New Details about SRAM’s ETAP Wireless Rear Derailleur

Although unannounced, everybody knows by now that SRAM is coming out with a wireless, electronic drivetrain. In the press, the system has become to be known as “eTap”. Judging from SRAM’s Valentine’s Day 2014 trademark application, which describes SRAM’s intent to use ETAP with “Bicycle parts, namely, gear shifting mechanisms, brakes, cranks and derailleurs,” the groupset will likely be branded as eTap.

Last week, SRAM’s patent application US 14/061138 published as US 2015/0111675, which provides details about SRAM’s new wireless rear derailleur. As BikeRadar has reported, the rear derailleur includes a lithium-ion battery 178:

SRAM Battery 1SRAM Battery 2

And, as seen in the below photos by RoadBikeReview, the battery will be interchangeable between front and rear derailleurs:

rd 1 roadbikereview fd 1 roadbikereview

An interesting innovation disclosed in the application is how the SRAM rear derailleur accounts for impacts without damaging the internal gearing – simply, the connection between the internal gears and the parallelogram includes a dutch spring mechanism that can absorb any impacts without transferring the impact to the internal gears.  In FIGs. 15a, 15b, and 15c below, the views are looking up from below the derailleur such that the rear wheel and in-board direction are to the right.  As shown below, the leg 52a of the spring 52 deflects to absorb an impact from the left.

SRAM 15a

SRAM 15b

SRAM 15c

In the event of a crash or other side impact (a force directed from left to right in FIGS. 15a, b and c), if the force of the impact overcomes the preload in the torsion-type dutch spring 52, the links of the linkage 32 rotate clockwise about their pivot pins 28, deflecting the leg 52a of the spring as shown in FIG. 15b. Thus, the linkage 32 is able to move without imparting any movement to the gears 106 in the gearbox 44. When the impact force is removed from the derailleur 20, the spring leg 52a will push against the drive arm 48 and cause the derailleur to go back to its normal state shown in FIG. 15a.

And, as expected in a wireless system, the derailleur includes a radio chip 194, but not much more than that is disclosed about the radio chip 194 in this application.

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Shimano’s Chainstay Derailleur and Chain Tensioner

To complement the SRAM narrow-wide chainring post, I was looking for patents by Shimano drawn to their 1x drivetrain chainrings in view this MBR article. I haven’t come across exactly what I’m looking for but I did find some Shimano patents and applications directed to chainstay derailleurs and chain tensioners. I haven’t seen these things on anything new, but Shimano is at least pursuing IP related to them – Shimano responded, on March 12, 2015, to a restriction requirement issued by the USPTO in US 20140357437.

FIG. 1 from US 2014-0357437 shows Shimano’s current iteration:

shimano app fig 1

And, US 7,905,805, issued to Shimano on March 15, 2011, highlights some of the advantages of placing the derailleur and chain tensioner on the chainstay:

Furthermore, the location of the tension device 250 at about mid-way between the gear changing device 232 and the front sprocket of the bicycle ensures that the expanse of unsupported drive chain 218 [] is minimized, as compared to other designs []. The above factors beneficially reduce the flopping movement [] of the chain 218 during the impact and absorption of the impact force, as compared to other designs.

In addition to the above benefits, the rear derailleur device 230 of the embodiment of the present invention allows for a reduction in the size and weight of the device adjacent the rear sprocket 216. For example, note that the gear changing device 232 is smaller in size and weight than the rear derailleur 330 in FIG. 6A. Additionally, the rear derailleur device 230 of the embodiment of the present invention reduces or prevents entanglement of the drive chain with the gear changing device 232 when the tension device 250 pivots due to impact.

I admit that I’ve been fortunate to never have a derailleur go into my rear wheel, but I’ve seen it and the frustration it’s caused. Could the chainstay derailleur and chain tensioner be the solution?

Application: US 14/066,943
Application Status: Response Filed on March 12, 2015, Published as US 2014-0357437
Assignee: Shimano, Inc.
Related Patents/Applications: Continuation in Part of US 13/910,043, under non-final rejection and published as US 2014-0357436.

Application: US 12/101,673
Application Status: Issued on March 15, 2011, as US 7,905,805
Assignee: Shimano, Inc.
Related Patents/Applications: N/A.

SRAM’s Single Chainring

The trend in mountain and cyclocross is to drop your extra chainrings and your front derailleur to run a 1x system. The hope is that removing the front derailleur will increase reliability and decrease weight. And, frankly, it looks pretty sharp.

