In this article, we’ll be discussing Height Adjustable Seat Posts for Bicycles by SRAM, US publication 20240166286. The publication date is May 23rd and the filing date is Feb 15th, 2023. This is not granted.
Brief Summary (tl;dr)
SRAM have cooked up another wireless and electronic seat post. This one moves the controller and battery to the lower tube rather than the upper tube on the current AXS. Rather than a geared valving system, this new system uses a solenoid and pilot valve to open and close fluid pathways to lock and unlock movement of the seat post. This could be simpler with less moving parts, less space required, and less power consumption.
An interesting alternative relates to the powering method, where the seat post includes a little wire coil with a charging magnet at the bottom. This seat post doesn’t have the battery. Instead, the seat post is slid into the seat tube, the charging magnet mates with another magnet at the bottom of the seat tube which is connected to a primary E-bike battery. In this system, the controller is also housed in the bike rather than the dropper, so the dropper only has a valve.
Background
SRAM are a leader in the wireless and electronic movement of cycling. Whether you like it or not, they’re pushing the concept forward with a team of smart folks that you’ll never know
While I’ve never used or torn apart the current Reverb AXS (or anything electronic for that matter), I’m 99% certain the system uses a motor and gearset to open and close a valve, which controls fluid flow between chambers. We can think of this as very similar to a manually-operated valve, but a motor just moves the valve.
The image below supports my thesis. It’s tough to find anything/one that’s broken apart the control module of a current Reverb, so I resorted to speculative images of previous applications. This shows a little motor 290 that moves a valve 222 which controls the fluid flow to lock or unlock the seat post freedom.
Look how complex this little shit is. When SRAM went from a lever-operated valve to a motor-operated valve, it seems like they kind of kept the concept of moving a valve the same, but the valve is operated with a motor rather than your hand.
Now that they’ve had some time to develop the electronic side of this system, it’s probably time to update the actual fluid actuation system.
Intro
SRAM are showing a new seat post. This trill new post has two specifically new dangles, one being a new valving system and the other being the powering system.
This new dingledongle uses a solenoid and valve rather than a motor, gearset, and valve. A solenoid is a wire coil that is configured to have a current pass through it. If we recall high school physics, we remember that an electrified coil produces a magnetic field. This field, when activated with electricity, can move a valve (or anything magnetic) relative to polarity.
A solenoid we’re all familiar with in a linear voice coil in a speaker. A current passes through a coil wrapped around a part of a cone to create a magnetic field, which interacts with the permanent (static) magnet. The voltage of the input current fluctuates, the cone goes up and down, and we have sound.
Solenoids are famous for their extreme simplicity and cost-effectiveness to move/control something. They’re simple, with zero moving parts, and can move super-fast. All you need is a current and the valve can open and close, nearly instantly.
Why
Position monitoring is the process of a controller executing a move command, and then feeding back the resultant move so the system can compare a command to a result. It sounds like SRAM are using an optical sensor that recognizes gear or cam rotations. I assume SRAM want to bounce that piece out of this new dropper.
The example solenoid-operated valves disclosed herein are advantageous because they do not require position monitoring as seen in known dropper seat posts. This greatly reduces manufacturing complexity and costs.
Solenoids are tiny.
Further the example solenoids disclosed herein only make small, linear movements. This reduces the space needed to incorporate the actuation components in the seat post.
Additionally, they state many times in this document about reduced power consumption, so that’s nice to hear.
This reduces power consumption of the solenoid…
What
FIGs. 2 and 3 show an external view of this new dropper. The most obvious thing we’re seeing here is the control module and battery sit at the top of lower tube rather than the upper tube like the currently-available Reverb.
FIG. 4 shows a closer view of the control module. This houses wireless gadgetry and circuitry.
So, what does this control module do? It takes a command from the button on the handlebar and turns it into a command – just like every other wireless thing on Earth.
The control module 222 includes a power supply (e.g., a battery) and circuitry (e.g., processor circuitry, logic circuitry, etc.) to operate the internal valve system.
FIGs. 5 and 6 show a cross-section of the dropper in an up-and-down position. Note the upper shaft moves relative to everything else. Nothing else moves. The circle notes the piston, controller, battery, and all the other things that make this dropper work, and what we’re about to talk about.
