Trek Invents Automatic Dropper Seatpost Concept - No More Sitting Down Required! 13

​By now we all know just how incredible dropper posts can be, because they truly do help you ride better by getting the seat out of the way on descents. They've always had one major drawback though - you have to sit down on the saddle in order to lower it. This can occasionally be very awkward when headed into an unexpected rough section or dip in the trail.

Well, the day is approaching when seatposts will drop themselves. In a US patent application published on June 4, 2015 (USPTO Application #20150151804), Trek Bicycles describes the inner workings of a post that uses a combination of air and coil springs to both raise and lower the saddle with the press of a bar-mounted remote button, eliminating the need to always sit down. Unlike Shimano's motorized automatic dropper, Trek's solution does so without a battery.

The provisional patent application was filed clear back in August 2011, indicating that this project has been in the works for quite a while.

How does the concept work? This excerpt from the patent application describes one possible version of an auto-drop post:

"In one embodiment, two springs can be used; one to store the energy needed to push the post from bottom to top, and another to pull the post down to the middle position during an auto-drop sequence. An air-spring can be used as the primary spring which pushes the post up. When the strong air-spring pushes the post up, it can stretch a weaker coil spring as the post rises. When the post is in the up position, the weak coil spring can be fully stretched and ready to pull down during the auto-drop sequence. To allow the coil spring to pull the post down, the post can unlock from the up position, and the bottom can fall out from below the strong air spring [meaning it has nothing to hold it up]. When this happens the weak coil spring can pull the post down to the middle, auto-drop position. Rider weight can further compress the post from middle to down position, and at the same time the post can be reloaded. The air-spring can be compressed to store energy to push the post back up when the rider is ready.... Advantageously, the simplified automatic drop seatpost does not require an external power source."

Key to the auto-drop function is a rotatable tube inside the seatpost that controls when the air spring is locked into place. It's shown here in the locked (Fig. 10) and unlocked (Fig. 11) positions. Activating the button spins the tube, allowing the post to be pulled down by the tensioned coil spring. The post is then locked into the middle auto-drop position using pawls.

Due to the laws of physics, unfortunately you can't expect a full drop from the automatic function, just half way. It's simply not possible to overcome all that stored energy without creating energy via a battery or compressed air - one of the biggest design challenges in coming up with this concept, and precisely why we haven't seen much like this before. You can thank Dave Camp (former DC Special creator and Trek engineer, now with SRAM) and Jose Gonzalez (Trek's Director of Suspension Design and Testing) for this solution.

Sitting on the seat and compressing the post all the way relieves the energy stored in the coil spring, recharges the air spring, a resets the control tube using a hydraulic piston, prepping the post to return to the fully extended position when you chose.

Camp told Vital, "We essentially wanted to create a panic button for those oh-shit moments, then you can sort things out later. It's a little limited in function and you have to go in order."

Compared to existing dropper posts, some drawbacks include being limited to just three positions (up/middle/down), and the fact that you'll have to compress it all the way by sitting on it before the post can be fully extended for the next climb. Of course it's possible to simply sit on the post from the get-go to lower it all the way, in which case it's ready to pop back up when you are.

We're told that this exact design will not go into production, as it faces some assembly complications due to the number of parts and precise alignment requirements. The general design concept - using one spring to pull down the other - is one that other companies may have to license in the future.

Though it's not our dream seatpost that can go fully up/down on command with an infinite number of stops (and be lightweight, cable-free, easily serviceable, and made of unobtanium), we're excited to see the gears beginning to turn toward a post that can get out of the way quickly and easily in case of emergency. The auto-drop feature promises to begin the next transformation of how we ride our bikes, allowing us to continue charging harder and harder into unfamiliar terrain.

The full patent is available for download here. Yay bikes!