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Yeah it would be pretty sweet if that kind of data was published, along with a few other specs. Would be useful for picking air shocks and deciding when a Float X or X2 is the better choice. And when Rockshox has 3 different types of air can I still can't keep up with exactly which is supposed to do what. You could see roughly what pressure in an X2 gives equivalent sag in a Float X if you swap it out.
I think you might be right the Float X is probably better for a Ripmo V2 though
In my ignorance I had assumed, apropos of nothing, that suspension tuners would have developed an heuristic for that by now, e.g. "above a certain leverage ratio (or other characteristic) = Float X2, below it = Float X", or something along those lines, although I'm sure it isn't that simple.
How difficult is it to measure the chamber volumes when it's already open for service? I imagine filling each chamber with an appropriate incompressible fluid, but I don't know enough about the insides of an air shock to know whether an "appropriate fluid" exists or if they'd tolerate that kind of thing in general.
What are your thoughts about the Hover Monocoque?
I kinda agree that the Secus already addressed these issues. There is no replacement for displacement, expanding lower and negative volumes in an external device was pretty innovative engineering.
Yeah theres definitely some rough guidelines we pick up, but measuring air springs accurately is tricky so a lot of it comes down to rider feedback and trends as much as measuremements. And part of that for me is not being able to 100% confidently measure the full stroke of an air shock accurately across a range of pressures without a way to validate those tests. Each stroke shock and even trunnion and standard eyelets have different volumes so its a big task to collect data on all of them.
Ive tried measuring a few different ways, all are pretty fiddly - you can fill it with oil or degreaser and weigh the shock before & after bit you still need to work our how much was in each chanber. The inside of the eyelets are awkward shapes so cant be directly measured either. It can be done, its just not always worth the amount of time it would take to work it out. Ive been playing with 3d scanning/photogrammetry and there is potential there for measuring things quite accurately though, so ill look at giving that a try for shock volume soon
Not too many sorry - we dont really get any intend product down here so have no direct experience with it apart from bouncing on 1 or 2 of their forks and shocks on tourists bikes. They did feel quite impressively smooth for air suspension though! Ive always been a coil fan so havent looked too closely at them otherwise, they seem really nice its just not my cup of tea
3D scanning might work (likely expensive), photogrammetry probably won't work as you need to look very deep into the air chamber to see the shape of it, it's shiny and usually black, so I doubt you'll get any meaningful results from photogrammetry.
3D scanning is much more likely to work as it also projects (in IR) patterns onto the surface plus looks at the object using two cameras and the part has to be covered with something like TiO2 to be nice and matte to prevent reflections. But you're again back to square zero where you have to measure each and every shock option, it will more or less be a throw-away shock as it will be hard to properly clean the TiO2 from all the surfaces, etc.
It's a very expensive endeavour for something that a) is likely something the manufacturers already have and need to develop the platform correctly and b) would be very easy for the manufacturers to share and c) would not give anything away design wise as those who could realistically benefit from it, easily buy competitor products and analyse them (it's VERY hard to imagine the like of Fox, Rock Shox, Suntour and Manitou don't have 3D scnaning, dynos and other equipment in house and can't afford 20 to 30k to investigate competitor products once those come out).cha
FWIW, if data was shared, starting volumes of both positive and negative chambers, piston surface area and equalisation stroke point is what would be needed to fully model the shock for an enthusiast (spring stiffness wise).
Possible (but not at all serious) solution: DIY CT scanner
Perhaps plow was the wrong term to use. It is decidedly less poppy in ride feel than the V3, much more eager to keep the back end on the ground.
I’ve always been suspicious that changing shock stroke changed the air volume on my X2.
I extended the stroke from 62.5 to 65 and it felt softer even at the same sag (by distance in mm, not by %). I put a volume spacer in and it felt similar to the prior stroke.
Absolutely, if that's what you are after. Even with a coil though, I thought the v2 was plenty "poppy". It's the nature of the dw link and relatively short chainstay. My terrain here in western canada tends to be higher speed stuff though, so I am definitely bent that way in terms of bike setup.
I'd agree that it's going down the rabbit hole to actually measure volumes, shaft displacement, piston area, transfer port locations and attempt to extrapolate a curve.
The layman can suss out 90% of what they need by simply calculating compression ratio. But it's all arbitrary in most cases anyways when we are talking about applying this to a trail bike like a ripmo. An x2 is easy enough to tune, throw some volume spacers in it. Add some lsc, you'll be popping around like Jeff KW in no time.
Just a quick question:
What does 'check tune' mean in Rock Shox rear shocks jargon?
What exactly does the compression ratio give you?
Unrelated-- how do we feel about there Bartlett? There's a good deal on one. My two riding buddies had the MRP Ribbon and both were disappointing to say the least, but this was years ago. IDK if MRP has updated their in house forks ever.
It would be nice to swap my 170mm fork to get 190mm with minimal AtC changes
I wouldn't have mentioned photogrammetry if it wasn't something I was already playing with......this was done with a smartphone and a relatively cheap app....that shaft is supposed to be 14.00mm btw
I can’t speak for the forks themselves but the MRP ramp control cartridge is the real deal 👌🏻
The check valve that stops oil flowing through the low speed rebound circuit on compression - either a separate small piston or part of the HBO piston in the recent generations. The old super deluxe had a preloaded shims stack but more recent ones normally aren't. Not sure how much difference it makes (I think they mostly use the same arrangement but list it several times anyway in the manual..)