FIG. 7 shows the valve for airing up this thing. I do believe the current AXS is filled through the bottom, so this is a departure from that. There’s a reason this is at the top now, which I go into later on.
Valving
As I said before, the current AXS system likely uses a little motor and gearset to move a valve. That’s pretty simple to understand and was simpler for SRAM to convert their typical lever-controlled system to a motor-controlled system.
SRAM have a few valving system options such as a pilot valve, a face valve, a spool valve, a pull valve, and a push valve. In this design, SRAM say they’re using a pilot, or pilot operated, solenoid valve [0084]. Even more so, this is what is called a ‘normally-closed’ solenoid valve because, in a non-energized state, the valve is closed, restricting fluid flow.
FIGs. 10 and 12 shows the guts of this thing. We are looking at the piston inside the dropper (circle FIG. 5). This shows the seals and bumpers and all that jazz, but I won’t go into that – way too much information. I’ll just show you the solenoid and plunger of the valve noted in the dank colors because MS Paint is pretty good now.
Note the spring biasing the plunger upward. This restricts flow when no power energizes the solenoid but allows for the plunger to move down when the solenoid is powered.
So, this is pretty simple. The button on the handlebar sends an ‘open’ signal to the controller. The controller sends a current to the solenoid, which opens the valve, which then allows fluid to pass through the fluid chambers (pressure equalization, and so on). Because fluid can now pass, the seat post can move freely. When the button isn’t pressed, the solenoid is de-energized, removing the magnetic field, which allows the valve to move back to a normally-closed state so fluid cannot pass between the chambers. That’s about it.
If you’d like to read the seemingly complex system of fluid flow, go to paragraphs [0092-95].
Here’s an exceedingly boring, yet informative, video on the valve.
There are a few more valve examples in the document if you care to dive in. They all appear to follow the same general concept.
Power
There’s an on-dropper battery but you also have the option to integrate the battery situation on the dropper to the big-battery on the E-bike. We’ll get into that in a minute.
FIGs. 8 and 9 show the bottom of the dropper. Wires 532 and 534 go from the controller/battery, down the sides of the lower shaft to wire contacts 800 and 802. The wire contacts then touch inner wire contacts 820 and 822. Then, the inner wire contacts then make contact with the pins 906 and 908, which sends power to the solenoid through inner wires 538 and 540. Good lord.
So, power has to go down the shaft, then back up the shaft to the solenoid in this order: Controller/battery → contacts 800 and 802 → inner wire contacts 820 and 822 → pins 906 and 908 → 538 and 540.
Now here’s an interesting piece to this. The document we’re reading is a continuation in part of another application (20240166285). If we dive into that one, we go down to FIGs. 27 and 28 which show this. This looks pretty familiar, right? Note the two wires at the bottom. This is showing a hard-wired system to an on-board battery, likely an E-bike battery.
Let’s take a quick step back at this new powering concept. FIGs. 12 and 13A show a seat post with a little coil of wire and a magnet terminal at the bottom. The magnet terminal mates with another magnetic power terminal. The image to the right shows the concept, but I’m fairly certain most of you understand it.
FIGs. 2-4 show an installation method. You just slide the seat post into the seat tube, the seat post magnet mates with another magnet terminal at the bottom of the seat tube which is connected to/near the motor assembly, which is then connected to the battery.
The use of the coil and magnet is pretty cool. You don’t need to actually line anything up down there, it’ll find its way there.
I’d also like to point out that the controlling method here is a little different, too. Component 600 is the shifter, which sends a signal to another controller NOT in the seat post, but rather the battery or motor or somewhere down there, as seen in FIG. 5. So, the seat post only contains a valving system and no other componentry.
Conclusion
If you have a Reverb, throw it away. It’s useless and cannot be used anymore. If you ain’t using a Preverb, then you ain’t it. You can’t be seen on throwback whips.
But seriously, it genuinely sounds like SRAM are trying to simplify a very complex manufacturing and design system with their current Reverb AXS. Lowing power consumption and availability of hooking it up to a big-ass-battery sounds good too. I hope it’s affordable, but I’m not their target market. I’m just happy my KS goes up and down when I need it to.
I don’t really have much else to say, this one was rougher than it should have been and I’d like to get out of this chair and go outside now. Let me know what you think. Have a great evening!
The post Height Adjustable Seat Posts for Bicycles by SRAM first appeared on WheelBased.