A Deeper Look at Lal Bikes' Supre Drive Patent
When Cedric Eveleigh told us about his Supre Drivetrain which splits apart the two functions of derailleurs (shifting gears and tensioning the chain), thereby dramatically reducing the chances of breaking derailleurs on the trail, we wondered why nobody had thought of that before. But in a sense, they had.
Cedric himself showed me this patent from 1937, which describes a drivetrain with an arm that selects the gear on the cassette, with a separate tensioner arm and pulley tucked behind the chainring. So why haven't we been using drivetrains like this since the late thirties? And what specifically is it that allowed Eveleigh's design to be granted this patent, which was just published? I got on the phone with Cedric to find out.
What's new?
The problem with the design from 1937 is that there isn't much space for the tensioner arm to move clockwise before it hits the upper chain span. That means the arm can only take up so much slack in the chain, so it was only compatible with very narrow-range cassettes, and certainly wouldn't work with modern wide-range cassettes combined with suspension systems that require even more chain growth.
The Supre drivetrain works with modern cassettes because it's designed around a high-pivot and idler suspension design. The idler pulley moves the upper chain span out of the way, making room for a tensioner arm with a much wider range of motion.
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Even so, Supre Drive requires the idler pulley to be positioned further forwards than on most high-pivot bikes to make room for the tensioner arm. And when we first reported on the Supre Drive, we showed a prototype bike that was only capable of running a 10-45t 11-speed cassette. But the drivetrain pictured above accommodates a 10-51t 12-speed cassette, which will make it more appealing to the mass market and therefore to bike brands.
This requires the idler pulley to be even further forward, but as the Supre drivetrain is aimed at OEMs who want to design bikes around it, Cedric sees this as a positive rather than an issue. "Fortunately, moving the idler pulley forward has the advantage of reduced cross-chaining angles," Cedric explains. "This reduces drag and wear, especially in the highest and lowest gears." It's certainly true that cross-chaining significantly increases drivetrain drag at the most extreme angles, so increasing the length of the upper chain span should help alleviate this problem.
Cedric's patent stipulates that the chain remains above the "clearance line", labelled here with number 121.
Eveleigh's patent application was granted on the basis that it was a novel combination of the frame-mounted tensioner, rear derailleur and high-pivot idler, plus a stipulation that his design kept the lower chain line above what's called the clearance line - a line drawn from the bottom of the chainring to the bottom of the largest cassette sprocket.
Cedric thinks the patent might have been granted without this stipulation, and patent documents are usually designed to be as vague as possible to keep the inventors' options open, but Cedric added this detail to make his application more watertight and because he couldn't foresee the need to ever make a drivetrain with a lower chain clearance, since getting the fragile bits higher up off the ground is kind of the point.
"It's possible that I might have been able to get that claim accepted by the examiner with just the tensioner separate from the derailleur and the idler pulley," Cedric explains. "But just for the reason of obviousness and to avoid unnecessary lawsuits [laughs] I decided to narrow my claim a little bit. When you go to lawyers and ask them to write a patent application, their reflex is to make the claim as broad as possible .... it could be applied to a lawnmower or something ... they're just trying to make as much money as possible. I'm motivated to just protect what I invented as it's specific to bikes. That's along the lines of why I narrowed the claim to have the chain remain over that clearance line because that makes it a bit more specific to what I actually contributed."
The brass tube on the right contains a coil spring and a hydraulic damper which control the motion of the tensioner arm via a cable.
Clutch development
In our conversation, Cedric went into more detail on his damper design for the tensioner arm. In most MTB derailleurs, the clutch (which is a form of damper) uses a one-way ratchet to apply friction via sliding surfaces to resist the movement of the cage in the forward direction. As we all know, this greatly reduces chain slap, noise and dropped chains, but it can make it harder to shift, particularly when moving into a larger sprocket. This means the clutch friction has to be a tradeoff between shifting performance and chain slap. Also, this test from Cycling Tips showed that the clutch in Shimano derailleurs can temporarily increase chain tension after shifting into a larger sprocket, and this measurably increases drivetrain drag in some situations.
An early version of the Supre drivetrain used a torsion spring and a one-way sliding friction damper in the tensioner arm, as you'd find in the cage in a derailleur. Cedric was struggling to find the right amount of friction to allow for consistent shifting while also providing enough resistance to reduce chain slap. His solution was to do away with the sliding friction damper ("clutch"), with its high static friction, and replace it with a speed-sensitive hydraulic damper, like you'd find in a shock.
