as far in figuring out how to make the actual shift happen, and I really like the idea! Could even make a switch for on the fly oval 🙂 I think current off road bikes need some sort of gearing at the BB area and not relying on a frame accepting a gearbox would be a huge advantage. Ground clearance would be an important factor though. I’d definitely want more segments for a smoother ring but I do see the drawback in increasing steps between gears. Best of luck with this!
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