Yup thats correct, a volume spacer contains about 5.5g of plastic on my scales and a 2.5mm travel spacer is 4.5g so thats near enough that same thing. Thats often been done intentionally, like RS travel spacers were large plastic discs so that they had a little more progression when you reduced the stroke
Average spring curve.
This is very different to trying to scan the insides of an aircan (or aircan). The problem is the flare right above the outer sealhead if it's present. And the outside technically doesn't help as you don't know the wall thickness.
Unless you cut it in half.
How?
What app is that? All the phone based ones I've messed with have been pretty bad so I gave up on them.
As far as figuring out spring curves, it would probably be easier and more accurate to measure the shock's actual spring curve and then fit it to an equation to approximate the curve at any pressure. If you know shock stroke used and initial positive pressure, you only have to back out initial negative pressure, negative piston area, positive piston area, initial negative air volume, and positive air volume. Pick five data points and that's a system of equations you can solve.
Nothing fancy, or particularly useful. Simply gives you an idea of spring rate progression vs a linear rate progression.
In the context of the OP, they're looking for "pop", as in a higher progression rate/compression ratio. That data might be useful to them in so far as to compare an x2 to something like a float x, in order to isolate spring performance vs having more valving in the x2. Case in point, ibis uses extremely light valving for the most part, I suspect in the OP's case, the tune is the major factor creating a difference between the two bikes, not necessarily the air spring volumes. Likely the v3 ripmo is on an ibis tune, and the v2 is an off the shelf mid tune x2. Comparing the two compression ratios would give him an idea. Of course the sensible thing is to simply compare the tunes.
I think that information is useful, but in a limited sense. Positive air spring volume is one number that's part of several other ratios that determine spring rate, like positive to negative volume ratio (e.g. MegNeg) and positive volume to air shaft displacement ratio (e.g. new Boxxer with a smaller seal head, requiring way higher pressures to create a more linear feel). You could be looking at two shocks with similar positive spring volumes that had very different spring rate curves depending on some of those other factors.
Yeah the air can is definitely tough - but at least it is easy to model and revolve in cad and scanned data can supplement the measurements you are able to get manually. Like you mention, the dimple position is super important so it would depend on how well you can determine that measurement too. Either way you would be needing manual drawing and measurements to get a final result, and its mostly inside the eyelet which has weird shapes you can't easily measure or draw with much accuracy. But if you are trying to measure things completely by hand and needing to fudge a bunch of the difficult parts then the end result isn't going to be useful
I'm not saying for sure this is a useful way to do things yet - but I've been playing around with it for a while since I thought it could be handy to make sensor mounts and check clearances in different frames. If I find enough use I might invest in an actual 3d scanner, but I have been dialling in a photogrammetry workflow and fairly impressed with what it can achieve - took some trial and error but there is potential there IMO for what I do. I hadn't really intended it to be used for detailed measurements like this but the accuracy has been better than I expected so I'm exploring it for now.
I'm not gonna lie - a big factor is simply the fact that I'm an adult with ADHD and unsupervised access to a workshop all day - I play around with all kinds of things that may become useful...or might not....but its fun figuring it out
@CascadeComponents - I'm using Kiri engine app and fairly pleased - I tried Polycam and thought that had better results but I ran in to some issues where I paid for the subscription but it didn't let me actually use it and kept getting errors. They fixed it eventually but its more expensive and that kind of made me reluctant to try again. After some persistence I found homemade scanning spray of baby powder & IPA plus a turntable and good lighting (I made 3d printed diffusers to go on cheap desk lamps) has been quite reliable.
I wasn't going to go on but I did actually get a scan from this monarch R which might bring it back on topic......the scan of the positive chamber gave a volume of 79.97cc (actually the threaded part of the air can needs to be subtracted but its a start), and the inside of the air can wasn't much good as expected but the outside is enough that I could model a useable part from it.
yeah that is possible - my dyno can only measure 50mm stroke though, plus it is a little awkward to fill a shock to a pressure, equalise the chambers and then mount in the machine (without damaging the shock if the dyno isn't perfectly at BDC), so ideally I would combine that data with accurate volume measurements to fill in the missing pieces. This is also why I haven't really gone too far down the road of measuring air springs, as useful as it might be. A proper spring rater would help - but I'm not sure its useful enough to justify the cost for me personally
The compression ratio would be a very good indicator of shock performance if it only had the positive chamber. With the negative chamber volume, piston area and equalisation point playing a role it doesn't give much usable data by it's own.
The shockwiz measures the compression ratio to know roughly where in the travel it sits by measuring the pressure. The keyword is roughly though.
Giving me U.S.E vibes:
Took way too long to find an image of this!
Right, piston surface area absolutely has a large effect on the system. You can't just take a high volume can and stuff it with spacers to get an equal volume to a smaller can and expect it to behave the same way due to that. That's what my pal with the X2 tried to do but it still didn't give the desired effect.
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