Structure Cycleworks

[Structure-Ryan]

I think I've grasped the concept now. This kind of feedback from the industry is fantastic!

Now, can it take a waterbottle, and what plans do you have for the future, and when the the Pinion Gearbox version coming to market?

Thanks! I'm a bike nerd, just like the rest of you, and it's even more fun when I'm talking about a bike I helped design!

I often edit my posts, which I understand makes it easy to miss the new information. From above: "As a fan of on-bike storage, it breaks my heart to have to tell you it's under the down tube. I'm working on squeezing one inside the main triangle on a future project, but don't hold your breath!"

The gearbox idea is very appealing. The ratio of sprung to unsprung mass is a huge problem with bike suspension performance and gearboxes are a great way to address it. This is why you'll notice every review of an e-bike *spits* mentions how good the suspension feels. You bet it does when there's four times as much mass stabilizing the sprung part of the chassis! I'm not convinced Pinion is the way to achieve this, though, as it's heavy, expensive, and - most damning - inefficient. I'm actually working on an idea that may be incorporated into a future model - again, don't hold your breath!

 

[PJO]

Among 98 companies analyzed, I've only spotted two that showed clear evidence of designing with this in mind: when I calculated "normalized reach" values (i.e. with compensation for stack), these companies' geometries were either consistent across models (i.e. consistent across varying stacks) or produced nice, round numbers at the normalized values.

Would be interested to know which two companies, care to share?

 

[Structure-Ryan]

Would be interested to know which two companies, care to share?

I've already gone a bit far by naming two companies in this thread! To be clear, the two mentioned earlier make great bikes, they just happen to nicely illustrate a couple of issues that aren't unique to those companies.

Two reasons I'm not going to name these companies:

1. Naming only two would be unfair to other that understand the relationship, but weren't as easily spotted.
2. More importantly, after making my observation, I didn't note the two companies and I don't feel like redoing the exercise!

 

[Zaf]

Thanks! I'm a bike nerd, just like the rest of you, and it's even more fun when I'm talking about a bike I helped design!

I often edit my posts, which I understand makes it easy to miss the new information. From above: "As a fan of on-bike storage, it breaks my heart to have to tell you it's under the down tube. I'm working on squeezing one inside the main triangle on a future project, but don't hold your breath!"

The gearbox idea is very appealing. The ratio of sprung to unsprung mass is a huge problem with bike suspension performance and gearboxes are a great way to address it. This is why you'll notice every review of an e-bike *spits* mentions how good the suspension feels. You bet it does when there's four times as much mass stabilizing the sprung part of the chassis! I'm not convinced Pinion is the way to achieve this, though, as it's heavy, expensive, and - most damning - inefficient. I'm actually working on an idea that may be incorporated into a future model - again, don't hold your breath!

Firstly, I didn't full appreciate having a bottle cage in the triangle until I start riding through sheepshit in NZ. But I'm going back to a bike with the system all the same in the coming months, it's not as big a drawback as people think, but better than no cage at all.
Secondly, RE: Pinion, you forgot to say "a most gorgeous example of engineering". I don't care if you lose 10% power, they're a goddamned marvel, whatever your alternative is, make sure it's as gorgeous.

Thirdly, it's Nicolai is one of the two isn't it?

 

[Structure-Ryan]

Firstly, I didn't full appreciate having a bottle cage in the triangle until I start riding through sheepshit in NZ. But I'm going back to a bike with the system all the same in the coming months, it's not as big a drawback as people think, but better than no cage at all.
Secondly, RE: Pinion, you forgot to say "a most gorgeous example of engineering". I don't care if you lose 10% power, they're a goddamned marvel, whatever your alternative is, make sure it's as gorgeous.

Thirdly, it's Nicolai is one of the two isn't it?

Yes, Pinion gearboxes are beautiful, but I'd rather hang art on my walls than use it to drag myself up hills at 80% efficiency!

I honestly don't recall who I noticed also accounts for stack when spec'ing reach, but if I had to guess, I'd choose Germans.

FINE, now I need to know, so I'll run a better analysis ...

Methodology:

The database currently tracks 845 models and sizes. I ran a series of standard stack values at 0.5 mm increments and set up functions to look for three types of relationships:

1. Round numbers (no decimal places) on all normalized reach values
2. Equal normalized reach values for corresponding sizes across models
3. Normalized reach values that increment by size with a linear relationship

Result:

Obvious correlations are still rare, but there are numerous possible correlations.

