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I think the balance you have is great. The averages and 95th looks great. Personally I only give my max speed a glance but I hardly tune for it. The reason being is that if everything else looks good, you are tuning your whole run for one max speed that could be on a drop or big hit. So in reality you’d be stiffening your bike the entire run just for 1 split second.
but to answer your question, my max speeds hit 5000-7000 depending on the track. But really the best is to try all the combinations you can, then find the numbers that feel best for you. I’ve tried soft and stiff setups, also help friends and everyone seems to like different feels.
First test build of the new logger. Same functionality as the last one (4 analog + I2C), but smaller and more tightly packaged. I'm on a mission to get the parts count (and cost) as low as I can without giving up any important functionality. The screen is a head scratcher. I find it a nice quality-of-life feature and it doesn't add much to the cost, but people seem to be able to live without having one. Feedback from users of other systems appreciated!
Do you need much more than on and off? And a light to indicate data acquisition.
Well, ultimately, no you don't really. But it depends on how much you want to be able to do on just the device, as opposed to getting out your phone or computer. Like turning wifi on and off, marking the zero points of sensors (or other calibration activities), turning sensors on and off, setting the sampling rate, indicating battery status etc. All of that can be managed with a couple of buttons and a few LEDs but past a certain point it gets a bit difficult to navigate. So it's a question of where to draw the line.
As you said, it's really nice to have indicators for connectivity (wifi/BT, sensors), show battery %, and recording status. I hate it when electronics of any form cheap out on a basic LCD in favor of colored LED lights, where you have to consult your horoscope to determine what slow blinking orange means (vs. fast blinking orange).
Follow up to this one.
I serviced the fork (lower leg service) which was basically new in the last video. There was some oil in it but definitely not the amount mentioned in the manual. I also maxed out the VIVID Air with 4 tokens since the data showed (for my newbie eyes) that the shock is working way more and blows through the travel in G-Outs and impacts after small drops. Both things made a very big difference! The fork is now way more active than before and also feels even better than it did before. I also feel more centered in the bike with the shock setup right now which is a big bonus for confidence in the rocky part of my testing lap. The video doesn't do justice in terms of speed, but the audio shows that the suspension works a lot.
I do think I overcorrected the shock, since the total movement is now less compared to the fork. 95th travel was actually perfectly balanced on this run but max travel was quite a bit lower for the shock.
I think I'll try it again with 3 tokens and that will hopefully be my alround setup then.
I'm now at a point where I feel the firmware and software work reliably. The next step is to simplify the electronics and write some manuals. I hope I'll be able to release the project in autumn!
Is there anything particular you guys want to see?
Very slick! I think a screen can be handy - mainly for sanity checks like zeroing sensors, or for live sag readings, check battery level etc. Nice to be able to run it standalone instead of doing a recording, download the data, skin through it and try again to double check everything is set up
This is sweet! I'd love to make something similar, would it be possible to pester you about what you used in this setup?
A few questions for folks: have people had much luck with string pots? I was thinking for things with shock tunnels (e.g forbidden) using string pots might be a better way to go.
Really starting to look at creating a DYI solution to play around with.
Yes, absolutely. The idea is that this is an open-source project. I don't have build guides etc written up for it but I am looking for people to try it out - once I've tested the new PCBs and made sure they work OK, I'm happy to send you one for the cost of postage along with a shopping list for the other minor bits required.
Same goes for anyone on here as long as (1) you send me some feedback, and (2) you understand that it's still basically a DIY project - I'll provide whatever help and support I can but there are practical limits.
instagram.com/bodaqs
I dabbled around with stringpots but didn't find them reliable enough mostly because the line can get snagged easily (branches, leaves, shoelaces etc.) and distort your data. The shock tunnels are indeed an annoying thing in regard to sensor mounting so I decided to move away from the shock and measure wheel travel directly with a link arm driven rotary encoder. Pretty much like a ride height sensor in a car.
I think Push uses a string pot in their system, ive never used one but i think they run pretty high tension and also very high price! I think rotary sensors like you've got are a really good balance of versatility and precision. The ones I tested in a string-pot style design could pick up crazy fast movement when i pulled the string out and let it snap back as fast as possible. It only lost tracking if it had to go past 360 degrees too quickly, which wouldn't happen when measuring a linkage pivot
The string pot works well, the only negative on ours is the mounting. The awkward shape almost always requires us to print a new mounting bracket for each bike to get proper alignment, whereas the linear pots typically can reuse mounting hardware. We just use the Aim pot but there's other options out there that might solve this issue.
FYI, KTM has used the string pot on the front for years.
Yeah that does look nice! they appear to have a lot of flexibility and are able to handle much more travel than a regular pot. In case it wasn't clear they do look really good, its just decent ones look to cost more than a linear sensor so is probably out of reach for most people.
Great! This would be awesome, working on some robotics/physical AI stuff for a job and I've been looking for a bike data acquisition setup that I can have free reign over. I'd rather have a board/setup someone has put together than trying to hobble one myself. I'm more of a software guy so the idea of running solder doesn't thrill me.
Sounds like what's needed is a roll-your-own string pot that can be built for about $10... coming soon to an open-source data acquisition project near you. Maybe.
This guy runs on the bench and can either emulate an analog pot or be read over I2C. It's built around an as5600 encoder: that plus a couple of bearings, a spring from a key lanyard, a 3d printed spool and a short piece of chrome shaft pulled out of an old scanner make up the driveline. It's multi-turn which keeps it compact (and the inertia low), but at the cost of having to deal with wrapping in software. But that's trivial at any realistic sample rate.