That means the resistance during slow movements like shifting is very low, but the resistance to faster movements associated with chain slap is very high. According to Eveleigh, that means there's less need to fine-tune the friction because there's much more damping bandwidth that works for both shifting and chain slap - you can have your cake and eat it too.
Another innovation is the spring which tensions the chain via the tensioner arm. In a conventional derailleur, shifting into the larger sprockets winds up a torsion spring in the cage's pivot, which increases the chain tension because the spring provides more force.
That means the resistance during slow movements like shifting is very low, but the resistance to faster movements associated with chain slap is very high. According to Eveleigh, that means there's less need to fine-tune the friction because there's much more damping bandwidth that works for both shifting and chain slap - you can have your cake and eat it too.
Another innovation is the spring which tensions the chain via the tensioner arm. In a conventional derailleur, shifting into the larger sprockets winds up a torsion spring in the cage's pivot, which increases the chain tension because the spring provides more force.
In the patent, the tensioner arm is shown connected to a spring in a cartridge (in this older version of the chain tensioner, the damper is in the tensioner arm, but in newer versions, the damper is in the cartridge).
This means the chain tension is significantly higher in the larger sprockets, and more chain tension means more drivetrain drag because chain links under higher tension have more friction when they articulate to pass through the jockey wheels.
In Eveleigh's design, the tensioner arm is driven by a cable that engages with a cam-shaped ramp on the arm with a variable radius - (this article explains a similar concept in more depth). This changes the leverage ratio between the tensioner arm and a linear coil spring in a cartridge that is hidden in the downtube. The change in leverage ratio is engineered to compensate for the increase in spring tension as it is stretched, keeping the chain tension roughly constant through all the gears.
I say "roughly constant" because Eveleigh actually designed the tension to drop off slightly in the larger sprockets (the opposite of a conventional derailleur). Eveleigh reasons that you don't need as much chain tension when you're climbing because chain slap and derailment are less of an issue at slower speeds.
Compared to typical derailleurs, his system has much less chain tension in the low gears, but it also has slightly less chain tension in the high gears. Normally, this would allow the chain to slap about through a larger range of motion, making it noisier and more likely to fall off. But the hydraulic damper is designed to solve that issue by applying more damping force at high speeds than a conventional clutch derailleur. The advantage of lower chain tension is reduced drivetrain drag. This, combined with extra-large jockey wheels and idler pulley, plus smaller cross-chain angles thanks to the longer upper chain span, are designed to minimise the drivetrain drag which is a drawback of idler drivetrains generally.
When asked about the packaging of the spring/damper cartridge, which in its current form is designed to be mounted in the downtube, Eveleigh was understandably tight-lipped. "I can tell you I'm working on a version that's much more compact."
I say "roughly constant" because Eveleigh actually designed the tension to drop off slightly in the larger sprockets (the opposite of a conventional derailleur). Eveleigh reasons that you don't need as much chain tension when you're climbing because chain slap and derailment are less of an issue at slower speeds.
Compared to typical derailleurs, his system has much less chain tension in the low gears, but it also has slightly less chain tension in the high gears. Normally, this would allow the chain to slap about through a larger range of motion, making it noisier and more likely to fall off. But the hydraulic damper is designed to solve that issue by applying more damping force at high speeds than a conventional clutch derailleur. The advantage of lower chain tension is reduced drivetrain drag. This, combined with extra-large jockey wheels and idler pulley, plus smaller cross-chain angles thanks to the longer upper chain span, are designed to minimise the drivetrain drag which is a drawback of idler drivetrains generally.
When asked about the packaging of the spring/damper cartridge, which in its current form is designed to be mounted in the downtube, Eveleigh was understandably tight-lipped. "I can tell you I'm working on a version that's much more compact."
The cam-shaped ramp is engineered to maintain near-constant chain tension throughout the range of gearing.
Production
Cedric told me he is working with "one major mountain bike company, three more nimble local manufacturing companies and a few small scale frame builders." Many of them are currently at the 2D design stage, working out their suspension kinematics around the Supre drivetrain and its unusual idler location.
Cedric says the system is pretty straightforward to design into a bike with a high-single-pivot and the idler connected to the swingarm. He has an information package including 3D models of the chain clearance in each gear, so bike brands can design their bikes to fit around it more or less as they would with a gearbox or e-bike motor. Bike companies who want a different suspension design (such s a four-bar linkage or a frame mounted idler pulley) will have a bit more back and forth with Lal Bikes to make sure it's compatible.