1x drivetrains used to require a chain guide to keep the chain on the chainring. Clutched rear derailleurs, like Shimano’s Shadow Plus and SRAM’s Type 2, keep tension on the chain to decrease chain dropping.

But, the narrow wide chainring is the final piece of the puzzle to reliably keeping the chain on without requiring a chain guide. Narrow wide is pretty descriptive – teeth of the chainring alternate between having a narrow width and a wide width. The wide teeth grip the links of the chain to hold the chain on the chainring.

After SRAM’s introduction of the XX1 mtb drivetrain, several manufacturers introduced their own narrow wides – for example, RaceFace and Wolf Tooth.

On October 21 and October 28, 2014, SRAM was awarded US design patents D715,699 and D716,191, respectively. Both design patents are drawn to narrow wide chainrings.

From D715,699:

619-2

619 4

619 5 and 6

From D716,191:

191 1

191 2

191 3 and 4

It is important to remember that it is the solid lines in the figures that define the covered, patented subject matter.

Application: 29/471, 384
Application Status: Patented – D715,699, Issued October 21, 2014
Assignee: SRAM, LLC
Related Applications: Continuation of US 13/311,735 (under final rejection)

Application: 29/473, 643
Application Status: Patented – D716,191, Issued October 28, 2014
Assignee: SRAM, LLC
Related Applications: Continuation of US 13/787,276 (under non-final rejection), which is a continuation-in-part of US 13/311,735 (under final rejection)

Trek’s Externally-Geared, Belt-Driven Mountain Bike

Conventional wisdom in the belt drive arena tells us that belt drive is only for single speed setups, and an internally geared hub or a gearbox is needed to change gear ratios.

Not so according to Trek. Trek is pursing a US patent application that shows a hardtail mountain bike with both belt drive and a rear derailleur. In March of 2012, Trek was issued a US design patent drawn to the chainring for this implementation.

Screen shot 2015-02-04 at 1.36.59 PM

One or both of the crankset and wheel hub cogs can include more than one cog having different circumferential sizes so as to alter the mechanical advantage provided between the pedals and the driven hub. … It is envisioned that, when provided in a multiple geared format, bicycle 30 be equipped with a front and/or a rear derailleur assembly to facilitate the manual lateral manipulation of the flexible drive member 80 in effectuating shifting of the gearing arrangement of bicycle 30 such that flexible drive member 80 cooperate with one of cogs 120200, or 300 as desired.”

In other words, Trek envisions belt-driven bikes to have both front and rear derailleurs.

Here’s a portion of Trek’s belt drive cassette:

Screen shot 2015-02-04 at 1.39.39 PM

In the cross-section of the cassette, you can see that the belt 80 is engaged in the largest cog and moveable to the right as indicated by arrow 434.

And, here’s a better look at the design of the cogs:

Screen shot 2015-02-04 at 1.43.50 PM

Screen shot 2015-02-04 at 1.43.22 PM

Looks like belt drive may be finding more applications soon.

Application: US 12/985,166
Application Status: Final Rejection – Early Response Due February 12, 2015
Assignee: Trek Bicycle Corp. (original assignee)
Related Patents/Applications: D655,225 (issued March 6, 2012)

Shimano’s Di2 Synchro-Shift

As much as I love all bikes, I’m a mountain biker at heart. And, I’m excited to see Shimano’s Di2 coming to XTR. Synchro-Shift operates both the front and rear derailleurs in response to input from one shifter. Or, another way, the rider only says, “I need a higher/lower gear,” and Synchro-Shift says, “Okay. We’ll move the front and rear derailleurs like this for you.” It’s like having a 1x drivetrain but with a front derailleur that you don’t have to mess with.

Shimano provides the below video showing Synchro-Shift for 2×11 and 3×11 drivetrains.

Last November, Shimano received US 8,882,122 drawn to this technology. The illustrated example provided in the patent is only for a 3×10 drivetrain, but you can see the similarities. FIG. 4 of the patent compared to 2:10 of the video:

FIG. 4

Screen shot 2015-02-04 at 1.13.53 PM

2:10

Screen shot 2015-02-03 at 1.53.29 PM

In the 3×11, at least in these examples, less time overall is spent in the smallest chainring – 3 gears when upshifting and 2 gears when downshifting vs. 5 gears up and 2 down for the 3×10.

Application: US 13/857,570
Application Status: Patented – US 8,882,122
A
ssignee: Shimano, Inc.
Related Patents/Applications: N/A