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Angeles Spade prototype suspension analysis

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Angeles Spade prototype suspension analysis

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flag AgrAde
Posted: Mar 25, 2023 at 0:14 Quote
At first glance this frame seemed really cool, it's a great looking frame. This is what I'm talking about:

https://www.pinkbike.com/news/first-look-angeles-spade-prototype-is-cncd-by-a-19-year-old.html

Looking at the photos and the cad model though, I noticed that the virtual pivot point was way above the chainline, meaning tonnes of anti-squat (and kickback), and that the shock would barely move during the beginning of the travel meaning it was probably hyper-progressive. It interested me enough that I imported the picture of the CAD model into Linkage and made a rough analysis of the frame, and it was bananas enough to compare to a couple other bikes and post on here, I think. What do you guys reckon? I wanted to post this because he's planning on selling it, and he's also said that the prototype is behaving how he wants it to.







Here's the frame itself in Linkage. I didn't bother to draw the triangles properly, didn't bother to set the seat tube angle, I got most of the geometry pretty close (but Linkage is annoying to import bikes into as it likes to fiddle with things), and the linkage geometry is as close as I could get it. It's not perfect, but it's close enough to get a general idea of the suspension behavior of the bike. The resulting graphs are not accurate, but they're well within the ballpark.

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I decided to compare it to a 2021 Stumpy Evo and a Nukeproof Giga. Seems a good comparison as the Stumpy has quite high AS for a trail bike, and the Giga has very low AS. These won't be perfect either, but again, pretty close.





So lets take a look at anti-squat and the resulting pedal kickback. In 32/50 gear we're looking at 200%+ AS at sag, compared to about 120% for the Stumpy and 85% ish for the Giga. I've never ridden a bike with such consistently high AS, or even seen one. There's a very high rate of kickback for the Angeles.

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In 32/24 the Angeles is up at 300%+ AS. I have no idea what that would feel like. Note where the zero line is on the AS graph. Still a very high rate of pedal kickback.

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in 32/10 we're now up at 600% AS. If we could go any smaller on the cassette we might end up on the moon. Again, note the zero line of the AS graph. PK is as you'd expect.

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Looking at Anti-rise, this is actually pretty normal as the Angeles' IC is fairly far forward, and moves forward and down as the suspension compresses, lowering the AR through the travel.

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And now, how progressive is this thing? The answer is, it's the most progressive frame that has ever been built, most likely. With a leverage ratio starting at around 10, and finishing at about 1 at bottom out, you're never going to actually get to that bottom out. The giga is fairly progressive and it looks linear on this graph compared to the Angeles.

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So what does that mean for how your suspension feels? I equipped all three bikes with a 500lb spring for the following wheel-force graph. The bike is soft enough through the mid stroke that you're going to need a very firm spring just to get any reasonable sag, but it will be so firm after that point that the usable travel will be quite minimal. No matter how firm a spring you use, you'll be sitting deep into the travel and have a very very soft initial stroke that will feel almost completely undamped.

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The same person isn't going to run the same spring rate in all three bikes though. For a 170-185lb rider, Push recommends a 550lb spring for the Stumpy and a 500lb spring for the Giga, so they're represented below. Exactly what sag that would result in depends how you measure it, but it should be about 30% sag for the Stumpy and 33% for the Giga. What spring could we choose for the Angeles to get 30-35% sag? I can't find one. So here it is with a 700lb spring, which is the firmest I think I've seen. We're still at 45% sag, and there's only 55mm of travel left before we're at the same wheel force as the Giga at full bottom out, which is probably a good yardstick for actual usable travel. The Giga at sag has 114mm of travel left, for comparison's sake.

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So yeah. Thoughts?
flag carlinojoevideo
Posted: Mar 25, 2023 at 7:43 Quote
I love the analysis and don’t see anything jumping out that could be wrong with your model.

Is it possible he never ran I though linkage? I’d be very interested to hear more.
flag Erk101852
Posted: Mar 25, 2023 at 17:22 Quote
I also put in linkage and have pretty near identical numbers, almost thought I set it up wrong based on the numbers I was getting.
flag AgrAde
Posted: Mar 27, 2023 at 0:27 Quote
Good to see it wasn't just me haha. I kinda hope he talks a bit more about how he came to the numbers he's got, or at least what he was going for. Looking forward to seeing how prototype two changes, but you'd think he'd be pretty confident in the first prototype considering the expense to have it produced.
flag anoplura
Posted: Mar 27, 2023 at 21:38 Quote
Looks like the Naild R3ACT redux. Minimize the shock damping and increase the rider's body weight impact on the suspension movement. The rider becomes the damping. It works a lot better than you'd think it would, but only at low speeds/smaller impacts. Good enough for a bike designer or average engineer, but not a racer...
flag AgrAde
Posted: Mar 28, 2023 at 1:45 Quote
God I remember the reviews of those bikes. You could really tell who could ride fast and load up the bike, and who couldn't, just by who hated the bike and who liked it. Same with the early Plus bikes.
flag R-M-R
Posted: Apr 14, 2023 at 12:31 Quote
anoplura wrote:
Looks like the Naild R3ACT redux. Minimize the shock damping and increase the rider's body weight impact on the suspension movement. The rider becomes the damping. It works a lot better than you'd think it would, but only at low speeds/smaller impacts.

That's equivalent to saying "this damping philosophy works only when you don't need damping".
flag anoplura
Posted: Apr 16, 2023 at 18:59 Quote
Yup. Hard agreed.

