Will SRAM quickly debut a self-charging wi-fi mountain bike derailleur with a dynamo generator inside? SRAM filed a patent on November tenth, 2022, detailing an digital rear derailleur with the means to re-charge itself while in use, negating the necessity for even a medium-sized detachable battery that requires charging off-the-bike. The 28-page doc describes using a generator coupled to the derailleur cage that may be activated to repeatedly cost the batteries by advantage of the rotation of the higher pulley wheel whereas pedaling.
An on-board energy-harvesting system will surely scale back pre-ride faff related to charging detachable batteries. It will additionally make any future SRAM AXS drivetrain carrying the know-how a viable choice for extremely long-distance endurance racers who now in any other case have to hold spare batteries. Nevertheless, one can think about that the mechanism described would end in some lack of watts from further drag throughout the drivetrain, on condition that it’s taking its vitality from rotation of the higher pulley wheel throughout pedaling.
We definitely shan’t be estimating what number of watts, however we will provide you with an summary of a number of the novelties described on this fairly unusual-looking derailleur which will or might not make it to manufacturing. Right here’s a more in-depth take a look at SRAM’s Self-Charging Auto-Shifting Rear Derailleur.
Function photos annotated by Cory Benson
SRAM’s Self-Charging Rear Derailleur Idea
The patent in query (US 20220355900 A1) particulars a bicycle derailleur that includes an energy-harvesting system. The primary few paragraphs point out one of many drawbacks of present digital derailleurs; the inconvenience of getting to recharge the battery, with the inherent threat of it operating out of juice while out on a protracted bike experience. These fortunate sufficient to personal an digital shifting drivetrain will know this all too properly; maybe not a lot as a result of they’ve run out of cost mid-ride, however extra doubtless as a result of they’ve forgotten to re-charge the battery earlier than heading out for his or her subsequent experience. One can think about the frustration.
SRAM’s patent revealed final November describes a self-charging derailleur that might eradicate this subject, that means its proprietor would now not have to stress over the cost state of the battery. They might use that psychological bandwidth to stress over extra vital issues, like hydration, fueling, and remembering their family members’ birthdays, for instance. (Ed’s observe: We really feel like J-M might have not too long ago missed an vital birthday!)
The derailleur depicted all through the doc seems to be extraordinarily compact. {The electrical} generator system, clutch, motor, shifting electronics and batteries are all housed on the derailleur cage meeting (as a substitute of their present location, additional aft on the b-knuckle), coupled to the rotation of the higher information pulley. That makes for a really peculiar-looking derailleur cage certainly, but in addition (I think about) a fairly costly one, too, ought to it ever should be changed.
So, how does it work?
Like most patents, this one particulars quite a lot of alternative ways by which it’d obtain its major aim, taking care to guarantee the reader that the mechanisms described inside “aren’t meant to restrict the scope” of the invention. The principle embodiment describes using a generator that’s housed on the derailleur’s cage meeting, which could be activated through quite a lot of completely different mechanisms to be able to re-charge a battery or batteries.
The principle mechanism described entails coupling rotation of the cage’s higher pulley wheel (through 35 in Fig. 30), to drive a pinion gear to activate a generator. Inside that mechanism, the patent describes use of a spur gear (339), pinion gear (338), belt, and an inner pulley wheel (41) to activate the generator base (46), stating a most well-liked gear ratio of 33.75:1. So, for each single rotation of the cage’s higher pulley wheel, the pinion gear inside {the electrical} generator system rotates 33.75 occasions. That might recommend that the generator is best at very excessive speeds.
On this state of affairs an, albeit very small, portion of the rider’s enter on the cranks is getting used to show the generator. So, it’s cheap to imagine that a few of your valuable watts can be misplaced to {the electrical} generator system to be able to cost the derailleur’s battery whereas pedaling. That mentioned, we think about that loss to be a lot lower than the losses related to a bigger hub dynamo.
The patent additionally describes use of a clutch (290) throughout the electrical generator system that forestalls rotation of the gears when the rider back-pedals. Clearly, such a state of affairs isn’t so widespread, but it surely does often occur to various levels on some full suspension mountain bikes throughout pedal kickback occasions that end result from chain progress.
The patent’s 22 pages element use of transistors, resistors, and capacitors, the features of which I shan’t fake to know past offering a clear stream of electrons to make the battery completely satisfied. However, the lengthy and the in need of it’s this: the on-board generator is, not directly, recharging the derailleur’s batteries in order that it, theoretically, ought to by no means run out of cost while on a experience. This may very well be a game-changer for the ultra-distance contingent who can’t run the chance of a battery shedding cost mid-adventure or endurance race, for worry of getting to single-speed it till they arrive at their subsequent refueling spot.
New Shifting Mechanics
Fig. 28 of the SRAM Patent Utility reveals fully new shifting mechanics, too. On the present SRAM AXS rear derailleurs, the shifter motor and battery are housed on the aft b-knuckle of the derailleur, in between the rear pivots of the parallelogram linkage that mediate shifts. Right here, on the brand new self-charging digital derailleur idea, the shifter motor is housed on the cage meeting, sequentially driving pinion gears, spur gears, a screw (81), a nut (91), and finally a drive pin (97), to rotate the outboard hyperlink (6) of the parallelogram to be able to execute a shift.
Sorry, you shan’t be getting any extra element out of me than that. Nevertheless, do you have to want to immerse your self within the mechanics of all of it, I can verify it’s all painstakingly spelled out on pages 8 and 9.
It strikes us that a whole lot of vital (and certain costly) componentry is positioned on the, arguably, extra weak a part of the derailleur – the cage. Regardless of this, the patent doc reads, “the motor and/or {the electrical} generator system could also be mounted on and moveable [sic] with the cage. If broken, the cage, together with the motor and electrical generator system, could also be rapidly and simply changed with out having to interchange the opposite parts of the derailleur”.
We’ll name the modular alternative idea a comfort prize.
When within the small cog/large gear, that greater mechanism on the cage does stick out fairly removed from the aircraft the place the derailleur hanger bolt contacts your body (15 under). However as you shift into a better gear/greater cog, the majority of the derailleur does seem to tuck up below the chainstay, staying near the cassette.
Lastly, an auto-shift perform can also be described. Diodes and resistors throughout the electrical generator system are used to sense the pace of the generator, which might then be used to find out the pace of the chain pulley, and subsequently the pace of the chain. That info, taken along with info delivered by different sensors on the bike (on the cranks and rear wheel, for instance) may very well be “used to carry out an automated shifting algorithm which retains the gear ratio at a preferable ratio for the rider”.
Will the SRAM Self-Charging Derailleur Make it to Manufacturing?
Who is aware of. We now have approached SRAM for touch upon the proposed know-how, however are but to listen to again. We are going to maintain you up to date ought to we study extra sooner or later.
The worst-kept secret within the bike trade proper now must be the upcoming arrival of a new SRAM AXS XX drivetrain. We now have coated this extensively as numerous Black Field Prototypes have cropped up on Professionals’ Cross-Nation Race Bikes. Evaluating these pictures with the diagrams seen right here, it is rather unlikely any of the self-charging know-how described herein can be a function of that drivetrain. We reckon it is going to be a number of years earlier than we see something like this rolled out to manufacturing, if in any respect.