 

[Zaf]

Yes, Pinion gearboxes are beautiful, but I'd rather hang art on my walls than use it to drag myself up hills at 80% efficiency!

I honestly don't recall who I noticed also accounts for stack when spec'ing reach, but if I had to guess, I'd choose Germans.

You think the overall power loss is that bad?
I have been reading up on it but it seems to be a hard equation to answer for the system. We know that a clean and well lubed chain and sprocket system is extremely efficient, but the belt drives are more efficient from a lower rotational mass, straight belt/chain line and better power transfer (for medium to high loads) than a chain (especially one that has diverted it's line). Then you have the gear power loss and different sump oil viscosity and immersion etc that reduce the gear boxes effect.

Anyway, I'll report back with some practical experience in the coming months.

 

[Structure-Ryan]

You think the overall power loss is that bad?
I have been reading up on it but it seems to be a hard equation to answer for the system. We know that a clean and well lubed chain and sprocket system is extremely efficient, but the belt drives are more efficient from a lower rotational mass, straight belt/chain line and better power transfer (for medium to high loads) than a chain (especially one that has diverted it's line). Then you have the gear power loss and different sump oil viscosity and immersion etc that reduce the gear boxes effect.

Anyway, I'll report back with some practical experience in the coming months.

My guess comes from the following:

• A conventional drivetrain in good condition is in the 90s.
• Most people don't perceive efficiency losses under about 10% (based on research in tire efficiency).
• Everyone notices the Pinion is less efficient.

If you have more detailed information, I would be keen to sharpen my understanding of it.

Regarding belt drives: My understanding is they're less efficient at typical loads. They could only be more efficient at a power output well beyond what anyone is going to sustain. Chainline losses are less than the losses of a gearbox, but a Shimano Alfine hub could tip that balance in favour of a two-sprocket belt (or chain) system.

The difference in rotational mass will have essentially zero contribution to total system efficiency.

EDIT: I just reread the BikeRadar article (based on Friction Facts results, which tend to be pretty good) and it seems the difference is small and the crossover point is lower than I thought. Unclear what will happen if both systems are tensioned with the proper preload, but the belt does have appeal, especially with an Alfine hub.

 

[Zaf]

Well the official stance from Pinion is the following:

What is the efficiency of a Pinion transmission?

The efficiency depends greatly on the load situation (input torque/speed), which in practice varies greatly during riding and therefore a single number for efficiency cannot be calculated. In contrast to hub gears with the usual up to three planetary gears shift in succession, Pinion only has two constant gear stages. And of course the chain or the toothed belt from the transmission to the rear wheel must also be considered. With Pinion they are always straight and there is also no loss of efficiency, which occurs with the use of a rear derailleur with a skewed chain. Thus the efficiency of a Pinion transmission is between a high-quality hub transmission and a new chain shifter running absolutely straight from front to back. If a chain shifter is dirty and skewed, the efficiency of Pinion is better.
​

Now obviously that's with their marketing bias on it, another quote that I read somewhere was that a change in tyre pressure will make a more noticable loss in efficiency than the switch between the gearbox and chain/derailleur system. Having a listen to a podcast about the system at the moment with the North American service representative, but it's always going to be a drawback with a gearbox option, how big an issue it is will vary from rider to rider.

 

[Structure-Ryan]

how big an issue it is will vary from rider to rider.

Very true. "Winch and plummet" type riders probably won't mind the loss of efficiency and will particularly appreciate a robust, compact system with better suspension. I enjoy pushing hard on both the climbs and the descents, so efficiency is a significant concern for me.

Even if the current Pinion system isn't ideal for me, I'm glad they exist and are providing a viable - sometimes superior - option for certain riders. Diversity keeps things interesting!

 

[Zaf]

Very true. "Winch and plummet" type riders probably won't mind the loss of efficiency and will particularly appreciate a robust, compact system with better suspension. I enjoy pushing hard on both the climbs and the descents, so efficiency is a significant concern for me.

Even if the current Pinion system isn't ideal for me, I'm glad they exist and are providing a viable - sometimes superior - option for certain riders. Diversity keeps things interesting!

That's an amazingly good description.

So the interesting point the guy just made on this podcast was in regards to the chain vs belt. Under light loads, the pin swivel interface of a chain is extremely efficient, once you go to a medium cadence and load on the chain all those links come under pressure and become less efficient than the belt drives, become more efficient under higher loads. He did not that it's only a lab test type difference, and not noticeable on the bike except for the noted smoothness of the belt drive.