Cedric thinks that one of the more nimble brands with in-house production will likely be the first to market with the Supre drivetrain.
After being unable to buy a single Pinion gearbox for a bike he designed around it in 2012, Cedric says he'll work with anyone who wants to use his system, no matter the scale. "Anyone who wants to can go ahead ... even the kids who are reaching out to me for a high school project, I'm like here are the specs let me know what you come up with."
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Even if the true number for all mtbers is half of that, it's still a lot of derailleurs.
And the Supre Drive doesn't have extra pulleys. There's the same number of pulleys as other high pivot bikes like the Norco Range, and there's actually one less pulley than high pivot bikes like the Forbiddens (because of their lower chain guide roller).
This happened to me about two miles from home but fortunately it was downhill to get home. Imagine you are on Lord of the Squirrels or biking the Colorado trail. I can see the benefit of protecting the derailleur a bit more than we do now.
OTOH, I think the concept looks really well thought out, and every component here is basically where it needs to be. I'd take this over a draggy gearbox / derailleur-in-a-can system, but I don't wreck enough standard drivetrains to warrant the extra up-front cost (which is probably quite a bit).
I wonder how differently I'd ride if I hadn't ever had to worry about derailleurs—hell I might even like skinnies.
Cedric, to me one of the best aspects of your design is the constant chain tension that's better optimized for a given gear. How come you haven't decided to make that primary point in terms of the positive effect on suspension performance it will have. Was that more of a marketing decision?
For me that's what has I'm sold on for your drivetrain. Not breaking derailleurs is just the icing.
* Derailleur
* Derailleur hanger
* Spokes
* Axles
* Chain stay
* Seat rails
* Rims
* Cassette driver
* Chain ring
* Cassette
* Pedals
* Crank arm
* Shifter
I look forward to breaking the rest.
Handlebars
Stem
Fork
I’m gonna save a few terabytes and not list everything I’ve broken. This is a very cool drive train concept. Congratulations on the patent. I look forward to seeing it in the wild.
Ooh. Forgot chains.
If I was paying 100s of pounds for mechs getting them hidden would be a _really_ good plan.
I had bend hangers and mechs with 1x10 and 1x11 but the difference is they don't go fubar because of it that fast. Most won't give a damn about that.
On 1x12 I need to sneeze to let it run bad.1
@steviestokes true, my nowadays is just 1x10 and my Enduro get a Kindernay gear hub because hwo often not shifting instantly. Or just being dead .
I just had the mud and diet part last weekend too. Was super crisp on the uphill. After the dirt was everywhere on after the downhill and I did pedal to the next mountain the shifting was bad and anfter the second on the way to the last it was horrible. Had to shift in between to get the gears right. After it was clean again it was just crisp as before. Na man it's winter and there will be mud everywhere.
As for the derailleur in a box being better, well yes there are advantages. But with reducing unsprung mass, I think that's overstated - swapping from NX to X01 cassette saves a lot of weight but IMO it makes no tangible difference to the suspension. And yes you can keep the derailleur out of the elements but the drive chain is still exposed to mud.
The main problem with them is that you need two chains (one for shifting and one for drive transmission) - the Shimano gearbox patent uses three chains. This adds drag because you have more chain articulation under tension, which IMO confines its use to DH.
Eveleigh's design should have less drag than a conventional high-pivot drivetrain and has the same or fewer parts.
Also understand some of the limitations ?
The Supre looks fine for a Forbidden type rig but again, not really necessary IMO for most applications. Your mileage may vary.
Last year I only had broken Carbon rim, spoke nippels and spokes, one brake rotor, 1 chain and one chainring.
Destroyed deraileurs 4, AXS included.
As for being more complex, it's no more complex than other high pivot drivetrains, arguably less so given there's no need for a lower roller guide (which most high pivots greatly benefit from even if it's not required).
The system also allows for larger pulleys, lower chain tension and a proper hydraulic tensioner damper, all of which could reduce drag and noise compared to a conventional high-pivot.
You need to try harder.
Please can nobody explain how a twig can wreck a bike, I don't want to know.
Let me tell you what. Wood is freakishly strong. I once had a low speed OTB where I was trying to crank up a little punchy climb with some stepping stone and put my front wheel between two while shifting my weight forward. The bike kicked out to the right and fell about 8 feet down a small cliff and I tumbled forward coming to a stop when my back hit a tree. It felt like I walked in front of Barry Bonds mid-swing. When I looked at the tree it was at most 2 inches in diameter. I was off the bike and not doing well for about two week and managed to break a shifter. And it was super hard to get the bike back onto the trail.
