In this article, we will be discussing an Adjustable Compliance Bicycle by Trek, US Patent 10,676,145. The publication date is June 9^th 2020 and the filing date is June 26^th, 2019. This patent is a continuation of application No. 16/145,626 filed on September 18^th 2018, which is now patent number 10,351,192. You’ll see that these two patents appear exactly the same but the claims are different, as each submitted patent is attempting to protect a different novelty of their compliance method. The 2018 and 2019 patents are for the IsoSpeed concepts that are already in production.

This publication is a very involved document, with a few continuation applications. Continuation refers to a patent that follows a prior application and claims priority to that application. The original patent was filed as a provisional (partial patent) dated May 2015. There was a non-provisional (full patent) dated in Nov 2016, a continuation dated July 2019, and yet another continuation (this article) dated June 2020.

Brief summary (tl;dr)

Trek has introduced another method of adjusting the deflection of a bike frame via an adjustable seat tube. The seat tube contains an adjustment plate that bolts to the back of the seat tube. Small objects are then sandwiched between the adjustment plate and the seat tube to provide multiple flexibility levels. One or more objects, depending on how flexible you want to ride, can be placed in numerous locations along the seat tube to dial frame flexibility. Additionally, the small objects can be different shapes or can be a full piece of metal or plastic to substitute for the objects. Therefore, a rider has multiple flexibility options based on the amount of objects the place into the back of the seat tube.

Background

This technology is in the field of compliance. More specifically, compliance of the frame and method of adjusting the seat tube for a more or less comfortable ride. Stiffness is defined as the ability for a solid body to resist deformation by an outside force. The opposite of stiffness is compliance, where a specific amount of flexibility can be designed into a solid body. Finite Element Analysis Programs such as FEMAP and NASTRAN allow engineers to design objects of a certain material and apply specific forces in specific directions to synthesize the flexibility properties of a solid object.

Compliance can influence the way a bike feels when ridden over rough or chattery terrain. In the case of this technology, Trek is looking to provide a more supple ride with a more compliant seat tube. Alternativly, if the seat tube is too compliant, the rider can adjust it to their preferences.

Intro

I know bikes are becoming more and more electronic these days, but there’s something about mechanical solutions to problems that feels right to me. Anyone can put a set of sensors and servos together to do pretty much anything these days. A creative mechanical solution to a mechanical problem is always fun see.

None of us are unfamiliar with Trek’s current push for compliance in their frames. Referred to as the marketing term IsoSpeed, Trek’s integrated compliance frames have been around for a few years. Trek state:

IsoSpeed diminishes the fatiguing impacts of the road, allowing the rider to remain fresher longer

Currently, IsoSpeed comes in two flavors, one in the steerer tube and one at the top tube/seat tube junction. The IsoSpeed in the steerer includes a compliant upper headseat assembly that effectively allows the fork to float in the steerer tube. Specialized has something similar with their Future Shock. Figure 21 below shows Trek’s front IsoSpeed from the patent in this article.

The rear IsoSpeed is a decoupling of the top tube and the seat tube, where the seat tube can move independently of the top tube. Figure 12 shows Trek’s rear IsoSpeed, again, from the patent in this article. I’m not sure if these are the current designs, but they were the original designs. I won’t go into detail about these designs because they’ve already been released.

So, Trek has just released a third patent in the compliance field. What more could they do?

Intended novelty

This publication is huge and has a few novelties and ideas. For this article, I will speak about just one aspect of the intended novelty, which does not appear to have been released to the public. The intended novelty of a part of this publication is to allow deflection of the seat tube. This is not the same as the IsoSpeed decoupler from previous bikes. Rather, an ‘adjustment plate’ is applied to the back of the seat tube, where stiffening ‘objects’ are placed between the adjustment plate and the seat tube.

Why

As with all other IsoSpeed ideas, Trek’s intent is to reduce fatigue so a rider can remain more alert and fresh through long rides. Anyone that has ridden a road bike on a rough track, or a gravel bike on anything offroad, knows the brutality that the terrain can do to the body. Hands hurt, ass goes numb, feet feel swollen. None of which are ideal for even short rides. With the industry’s severe distrust of bike manufacturer’s marketing teams, Trek’s entire IsoSpeed push may not be a gimmick. Companies typically won’t spend the money or time to patent marketing ploys.