But it's worth repeating that it does work well enough to fool some people who really should know better - at least some of the time. See also: Every iteration of the GT iDrive which works via a similar concept.

R-M-R wrote:
anoplura wrote:
Looks like the Naild R3ACT redux. Minimize the shock damping and increase the rider's body weight impact on the suspension movement. The rider becomes the damping. It works a lot better than you'd think it would, but only at low speeds/smaller impacts.

That's equivalent to saying "this damping philosophy works only when you don't need damping".
flag R-M-R
Posted: Apr 16, 2023 at 19:50 Quote
Can you elaborate on the iDrive point?
flag anoplura
Posted: May 3, 2023 at 18:51 Quote
In every version of iDrive, the movement of the rear wheel is coupled to the bottom bracket. The earliest versions were just variations on a URT*, where the bottom bracket was part of the swingarm. This means that for the rear shock to compress, the force on the rear wheel must be strong enough to overcome the rider's weight (which is acting to extend/lock-out the rear suspension) OR the force on the front wheel must be strong enough to essentially fold the bike in the middle, with the rider's weight on the bottom bracket essentially becoming the fulcrum.

*Unified Rear Triangle, or more accurately Unsuspended Rear Triangle.

I'd post links to images, but the forum software accuses me of spamming every time I do that lately, so you'll have to do your own image search.

Anyway, if you look through the history of the design, you'll see that they started out with a standard URT layout with a high-forward pivot point - OK for climbing, but pretty bad everywhere else. They then moved the pivot closer to the bottom bracket - reducing the "lockout" effect of the rider's weight - and then added linkages to uncouple the rider's effect on the rear axle even further.

The fact that they finally punted and went with the "Horst Link" design** for all subsequent bikes tells you all you need to know.

**I was there when the AMP forks and later frame were invented. The only reason the pivot was on the chainstay was for compatibility with RIM BRAKES.

There is no reason - other than aesthetics and (shock, water bottle, etc.) packaging - to not just use a single pivot. ...And if you are going to use a multi-link design, a dual-short-link (VPP, DW-Link, etc.) is always going to look better and perform better than having an unnecessary pivot point way out near the axle.
flag R-M-R
Posted: May 4, 2023 at 11:39 Quote
I would like to offer some different interpretations.


Re: i-Drive is similar to a URT

The problem with URTs was that the BB "rises" with the rear wheel, if the front triangle is the frame of reference. Thus, the rider becomes part of the unsprung mass. The i-Drive separates the BB movement from the rear triangle. Depending on how it's configured, the BB could move up, down, horizontally, etc., relative to the front triangle, thus potentially eliminating one of the worst traits of the URT.

Imagine, for example, if the BB dropped when the suspension compressed. Unlike a traditional URT that becomes firmer when the rider stands, this hypothetical i-Drive configuration would become softer when the rider stands. All rear suspension systems "essentially fold the bike in the middle" and we need only look at the effective spring rates in each circumstance; this is more complicated when the mass of the swingarm becomes significant (i.e. if this mass includes the rider), but it's still possible to use the standard calculations.

Now imagine an i-Drive configuration in which the BB remained perfectly static during compression. This would behave exactly like a traditional single-pivot, albeit with unnecessary complexity. No one would create such a bike, but it illustrates how the i-Drive quite different from a URT and can act like a single-pivot, URT, or something completely different, depending on the configuration. With a true URT, you're correct that the offset between the BB and the pivot provides a quick, visual indication of how much of the rider's mass is being "lifted" during suspension compression, but this relationship is no longer valid when the BB moves independently of the rear triangle.


Re: Advantages of i-Drive

The i-Drive concept allows a designer to use any type of linkage they like with a higher virtual pivot than would be practical without either a floating BB or indirect drivetrain (ex. idler). A high-pivot design without the excess drag of an idler is very appealing, though there's always a catch: in this case, it's additional pivots and a changing relationship between the location of the rider's hips feet.


Re: GT changing to a classic Horst

Many companies have changed suspension designs. It is too great a generalization to say one design is intrinsically and universally superior. Reasons for changes can include ease of manufacturing and personal preferences - whether aesthetic or technical - of the people involved. GT made the switch when they hired Luis Arraiz, former designer of K9 bikes. Luis is a fan of four-bar designs and indirect drivetrains, so it seems he opted for a safe Horst design and added an indirect drivetrain on models that prioritize suspension function over pedaling efficiency.


Re: SS (short-short) link vs. LS (long-short)

It is untrue that "if you are going to use a multi-link design, a dual-short-link (VPP, DW-Link, etc.) is always going to look better and perform better than having an unnecessary pivot point way out near the axle". The pivot near the axle - and on the chainstay - is necessary for a LS (ex. Horst) to be a four-bar. LS and SS are essentially the same design: if you shrink the chainstay down to a couple inches, it becomes a SS. They are both four-bar systems, just with different lengths of lower link. The SS design enables / forces the kinematics to change more rapidly throughout the travel, which can be a good or bad thing, depending on what properties you favour. The LS design enables / forces the kinematics to be more stable, which - again - can be good or bad. Neither is intrinsically better, stiffer, stronger, etc. I'll leave the question of aesthetics up to you and the industrial designers, as the design services I provide to the bike industry are on the engineering side.
flag AgrAde
Posted: Dec 2, 2023 at 16:20 Quote
Predictably, Angeles threw away this suspension layout after the first prototype, with #2 having a conventional Horst link.
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