No joke, a couple months ago I had a wispy little twig poke me through a hole in my helmet. I kept rolling and it got wedged in there. Pulled my head backwards and I looped out. Twigs just wanna cause chaos.
Hope you get a sell-able product as I have prior art on this design!
If Cedric's system can come extremely close to standard derailleur efficiency while having the advantages of a HP bike, while not weighing more than a standard HP bike (which are consistently heavier already) and importantly removing some unsprung weight in the deal, he really has something.
As I've never broken a derailleur it's just not a concern for me but it's appealing to remove it from ever occurring.
GL to him.
These numbers might help you to make it clearer to people that the total pivoting angle for the chain in your system is not actually that much more than that of some existing systems, despite appearances perhaps suggesting otherwise.
Still though, the Supre numbers compare well with the other designs!
This new system looks complicated. But I don't think more-so than a gear box. Is it as reliable? Maybe. Is it more efficient? Probably. Is it lighter? Uh... at least it uses a bog standard cogset. I doubt there will ever be a drivetrain that makes everyone happy.
I see this as an exciting innovation that isn't going to make everyone happy, but will do good to move tech forward.
SRAM steel chainrings are pretty cheap also.
I was brimming with joy when SRAM announced it. Cheaper and last longer! But my local SRAM dealer had other ideas and never thought of stocking it here. So my primary option now are Chinese made alloy chainrings, priced at 5-7 USD (depending on BCD pattern). A lot of options in popular BCD patterns (104, 96 asymmetric, etc.) from 32T to 36T but nothing on 26/28T BCD64 at that price level. Cheapest direct mount 26T chainring I can find is around 20 USD, used, alloy not steel, not SRAM either..
The squat thing was more like a joke, but time is made, not had. I know, sometimes it just doesn't work out.
Buying online directly from overseas is an option, but the cost of shipment and customs will add up.
Yeah, if I manage to made some time, I'd rather have it spent on the mountains than in the gym doing leg day.
-the layout of the drivetrain
-the spring/ damper on the tensioner.
It seems like either innovation could work without the other. Like, you could have this drivetrain layout with a much simpler tensioner spring. Or you could have a conventional drivetrain layout, but have the rear derailleur tensioned by the spring-and-damper-in-a-stick, which could be attached to the chainstay.
Why not build some movement into a derailleur during high impact? IE what modern car mirrors will do if they're struck.
The problem with a gearbox is the added cost to an already expensive bike, and yes for some applications the added friction is a no no.
I love the idea of a gearbox on the right bike, but the lack of choice of bikes that use it and the cost isn't for me.
This idea should keep the cost down, weight down and also maintain the drivetrains efficiencies above that of a gearbox.
I have recently had the misfortune of wrecking a rear mech and it was about £40 more expensive to replace the 11speed GX mech than it would have been a couple of years ago. I can't see these prices ever dropping back to where they were before the pandemic.
I am for ever, (feels like every couple of rides) having to either realign my hanger with a tool or replace it.
Again there's a cost to replacing the hangers at £25 each, it soon mounts up.
We pay a small fortune to have a "quality" mech and drivetrain so that we can have crisp and precise shifting, only for it to work like a budget setup within a couple of rides.
I think this approach could well prove to be a better solution.
Well done to you Sir, I wish you all the success.
also, try to ignore the hate. the people saying they broke a derailleur twice in their lifetime either ride very slow all the time, or never, ever crash. i've had rocks break and bend my derailleur, sticks that caused the same damage, and usually have to tune it up once a month. so i'm all for getting it up and out of the way.
Because while the forward high idler creates less "chain crossing", there's a lot of crossing under, can't that crossing pull on the derailleur "outward" and make the gear jump back ?
Is the derailleur strong enough ?
My guesses as to why:
(a) he doesn't want to lock mfrs into making elevated chainstay Orange lookalike bikes (but if people wanted to make elevated chainstay bikes, they could probably just clock the tensioner mounts differently to reduce wrap)
(b) he wants to keep a minimum chainwring wrap in the biggest cog to avoid wear. Currently the bigest-cog chainring wrap is pretty similar to what you see on standard drivetrains.
Uh yeah, because when you look at a gearbox you just see the box. Pretty fiddly once you get inside there!
Cedric, this thing is awesome. Can’t wait to see the first production version.
Here, hold my beer!