What

In this part of the publication, Trek are trying to dial in a user-friendly method for an adjustable amount of flexibility into the seat tube with an adjustment plate. The adjustment plate accepts small objects (balls) in different seat tube locations, where the small objects are forced against indents in the back of the seat tube when the adjustment plate is bolted to the seat tube.

Because Trek does not explicitly say it, I can only assume that the objects’ locations allow numerous flexibility options. I am unsure as to whether the number of objects used dictates the flexibility of the seat tube or the location of the objects dictates the flexibility. Either way, it appears to be a brilliantly creative solution to a complex problem. Additionally, as this solution appears complex and expensive to implement, some serious stress analysis must support the design. Unique tooling and quality control will need to be used to create the indents in the frame and heavy FEA would need to be done to ensure a repeatable application of the idea. However, Trek are no dummies. They know their market and the enthusiasm cyclist maintain toward customizing their bikes. Bike enthusiasts love to tinker with our bikes, and this is just another dial to turn. 

How

Trek has written very little about this part of the concept in the publication. We’ll try to break down their methodology from what can be found in this document.

Figure 29 shows an isometric view of the idea. The only thing that should be noted here is adjustable plate 2710, indents 2740 in the adjustable plate 2710, and object 2720. Everything else is ancillary.

Figure 30 shows another isometric view of the idea in question. Here, adjustment plate 2710 bolts to the back of the seat tube 22. Seat tube 22 contains indents 2840, where objects 2720 and 2820 (2720 is poorly drawn) are installed between the indents 2740 and indents 2840. Trek is vague on the shape of the object, and rightfully so. Trek, and the writers of this publication, do not want to box themselves into one shape, as other shapes may provide different compliance characteristics. Trek states,

‘The first object 2720 and the second object 2820 can be a sphere, cylinder or any other shape’.

As I said before, I am unsure whether the compliance adjustment comes from the number of objects or the objects’ location. Trek does state

One, two, three, or more objects can be placed in between 65 first indents 2740 and second indents 2840

suggesting that multiple objects may be used, but are unclear as to if more equals stiffer or more flexible. I would wager that more objects create a stiffer ride.

Figure 32 shows a side view of the seat tube 22 with the adjustment plate 2710 and the objects 2720 and 2820 installed. You can see how the adjustable plate screws into the back of the seat tube, applying pressure to the objects against the seat tube.

Lastly, Figure 33 shows a detailed z-axis cross-section of the seat tube 22. Trek show that the object 2720 is pressed against the seat tube 22 when the adjustment plate 2710 is bolted to the frame. I would almost liken this to a vertebral column, providing a level of stiffness to portions of the seat tube where the objects are installed.

It is important to note that Trek has also included another possible option that may be used to adjust the seat tube’s flexibility. Trek states

In another embodiment, a strip of material can be placed in between the adjustment plate 2710 and the adjustable seat tube 22

Therefore, the objects might be replaced with a strip of metal or plastic to control seat tube flexibility. Again, Trek does not want to box themselves into a single concept, and they believe a piece of material may provide similar compliance characteristics.

Lastly, one very interesting item about this patent is that it has been assigned to JP Morgan as a collateral agent. Why? No idea. I’m sure there are some banking folk that can answer this one.

In the end, Trek has introduced yet another compliance adjustment device. IsoSpeed may now offer flexible steerer tubes, flexible frame junctions, and flexible seat tubes. But is this level complexity worth the potentially minor improvement of a more supple ride? Do you want more parts to break or lose? Is a Thudbuster or softer seat out of the question for you? Is this level of technology for the elite riders looking to shave a few seconds off huge rides, or will you be taking this to your local races looking to (literally) flex on your competition?

Lastly, I have read numerous patents and have to say that the attorneys and writers of this patent did a great job on this one. The inventive concept is clear, the drawings are easily understood, and the claims define the scope of the invention very well.

If you think you see something wrong in this article, please email me. We can’t have misinformation out there. Even if you’re not 100% sure you’re right, I’d still like to hear from you.