There are some serious advantages to the maintenance side of things and longevity of the drivetrain with it. I think you need to keep hold of a bike one with one and ride it fairly solidly for a year or two to make the initial outlay cost effective. Seems people who own them seem to love them though, which is always a good sign.

Anyway, i think I've derailed (hurrrr) this conversation enough. What are your thoughts on longer chainstays in order to keep rider weight position more central between the axles? Do you prefer them for handling? are you swayed by market pressure in trying to tuck them in as closely as possible?

 

[Structure-Ryan]

[belts, chainstay length, etc.]

Wish I could take credit for the phrase, but the Brits beat me to it.

Regardless of whether chains or belts are more efficient, it sounds like the difference is only a watt or two. If so, then the longevity, low maintenance, and reduced unsprung weight of a belt system tip the balance. I'll try a belt system if you buy a Structure. Deal?

So, chainstays. Let's look at AM/enduro bikes by wheel size:

650b
Average: 432 mm
Std dev: 7 mm

29"
Average: 438 mm
Std dev: 8 mm

There really isn't much in it. People get worked up about a couple millimeters, then casually spec stems that span a range of 35 mm, slide saddles around by 35 mm, and position cleats in a range of 15 mm.

Keeping in mind that we're talking about only a few millimeters and the differences are subtle: short stays are fun because they encourage cuttie turns, but they're less stable and can take weight off the front, leading to understeer; long stays are smooth, stable, and promote balanced loading of the tires.

Unlike front end geometry, chainstay length is more a matter of preferred ride feel than safety. The only rear geometry configuration I dislike is a slack seat tube angle and short stays because it's a chore to keep the front wheel down when climbing, but that's the fault of the seat tube angle, not the stays.

I gave the SCW 1 435 mm stays: short enough to be fun and long enough to balance our range of front-centre lengths. Also long enough to fit 2.6" tires with decent mud clearance and an adequate chainstay bridge (stiffness).

It would be ideal to vary the length of the stays by a few millimeters per size, but that assumes two things:

1. My concept of rear end feel is so perfect that it must be held constant across all sizes.
2. Customers are willing to pay a few hundred extra for this perfect chainstay length (carbon molds aren't cheap!).

There are dozens of design parameters that make a bigger difference to the overall experience than chainstay length, but few people give much attention to things like pivot axle diameters, bearing offset, use of woven material in impact areas, fastener head size, grade of aluminum in bonded inserts, etc. I don't mean to be condescending; it's a fair question, it's just something I get asked frequently and I want to give some attention to less sexy - but very important - issues!

 

[hifiandmtb]

Ok, now we are talking about rear end dimensions...what's your take on the importance of Boost?

If you ignore the need for a FD, can you get away with old-school 142 & still fit decently baggy tyres?

 

[Structure-Ryan]

Ok, now we are talking about rear end dimensions...what's your take on the importance of Boost?

If you ignore the need for a FD, can you get away with old-school 142 & still fit decently baggy tyres?

As long as crank Q-factor doesn't need to be widened, I'm all for wide hubs. Shame we didn't go straight to Super Boost.

There's no definitive answer for how wide a tire you can fit with 142 and maintain both adequate clearance and tolerable chainline. Feel free to experiment with different chainring offsets; the "official" chainline number is just a suggestion and it isn't even aligned with the middle of the cassette. The SCW 1 uses Boost spacing, but will be spec'd with non-Boost chainrings, for example.

You can try to squeeze in a larger tire by using a ring with greater chainline (an offset that places it more outboard) and downsizing the ring to ensure you spend more time on the outboard end of your cassette. Downsizing won't help if your chain doesn't clear the tire at all, but it will reduce annoying tire snagging and mud clearance issues. Don't expect to be able to backpedal when using the innermost sprockets when using a chainline that's shifted this far outboard; it's definitely a workaround, not an ideal set-up.

 

[hifiandmtb]

That link is an utterly excellent explanation of chainline, thanks for that!

 

[Tubbsy]

It lives!

Video: Structure Cycleworks’ Carbon Enduro Bike and Linkage Fork - Sea Otter 2019 - Pinkbike

Bored by "normal" linkage forks? The all-carbon SCW 1 enduro bike promises out-of-this-world handling thanks to its integrated linkage front-end.

www.pinkbike.com

 

[Zaf]

Removed by user

 

[hifiandmtb]

Just no.

 

[Ultra Lord]

Not the easiest fap is it @Zaf

 

[Zaf]

Removed by user

 

[nzhumpy]

Just opened that link and had a looksey...bugger me you're going to need to do a whole lot more of the fappy fappy to keep all those linkages running smooth....