I'm planning to run this back to back with a linear pot over the next couple of weeks and will report results. If there's interest (and it works!) I'll publish the design.
Awesome, sounds sweet and looks tidy. I too raid every old appliance for any useable material! Will be keen to see how it goes on the trail, the one I made worked out to 125mm of string travel per turn, and to count turns the code would detect as it crossed 0* if the last sample was more or less than 180 degrees. Was extremely responsive when measuring within a single turn (so a shock would be no issue) but multiple turns at full speed (just pulling it out and letting it rip back in) would lose count even with the poll rate maxed out. I didn't test how fast that speed was but if the inertia is low and the spring can keep up it should work really well
Depending on your microcontroller an interrupt based approach would likely be faster and more reliable. Interrupts won't be blocked by the main execution loop.
For anyone who wants to talk specific technical details or ask questions related to hardware, processing, or component sourcing feel free to hop in the Discord here (not to replace this thread; just to prevent it getting too sidetracked on specifics). We can also set up a file sharing server or shared github if people want to collaborate.
That's incredibly generous Geoff. Feel like I'm re-writing Shakespeare a bit here :-)
String pot update... next iteration done and ready to ride. Testing duties will be delegated as I'm recovering from shoulder surgery but hopefully will have some results to share soon.
anyone stumbled upon https://trailmetry.com?
seems to be a one guy show, with lots of current development. sensors were just 15$ each, but currently only read at 100Hz. should arrive next week.
The website is all AI generated so I'd have my doubts. The sensors are so cheap I can see it being worth a shot.
Has anyone in this thread tried accelerometers for suspension data?
I'm intrigued. I've been watching this thread for awhile and registered to see how this all works out. It's cheap enough that I ordered sensors, too, but there's definitely a 'too good to be true' vibe. It'd be interesting to compare to one of the existing systems out there.
I'm interested in trying one of the homebrew Raspberry Pi setups, too, but haven't found the time to deal with it yet.
Seems like a bunch of red flags to me with that set up. I’m not sure how you would get Suspension speeds based on air pressure, but if someone actually gets the hardware, let us know!
nick from Downamics I believe has been trying to get Suspension speed algorithm from on the axles. The Syn system has great ones that you can put all over the
Yeah that looks like an off-the-shelf unit (with generic libraries available on github) and Trailmetry is mostly just the app. Weird how it needs to be on a moving part of the suspension, but its on the fork crown up front but the shock body on the rear? Definitely weird....
The Stendec systems used acelerometers for suspension measurement and Downamics has been trying it too. In theory they are a good way to measure damping and actual wheel movement (eg it is possible/common that your wheels are moving up from bump but due to things like friction there is no movement detected at the damper) but inferring position at any point is super hard. You are integrating twice which exaggerates any slight amount of noise so you need to deal with that. I don't think its impossible, maybe you could vibe code something to work it out. Or maybe thats the type of thing machine learning could be used for when the data is processed later...
Definitely some potential in them, I have a pile of different accelerometers in my tinkering pile and they are simpler to mount than a position sensor - you are just probably trading off easy position data which is the best for working out spring rate, for a more overall picture of damping performance
The only way I see to have any meaningfull data from accelerometers to get suspension movement is if you have two accelerometers at each end of the suspension unit (fork crown and lowers or both shock ends) and compare the two. The difference between the two will be what actually moves the moveable part of the shock, from that you could get speeds and then movements.
But you're not doing that with 25 USD BT accelerometers. You'd need a serious DAQ with synced channels to do that kind of measurements.
As said, that website is full of red flags and screams scam.
Here is my modified version of the KPM-12J Potentiometer.
I covered the pot with two sliding carbon tubes together with two 3D printed endcaps. It adds 35g to the pot but provides a whole lot of stiffness and protection against dirt and grime 😁
I also made another short video trying to explain a bit about TRAZER for those who are interested :-)
Yeah you’d definitely need a few accelerometers to figure out the shaft speeds. Easier to figure out on fork, but shock you’d also need to include the leverage ratio some how. Like sensor on axle and top of fork, rear axle and BB. Then algorithm to try and figure out some data.
...and it looks killer! Nice work.
If you really want to go forward with measuring suspension movement with accelerometers, besides having a really good DAQ (think Dewesoft or NI grade of equipment) the best way to do it is to have single axis accelerometers with the working axis aligned AS CLOSE AS POSSIBLE with the shock/fork axis of travel and have each mounted on either end of the two moving parts. The alternative is to have three axis accelerometers and align two of the axes, but that will just give you general noise on the other two axes and complicate the acquiring part (you need 6 instead of 2 channels per bike end).
The thing is that even measuring these two positions you will still get A LOT of noise from the bike moving around. That's why you need two and to compare the two (hence why you need the two channels synced). The difference between the two measured points is actually what the shock (or fork) is doing.
If you're measuring or comparing the BB vs. the axle, you really need a three axis accelerometer on either end as the movement is not linear, if you assume it is, you need to mount the two according to how you linearize the rear axle movement, the accelerometer on the rear axle will still rotate in the travel giving you skewed readings, if you're using a 3-axis accelerometer you have the above problems PLUS you need to incorporate how the axle is moving into your analysis, the bike is still moving around, etc. etc. etc.
All that and measuring accelerometer requires some more specialized equipment even if using just one accelerometer channel. Accelerometer work on an electric charge principle and you have to measure that and then transform it into voltage and so on. It's not as simple as measuring resistance (voltage drop) or voltage which is fairly simple even for the home gamer making DIY DAQ equipment.
TL;DR: just use linear pots for the suspension movement and be done with it.
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